fix #26 (backend,frontend): Frontend can't apply codecs filters correctly

fix #22 (backend,frontend): the backend and frontend had whitelists that only included audio formats
fix #27 (core): no write permissions fail
2026-09-02 21:24:18 +05:00 · 2026-09-02 20:12:00 +05:00 · 2026-09-02 19:36:28 +05:00 · 2026-09-02 19:14:57 +05:00 · 2026-09-02 18:30:53 +05:00 · 2026-09-02 16:57:10 +05:00
27 changed files with 1558 additions and 446 deletions
@@ -1,20 +1,124 @@
-"""Global constants and default values."""
+# audio_splitter/constants.py
+"""Global constants for the audio splitter.

-# Mapping from user‑friendly format names to FFmpeg format identifiers,
-# file extensions, and whether the container is audio‑only.
-FORMAT_INFO = {
-    'mp3':      {'ffmpeg': 'mp3',      'ext': '.mp3',  'audio_only': True},
-    'm4a':      {'ffmpeg': 'mp4',      'ext': '.m4a',  'audio_only': True},
-    'mp4':      {'ffmpeg': 'mp4',      'ext': '.mp4',  'audio_only': False},
-    'mkv':      {'ffmpeg': 'matroska', 'ext': '.mkv',  'audio_only': False},
-    'matroska': {'ffmpeg': 'matroska', 'ext': '.mkv',  'audio_only': False},
-    'ogg':      {'ffmpeg': 'ogg',      'ext': '.ogg',  'audio_only': True},
-    'opus':     {'ffmpeg': 'ogg',      'ext': '.opus', 'audio_only': True},
-    'flac':     {'ffmpeg': 'flac',     'ext': '.flac', 'audio_only': True},
-    'wav':      {'ffmpeg': 'wav',      'ext': '.wav',  'audio_only': True},
-    'aac':      {'ffmpeg': 'adts',     'ext': '.aac',  'audio_only': True},
+This file serves as the single source of truth for:
+- Container formats and their properties
+- Audio codecs and their recommended containers
+- Video codec support per container
+- File extensions for each codec/container combination
+- Compatibility matrix for codec/container validation
+
+Codec != Container != File Extension.
+Example: Opus (codec) → Ogg (container) → .opus (extension)
+"""
+from typing import Dict, Optional
+
+# ------------------------------------------------------------------------------
+# Container information
+# ------------------------------------------------------------------------------
+CONTAINER_INFO = [
+    # Audio-only containers
+    {'name': 'mp3', 'ffmpeg': 'mp3', 'extension': '.mp3', 'supports_video': True, 'supports_subs': False},
+    {'name': 'm4a', 'ffmpeg': 'mp4', 'extension': '.m4a', 'supports_video': False, 'supports_subs': False},
+    {'name': 'flac', 'ffmpeg': 'flac', 'extension': '.flac', 'supports_video': False, 'supports_subs': False},
+    {'name': 'wav', 'ffmpeg': 'wav', 'extension': '.wav', 'supports_video': False, 'supports_subs': False},
+    {'name': 'aac', 'ffmpeg': 'adts', 'extension': '.aac', 'supports_video': False, 'supports_subs': False},
+    # Containers that support video and subtitles
+    {'name': 'mp4', 'ffmpeg': 'mp4', 'extension': '.mp4', 'supports_video': True, 'supports_subs': True},
+    {'name': 'mkv', 'ffmpeg': 'matroska', 'extension': '.mkv', 'supports_video': True, 'supports_subs': True},
+    {'name': 'ogg', 'ffmpeg': 'ogg', 'extension': '.ogg', 'supports_video': True, 'supports_subs': True},
+    {'name': 'webm', 'ffmpeg': 'webm', 'extension': '.webm', 'supports_video': True, 'supports_subs': False},
+]
+
+# Container name lookup set for fast membership checks
+CONTAINER_NAMES = {container['name'] for container in CONTAINER_INFO}
+
+
+def get_container_info(container_name: str) -> Optional[Dict]:
+    """Return container info dict or None if not found."""
+    for container in CONTAINER_INFO:
+        if container['name'] == container_name:
+            return container
+    return None
+
+
+# ------------------------------------------------------------------------------
+# Codec information
+# ------------------------------------------------------------------------------
+CODEC_INFO = [
+    # Audio codecs
+    {'name': 'opus', 'ffmpeg': 'libopus', 'recommended_container': 'ogg', 'recommended_extension': '.opus', 'codec_type': 'audio'},
+    {'name': 'vorbis', 'ffmpeg': 'libvorbis', 'recommended_container': 'ogg', 'recommended_extension': '.ogg', 'codec_type': 'audio'},
+    {'name': 'flac', 'ffmpeg': 'flac', 'recommended_container': 'flac', 'recommended_extension': '.flac', 'codec_type': 'audio'},
+    {'name': 'aac', 'ffmpeg': 'aac', 'recommended_container': 'mp4', 'recommended_extension': '.m4a', 'codec_type': 'audio'},
+    {'name': 'mp3', 'ffmpeg': 'libmp3lame', 'recommended_container': 'mp3', 'recommended_extension': '.mp3', 'codec_type': 'audio'},
+    {'name': 'alac', 'ffmpeg': 'alac', 'recommended_container': 'mp4', 'recommended_extension': '.m4a', 'codec_type': 'audio'},
+    {'name': 'pcm_s16le', 'ffmpeg': 'pcm_s16le', 'recommended_container': 'wav', 'recommended_extension': '.wav', 'codec_type': 'audio'},
+    # Video codecs (including cover images)
+    {'name': 'theora', 'ffmpeg': 'libtheora', 'recommended_container': 'ogg', 'recommended_extension': '.ogv', 'codec_type': 'video'},
+    {'name': 'vp8', 'ffmpeg': 'libvpx', 'recommended_container': 'webm', 'recommended_extension': '.webm', 'codec_type': 'video'},
+    {'name': 'vp9', 'ffmpeg': 'libvpx-vp9', 'recommended_container': 'webm', 'recommended_extension': '.webm', 'codec_type': 'video'},
+    {'name': 'av1', 'ffmpeg': 'libaom-av1', 'recommended_container': 'mkv', 'recommended_extension': '.mkv', 'codec_type': 'video'},
+    {'name': 'h264', 'ffmpeg': 'libx264', 'recommended_container': 'mp4', 'recommended_extension': '.mp4', 'codec_type': 'video'},
+    {'name': 'h265', 'ffmpeg': 'libx265', 'recommended_container': 'mp4', 'recommended_extension': '.mp4', 'codec_type': 'video'},
+    {'name': 'png', 'ffmpeg': 'png', 'recommended_container': 'ogg', 'recommended_extension': '.png', 'codec_type': 'video'},
+    {'name': 'mjpeg', 'ffmpeg': 'mjpeg', 'recommended_container': 'ogg', 'recommended_extension': '.jpg', 'codec_type': 'video'},
+    # Subtitle codecs
+    {'name': 'srt', 'ffmpeg': 'srt', 'recommended_container': 'mkv', 'recommended_extension': '.srt', 'codec_type': 'subtitle'},
+    {'name': 'ass', 'ffmpeg': 'ass', 'recommended_container': 'mkv', 'recommended_extension': '.ass', 'codec_type': 'subtitle'},
+    {'name': 'vtt', 'ffmpeg': 'webvtt', 'recommended_container': 'webm', 'recommended_extension': '.vtt', 'codec_type': 'subtitle'},
+]
+
+# Map codec name → recommended container
+CODEC_TO_CONTAINER_MAP = {codec['name']: codec['recommended_container'] for codec in CODEC_INFO}
+CODEC_TO_EXTENSION_MAP = {codec['name']: codec['recommended_extension'] for codec in CODEC_INFO}
+
+# Map codec name → FFmpeg encoder name
+CODEC_NAME_TO_FFMPEG = {codec['name']: codec['ffmpeg'] for codec in CODEC_INFO}
+
+# ------------------------------------------------------------------------------
+# Compatibility matrix: container → supported audio and video codecs
+# ------------------------------------------------------------------------------
+# Each container entry maps to a dict with 'audio' and 'video' keys.
+# - 'audio': list of audio codec names that are supported in this container.
+#            Use None to indicate that any audio codec is supported.
+# - 'video': list of video codec names that are supported in this container.
+#            Use None to indicate that any video codec is supported.
+#            Empty list means no video support (audio-only container).
+COMPATIBILITY_MATRIX = {
+    'mp3': {'audio': ['mp3'], 'video': ['png', 'mjpeg']},
+    'm4a': {'audio': ['aac', 'alac', 'opus', 'flac'], 'video': []},
+    'mp4': {'audio': ['aac', 'alac', 'opus', 'flac', 'mp3'], 'video': ['h264', 'h265', 'vp9', 'av1']},
+    'mkv': {'audio': None, 'video': None},
+    'ogg': {'audio': ['opus', 'vorbis', 'flac'], 'video': ['theora', 'vp8', 'png', 'mjpeg']},
+    'webm': {'audio': ['opus', 'vorbis'], 'video': ['vp8', 'vp9', 'av1']},
+    'flac': {'audio': ['flac'], 'video': ['png', 'mjpeg']},
+    'wav': {'audio': ['pcm_s16le'], 'video': []},
+    'aac': {'audio': ['aac'], 'video': []},
 }

-# Default characters to replace when --replace-bad-chars is enabled.
-# Includes common punctuation, single quote, and a trailing space.
-DEFAULT_BAD_CHARS = r',!@#№$;:%^&?*(){}[]\/<>+=~`\' '
+# ------------------------------------------------------------------------------
+# Helper functions for compatibility checking
+# ------------------------------------------------------------------------------
+def is_audio_codec_supported(container: str, audio_codec: str) -> bool:
+    """Check if an audio codec is supported in the given container."""
+    entry = COMPATIBILITY_MATRIX.get(container, {})
+    supported = entry.get('audio')
+    if supported is None:
+        return True
+    return audio_codec in supported
+
+
+def is_video_codec_supported(container: str, video_codec: str) -> bool:
+    """Check if a video codec is supported in the given container."""
+    entry = COMPATIBILITY_MATRIX.get(container, {})
+    supported = entry.get('video')
+    if supported is None:
+        return True
+    return video_codec in supported
+
+
+# ------------------------------------------------------------------------------
+# Default bad characters (for filename sanitization)
+# ------------------------------------------------------------------------------
+DEFAULT_BAD_CHARS = r'!@#№$;:%^&?*(){}[]\/<>+=~`\'|," '
@@ -1,36 +1,87 @@
-"""Core logic: orchestrates the splitting process."""
+# audio_splitter/core.py
+"""Core splitting logic – orchestrates the entire split process."""

 import os
 import subprocess
+import sys
+from typing import List, Dict, Any

-from .constants import FORMAT_INFO
-from .ffmpeg import get_audio_duration, get_stream_info, get_metadata, build_ffmpeg_command
-from .formats import determine_output_format, validate_format_compatibility
+from .constants import (
+    CONTAINER_INFO,
+    CONTAINER_NAMES,
+    CODEC_TO_EXTENSION_MAP,
+    CODEC_NAME_TO_FFMPEG,
+)
+from .ffmpeg import (
+    get_audio_duration,
+    get_stream_info,
+    get_metadata,
+    build_ffmpeg_command,
+    is_attached_picture,
+    extract_cover_image,
+)
+from .formats import (
+    determine_output_format,
+    validate_format_compatibility,
+)
+from .handlers import get_handler, needs_drop_video
 from .timestamp import parse_track_timestamps, resolve_end_times
 from .filename import build_filename
 from .metadata import build_metadata_dict
 from .utils import format_time


-def split_audio(input_file, output_directory, tracks, args):
+def split_audio(input_file: str, output_directory: str, tracks: List[Dict[str, Any]], args) -> None:
    """
    Main orchestration function: split the audio file into tracks.

    Args:
        input_file: Path to the input media file.
        output_directory: Directory where output files will be saved.
-        tracks: List of dicts, each containing parsed fields.
-        args: Parsed command‑line arguments (namespace).
+        tracks: List of dicts, each containing parsed fields (ts, tn, an, ...).
+        args: Parsed command‑line arguments (namespace) with attributes:
+            - container: output container name (or None for auto-detect)
+            - audio_codec: audio codec (copy or encoder)
+            - video_codec: video codec (copy or encoder)
+            - subtitle_codec: subtitle codec (copy or encoder)
+            - video_quality: integer or None
+            - drop_video: bool
+            - drop_subs: bool
+            - number_tracks: bool
+            - output_template: str
+            - replace_bad_chars: bool
+            - replacement_char: str
+            - bad_chars: str
+            - skip_existing: bool
+            - album: str or None
+            - comment: str or None
+            - no_comment: bool
+            - comment_stream: int or None
+            - merge_comments: bool
+            - comment_separator: str
+            - delete_original: bool
+            - cover_image: List[str] or None (optional, CLI list of cover image paths)

    Raises:
        RuntimeError: If no audio stream is found.
-        ValueError: If timestamp parsing or format compatibility fails.
+        ValueError: If compatibility validation fails.
    """
    # --------------------------------------------------------------------------
    # 1. Setup
    # --------------------------------------------------------------------------
    os.makedirs(output_directory, exist_ok=True)

+    # Check write permission on output directory.
+    try:
+        test_file = os.path.join(output_directory, f'.write_test_{os.getpid()}')
+        with open(test_file, 'w') as f:
+            f.write('test')
+        os.remove(test_file)
+    except PermissionError:
+        raise RuntimeError(
+            f"Error: No write permission for output directory: {output_directory}"
+        )
+
    total_duration = get_audio_duration(input_file)
    stream_info = get_stream_info(input_file)

@@ -42,26 +93,62 @@ def split_audio(input_file, output_directory, tracks, args):
        raise RuntimeError("No audio stream found in input file.")

    # --------------------------------------------------------------------------
-    # 2. Format decision
+    # 2. Determine output container
    # --------------------------------------------------------------------------
-    output_format = determine_output_format(stream_info, args.format, args.transcode_to, input_file=input_file)
-    print(f"Output container: {output_format}")
-
-    validate_format_compatibility(output_format, stream_info,
-                                  args.drop_video, args.drop_subs)
-
-    # Determine file extension.
-    extension_info = FORMAT_INFO.get(output_format, {})
-    extension = extension_info.get('ext', '.mkv')
+    user_container = getattr(args, 'container', None)
+    output_container = determine_output_format(
+        stream_info,
+        user_format=user_container,
+        transcode_audio=args.audio_codec if args.audio_codec != 'copy' else None,
+        input_file=input_file
+    )
+    print(f"Output container: {output_container}")

    # --------------------------------------------------------------------------
-    # 3. Parse timestamps
+    # 3. Validate compatibility
+    # --------------------------------------------------------------------------
+    try:
+        validate_format_compatibility(
+            container=output_container,
+            stream_info=stream_info,
+            drop_video=args.drop_video,
+            drop_subs=args.drop_subs,
+            input_file=input_file,
+            audio_codec=args.audio_codec,
+            video_codec=args.video_codec,
+        )
+    except ValueError as e:
+        raise RuntimeError(f"Compatibility error: {e}")
+
+    # --------------------------------------------------------------------------
+    # 4. Determine output audio codec and extension
+    # --------------------------------------------------------------------------
+    # Determine the audio codec that will be used in the output
+    if args.audio_codec != 'copy':
+        output_audio_codec = args.audio_codec
+    else:
+        output_audio_codec = stream_info.get('audio_codec', '')
+
+    # Choose extension based on the output container, not the audio codec.
+    # When user specifies --container, the file extension must match the container.
+    container_info = next((c for c in CONTAINER_INFO if c['name'] == output_container), None)
+    if container_info:
+        extension = container_info['extension']
+    elif output_audio_codec in CODEC_TO_EXTENSION_MAP:
+        extension = CODEC_TO_EXTENSION_MAP[output_audio_codec]
+    else:
+        extension = '.mkv'
+
+    print(f"Output extension: {extension}")
+
+    # --------------------------------------------------------------------------
+    # 5. Parse timestamps
    # --------------------------------------------------------------------------
    track_times = parse_track_timestamps(tracks)
    resolved_times = resolve_end_times(track_times, total_duration)

    # --------------------------------------------------------------------------
-    # 4. Fetch original metadata (for fallbacks)
+    # 6. Fetch original metadata (for fallbacks)
    # --------------------------------------------------------------------------
    input_metadata = get_metadata(input_file)
    original_album = input_metadata.get('album')
@@ -78,7 +165,39 @@ def split_audio(input_file, output_directory, tracks, args):
            print(f"  Stream {idx}: '{comment}'")

    # --------------------------------------------------------------------------
-    # 5. Process each track
+    # 7. Handle attached picture (cover art)
+    # --------------------------------------------------------------------------
+    user_cover_images = getattr(args, 'cover_image', None)
+    # Resolve per-track cover images: single image reused, or one-per-track
+    track_cover_images = []
+    if user_cover_images:
+        for img in user_cover_images:
+            if os.path.exists(img):
+                track_cover_images.append(img)
+            else:
+                print(f"Warning: Cover image not found, skipping: {img}")
+    # Extract cover from input if no user cover and input has video
+    if not track_cover_images and not args.drop_video and stream_info.get('has_video'):
+        if is_attached_picture(input_file):
+            cover_image_path = os.path.join(output_directory, 'cover.png')
+            if extract_cover_image(input_file, cover_image_path):
+                track_cover_images.append(cover_image_path)
+                print("Extracted cover image for all tracks.")
+            else:
+                track_cover_images = []
+
+    # Check if we need special handling (e.g., Opus files need opustags)
+    # Use output_audio_codec (not input_audio_codec) so the handler is resolved
+    # against the actual output codec (e.g., transcoding aac→opus in ogg).
+    input_audio_codec = stream_info.get('audio_codec')
+    cover_handler = get_handler(output_container, output_audio_codec)
+    needs_drop = needs_drop_video(output_container, output_audio_codec)
+    if track_cover_images and needs_drop:
+        print(f"Using special handler for {output_container} + {output_audio_codec}")
+        print("Temporarily dropping video for opustags post-processing.")
+
+    # --------------------------------------------------------------------------
+    # 8. Process each track
    # --------------------------------------------------------------------------
    for idx, track in enumerate(tracks, start=1):
        start_seconds, end_seconds = resolved_times[idx - 1]
@@ -91,31 +210,62 @@ def split_audio(input_file, output_directory, tracks, args):
        track_name = track.get('tn', 'Unknown')

        # ----------------------------------------------------------------------
-        # 5a. Build filename
+        # 8a. Build filename
        # ----------------------------------------------------------------------
        clean_filename = build_filename(track, idx, extension, args)
        output_path = os.path.join(output_directory, clean_filename)

        # ----------------------------------------------------------------------
-        # 5b. Handle existing files
+        # 8b. Handle existing files
        # ----------------------------------------------------------------------
        if args.skip_existing and os.path.exists(output_path):
            print(f"Skipping track {idx}: {output_path} already exists.")
            continue

        # ----------------------------------------------------------------------
-        # 5c. Build metadata
+        # 8c. Build metadata
        # ----------------------------------------------------------------------
        metadata = build_metadata_dict(track, idx, input_metadata, args)

        # ----------------------------------------------------------------------
-        # 5d. Build and execute FFmpeg command
+        # 8d. Build and execute FFmpeg command
        # ----------------------------------------------------------------------
+        # Map codec names to FFmpeg encoder names
+        audio_enc = args.audio_codec
+        if audio_enc != 'copy':
+            audio_enc = CODEC_NAME_TO_FFMPEG.get(audio_enc, audio_enc)  # fallback to itself if not found
+        video_enc = args.video_codec
+        if video_enc != 'copy':
+            video_enc = CODEC_NAME_TO_FFMPEG.get(video_enc, video_enc)
+        subtitle_enc = args.subtitle_codec
+        if subtitle_enc != 'copy':
+            subtitle_enc = CODEC_NAME_TO_FFMPEG.get(subtitle_enc, subtitle_enc)
+        
+        # Then build command with these mapped encoders
+        # Use temporary drop_video for handlers that need it
+        effective_drop_video = args.drop_video or (track_cover_images and needs_drop)
+        # For handlers that need opustags post-processing, don't pass cover_image_path
+        # to ffmpeg - it will process audio-only, then handler adds cover afterward
+        per_track_cover = (
+            track_cover_images[idx - 1] if len(track_cover_images) == len(tracks)
+            else (track_cover_images[0] if track_cover_images else None)
+        )
+        ffmpeg_cover_path = None if (per_track_cover and needs_drop) else per_track_cover
        cmd = build_ffmpeg_command(
-            input_file, start_seconds, duration_seconds, output_path,
-            stream_info, output_format, args.transcode_to,
-            args.drop_video, args.drop_subs,
-            metadata=metadata
+            input_file=input_file,
+            start_seconds=start_seconds,
+            duration_seconds=duration_seconds,
+            output_path=output_path,
+            stream_info=stream_info,
+            format_opt=output_container,
+            audio_codec=audio_enc,
+            video_codec=video_enc,
+            subtitle_codec=subtitle_enc,
+            metadata=metadata,
+            cover_image_path=ffmpeg_cover_path,
+            video_quality=getattr(args, 'video_quality', None),
+            drop_video=effective_drop_video,
+            drop_subs=args.drop_subs,
        )

        print(f"Extracting track {idx}: {track_name} "
@@ -128,3 +278,28 @@ def split_audio(input_file, output_directory, tracks, args):
            print(result.stderr)
        else:
            print(f"  -> Saved to: {output_path}")
+            # Apply cover image handler if needed
+            if per_track_cover and needs_drop:
+                print(f"Applying cover image via {output_container} handler...")
+                if not cover_handler(
+                    input_file=input_file,
+                    cover_image_path=per_track_cover,
+                    output_path=output_path,
+                    stream_info=stream_info,
+                    audio_codec=audio_enc,
+                    video_codec=video_enc,
+                    video_quality=getattr(args, 'video_quality', None),
+                    drop_video=args.drop_video,
+                    drop_subs=args.drop_subs,
+                ):
+                    print(f"Warning: Failed to attach cover image to {output_path}")
+
+    # --------------------------------------------------------------------------
+    # 9. Delete original file if requested
+    # --------------------------------------------------------------------------
+    if getattr(args, 'delete_original', False):
+        try:
+            os.remove(input_file)
+            print(f"Deleted original file: {input_file}")
+        except OSError as e:
+            print(f"Warning: Could not delete original file: {e}")
@@ -1,10 +1,12 @@
-"""FFmpeg/FFprobe interaction utilities for the CLI and web backend."""
+# audio_splitter/ffmpeg.py
+"""FFmpeg/FFprobe interaction utilities."""

 import json
+import os
 import subprocess
 from typing import Dict, List, Optional, Tuple

-from .constants import FORMAT_INFO
+from .constants import CONTAINER_INFO
 from .utils import format_time


@@ -75,6 +77,28 @@ def get_audio_codec(input_file: str) -> Optional[str]:
    return codec if codec else None


+def get_video_codec(input_file: str) -> Optional[str]:
+    """
+    Return the codec name of the first video stream.
+
+    Args:
+        input_file: Path to the media file.
+
+    Returns:
+        Codec name as a lowercase string, or None if no video stream exists.
+    """
+    cmd = [
+        'ffprobe', '-v', 'error',
+        '-select_streams', 'v:0',
+        '-show_entries', 'stream=codec_name',
+        '-of', 'default=noprint_wrappers=1:nokey=1',
+        input_file
+    ]
+    result = subprocess.run(cmd, capture_output=True, text=True, check=False)
+    codec = result.stdout.strip().lower()
+    return codec if codec else None
+
+
 def get_stream_info(input_file: str) -> Dict[str, any]:
    """
    Collect information about the streams present in the input file.
@@ -136,7 +160,7 @@ def get_metadata(input_file: str) -> Dict[str, any]:

 def get_container_format(input_file: str) -> Optional[str]:
    """
-    Retrieve the container format name (e.g., 'mp4', 'mp3', 'matroska') from the input file.
+    Retrieve the container format name (e.g., 'mp4', 'mp3', 'mkv') from the input file.

    Args:
        input_file: Path to the media file.
@@ -156,69 +180,237 @@ def get_container_format(input_file: str) -> Optional[str]:
    format_name = result.stdout.strip().split(',')[0]  # take first if multiple
    if not format_name:
        return None
-    # Normalize common aliases to names used in FORMAT_INFO (container only, not codec-specific)
-    # This mapping is purely for container identification.
+    # Normalize common aliases to names used in CONTAINER_INFO
    mapping = {
-        'mpeg': 'mp3',       # MPEG-1/2 audio (MP3) container
+        'mpeg': 'mp3',
        'mp2': 'mp3',
        'mp4': 'mp4',
-        'm4a': 'mp4',        # M4A is MP4 container
-        'mov': 'mp4',        # QuickTime is MP4-like
+        'm4a': 'mp4',
+        'mov': 'mp4',
        '3gp': 'mp4',
-        'matroska': 'matroska',
-        'webm': 'matroska',  # WebM uses Matroska container
+        'matroska': 'mkv',
+        'webm': 'mkv',
        'ogg': 'ogg',
        'flac': 'flac',
        'wav': 'wav',
        'aac': 'aac',
        'opus': 'opus',
        'mp3': 'mp3',
-        'adts': 'aac',       # raw AAC in ADTS container
-        'amr': 'amr',        # AMR container (rare)
+        'adts': 'aac',
+        'amr': 'amr',
    }
    return mapping.get(format_name, format_name)


-def build_ffmpeg_command(input_file: str, start_seconds: int, duration_seconds: int,
-                         output_path: str, stream_info: Dict, format_opt: Optional[str],
-                         transcode_audio: Optional[str], drop_video: bool, drop_subs: bool,
-                         metadata: Optional[Dict] = None) -> List[str]:
-    """
-    Construct the FFmpeg command line as a list of arguments.
+MAX_COVER_IMAGE_SIZE_MB = 4

-    Args:
-        input_file: Path to the input media file.
-        start_seconds: Start time for the segment (in seconds).
-        duration_seconds: Duration of the segment (in seconds).
-        output_path: Destination path for the output file.
-        stream_info: Dictionary from get_stream_info().
-        format_opt: Output container format (e.g., 'mp3').
-        transcode_audio: Audio codec to transcode to (or None).
-        drop_video: True to remove video streams.
-        drop_subs: True to remove subtitle streams.
-        metadata: Optional dict of metadata key/value pairs to write.
+
+def has_cover_or_video(input_file: str) -> bool:
+    """
+    Check if the input file contains a cover image (attached picture) or any video track.

    Returns:
-        A list of command‑line arguments suitable for subprocess.run().
+        True if a cover image or video stream is detected, False otherwise.
    """
    cmd = [
-        'ffmpeg',
-        '-i', input_file,
-        '-ss', format_time(start_seconds),
-        '-t', format_time(duration_seconds)
+        'ffprobe', '-v', 'quiet',
+        '-print_format', 'json',
+        '-select_streams', 'v',
+        '-show_entries', 'stream=codec_type,codec_name,disposition',
+        input_file
    ]
+    result = subprocess.run(cmd, capture_output=True, text=True, check=False)
+    if result.returncode != 0:
+        return False

-    # Clear all original metadata.
+    try:
+        data = json.loads(result.stdout)
+        streams = data.get('streams', [])
+        return len(streams) > 0
+    except (json.JSONDecodeError, KeyError):
+        return False
+
+
+def validate_cover_images(cover_images: List[str], num_tracks: int) -> None:
+    """
+    Validate cover image(s) before splitting.
+
+    Checks:
+        - Each file exists
+        - Only PNG and JPEG formats are accepted
+        - Single image OR count matches number of tracks
+        - File size warning for images > 4 MB
+
+    Args:
+        cover_images: List of cover image paths (single image or multiple).
+        num_tracks: Number of tracks in the tracklist.
+
+    Raises:
+        ValueError: If validation fails.
+    """
+    if len(cover_images) == 0:
+        return
+
+    if len(cover_images) == 1 and num_tracks > 1:
+        # Single image is fine - will be reused for all tracks
+        pass
+    elif len(cover_images) == num_tracks:
+        pass
+    else:
+        raise ValueError(
+            f"Cover image count ({len(cover_images)}) must be 1 or match "
+            f"the number of tracks ({num_tracks})."
+        )
+
+    for img_path in cover_images:
+        if not os.path.exists(img_path):
+            raise ValueError(f"Cover image not found: {img_path}")
+
+        ext = os.path.splitext(img_path)[1].lower()
+        if ext not in ('.png', '.jpg', '.jpeg'):
+            raise ValueError(
+                f"Unsupported cover image format '{ext}' for '{img_path}'. "
+                f"Only PNG and JPEG are supported."
+            )
+
+        size_mb = os.path.getsize(img_path) / (1024 * 1024)
+        if size_mb > MAX_COVER_IMAGE_SIZE_MB:
+            print(
+                f"Warning: Cover image '{img_path}' is {size_mb:.1f} MB "
+                f"(exceeds {MAX_COVER_IMAGE_SIZE_MB} MB limit). "
+                f"Large images may cause issues."
+            )
+
+
+def is_attached_picture(input_file: str) -> bool:
+    """
+    Check if the input file has a video stream that is an attached picture (cover art).
+
+    Detection logic:
+        1. If there is a video stream with disposition.attached_pic == 1, return True.
+        2. Otherwise, if there is exactly one video stream and its codec is an image
+           format (PNG, MJPEG, JPEG, GIF, BMP), return True.
+
+    Returns:
+        True if a cover image is detected, False otherwise.
+    """
+    cmd = [
+        'ffprobe', '-v', 'quiet',
+        '-print_format', 'json',
+        '-select_streams', 'v',
+        '-show_entries', 'stream=codec_name,disposition',
+        input_file
+    ]
+    result = subprocess.run(cmd, capture_output=True, text=True, check=False)
+    if result.returncode != 0:
+        return False
+
+    try:
+        data = json.loads(result.stdout)
+        streams = data.get('streams', [])
+        if not streams:
+            return False
+
+        # Check each stream
+        for stream in streams:
+            codec = stream.get('codec_name', '').lower()
+            disposition = stream.get('disposition', {})
+            # If attached_pic is set, it's a cover image
+            if disposition.get('attached_pic') == 1:
+                return True
+            # If not, check if it's an image codec and we have exactly one video stream
+            if codec in ('png', 'mjpeg', 'jpeg', 'gif', 'bmp'):
+                # If there is exactly one video stream, treat it as cover
+                if len(streams) == 1:
+                    return True
+        return False
+    except (json.JSONDecodeError, KeyError):
+        return False
+
+
+def extract_cover_image(input_file: str, output_path: str) -> bool:
+    """
+    Extract the first frame of the video stream (assumed to be an attached picture)
+    and save it to output_path.
+
+    Returns:
+        True if extraction succeeded, False otherwise.
+    """
+    cmd = [
+        'ffmpeg', '-i', input_file,
+        '-map', '0:v:0',
+        '-frames:v', '1',
+        '-y',
+        output_path
+    ]
+    result = subprocess.run(cmd, capture_output=True, text=True, check=False)
+    if result.returncode != 0:
+        print(f"Failed to extract cover image: {result.stderr}")
+        return False
+    return True
+
+
+def _build_inputs(cmd: List[str], input_file: str, cover_image_path: Optional[str]) -> None:
+    """Add input files to the command."""
+    if cover_image_path:
+        cmd.extend(['-i', cover_image_path])
+    cmd.extend(['-i', input_file])
+
+
+def _build_time_options(cmd: List[str], start_seconds: int, duration_seconds: int) -> None:
+    """Add time-based options to the command."""
+    cmd.extend(['-ss', format_time(start_seconds), '-t', format_time(duration_seconds)])
+
+
+def _build_metadata(cmd: List[str], metadata: Optional[Dict]) -> None:
+    """Add metadata options to the command."""
    cmd.append('-map_metadata')
    cmd.append('-1')
-
-    # Apply custom metadata.
    if metadata:
        for key, value in metadata.items():
            if value is not None and value != '':
                cmd.extend(['-metadata', f"{key}={value}"])

-    # Stream mapping.
+
+def _build_cover_image_mapping(
+    cmd: List[str],
+    audio_codec: Optional[str],
+    video_codec: Optional[str],
+    video_quality: Optional[int],
+) -> None:
+    """Build stream mapping for cover image extraction (audio + cover video)."""
+    cmd.extend(['-map', '1:a:0', '-map', '0:v:0'])
+
+    if video_codec and video_codec != 'copy':
+        cmd.extend(['-c:v', video_codec])
+    else:
+        cmd.extend(['-c:v', 'png'])
+
+    if audio_codec and audio_codec != 'copy':
+        cmd.extend(['-c:a', audio_codec])
+    else:
+        cmd.extend(['-c:a', 'copy'])
+
+    # Preserve attached_pic disposition for cover image
+    cmd.extend(['-disposition', 'attached_pic'])
+
+    cmd.append('-sn')
+
+    if video_quality is not None:
+        cmd.extend(['-q:v', str(video_quality)])
+
+
+def _build_standard_mapping(
+    cmd: List[str],
+    stream_info: Dict,
+    audio_codec: Optional[str],
+    video_codec: Optional[str],
+    subtitle_codec: Optional[str],
+    video_quality: Optional[int],
+    drop_video: bool,
+    drop_subs: bool,
+) -> None:
+    """Build stream mapping for standard extraction (no cover image)."""
    if drop_video and drop_subs:
        cmd.extend(['-map', '0:a:0'])
    elif drop_video:
@@ -228,32 +420,97 @@ def build_ffmpeg_command(input_file: str, start_seconds: int, duration_seconds:
    else:
        cmd.extend(['-map', '0'])

-    # Audio codec.
-    if transcode_audio:
-        cmd.extend(['-c:a', transcode_audio])
-        if transcode_audio in ('libmp3lame', 'mp3'):
-            cmd.extend(['-b:a', '192k'])
-        elif transcode_audio in ('libopus', 'opus'):
-            cmd.extend(['-b:a', '128k'])
+    if audio_codec and audio_codec != 'copy':
+        cmd.extend(['-c:a', audio_codec])
    else:
        cmd.extend(['-c:a', 'copy'])

-    # Video codec.
-    if not drop_video and stream_info['has_video']:
-        cmd.extend(['-c:v', 'copy'])
+    if not drop_video and stream_info.get('has_video'):
+        if video_codec and video_codec != 'copy':
+            cmd.extend(['-c:v', video_codec])
+            if video_quality is not None:
+                cmd.extend(['-q:v', str(video_quality)])
+        else:
+            cmd.extend(['-c:v', 'copy'])
    else:
        cmd.append('-vn')

-    # Subtitle codec.
-    if not drop_subs and stream_info['has_subtitle']:
-        cmd.extend(['-c:s', 'copy'])
+    if not drop_subs and stream_info.get('has_subtitle'):
+        if subtitle_codec and subtitle_codec != 'copy':
+            cmd.extend(['-c:s', subtitle_codec])
+        else:
+            cmd.extend(['-c:s', 'copy'])
    else:
        cmd.append('-sn')

-    # Output format.
+
+def _build_format(cmd: List[str], format_opt: Optional[str]) -> None:
+    """Add output format option if specified."""
    if format_opt:
-        ffmpeg_format = FORMAT_INFO.get(format_opt, {}).get('ffmpeg', format_opt)
+        ffmpeg_format = next((c['ffmpeg'] for c in CONTAINER_INFO if c['name'] == format_opt), format_opt)
        cmd.extend(['-f', ffmpeg_format])

+
+def _build_output(cmd: List[str], output_path: str) -> None:
+    """Add output file to the command."""
    cmd.extend(['-y', output_path])
+
+
+def build_ffmpeg_command(
+    input_file: str,
+    start_seconds: int,
+    duration_seconds: int,
+    output_path: str,
+    stream_info: Dict,
+    format_opt: Optional[str],
+    audio_codec: Optional[str] = 'copy',
+    video_codec: Optional[str] = 'copy',
+    subtitle_codec: Optional[str] = 'copy',
+    metadata: Optional[Dict] = None,
+    cover_image_path: Optional[str] = None,
+    video_quality: Optional[int] = None,
+    drop_video: bool = False,
+    drop_subs: bool = False,
+) -> List[str]:
+    """
+    Construct the FFmpeg command line as a list of arguments.
+
+    Args:
+        input_file: Path to the input media file.
+        start_seconds: Start time for the segment (in seconds).
+        duration_seconds: Duration of the segment (in seconds).
+        output_path: Destination path for the output file.
+        stream_info: Dictionary from get_stream_info().
+        format_opt: Output container format (e.g., 'mp3', 'mkv').
+        audio_codec: Audio codec to use ('copy' or encoder name like 'libopus').
+        video_codec: Video codec to use ('copy' or encoder name).
+        subtitle_codec: Subtitle codec to use ('copy' or encoder name).
+        metadata: Optional dict of metadata key/value pairs to write.
+        cover_image_path: Path to extracted cover image (if any).
+        video_quality: Quality value for video encoder (e.g., 1-31, lower=better).
+        drop_video: If True, remove video streams.
+        drop_subs: If True, remove subtitle streams.
+
+    Returns:
+        A list of command‑line arguments suitable for subprocess.run().
+    """
+    cmd = ['ffmpeg']
+
+    _build_inputs(cmd, input_file, cover_image_path)
+    _build_time_options(cmd, start_seconds, duration_seconds)
+    _build_metadata(cmd, metadata)
+
+    if cover_image_path:
+        _build_cover_image_mapping(cmd, audio_codec, video_codec, video_quality)
+    else:
+        _build_standard_mapping(
+            cmd, stream_info, audio_codec, video_codec, subtitle_codec,
+            video_quality, drop_video, drop_subs
+        )
+
+    _build_format(cmd, format_opt)
+    _build_output(cmd, output_path)
+
    return cmd
+
+
@@ -41,7 +41,18 @@ def build_filename(track, idx, extension, args):
        clean_filename = apply_replacement(raw_filename,
                                           args.bad_chars,
                                           args.replacement_char)
-        clean_filename = cleanup_good_chars(clean_filename, args.replacement_char)
+        # Split off the file extension before cleanup so trailing
+        # replacement chars don't leak into the name portion.
+        name_part, _, ext_part = clean_filename.rpartition('.')
+        clean_filename = cleanup_good_chars(name_part, args.replacement_char)
+        # Strip leading/trailing separator characters (replacement char,
+        # hyphen, etc.) that may result from empty fields or bad-char
+        # sequences adjacent to template separators.
+        clean_filename = clean_filename.strip(f'{args.replacement_char}-')
+        # Fallback: if cleanup leaves an empty name, use the track number.
+        if not clean_filename:
+            clean_filename = f"{idx:02d}"
+        clean_filename = f"{clean_filename}.{ext_part}"
    else:
        clean_filename = raw_filename
        # Warn about unsafe characters.
@@ -1,19 +1,28 @@
+# audio_splitter/formats.py
 """Container format decision and validation."""

 from typing import Dict, Optional

-from .constants import FORMAT_INFO
+from .constants import (
+    CONTAINER_NAMES,
+    CONTAINER_INFO,
+    CODEC_TO_CONTAINER_MAP,
+    COMPATIBILITY_MATRIX,
+    is_audio_codec_supported,
+    is_video_codec_supported,
+)
+from .defaults import DEFAULT_FORMAT


 def determine_default_format(container: Optional[str], codec: Optional[str]) -> Optional[str]:
    """
    Given the container format and audio codec, determine the recommended output format.

-    This is used when the user has not explicitly specified a format.
-    It prioritizes the codec to choose the most appropriate container/extension.
+    Uses the CODEC_TO_CONTAINER_MAP to map codec → container.
+    If the codec is not found, it falls back to the container.

    Args:
-        container: Container name (e.g., 'ogg', 'mp4', 'matroska') as returned by get_container_format().
+        container: Container name (e.g., 'ogg', 'mp4', 'mkv') as returned by get_container_format().
        codec: Audio codec name (e.g., 'opus', 'aac', 'mp3') as returned by get_audio_codec().

    Returns:
@@ -22,37 +31,13 @@ def determine_default_format(container: Optional[str], codec: Optional[str]) ->
    if not container:
        return None

-    # Codec-based decisions (highest priority)
-    if codec == 'opus':
-        return 'opus'
-    if codec in ('aac', 'alac', 'he-aac'):
-        return 'm4a'
-    if codec == 'mp3':
-        return 'mp3'
-    if codec == 'vorbis':
-        return 'ogg'
-    if codec == 'flac':
-        return 'flac'
+    if codec and codec in CODEC_TO_CONTAINER_MAP:
+        fmt = CODEC_TO_CONTAINER_MAP[codec]
+        if fmt in CONTAINER_NAMES:
+            return fmt

-    # Container-based fallback (lower priority)
-    if container in ('mp4', 'm4a', 'mov', '3gp'):
-        return 'mp4'
-    if container in ('matroska', 'webm'):
-        return 'matroska'
-    if container in ('ogg',):
-        return 'ogg'
-    if container in ('mp3', 'mpeg'):
-        return 'mp3'
-    if container == 'flac':
-        return 'flac'
-    if container == 'wav':
-        return 'wav'
-    if container == 'aac':
-        return 'aac'
-    if container == 'opus':
-        return 'opus'
-    if container == 'amr':
-        return 'amr'
+    if container in CONTAINER_NAMES:
+        return container

    return None

@@ -62,69 +47,91 @@ def determine_output_format(stream_info: Dict, user_format: Optional[str],
    """
    Decide which container format to use.

-    If user_format is provided, use it.
+    If user_format is provided, map it to the correct container if it's a codec name.
    Else, try to detect the input file's container and codec, and use the recommended format.
    If detection fails or format is not supported, fallback to:
      - MKV if video/subtitles exist
      - MP3 if the audio codec is MP3
      - MP4 (M4A) otherwise
-
-    Args:
-        stream_info: Dict from get_stream_info().
-        user_format: User‑requested format (or None).
-        transcode_audio: Audio codec to transcode to (or None) (unused in this function).
-        input_file: Path to the input file (optional, used to detect container and codec).
-
-    Returns:
-        A format name that exists in FORMAT_INFO.
    """
    if user_format:
+        # Map codec names to their correct containers
+        # e.g., 'opus' -> 'ogg', 'aac' -> 'mp4', etc.
+        if user_format in CODEC_TO_CONTAINER_MAP:
+            return CODEC_TO_CONTAINER_MAP[user_format]
        return user_format

-    # If input_file is provided, try to detect container and codec
    if input_file:
        try:
            from .ffmpeg import get_container_format, get_audio_codec
            container = get_container_format(input_file)
-            codec = get_audio_codec(input_file)
-            fmt = determine_default_format(container, codec)
-            if fmt in FORMAT_INFO:
+            audio_codec = get_audio_codec(input_file)
+            fmt = determine_default_format(container, audio_codec)
+            if fmt in CONTAINER_NAMES:
                return fmt
        except Exception:
-            # If detection fails, fall through to legacy logic
            pass

-    # Fallback: legacy behavior
+    # Fallback
    if stream_info.get('has_video') or stream_info.get('has_subtitle'):
-        return 'matroska'
+        return 'mkv'
    audio_codec = stream_info.get('audio_codec', '')
    if audio_codec == 'mp3':
        return 'mp3'
    else:
-        return 'mp4'  # .m4a
+        return 'mp4'


-def validate_format_compatibility(format_name: str, stream_info: Dict,
-                                  drop_video: bool, drop_subs: bool) -> None:
+def validate_format_compatibility(
+    container: str,
+    stream_info: Dict,
+    drop_video: bool,
+    drop_subs: bool,
+    input_file: Optional[str] = None,
+    audio_codec: Optional[str] = None,
+    video_codec: Optional[str] = None,
+) -> None:
    """
-    Ensure the chosen container can accommodate the streams we intend to keep.
+    Ensure the chosen container and codec combination is valid.

    Raises:
-        ValueError: If the format is incompatible with the intended streams.
+        ValueError: If the combination is incompatible.
    """
-    info = FORMAT_INFO.get(format_name)
+    info = next((c for c in CONTAINER_INFO if c['name'] == container), None)
    if not info:
-        print(f"Warning: Unknown format '{format_name}'. Proceeding, but may fail.")
+        print(f"Warning: Unknown container '{container}'. Proceeding, but may fail.")
        return

-    if info['audio_only']:
-        if stream_info.get('has_video') and not drop_video:
+    # Check if container is audio-only and video is present (unless dropped)
+    if not info['supports_video'] and stream_info.get('has_video') and not drop_video:
+        raise ValueError(
+            f"Container '{container}' does not support video streams. "
+            "Please use --drop-video or choose a container that supports video (e.g., MKV, MP4)."
+        )
+
+    # Determine actual audio codec for validation
+    # When 'copy' is used, we must still validate the input codec against the container
+    actual_audio_codec = audio_codec if audio_codec and audio_codec != 'copy' else stream_info.get('audio_codec')
+    if actual_audio_codec:
+        if not is_audio_codec_supported(container, actual_audio_codec):
            raise ValueError(
-                f"Format '{format_name}' does not support video streams. "
-                "Please use --drop-video or choose a container that supports video."
-            )
-        if stream_info.get('has_subtitle') and not drop_subs:
-            raise ValueError(
-                f"Format '{format_name}' does not support subtitle streams. "
-                "Please use --drop-subs or choose a container that supports subtitles."
+                f"Container '{container}' does not support audio codec '{actual_audio_codec}'. "
+                f"Please choose a different container or audio codec."
            )
+
+    # Check if video codec is supported (if video is present and not dropped)
+    if stream_info.get('has_video') and not drop_video:
+        # Determine the video codec from input file if not provided
+        if video_codec is None and input_file:
+            from .ffmpeg import get_video_codec
+            video_codec = get_video_codec(input_file)
+        # When 'copy' is used, validate the input video codec against the container
+        if video_codec == 'copy' and input_file:
+            from .ffmpeg import get_video_codec
+            video_codec = get_video_codec(input_file)
+        if video_codec:
+            if not is_video_codec_supported(container, video_codec):
+                raise ValueError(
+                    f"Container '{container}' does not support video codec '{video_codec}'. "
+                    f"Please choose a different container, drop video, or transcode video to a supported codec."
+                )
@@ -0,0 +1,167 @@
+# audio_splitter/handlers.py
+"""Handler system for cover image attachment.
+
+This module provides a registry of handlers for different
+codec + image combinations. Each handler is responsible for
+attaching the cover image to the output file in the appropriate way.
+"""
+
+import os
+import subprocess
+from typing import Dict, Optional
+
+
+def _run_opustags(input_file: str, cover_image_path: str, output_path: Optional[str] = None) -> bool:
+    """
+    Run opustags to attach a cover image to an Opus file.
+
+    Args:
+        input_file: Path to the input Opus file.
+        cover_image_path: Path to the cover image.
+        output_path: Optional output path (if None, overwrites input).
+
+    Returns:
+        True if successful, False otherwise.
+    """
+    cmd = ['opustags', '--set-cover', cover_image_path, input_file]
+
+    if output_path:
+        cmd.extend(['-o', output_path, '-y'])
+    else:
+        cmd.extend(['-i'])
+
+    result = subprocess.run(cmd, capture_output=True, text=True, check=False)
+    if result.returncode != 0:
+        print(f"opustags failed: {result.stderr}")
+        return False
+    return True
+
+
+def _handler_default(
+    input_file: str,
+    cover_image_path: str,
+    output_path: str,
+    stream_info: Dict,
+    audio_codec: str,
+    video_codec: str,
+    video_quality: Optional[int],
+    drop_video: bool,
+    drop_subs: bool,
+) -> bool:
+    """
+    Default handler: use ffmpeg with -disposition attached_pic.
+
+    This is the standard approach for formats like MP3, FLAC, etc.
+    """
+    # This handler doesn't do anything - the cover is already handled
+    # by the ffmpeg command in core.py via build_ffmpeg_command()
+    # We just return True to indicate success.
+    return True
+
+
+def _handler_opus_with_cover(
+    input_file: str,
+    cover_image_path: str,
+    output_path: str,
+    stream_info: Dict,
+    audio_codec: str,
+    video_codec: str,
+    video_quality: Optional[int],
+    drop_video: bool,
+    drop_subs: bool,
+) -> bool:
+    """
+    Handler for Opus files with cover image.
+
+    Uses opustags to attach the cover image after the file is processed.
+    """
+    return _run_opustags(output_path, cover_image_path)
+
+
+def _handler_mp3_with_cover(
+    input_file: str,
+    cover_image_path: str,
+    output_path: str,
+    stream_info: Dict,
+    audio_codec: str,
+    video_codec: str,
+    video_quality: Optional[int],
+    drop_video: bool,
+    drop_subs: bool,
+) -> bool:
+    """
+    Handler for MP3 files with cover image.
+
+    Uses ffmpeg with -disposition attached_pic.
+    """
+    # MP3 handler - the cover is already attached by ffmpeg in core.py
+    return True
+
+
+def _handler_flac_with_cover(
+    input_file: str,
+    cover_image_path: str,
+    output_path: str,
+    stream_info: Dict,
+    audio_codec: str,
+    video_codec: str,
+    video_quality: Optional[int],
+    drop_video: bool,
+    drop_subs: bool,
+) -> bool:
+    """
+    Handler for FLAC files with cover image.
+
+    Uses ffmpeg with -disposition attached_pic.
+    """
+    # FLAC handler - the cover is already attached by ffmpeg in core.py
+    return True
+
+
+# Handler registry: maps (output_container, input_codec) to handler function
+HANDLER_REGISTRY: Dict[tuple, callable] = {
+    ('opus', 'opus'): _handler_opus_with_cover,
+    ('ogg', 'opus'): _handler_opus_with_cover,
+    ('mp3', 'mp3'): _handler_mp3_with_cover,
+    ('flac', 'flac'): _handler_flac_with_cover,
+}
+
+
+def get_handler(output_container: str, input_audio_codec: Optional[str] = None):
+    """
+    Get the appropriate handler for the given container and input codec.
+
+    Args:
+        output_container: Output container format (e.g., 'opus', 'mp3', 'flac').
+        input_audio_codec: Input audio codec (e.g., 'opus', 'mp3', 'flac').
+
+    Returns:
+        Handler function, or the default handler if no specific handler is found.
+    """
+    if input_audio_codec:
+        key = (output_container, input_audio_codec)
+        if key in HANDLER_REGISTRY:
+            return HANDLER_REGISTRY[key]
+
+    # Fall back to container-only key
+    if (output_container, None) in HANDLER_REGISTRY:
+        return HANDLER_REGISTRY[(output_container, None)]
+
+    # Default handler
+    return _handler_default
+
+
+def needs_drop_video(output_container: str, input_audio_codec: Optional[str] = None) -> bool:
+    """
+    Check if the handler requires dropping video even if user didn't specify --drop-video.
+
+    Args:
+        output_container: Output container format.
+        input_audio_codec: Input audio codec.
+
+    Returns:
+        True if video should be dropped, False otherwise.
+    """
+    handler = get_handler(output_container, input_audio_codec)
+    # The opus handler requires dropping video
+    return handler == _handler_opus_with_cover
@@ -1,11 +1,18 @@
-"""Command‑line interface and entry point."""
+#!/usr/bin/env python3
+"""
+Audio Splitter – Command‑Line Interface
+
+Split an audio file into tracks using a tracklist file.
+
+Usage:
+    audio_splitter input.mp3 tracklist.txt [OPTIONS]
+"""

-import argparse
 import os
 import sys
 import subprocess
+import argparse

-from .constants import DEFAULT_BAD_CHARS
 from .defaults import (
    DEFAULT_FORMAT,
    DEFAULT_OUTPUT_TEMPLATE,
@@ -24,50 +31,164 @@ from .defaults import (
    DEFAULT_REPLACE_BAD_CHARS,
    DEFAULT_SKIP_EXISTING,
    DEFAULT_DELETE_ORIGINAL,
-    DEFAULT_TRANSCODE_TO,
 )
+from .constants import CONTAINER_NAMES
 from .core import split_audio
 from .tracklist import read_tracklist, parse_format
+from .ffmpeg import has_cover_or_video, validate_cover_images
+

 def main():
-    parser = argparse.ArgumentParser(description="Split audio file using a tracklist.")
+    parser = argparse.ArgumentParser(
+        description="Split an audio file into tracks using a tracklist.",
+        epilog="Tracklist format: mm:ss track_name - author_name (or custom with --tracklist-format)"
+    )
+
+    # Positional
    parser.add_argument('input_file', help='Input audio file')
    parser.add_argument('tracklist_file', help='Tracklist file')

-    # Output options
-    parser.add_argument('--format', default=DEFAULT_FORMAT, help=f"Output container format (default: {DEFAULT_FORMAT})")
-    parser.add_argument('--transcode-to', default=DEFAULT_TRANSCODE_TO, help="Audio codec to transcode to (default: copy)")
-    parser.add_argument('--drop-video', action='store_true', default=DEFAULT_DROP_VIDEO, help="Drop video streams")
-    parser.add_argument('--drop-subs', action='store_true', default=DEFAULT_DROP_SUBS, help="Drop subtitle streams")
+    # Container and codec options
+    parser.add_argument(
+        '--container',
+        default=None,
+        help="Output container format (auto-detect if not specified)"
+    )
+    parser.add_argument(
+        '--audio-codec',
+        default='copy',
+        help="Audio codec (copy or encoder name, e.g., libopus)"
+    )
+    parser.add_argument(
+        '--video-codec',
+        default='copy',
+        help="Video codec (copy or encoder name, e.g., libx264)"
+    )
+    parser.add_argument(
+        '--subtitle-codec',
+        default='copy',
+        help="Subtitle codec (copy or encoder name, e.g., srt)"
+    )
+    parser.add_argument(
+        '--video-quality', '-vq',
+        type=int,
+        default=None,
+        help="Video quality (integer, encoder-specific; usually 1-31, lower=better). "
+             "If omitted, FFmpeg default is used."
+    )
+    parser.add_argument(
+        '--drop-video',
+        action='store_true',
+        default=DEFAULT_DROP_VIDEO,
+        help="Drop video streams"
+    )
+    parser.add_argument(
+        '--drop-subs',
+        action='store_true',
+        default=DEFAULT_DROP_SUBS,
+        help="Drop subtitle streams"
+    )

    # Filename options
-    parser.add_argument('--number-tracks', action='store_true', default=DEFAULT_NUMBER_TRACKS, help="Prepend track numbers")
-    parser.add_argument('--output-template', default=DEFAULT_OUTPUT_TEMPLATE, help=f"Output filename template (default: {DEFAULT_OUTPUT_TEMPLATE})")
-    parser.add_argument('--replace-bad-chars', action='store_true', default=DEFAULT_REPLACE_BAD_CHARS, help="Replace bad characters")
-    parser.add_argument('--replacement-char', default=DEFAULT_REPLACEMENT_CHAR, help=f"Replacement character (default: {DEFAULT_REPLACEMENT_CHAR})")
-    parser.add_argument('--bad-chars', default=DEFAULT_BAD_CHARS, help=f"Bad characters to replace (default: {DEFAULT_BAD_CHARS})")
-    parser.add_argument('--skip-existing', action='store_true', default=DEFAULT_SKIP_EXISTING, help="Skip existing output files")
+    parser.add_argument(
+        '--number-tracks',
+        action='store_true',
+        default=DEFAULT_NUMBER_TRACKS,
+        help="Prepend track numbers"
+    )
+    parser.add_argument(
+        '--output-template',
+        default=DEFAULT_OUTPUT_TEMPLATE,
+        help="Output filename template (default: %(default)s)"
+    )
+    parser.add_argument(
+        '--replace-bad-chars',
+        action='store_true',
+        default=DEFAULT_REPLACE_BAD_CHARS,
+        help="Replace bad characters"
+    )
+    parser.add_argument(
+        '--replacement-char',
+        default=DEFAULT_REPLACEMENT_CHAR,
+        help="Replacement character (default: %(default)s)"
+    )
+    parser.add_argument(
+        '--bad-chars',
+        default=DEFAULT_BAD_CHARS,
+        help="Bad characters to replace (default: %(default)s)"
+    )
+    parser.add_argument(
+        '--skip-existing',
+        action='store_true',
+        default=DEFAULT_SKIP_EXISTING,
+        help="Skip existing output files"
+    )

-    # Metadata options
+    # Metadata
    parser.add_argument('--album', default=DEFAULT_ALBUM, help="Album name")
    parser.add_argument('--comment', default=DEFAULT_COMMENT, help="Comment")
-    parser.add_argument('--no-comment', action='store_true', default=DEFAULT_NO_COMMENT, help="Ignore comment")
-    parser.add_argument('--comment-stream', type=int, default=DEFAULT_COMMENT_STREAM, help="Comment stream index")
-    parser.add_argument('--merge-comments', action='store_true', default=DEFAULT_MERGE_COMMENTS, help="Merge all comments")
-    parser.add_argument('--comment-separator', default=DEFAULT_COMMENT_SEPARATOR, help=f"Separator for merged comments (default: {DEFAULT_COMMENT_SEPARATOR})")
+    parser.add_argument(
+        '--no-comment',
+        action='store_true',
+        default=DEFAULT_NO_COMMENT,
+        help="Ignore comment"
+    )
+    parser.add_argument(
+        '--comment-stream',
+        type=int,
+        default=DEFAULT_COMMENT_STREAM,
+        help="Comment stream index"
+    )
+    parser.add_argument(
+        '--merge-comments',
+        action='store_true',
+        default=DEFAULT_MERGE_COMMENTS,
+        help="Merge all comments"
+    )
+    parser.add_argument(
+        '--comment-separator',
+        default=DEFAULT_COMMENT_SEPARATOR,
+        help="Separator for merged comments (default: %(default)s)"
+    )

    # Tracklist format
-    parser.add_argument('--tracklist-format', default=DEFAULT_TRACKLIST_FORMAT, help=f"Tracklist format (default: {DEFAULT_TRACKLIST_FORMAT})")
+    parser.add_argument(
+        '--tracklist-format',
+        default=DEFAULT_TRACKLIST_FORMAT,
+        help="Tracklist format (default: %(default)s)"
+    )
+
+    # Cover image
+    parser.add_argument(
+        '--cover-image',
+        nargs='+',
+        metavar='IMAGE',
+        default=None,
+        help="Cover image path(s). Single image applied to all tracks, "
+             "or one per track (must match track count)."
+    )

    # Other
-    parser.add_argument('--delete-original', action='store_true', default=DEFAULT_DELETE_ORIGINAL, help="Delete original file after split")
-    parser.add_argument('--dry-run', action='store_true', help="Parse and display tracklist without splitting")
+    parser.add_argument(
+        '--delete-original',
+        action='store_true',
+        default=DEFAULT_DELETE_ORIGINAL,
+        help="Delete original file after split"
+    )
+    parser.add_argument(
+        '--dry-run',
+        action='store_true',
+        help="Parse and display tracklist without splitting"
+    )
+    parser.add_argument(
+        '--output-dir', '-o',
+        default=None,
+        help="Output directory (default: <input_basename>_splits)"
+    )

    args = parser.parse_args()

-    # --------------------------------------------------------------------------
-    # Input validation
-    # --------------------------------------------------------------------------
+    # Validate input
    if not os.path.exists(args.input_file):
        print(f"Error: Input file not found: {args.input_file}")
        sys.exit(1)
@@ -76,12 +197,13 @@ def main():
        print(f"Error: Tracklist file not found: {args.tracklist_file}")
        sys.exit(1)

-    # Ensure the replacement character is a single character.
-    if len(args.replacement_char) != 1:
-        print("Error: --replacement-char must be a single character.")
+    # Validate container if provided
+    if args.container and args.container not in CONTAINER_NAMES:
+        print(f"Error: Invalid container '{args.container}'. "
+              f"Valid containers: {', '.join(sorted(CONTAINER_NAMES))}.")
        sys.exit(1)

-    # Check that FFmpeg is installed.
+    # Check FFmpeg
    try:
        subprocess.run(['ffmpeg', '-version'], capture_output=True, check=True)
    except (subprocess.CalledProcessError, FileNotFoundError):
@@ -89,14 +211,14 @@ def main():
        print("  - https://ffmpeg.org/download.html")
        sys.exit(1)

-    # Parse the tracklist using the user‑provided format.
+    # Parse tracklist format
    try:
        tokens = parse_format(args.tracklist_format)
-    except ValueError as error:
-        print(f"Error in --tracklist-format: {error}")
+    except ValueError as e:
+        print(f"Error in --tracklist-format: {e}")
        sys.exit(1)

-    # Read and parse the tracklist file.
+    # Read tracklist
    tracks = read_tracklist(args.tracklist_file, tokens)
    if not tracks:
        print("Error: No valid tracks found in tracklist file.")
@@ -104,7 +226,21 @@ def main():

    print(f"Found {len(tracks)} tracks.")

-    # Dry‑run mode: display parsed data and exit.
+    # Validate cover images if provided
+    if args.cover_image:
+        # Check if input already has cover image or video track
+        # Allow if --drop-video is specified (user wants to discard existing video)
+        if has_cover_or_video(args.input_file) and not args.drop_video:
+            print("Error: Input file already contains a cover image or video track. "
+                  "Remove it first, or use --drop-video to discard video streams.")
+            sys.exit(1)
+
+        try:
+            validate_cover_images(args.cover_image, len(tracks))
+        except ValueError as e:
+            print(f"Error: {e}")
+            sys.exit(1)
+
    if args.dry_run:
        print("\nParsed tracklist:")
        print("-" * 60)
@@ -118,34 +254,22 @@ def main():
                print(f"{idx:3d} | " + " | ".join(values))
        print("-" * 60)
        print("Dry‑run complete. No files were created.")
-        sys.exit(0)
+        return

-    # Determine the output directory.
+    # Determine output directory
    if args.output_dir:
        output_dir = args.output_dir
-        print(f"Using custom output directory: {output_dir}")
    else:
        base_name = os.path.splitext(os.path.basename(args.input_file))[0]
        output_dir = base_name + "_splits"
-        print(f"Using default output directory: {output_dir}")

-    # Run the splitter.
+    # Run split
    try:
        split_audio(args.input_file, output_dir, tracks, args)
-    except (RuntimeError, ValueError) as error:
-        print(f"Error: {error}")
+    except Exception as e:
+        print(f"Error during split: {e}")
        sys.exit(1)

-    # --------------------------------------------------------------------------
-    # Delete original file if requested and successful.
-    # --------------------------------------------------------------------------
-    if args.delete_original:
-        try:
-            os.remove(args.input_file)
-            print(f"Deleted original file: {args.input_file}")
-        except OSError as e:
-            print(f"Warning: Could not delete original file: {e}")
-
    print("Done!")


@@ -73,4 +73,15 @@ def resolve_end_times(track_times, total_duration):
            if end_sec <= start_sec:
                raise ValueError(f"Track {idx+1}: end time ({end_sec}) is not after start ({start_sec})")
        resolved.append((start_sec, end_sec))
+
+    # Warn about overlapping intervals
+    for idx in range(len(resolved) - 1):
+        cur_end = resolved[idx][1]
+        next_start = resolved[idx + 1][0]
+        if cur_end > next_start:
+            print(
+                f"Warning: Track {idx+1} ends at {cur_end}s but Track {idx+2} starts at "
+                f"{next_start}s — timestamps overlap by {cur_end - next_start:.1f}s."
+            )
+
    return resolved
@@ -1,9 +1,10 @@
 FROM python:3.13-slim

-# Install FFmpeg, system dependencies, and gosu from APT
+# Install FFmpeg, opustags, system dependencies, and gosu from APT
 RUN apt-get update && \
    apt-get install -y --no-install-recommends \
        ffmpeg \
+        opustags \
        ca-certificates \
        gosu \
        && \
@@ -1,3 +1,3 @@
 """API route handlers."""

-from . import upload, split, split_file, status, download, formats, info
+from . import upload, split, split_file, status, download, websocket, formats, info
@@ -1,8 +1,9 @@
+# web/backend/api/formats.py
 """Endpoint to expose format information to the frontend."""

 from fastapi import APIRouter

-from backend.constants import FORMAT_INFO
+from audio_splitter.constants import CONTAINER_INFO, CODEC_INFO, COMPATIBILITY_MATRIX

 router = APIRouter(prefix="/api", tags=["formats"])

@@ -10,16 +11,10 @@ router = APIRouter(prefix="/api", tags=["formats"])
@router.get("/formats")
 async def get_formats():
    """
-    Return the list of supported container formats with their properties.
+    Return the list of supported containers, codecs, and compatibility matrix.
    """
    return {
-        "formats": [
-            {
-                "name": name,
-                "ffmpeg": info["ffmpeg"],
-                "extension": info["ext"],
-                "audio_only": info["audio_only"],
-            }
-            for name, info in FORMAT_INFO.items()
-        ]
+        "containers": CONTAINER_INFO,
+        "codecs": CODEC_INFO,
+        "compatibility": COMPATIBILITY_MATRIX,
    }
@@ -9,7 +9,7 @@ from backend.services.task_manager import task_manager
 # Import core functions
 from audio_splitter.ffmpeg import get_stream_info, get_container_format, get_audio_codec
 from audio_splitter.formats import determine_default_format
-from audio_splitter.constants import FORMAT_INFO
+from audio_splitter.constants import CONTAINER_NAMES
 from audio_splitter.defaults import DEFAULT_FORMAT

 router = APIRouter(prefix="/api", tags=["info"])
@@ -63,7 +63,7 @@ async def get_recommended_format(task_id: str):
        # Fallback if detection fails or format is unsupported
        if fmt is None:
            fmt = DEFAULT_FORMAT
-        if fmt not in FORMAT_INFO:
+        if fmt not in CONTAINER_NAMES:
            fmt = "mp3"  # ultimate fallback

        return {"format": fmt}
@@ -1,4 +1,4 @@
-"""Split task endpoint."""
+"""Split task endpoint (JSON tracklist)."""

 from fastapi import APIRouter, HTTPException, BackgroundTasks

@@ -24,6 +24,29 @@ async def start_split(request: SplitRequest, background_tasks: BackgroundTasks):
            detail=f"Task {task_id} is already {status['status']}"
        )

+    # Build options dict from request
+    options = {
+        "container": request.container,
+        "audio_codec": request.audio_codec,
+        "video_codec": request.video_codec,
+        "subtitle_codec": request.subtitle_codec,
+        "video_quality": request.video_quality,
+        "drop_video": request.drop_video,
+        "drop_subs": request.drop_subs,
+        "number_tracks": request.number_tracks,
+        "replace_bad_chars": request.replace_bad_chars,
+        "replacement_char": request.replacement_char,
+        "bad_chars": request.bad_chars,
+        "skip_existing": request.skip_existing,
+        "output_template": request.output_template,
+        "album": request.album,
+        "comment": request.comment,
+        "no_comment": request.no_comment,
+        "comment_stream": request.comment_stream,
+        "merge_comments": request.merge_comments,
+        "comment_separator": request.comment_separator,
+    }
+
    task_manager.update_task(
        task_id,
        status=TaskStatus.PROCESSING,
@@ -31,9 +54,14 @@ async def start_split(request: SplitRequest, background_tasks: BackgroundTasks):
        message="Preparing to split..."
    )

-    background_tasks.add_task(run_split_task, task_id, request.tracklist, request.options)
+    background_tasks.add_task(
+        run_split_task,
+        task_id,
+        request.tracklist,
+        options
+    )

    return SplitResponse(
        task_id=task_id,
        status=TaskStatus.PROCESSING
-    )
+    )
@@ -2,6 +2,7 @@

 import json
 from pathlib import Path
+from typing import Optional

 from fastapi import APIRouter, UploadFile, File, Form, HTTPException, BackgroundTasks

@@ -13,7 +14,6 @@ from backend.models.response import SplitResponse, TaskStatus

 router = APIRouter(prefix="/api", tags=["split"])

-# Import CLI tracklist parsing functions
 from audio_splitter.tracklist import parse_format, read_tracklist


@@ -22,29 +22,33 @@ async def split_from_file(
    background_tasks: BackgroundTasks,
    task_id: str = Form(...),
    tracklist_file: UploadFile = File(...),
-    options: str = Form("{}"),
+    # New fields
+    container: Optional[str] = Form(None),
+    audio_codec: str = Form("copy"),
+    video_codec: str = Form("copy"),
+    subtitle_codec: str = Form("copy"),
+    video_quality: Optional[int] = Form(None),
+    drop_video: bool = Form(False),
+    drop_subs: bool = Form(False),
+    number_tracks: bool = Form(False),
+    replace_bad_chars: bool = Form(False),
+    replacement_char: str = Form("_"),
+    bad_chars: str = Form(r'!@#№$;:%^&?*(){}[]\/<>+=~`\' '),
+    skip_existing: bool = Form(False),
+    output_template: str = Form("%an-%tn.%ext"),
+    album: Optional[str] = Form(None),
+    comment: Optional[str] = Form(None),
+    no_comment: bool = Form(False),
+    comment_stream: Optional[int] = Form(None),
+    merge_comments: bool = Form(False),
+    comment_separator: str = Form("; "),
+    options: str = Form("{}"),  # backward-compatible, but we now use explicit fields
    tracklist_format: str = Form("%ts %tn - %an"),
 ):
-    """
-    Start a splitting task using a tracklist file.
-
-    This endpoint accepts a plain text tracklist file (like the CLI does)
-    and parses it using the same logic.
-
-    Args:
-        task_id: Task ID from upload.
-        tracklist_file: Tracklist file (text/plain).
-        options: JSON string of all CLI options.
-        tracklist_format: Format string for parsing (default: "%ts %tn - %an").
-
-    Returns:
-        SplitResponse with task_id and status.
-    """
    # Validate task exists
    if not task_manager.has_task(task_id):
        raise HTTPException(status_code=404, detail=f"Task {task_id} not found")

-    # Check if task is already processing
    status = task_manager.get_status(task_id)
    if status and status["status"] in (TaskStatus.PROCESSING, TaskStatus.DONE):
        raise HTTPException(
@@ -52,14 +56,12 @@ async def split_from_file(
            detail=f"Task {task_id} is already {status['status']}"
        )

-    # Validate file type
    if not tracklist_file.filename.endswith(('.txt', '.text')):
        raise HTTPException(
            status_code=400,
            detail="Tracklist file must be a text file (.txt or .text)"
        )

-    # Read and parse the tracklist file
    try:
        content = await tracklist_file.read()
        text = content.decode('utf-8')
@@ -75,17 +77,13 @@ async def split_from_file(
            detail="Tracklist file is empty"
        )

-    # Parse the tracklist using CLI logic
+    # Parse tracklist using CLI logic
    try:
-        # Parse the format string into tokens
        tokens = parse_format(tracklist_format)
-
-        # Write the content to a temporary file (read_tracklist expects a file path)
        temp_tracklist_path = settings.temp_dir / task_id / "tracklist.txt"
        temp_tracklist_path.parent.mkdir(parents=True, exist_ok=True)
        temp_tracklist_path.write_text(text, encoding='utf-8')

-        # Parse the tracklist file using CLI logic
        tracklist_dicts = read_tracklist(str(temp_tracklist_path), tokens)

    except Exception as e:
@@ -100,7 +98,7 @@ async def split_from_file(
            detail="No valid tracks found in tracklist file"
        )

-    # Convert dicts to TracklistEntry objects (same as JSON endpoint)
+    # Convert dicts to TracklistEntry objects
    try:
        tracklist_entries = [TracklistEntry(**entry) for entry in tracklist_dicts]
    except Exception as e:
@@ -109,14 +107,28 @@ async def split_from_file(
            detail=f"Invalid tracklist data: {str(e)}"
        )

-    # Parse options JSON
-    try:
-        options_dict = json.loads(options)
-    except json.JSONDecodeError:
-        raise HTTPException(
-            status_code=400,
-            detail="Invalid JSON in options field"
-        )
+    # Build options dict from explicit fields (ignore `options` parameter)
+    options = {
+        "container": container,
+        "audio_codec": audio_codec,
+        "video_codec": video_codec,
+        "subtitle_codec": subtitle_codec,
+        "video_quality": video_quality,
+        "drop_video": drop_video,
+        "drop_subs": drop_subs,
+        "number_tracks": number_tracks,
+        "replace_bad_chars": replace_bad_chars,
+        "replacement_char": replacement_char,
+        "bad_chars": bad_chars,
+        "skip_existing": skip_existing,
+        "output_template": output_template,
+        "album": album,
+        "comment": comment,
+        "no_comment": no_comment,
+        "comment_stream": comment_stream,
+        "merge_comments": merge_comments,
+        "comment_separator": comment_separator,
+    }

    # Update task status
    task_manager.update_task(
@@ -126,12 +138,11 @@ async def split_from_file(
        message="Preparing to split..."
    )

-    # Start background task
    background_tasks.add_task(
        run_split_task,
        task_id,
-        tracklist_entries,  # now TracklistEntry objects
-        options_dict
+        tracklist_entries,
+        options
    )

    return SplitResponse(
@@ -14,7 +14,8 @@ router = APIRouter(prefix="/api", tags=["upload"])

 ALLOWED_EXTENSIONS = {
    ".mp3", ".flac", ".wav", ".m4a", ".ogg", ".opus",
-    ".aac", ".wma", ".aiff", ".alac", ".ac3"
+    ".aac", ".wma", ".aiff", ".alac", ".ac3",
+    ".mp4", ".mkv", ".webm",
 }


@@ -1,12 +0,0 @@
-FORMAT_INFO = {
-    'mp3':      {'ffmpeg': 'mp3',      'ext': '.mp3',  'audio_only': True},
-    'm4a':      {'ffmpeg': 'mp4',      'ext': '.m4a',  'audio_only': True},
-    'mp4':      {'ffmpeg': 'mp4',      'ext': '.mp4',  'audio_only': False},
-    'mkv':      {'ffmpeg': 'matroska', 'ext': '.mkv',  'audio_only': False},
-    'matroska': {'ffmpeg': 'matroska', 'ext': '.mkv',  'audio_only': False},
-    'ogg':      {'ffmpeg': 'ogg',      'ext': '.ogg',  'audio_only': True},
-    'opus':     {'ffmpeg': 'ogg',      'ext': '.opus', 'audio_only': True},
-    'flac':     {'ffmpeg': 'flac',     'ext': '.flac', 'audio_only': True},
-    'wav':      {'ffmpeg': 'wav',      'ext': '.wav',  'audio_only': True},
-    'aac':      {'ffmpeg': 'adts',     'ext': '.aac',  'audio_only': True},
-}
@@ -17,19 +17,16 @@ class TracklistEntry(BaseModel):

    @validator("ts")
    def validate_timestamp(cls, v: str) -> str:
-        """Basic timestamp validation (format and range)."""
        v = v.strip()
        if not v:
            raise ValueError("Timestamp cannot be empty")

-        # Check for range format (start-end)
        if "-" in v:
            parts = v.split("-", 1)
            start = parts[0].strip()
            end = parts[1].strip()
            if not start or not end:
                raise ValueError("Invalid range format. Expected 'start-end'")
-            # Validate each part with the same logic
            for ts in [start, end]:
                cls._validate_single_timestamp(ts)
        else:
@@ -39,7 +36,6 @@ class TracklistEntry(BaseModel):

    @staticmethod
    def _validate_single_timestamp(ts: str) -> None:
-        """Validate a single timestamp (mm:ss or HH:MM:SS)."""
        parts = ts.split(":")
        if len(parts) not in (2, 3):
            raise ValueError(f"Invalid timestamp format: {ts}. Expected mm:ss or HH:MM:SS")
@@ -55,4 +51,30 @@ class SplitRequest(BaseModel):

    task_id: str = Field(..., description="Task ID from upload")
    tracklist: List[TracklistEntry] = Field(..., description="List of tracks")
-    options: dict = Field(default_factory=dict, description="All CLI options")
+
+    # Container and codec options
+    container: Optional[str] = Field(None, description="Output container (auto-detect if None)")
+    audio_codec: Optional[str] = Field("copy", description="Audio codec (copy or encoder name)")
+    video_codec: Optional[str] = Field("copy", description="Video codec (copy or encoder name)")
+    subtitle_codec: Optional[str] = Field("copy", description="Subtitle codec (copy or encoder name)")
+    video_quality: Optional[int] = Field(None, description="Video quality (encoder-specific integer)")
+
+    # Stream handling
+    drop_video: bool = Field(False, description="Remove video streams")
+    drop_subs: bool = Field(False, description="Remove subtitle streams")
+
+    # Filename options
+    number_tracks: bool = Field(False, description="Prepend track numbers")
+    replace_bad_chars: bool = Field(False, description="Replace bad characters")
+    replacement_char: str = Field("_", description="Replacement character")
+    bad_chars: str = Field(r'!@#№$;:%^&?*(){}[]\/<>+=~`\' ', description="Bad characters to replace")
+    skip_existing: bool = Field(False, description="Skip existing files")
+    output_template: str = Field("%an-%tn.%ext", description="Output filename template")
+
+    # Metadata options
+    album: Optional[str] = Field(None, description="Album name")
+    comment: Optional[str] = Field(None, description="Comment")
+    no_comment: bool = Field(False, description="Ignore comment")
+    comment_stream: Optional[int] = Field(None, description="Comment stream index")
+    merge_comments: bool = Field(False, description="Merge all comments")
+    comment_separator: str = Field("; ", description="Separator for merged comments")
@@ -1 +1 @@
-"""Business logic services."""
+"""Business logic services."""
@@ -2,10 +2,10 @@

 import os
 import sys
-import time
+import shutil
 from pathlib import Path
-from types import SimpleNamespace
-from typing import Dict, List, Any
+from typing import List, Dict, Any
+import time

 from backend.config import settings
 from backend.services.task_manager import task_manager
@@ -13,31 +13,12 @@ from backend.services.file_manager import FileManager
 from backend.models.request import TracklistEntry
 from backend.models.response import TaskStatus

-# Import central defaults
-from audio_splitter.defaults import (
-    DEFAULT_FORMAT,
-    DEFAULT_OUTPUT_TEMPLATE,
-    DEFAULT_REPLACEMENT_CHAR,
-    DEFAULT_BAD_CHARS,
-    DEFAULT_ALBUM,
-    DEFAULT_COMMENT,
-    DEFAULT_NO_COMMENT,
-    DEFAULT_COMMENT_STREAM,
-    DEFAULT_MERGE_COMMENTS,
-    DEFAULT_COMMENT_SEPARATOR,
-    DEFAULT_DROP_VIDEO,
-    DEFAULT_DROP_SUBS,
-    DEFAULT_NUMBER_TRACKS,
-    DEFAULT_REPLACE_BAD_CHARS,
-    DEFAULT_SKIP_EXISTING,
-    DEFAULT_DELETE_ORIGINAL,
-    DEFAULT_TRANSCODE_TO,
-)
-

 def run_split_task(task_id: str, tracklist: List[TracklistEntry], options: Dict[str, Any]) -> None:
    try:
-        task_manager.update_task_with_progress(task_id, progress=5, message="Initializing...")
+        task_manager.update_task_with_progress(
+            task_id, progress=5, message="Initializing..."
+        )

        input_path = FileManager.get_input_path(task_id)
        if not input_path or not input_path.exists():
@@ -45,7 +26,6 @@ def run_split_task(task_id: str, tracklist: List[TracklistEntry], options: Dict[

        output_dir = FileManager.ensure_output_dir(task_id)

-        # Convert tracklist to dicts (CLI format)
        tracks = []
        for entry in tracklist:
            track_dict = {
@@ -58,25 +38,30 @@ def run_split_task(task_id: str, tracklist: List[TracklistEntry], options: Dict[
            }
            tracks.append(track_dict)

-        # Build args namespace using defaults where options not provided
+        from types import SimpleNamespace
+
+        # Build args namespace using the new fields
        args = SimpleNamespace(
-            format=options.get("format", DEFAULT_FORMAT),
-            transcode_to=options.get("transcode_to", DEFAULT_TRANSCODE_TO),
-            drop_video=options.get("drop_video", DEFAULT_DROP_VIDEO),
-            drop_subs=options.get("drop_subs", DEFAULT_DROP_SUBS),
-            number_tracks=options.get("number_tracks", DEFAULT_NUMBER_TRACKS),
-            replace_bad_chars=options.get("replace_bad_chars", DEFAULT_REPLACE_BAD_CHARS),
-            replacement_char=options.get("replacement_char", DEFAULT_REPLACEMENT_CHAR),
-            bad_chars=options.get("bad_chars", DEFAULT_BAD_CHARS),
-            skip_existing=options.get("skip_existing", DEFAULT_SKIP_EXISTING),
-            output_template=options.get("output_template", DEFAULT_OUTPUT_TEMPLATE),
-            album=options.get("album", DEFAULT_ALBUM),
-            comment=options.get("comment", DEFAULT_COMMENT),
-            no_comment=options.get("no_comment", DEFAULT_NO_COMMENT),
-            comment_stream=options.get("comment_stream", DEFAULT_COMMENT_STREAM),
-            merge_comments=options.get("merge_comments", DEFAULT_MERGE_COMMENTS),
-            comment_separator=options.get("comment_separator", DEFAULT_COMMENT_SEPARATOR),
-            delete_original=DEFAULT_DELETE_ORIGINAL,  # never delete in web
+            container=options.get("container"),  # None -> auto-detect
+            audio_codec=options.get("audio_codec", "copy"),
+            video_codec=options.get("video_codec", "copy"),
+            subtitle_codec=options.get("subtitle_codec", "copy"),
+            video_quality=options.get("video_quality"),
+            drop_video=options.get("drop_video", False),
+            drop_subs=options.get("drop_subs", False),
+            number_tracks=options.get("number_tracks", False),
+            replace_bad_chars=options.get("replace_bad_chars", False),
+            replacement_char=options.get("replacement_char", "_"),
+            bad_chars=options.get("bad_chars", r'!@#№$;:%^&?*(){}[]\/<>+=~`\' '),
+            skip_existing=options.get("skip_existing", False),
+            output_template=options.get("output_template", "%an-%tn.%ext"),
+            album=options.get("album", None),
+            comment=options.get("comment", None),
+            no_comment=options.get("no_comment", False),
+            comment_stream=options.get("comment_stream", None),
+            merge_comments=options.get("merge_comments", False),
+            comment_separator=options.get("comment_separator", "; "),
+            delete_original=False,
        )

        project_root = Path(__file__).parent.parent.parent.parent
@@ -85,7 +70,13 @@ def run_split_task(task_id: str, tracklist: List[TracklistEntry], options: Dict[

        from audio_splitter.core import split_audio

-        task_manager.update_task_with_progress(task_id, progress=10, message="Starting split...")
+        # Cover image handling is now done internally by split_audio()
+        # via the handler system (opustags for Opus, ffmpeg for others)
+        args.cover_image = None
+
+        task_manager.update_task_with_progress(
+            task_id, progress=10, message="Starting split..."
+        )

        split_audio(str(input_path), str(output_dir), tracks, args)

@@ -68,16 +68,15 @@ const App: React.FC = () => {
    reset()
  }

-  const isSplitDisabled = !taskId || !isValid || entries.length === 0 || isProcessing || !!formatError
+  const isSplitDisabled =
+    !taskId ||
+    !isValid ||
+    entries.length === 0 ||
+    isProcessing ||
+    !!formatError

  return (
-    <ThemeProvider
-      theme={createTheme({
-        palette: {
-          mode: theme,
-        },
-      })}
-    >
+    <ThemeProvider theme={createTheme({ palette: { mode: theme } })}>
      <CssBaseline />
      <Layout>
        <Grid container spacing={3}>
@@ -1,5 +1,12 @@
 import axios from 'axios'
-import { TracklistEntry, SplitOptions, TaskStatus } from '../types'
+import {
+  TracklistEntry,
+  SplitOptions,
+  TaskStatus,
+  FormatsResponse,
+  UploadResponse,
+  SplitResponse,
+} from '../types'

 export const api = axios.create({
  baseURL: '/api',
@@ -8,16 +15,14 @@ export const api = axios.create({
  },
 })

-export const uploadFile = async (file: File): Promise<{ task_id: string; filename: string; size: number }> => {
+export const uploadFile = async (file: File): Promise<UploadResponse> => {
  const formData = new FormData()
  formData.append('file', file)
-
  const response = await api.post('/upload', formData, {
    headers: {
      'Content-Type': 'multipart/form-data',
    },
  })
-
  return response.data
 }

@@ -25,12 +30,32 @@ export const startSplit = async (
  task_id: string,
  tracklist: TracklistEntry[],
  options: SplitOptions
-): Promise<{ task_id: string; status: string }> => {
-  const response = await api.post('/split', {
+): Promise<SplitResponse> => {
+  // Build request payload (only send fields that are not undefined)
+  const payload: any = {
    task_id,
    tracklist,
-    options,
-  })
+    container: options.container, // null means auto-detect
+    audio_codec: options.audio_codec,
+    video_codec: options.video_codec,
+    subtitle_codec: options.subtitle_codec,
+    video_quality: options.video_quality,
+    drop_video: options.drop_video,
+    drop_subs: options.drop_subs,
+    number_tracks: options.number_tracks,
+    replace_bad_chars: options.replace_bad_chars,
+    replacement_char: options.replacement_char,
+    bad_chars: options.bad_chars,
+    skip_existing: options.skip_existing,
+    output_template: options.output_template,
+    album: options.album || null,
+    comment: options.comment || null,
+    no_comment: options.no_comment,
+    comment_stream: options.comment_stream,
+    merge_comments: options.merge_comments,
+    comment_separator: options.comment_separator,
+  }
+  const response = await api.post('/split', payload)
  return response.data
 }

@@ -47,8 +72,7 @@ export const getDownloadZipUrl = (task_id: string): string => {
  return `/api/download/${task_id}/splits.zip`
 }

-// New functions for format validation feature
-export const getFormatInfo = async (): Promise<{ formats: Array<{ name: string; audio_only: boolean }> }> => {
+export const getFormats = async (): Promise<FormatsResponse> => {
  const response = await api.get('/formats')
  return response.data
 }
@@ -1,4 +1,4 @@
-import React, { useEffect } from 'react'
+import React, { useEffect, useMemo } from 'react'
 import {
  Box,
  Paper,
@@ -16,7 +16,14 @@ import { ExpandMore, ExpandLess } from '@mui/icons-material'
 import { useOptionsStore } from '../stores/optionsStore'
 import { useUploadStore } from '../stores/uploadStore'
 import { useValidationStore } from '../stores/validationStore'
+import { getFormats } from '../api/client'
+import { SplitOptions } from '../types'
+import { useFilterCodecs } from '../hooks/useFilterCodecs'
+import { useFormatValidation } from '../hooks/useFormatValidation'

+// ------------------------------------------------------------------------------
+// Section component (collapsible)
+// ------------------------------------------------------------------------------
 interface SectionProps {
  title: string
  children: React.ReactNode
@@ -25,7 +32,6 @@ interface SectionProps {

 const Section: React.FC<SectionProps> = ({ title, children, defaultExpanded = false }) => {
  const [expanded, setExpanded] = React.useState(defaultExpanded)
-
  return (
    <Box sx={{ mb: 2 }}>
      <Box
@@ -51,54 +57,64 @@ const Section: React.FC<SectionProps> = ({ title, children, defaultExpanded = fa
  )
 }

+// ------------------------------------------------------------------------------
+// Main OptionsPanel
+// ------------------------------------------------------------------------------
 export const OptionsPanel: React.FC = () => {
-  const { options, setOptions } = useOptionsStore()
+  const {
+    options,
+    setOptions,
+    containers,
+    codecs,
+    compatibility,
+    setContainers,
+    setCodecs,
+    setCompatibility,
+  } = useOptionsStore()
+
  const { hasVideo } = useUploadStore()
  const { formatError, setFormatError } = useValidationStore()

-  // Audio-only formats from backend constants (hardcoded for now)
-  const audioOnlyFormats = ['mp3', 'm4a', 'ogg', 'opus', 'flac', 'wav', 'aac']
-
-  const handleFormatChange = (e: React.ChangeEvent<HTMLInputElement>) => {
-    const newFormat = e.target.value
-    setOptions({ format: newFormat })
-
-    // Validate format
-    if (audioOnlyFormats.includes(newFormat) && hasVideo && !options.drop_video) {
-      setFormatError(
-        `Format '${newFormat}' does not support video streams. Please enable "Drop video" or choose a container that supports video (e.g., MKV, MP4).`
-      )
-    } else {
-      setFormatError(null)
-    }
-  }
-
-  const handleDropVideoChange = (e: React.ChangeEvent<HTMLInputElement>) => {
-    const checked = e.target.checked
-    setOptions({ drop_video: checked })
-    // Re-validate format
-    if (audioOnlyFormats.includes(options.format) && hasVideo && !checked) {
-      setFormatError(
-        `Format '${options.format}' does not support video streams. Please enable "Drop video" or choose a container that supports video (e.g., MKV, MP4).`
-      )
-    } else {
-      setFormatError(null)
-    }
-  }
-
-  // Re-validate when hasVideo changes (e.g., after upload)
+  // Fetch formats on mount
  useEffect(() => {
-    const shouldShowError = audioOnlyFormats.includes(options.format) && hasVideo && !options.drop_video
-    const newError = shouldShowError
-      ? `Format '${options.format}' does not support video streams. Please enable "Drop video" or choose a container that supports video (e.g., MKV, MP4).`
-      : null
-
-    // Only update if the error state actually changes
-    if (newError !== formatError) {
-      setFormatError(newError)
+    const fetchFormats = async () => {
+      try {
+        const data = await getFormats()
+        setContainers(data.containers || [])
+        setCodecs(data.codecs || [])
+        setCompatibility(data.compatibility || {})
+      } catch (err) {
+        console.error('Failed to fetch formats:', err)
+      }
    }
-  }, [hasVideo, options.format, options.drop_video, formatError, setFormatError])
+    fetchFormats()
+  }, [setContainers, setCodecs, setCompatibility])

+  // --------------------------------------------------------------
+  // Filter codec options based on selected container
+  // --------------------------------------------------------------
+  const { filteredAudioCodecs, filteredVideoCodecs } = useFilterCodecs(compatibility, options.container, codecs)
+
+  // --------------------------------------------------------------
+  // Validate compatibility
+  // --------------------------------------------------------------
+  useFormatValidation(options, hasVideo, compatibility, containers, setFormatError)
+
+  // --------------------------------------------------------------
+  // Handlers
+  // --------------------------------------------------------------
+  const handleChange = (field: keyof SplitOptions, value: any) => {
+    setOptions({ [field]: value })
+  }
+
+  const handleContainerChange = (e: React.ChangeEvent<HTMLInputElement>) => {
+    const value = e.target.value === '' ? null : e.target.value
+    handleChange('container', value)
+  }
+
+  // --------------------------------------------------------------
+  // Render
+  // --------------------------------------------------------------
  return (
    <Paper sx={{ p: 3 }}>
      <Typography variant="h6" sx={{ mb: 2 }}>
@@ -111,60 +127,101 @@ export const OptionsPanel: React.FC = () => {
        </Alert>
      )}

-      {/* Output Settings */}
+      {/* ------------------------------------------------------------------------
+          Output Settings
+      ------------------------------------------------------------------------ */}
      <Section title="Output Settings" defaultExpanded>
        <Box sx={{ display: 'flex', flexDirection: 'column', gap: 2 }}>
+          {/* Container dropdown */}
          <TextField
            label="Container"
            select
-            value={options.format}
-            onChange={handleFormatChange}
+            value={options.container ?? ''}
+            onChange={handleContainerChange}
            fullWidth
            size="small"
            error={!!formatError}
            helperText={
-              formatError || "Determines the output file extension and container structure."
+              formatError || "Select a container (auto-detect if empty)."
            }
          >
-            <MenuItem value="mp3">MP3 (.mp3)</MenuItem>
-            <MenuItem value="m4a">M4A (.m4a)</MenuItem>
-            <MenuItem value="mkv">MKV (.mkv)</MenuItem>
-            <MenuItem value="mp4">MP4 (.mp4)</MenuItem>
-            <MenuItem value="ogg">OGG (.ogg)</MenuItem>
-            <MenuItem value="opus">OPUS (.opus)</MenuItem>
-            <MenuItem value="flac">FLAC (.flac)</MenuItem>
-            <MenuItem value="wav">WAV (.wav)</MenuItem>
-            <MenuItem value="aac">AAC (.aac)</MenuItem>
+            <MenuItem value="">Auto-detect</MenuItem>
+            {containers.map((c) => (
+              <MenuItem key={c.name} value={c.name}>
+                {c.name.toUpperCase()} ({c.extension})
+              </MenuItem>
+            ))}
          </TextField>

-          {/* Transcode option – remains unchanged but clearly labeled */}
+          {/* Audio Codec dropdown */}
          <TextField
-            label="Audio Codec (Transcode)"
+            label="Audio Codec"
            select
-            value={options.transcode_to || ''}
-            onChange={(e) => handleChange('transcode_to', e.target.value || undefined)}
+            value={options.audio_codec}
+            onChange={(e) => handleChange('audio_codec', e.target.value)}
            fullWidth
            size="small"
-            helperText="Select an audio codec to re-encode, or keep 'Copy' to preserve the original."
+            helperText="Audio codec (copy = keep original)"
          >
-            <MenuItem value="">Copy (no transcoding)</MenuItem>
-            <MenuItem value="libmp3lame">MP3 (LAME)</MenuItem>
-            <MenuItem value="aac">AAC</MenuItem>
-            <MenuItem value="libopus">OPUS</MenuItem>
+            <MenuItem value="copy">Copy (original)</MenuItem>
+            {filteredAudioCodecs.map((c) => (
+              <MenuItem key={c.name} value={c.name}>
+                {c.name.toUpperCase()}
+              </MenuItem>
+            ))}
          </TextField>

+          {/* Video Codec dropdown */}
+          <TextField
+            label="Video Codec"
+            select
+            value={options.video_codec}
+            onChange={(e) => handleChange('video_codec', e.target.value)}
+            fullWidth
+            size="small"
+            helperText="Video codec (copy = keep original)"
+            disabled={!hasVideo || options.drop_video}
+          >
+            <MenuItem value="copy">Copy (original)</MenuItem>
+            {filteredVideoCodecs.map((c) => (
+              <MenuItem key={c.name} value={c.name}>
+                {c.name.toUpperCase()}
+              </MenuItem>
+            ))}
+          </TextField>
+
+          {/* Video Quality */}
+          <TextField
+            label="Video Quality"
+            type="number"
+            value={options.video_quality ?? ''}
+            onChange={(e) => {
+              const val = e.target.value === '' ? null : parseInt(e.target.value, 10)
+              handleChange('video_quality', val)
+            }}
+            fullWidth
+            size="small"
+            disabled={!hasVideo || options.drop_video}
+            helperText="Optional quality value (encoder-specific; e.g., 1-31 for libx264, 0-10 for Theora)"
+            InputProps={{
+              inputProps: { min: 0, max: 51, step: 1 },
+            }}
+          />
+
+          {/* Drop video (if video present) */}
          {hasVideo && (
            <FormControlLabel
              control={
                <Switch
                  checked={options.drop_video}
-                  onChange={handleDropVideoChange}
+                  onChange={(e) => handleChange('drop_video', e.target.checked)}
                />
              }
              label="Drop video streams"
            />
          )}

+          {/* Drop subtitles */}
          <FormControlLabel
            control={
              <Switch
@@ -177,7 +234,9 @@ export const OptionsPanel: React.FC = () => {
        </Box>
      </Section>

-      {/* Filename Settings */}
+      {/* ------------------------------------------------------------------------
+          Filename Settings
+      ------------------------------------------------------------------------ */}
      <Section title="Filename Settings">
        <Box sx={{ display: 'flex', flexDirection: 'column', gap: 2 }}>
          <TextField
@@ -233,7 +292,9 @@ export const OptionsPanel: React.FC = () => {
        </Box>
      </Section>

-      {/* Metadata Settings */}
+      {/* ------------------------------------------------------------------------
+          Metadata Settings
+      ------------------------------------------------------------------------ */}
      <Section title="Metadata Settings">
        <Box sx={{ display: 'flex', flexDirection: 'column', gap: 2 }}>
          <TextField
@@ -264,7 +325,7 @@ export const OptionsPanel: React.FC = () => {
            type="number"
            value={options.comment_stream ?? ''}
            onChange={(e) =>
-              handleChange('comment_stream', e.target.value === '' ? null : parseInt(e.target.value))
+              handleChange('comment_stream', e.target.value === '' ? null : parseInt(e.target.value, 10))
            }
            size="small"
            disabled={options.no_comment}
@@ -289,7 +350,9 @@ export const OptionsPanel: React.FC = () => {
        </Box>
      </Section>

-      {/* Tracklist Settings */}
+      {/* ------------------------------------------------------------------------
+          Tracklist Settings
+      ------------------------------------------------------------------------ */}
      <Section title="Tracklist Settings" defaultExpanded>
        <Box sx={{ display: 'flex', flexDirection: 'column', gap: 2 }}>
          <TextField
@@ -304,9 +367,4 @@ export const OptionsPanel: React.FC = () => {
      </Section>
    </Paper>
  )
-
-  // Helper function for option updates
-  function handleChange(field: string, value: any) {
-    setOptions({ [field]: value })
-  }
 }
@@ -7,7 +7,7 @@ import { useOptionsStore } from '../stores/optionsStore'  // NEW
 import { uploadFile, getTaskInfo, getRecommendedFormat } from '../api/client'  // NEW
 import { useTaskStore } from '../stores/taskStore'

-const ALLOWED_EXTENSIONS = ['.mp3', '.flac', '.wav', '.m4a', '.ogg', '.opus', '.aac', '.wma', '.aiff', '.alac', '.ac3']
+const ALLOWED_EXTENSIONS = ['.mp3', '.flac', '.wav', '.m4a', '.ogg', '.opus', '.aac', '.wma', '.aiff', '.alac', '.ac3', '.mp4', '.mkv', '.webm']

 export const UploadZone: React.FC = () => {
  const {
@@ -70,9 +70,10 @@ export const UploadZone: React.FC = () => {

          // Fetch recommended format and update options
          try {
+            // Inside UploadZone.tsx, after fetching recommended format:
            const rec = await getRecommendedFormat(taskId)
-            // Update only the format; keep other options (e.g., transcode_to) as defaults
-            setOptions({ format: rec.format })
+            // Update options store with container (not format)
+            setOptions({ container: rec.format })
          } catch (err) {
            console.warn('Failed to fetch recommended format, using default', err)
          }
@@ -95,7 +96,7 @@ export const UploadZone: React.FC = () => {
  const { getRootProps, getInputProps, isDragActive } = useDropzone({
    onDrop,
    accept: {
-      'audio/*': ALLOWED_EXTENSIONS,
+      'media/*': ALLOWED_EXTENSIONS
    },
    multiple: false,
    disabled: isUploading,
@@ -0,0 +1,31 @@
+import { useMemo } from 'react'
+import { CodecInfo } from '../types'
+
+export interface CompatibilityEntry {
+  audio: string[] | null
+  video: string[] | null
+}
+
+export function useFilterCodecs(
+  compatibility: Record<string, CompatibilityEntry>,
+  container: string | null,
+  codecs: CodecInfo[]
+) {
+  const filteredAudioCodecs = useMemo(() => {
+    const entry = compatibility?.[container || '']
+    if (!entry) return codecs.filter(c => c.codec_type === 'audio')
+    const audioList = entry.audio
+    if (audioList === null) return codecs.filter(c => c.codec_type === 'audio')
+    return codecs.filter(c => c.codec_type === 'audio' && audioList.includes(c.name))
+  }, [compatibility, container, codecs])
+
+  const filteredVideoCodecs = useMemo(() => {
+    const entry = compatibility?.[container || '']
+    if (!entry) return codecs.filter(c => c.codec_type === 'video')
+    const videoList = entry.video
+    if (videoList === null) return codecs.filter(c => c.codec_type === 'video')
+    return codecs.filter(c => c.codec_type === 'video' && videoList.includes(c.name))
+  }, [compatibility, container, codecs])
+
+  return { filteredAudioCodecs, filteredVideoCodecs }
+}
@@ -0,0 +1,56 @@
+import { useEffect } from 'react'
+import { ContainerInfo } from '../types'
+import { CompatibilityEntry } from './useFilterCodecs'
+
+export function useFormatValidation(
+  options: {
+    container: string | null
+    audio_codec: string
+    video_codec: string
+    drop_video: boolean
+  },
+  hasVideo: boolean,
+  compatibility: Record<string, CompatibilityEntry>,
+  containers: ContainerInfo[],
+  setFormatError: (error: string | null) => void
+) {
+  useEffect(() => {
+    const selectedContainer = containers.find(c => c.name === options.container)
+    if (!selectedContainer?.supports_video && hasVideo && !options.drop_video) {
+      setFormatError(
+        `Container '${options.container}' does not support video streams. Please enable "Drop video" or choose a container that supports video.`
+      )
+      return
+    }
+
+    // Check audio codec compatibility
+    if (options.audio_codec && options.audio_codec !== 'copy' && options.container) {
+      const entry = compatibility?.[options.container]
+      if (entry) {
+        const audioList = entry.audio
+        if (audioList !== null && !audioList.includes(options.audio_codec)) {
+          setFormatError(
+            `Audio codec '${options.audio_codec}' is not supported by container '${options.container}'.`
+          )
+          return
+        }
+      }
+    }
+
+    // Check video codec compatibility
+    if (options.video_codec && options.video_codec !== 'copy' && options.container && hasVideo && !options.drop_video) {
+      const entry = compatibility?.[options.container]
+      if (entry) {
+        const videoList = entry.video
+        if (videoList !== null && !videoList.includes(options.video_codec)) {
+          setFormatError(
+            `Video codec '${options.video_codec}' is not supported by container '${options.container}'.`
+          )
+          return
+        }
+      }
+    }
+
+    setFormatError(null)
+  }, [options.container, options.audio_codec, options.video_codec, options.drop_video, hasVideo, compatibility, containers, setFormatError])
+}
@@ -1,6 +1,5 @@
-// web/frontend/src/stores/optionsStore.ts
 import { create } from 'zustand'
-import { SplitOptions } from '../types'
+import { SplitOptions, ContainerInfo, CodecInfo } from '../types'
 import {
  DEFAULT_FORMAT,
  DEFAULT_OUTPUT_TEMPLATE,
@@ -17,13 +16,16 @@ import {
  DEFAULT_NUMBER_TRACKS,
  DEFAULT_REPLACE_BAD_CHARS,
  DEFAULT_SKIP_EXISTING,
-  DEFAULT_TRANSCODE_TO,
  DEFAULT_TRACKLIST_FORMAT,
 } from '../constants/generated'

+// We use DEFAULT_FORMAT only as a fallback; container default is null (auto-detect)
 const DEFAULT_OPTIONS: SplitOptions = {
-  format: DEFAULT_FORMAT,
-  transcode_to: DEFAULT_TRANSCODE_TO ?? '',
+  container: null,
+  audio_codec: 'copy',
+  video_codec: 'copy',
+  subtitle_codec: 'copy',
+  video_quality: null,
  drop_video: DEFAULT_DROP_VIDEO,
  drop_subs: DEFAULT_DROP_SUBS,
  number_tracks: DEFAULT_NUMBER_TRACKS,
@@ -43,15 +45,33 @@ const DEFAULT_OPTIONS: SplitOptions = {

 interface OptionsState {
  options: SplitOptions
-  setOptions: (options: Partial<SplitOptions>) => void
+  containers: ContainerInfo[]
+  codecs: CodecInfo[]
+  compatibility: Record<string, { audio: string[] | null; video: string[] | null }>
+  setOptions: (newOptions: Partial<SplitOptions>) => void
+  setContainers: (containers: ContainerInfo[]) => void
+  setCodecs: (codecs: CodecInfo[]) => void
+  setCompatibility: (compat: Record<string, { audio: string[] | null; video: string[] | null }>) => void
  reset: () => void
 }

 export const useOptionsStore = create<OptionsState>((set) => ({
  options: { ...DEFAULT_OPTIONS },
+  containers: [],
+  codecs: [],
+  compatibility: {},
  setOptions: (newOptions) =>
    set((state) => ({
      options: { ...state.options, ...newOptions },
    })),
-  reset: () => set({ options: { ...DEFAULT_OPTIONS } }),
+  setContainers: (containers) => set({ containers }),
+  setCodecs: (codecs) => set({ codecs }),
+  setCompatibility: (compatibility) => set({ compatibility }),
+  reset: () =>
+    set({
+      options: { ...DEFAULT_OPTIONS },
+      containers: [],
+      codecs: [],
+      compatibility: {},
+    }),
 }))
@@ -22,8 +22,11 @@ export interface TaskStatus {
 }

 export interface SplitOptions {
-  format: string
-  transcode_to?: string
+  container: string | null          // null = auto-detect
+  audio_codec: string               // 'copy' or encoder name
+  video_codec: string               // 'copy' or encoder name
+  subtitle_codec: string            // 'copy' or encoder name
+  video_quality: number | null      // encoder-specific integer
  drop_video: boolean
  drop_subs: boolean
  number_tracks: boolean
@@ -38,7 +41,34 @@ export interface SplitOptions {
  comment_stream: number | null
  merge_comments: boolean
  comment_separator: string
-  tracklist_format: string
+  tracklist_format: string          // for frontend parsing
+}
+
+export interface ContainerInfo {
+  name: string
+  ffmpeg: string
+  extension: string
+  supports_video: boolean
+  supports_subs: boolean
+}
+
+export interface CodecInfo {
+  name: string
+  ffmpeg: string
+  recommended_container: string
+  recommended_extension: string
+  codec_type: 'audio' | 'video' | 'subtitle'
+}
+
+export interface CompatibilityEntry {
+  audio: string[] | null
+  video: string[] | null
+}
+
+export interface FormatsResponse {
+  containers: ContainerInfo[]
+  codecs: CodecInfo[]
+  compatibility: Record<string, CompatibilityEntry>
 }

 export interface UploadResponse {
Author	SHA1	Message	Date
max	2ab85b64ff	fix #26 (backend,frontend): Frontend can't apply codecs filters correctly	2026-09-02 21:24:18 +05:00
max	cf0b9f62cb	fix #22 (backend,frontend): the backend and frontend had whitelists that only included audio formats	2026-09-02 20:12:00 +05:00
max	1b0767af90	fix #27 (core): no write permissions fail	2026-09-02 19:36:28 +05:00
max	a8b0c538ff	fix #25 (core): wrong output filename extensions when they are autodetected	2026-09-02 19:14:57 +05:00
max	3a41bd2920	fix #18 (core): malformed names of output files	2026-09-02 18:30:53 +05:00
max	78ec4dd63a	Fix #28 : warn when timestamps overlap Add overlap detection in resolve_end_times. When consecutive tracks have overlapping time ranges (end of track N > start of track N+1), a warning is printed but processing continues as before.	2026-09-02 16:57:10 +05:00
max	8b67de59a3	Fix #29 : validate --container against known containers Before this fix, passing an invalid container name (e.g., 'nonexistent') was passed directly to FFmpeg, which would fail with a cryptic error. Now the container name is validated against CONTAINER_NAMES before any processing begins, and a clear error message listing valid containers is shown.	2026-09-02 15:41:38 +05:00
max	25e8c0293e	feat (core): allows user to add an external cover image to split tracks	2026-09-02 11:42:47 +05:00
max	e36c1d69ed	minor (core): updates DEFAULT_BAD_CHARS	2026-09-01 15:54:38 +05:00
max	e77434cf30	feat (core): updates codecs info in constants.py	2026-09-01 15:47:02 +05:00
max	90d73d0e74	refact (core): removes useless fields from CODEC_INFO	2026-09-01 13:08:28 +05:00
max	7a7b63b03b	refact (core): simplifies constants.py, removes redundancy, updates dependent code	2026-09-01 12:17:21 +05:00
max	a67acc31b7	feat (back): removes cover image handling, since it's in core now	2026-08-31 19:50:44 +05:00
max	5f68eccdbf	feat (core): If user_format is provided, map it to the correct container if it's a codec name	2026-08-31 19:48:31 +05:00
max	156dfa693f	update (core): new values for codec/container/file_extension compatibility	2026-08-31 14:20:02 +05:00
max	580837fa73	feature (core): adds special handlers for audio+cover_image cases	2026-08-31 14:19:07 +05:00
max	747a349877	fix (core): checks the compatibility even if default options are used	2026-08-30 19:00:12 +05:00
max	6f6637a9a2	REFACTOR (BACKEND): removes an useless file	2026-08-30 15:48:28 +05:00
max	5e02184c8f	REFACTOR (FRONTEND): exports some functionality from web/frontend/src/components/OptionsPanel.tsx into separated hooks	2026-08-30 15:26:02 +05:00
max	e935241fd8	REFACTOR (CORE): splits build_ffmpeg_command method into one orchestrator and helper methods	2026-08-30 14:47:13 +05:00
max	8e0d345ba7	FIX: maps codecs names and ffmpeg encoders correctly	2026-08-28 15:41:21 +05:00
max	3533525df0	FEATURE: propagate improvements from CLI and web-API versions to web-frontend	2026-08-28 15:40:38 +05:00
max	834239674a	FEATURE: propogate improvements from CLI version to web-backend	2026-08-28 13:24:46 +05:00
max	748532be7c	FIX: codec/container/file_extension autodetection when default values are used	2026-08-28 11:04:40 +05:00
max	f3abbb8f0c	FEATURE: adds quality flag for video stream	2026-08-25 17:00:43 +05:00
max	690c5f98c6	FEATURE: adds strict codec/container/file_extension verification, renames ambiguous options, adds flexible transcoding	2026-08-25 10:40:48 +05:00
max	262d458ce4	FEATURE: codecs/containers/file_extensions inconsistency fixed	2026-08-21 15:59:05 +05:00
max	7af2600ed8	FEATURE: all versions use single source of truth for codec/container/file_extension info	2026-08-21 14:58:55 +05:00
max	d08045bf02	Merge pull request 'fix(frontend): frontend functional bugs' (#9 ) from frontend_bugs into dev Reviewed-on: #9	2026-08-21 13:35:17 +04:00