audio_splitter/constants.py

@@ -11,56 +11,62 @@ This file serves as the single source of truth for:
 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', 'audio_only': True, 'supports_video': False, 'supports_subs': False},
+    {'name': 'mp3', 'ffmpeg': 'mp3', 'extension': '.mp3', 'supports_video': True, 'supports_subs': False},
-    {'name': 'm4a', 'ffmpeg': 'mp4', 'extension': '.m4a', 'audio_only': True, 'supports_video': False, 'supports_subs': False},
+    {'name': 'm4a', 'ffmpeg': 'mp4', 'extension': '.m4a', 'supports_video': False, 'supports_subs': False},
-    {'name': 'flac', 'ffmpeg': 'flac', 'extension': '.flac', 'audio_only': True, 'supports_video': False, 'supports_subs': False},
+    {'name': 'flac', 'ffmpeg': 'flac', 'extension': '.flac', 'supports_video': False, 'supports_subs': False},
-    {'name': 'wav', 'ffmpeg': 'wav', 'extension': '.wav', 'audio_only': True, 'supports_video': False, 'supports_subs': False},
+    {'name': 'wav', 'ffmpeg': 'wav', 'extension': '.wav', 'supports_video': False, 'supports_subs': False},
-    {'name': 'aac', 'ffmpeg': 'adts', 'extension': '.aac', 'audio_only': True, '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', 'audio_only': False, 'supports_video': True, 'supports_subs': True},
+    {'name': 'mp4', 'ffmpeg': 'mp4', 'extension': '.mp4', 'supports_video': True, 'supports_subs': True},
-    {'name': 'mkv', 'ffmpeg': 'matroska', 'extension': '.mkv', 'audio_only': False, 'supports_video': True, 'supports_subs': True},
+    {'name': 'mkv', 'ffmpeg': 'matroska', 'extension': '.mkv', 'supports_video': True, 'supports_subs': True},
-    {'name': 'matroska', 'ffmpeg': 'matroska', 'extension': '.mkv', 'audio_only': False, 'supports_video': True, 'supports_subs': True},
+    {'name': 'ogg', 'ffmpeg': 'ogg', 'extension': '.ogg', 'supports_video': True, 'supports_subs': True},
-    {'name': 'ogg', 'ffmpeg': 'ogg', 'extension': '.ogg', 'audio_only': False, 'supports_video': True, 'supports_subs': True},
+    {'name': 'webm', 'ffmpeg': 'webm', 'extension': '.webm', 'supports_video': True, 'supports_subs': False},
-    {'name': 'webm', 'ffmpeg': 'webm', 'extension': '.webm', 'audio_only': False, 'supports_video': True, 'supports_subs': False},
 ]
 
-# Legacy FORMAT_INFO for backward compatibility
+# Container name lookup set for fast membership checks
-FORMAT_INFO = {
+CONTAINER_NAMES = {container['name'] for container in CONTAINER_INFO}
-    container['name']: {
+
-        'ffmpeg': container['ffmpeg'],
+
-        'ext': container['extension'],
+def get_container_info(container_name: str) -> Optional[Dict]:
-        'audio_only': container['audio_only'],
+    """Return container info dict or None if not found."""
-    }
+    for container in CONTAINER_INFO:
-    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', 'supports_transcoding': True, 'supports_video': False},
+    {'name': 'opus', 'ffmpeg': 'libopus', 'recommended_container': 'ogg', 'recommended_extension': '.opus', 'codec_type': 'audio'},
-    {'name': 'vorbis', 'ffmpeg': 'libvorbis', 'recommended_container': 'ogg', 'recommended_extension': '.ogg', 'supports_transcoding': True, 'supports_video': False},
+    {'name': 'vorbis', 'ffmpeg': 'libvorbis', 'recommended_container': 'ogg', 'recommended_extension': '.ogg', 'codec_type': 'audio'},
-    {'name': 'flac', 'ffmpeg': 'flac', 'recommended_container': 'flac', 'recommended_extension': '.flac', 'supports_transcoding': True, 'supports_video': False},
+    {'name': 'flac', 'ffmpeg': 'flac', 'recommended_container': 'flac', 'recommended_extension': '.flac', 'codec_type': 'audio'},
-    {'name': 'aac', 'ffmpeg': 'aac', 'recommended_container': 'mp4', 'recommended_extension': '.m4a', 'supports_transcoding': True, 'supports_video': False},
+    {'name': 'aac', 'ffmpeg': 'aac', 'recommended_container': 'mp4', 'recommended_extension': '.m4a', 'codec_type': 'audio'},
-    {'name': 'mp3', 'ffmpeg': 'libmp3lame', 'recommended_container': 'mp3', 'recommended_extension': '.mp3', 'supports_transcoding': True, 'supports_video': False},
+    {'name': 'mp3', 'ffmpeg': 'libmp3lame', 'recommended_container': 'mp3', 'recommended_extension': '.mp3', 'codec_type': 'audio'},
-    {'name': 'alac', 'ffmpeg': 'alac', 'recommended_container': 'mp4', 'recommended_extension': '.m4a', 'supports_transcoding': True, 'supports_video': False},
+    {'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', 'supports_transcoding': True, 'supports_video': False},
+    {'name': 'pcm_s16le', 'ffmpeg': 'pcm_s16le', 'recommended_container': 'wav', 'recommended_extension': '.wav', 'codec_type': 'audio'},
-    # Video codecs
+    # Video codecs (including cover images)
-    {'name': 'theora', 'ffmpeg': 'libtheora', 'recommended_container': 'ogg', 'recommended_extension': '.ogv', 'supports_transcoding': True, 'supports_video': True},
+    {'name': 'theora', 'ffmpeg': 'libtheora', 'recommended_container': 'ogg', 'recommended_extension': '.ogv', 'codec_type': 'video'},
-    {'name': 'vp8', 'ffmpeg': 'libvpx', 'recommended_container': 'webm', 'recommended_extension': '.webm', 'supports_transcoding': True, 'supports_video': True},
+    {'name': 'vp8', 'ffmpeg': 'libvpx', 'recommended_container': 'webm', 'recommended_extension': '.webm', 'codec_type': 'video'},
-    {'name': 'vp9', 'ffmpeg': 'libvpx-vp9', 'recommended_container': 'webm', 'recommended_extension': '.webm', 'supports_transcoding': True, 'supports_video': True},
+    {'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', 'supports_transcoding': True, 'supports_video': True},
+    {'name': 'av1', 'ffmpeg': 'libaom-av1', 'recommended_container': 'mkv', 'recommended_extension': '.mkv', 'codec_type': 'video'},
-    {'name': 'h264', 'ffmpeg': 'libx264', 'recommended_container': 'mp4', 'recommended_extension': '.mp4', 'supports_transcoding': True, 'supports_video': True},
+    {'name': 'h264', 'ffmpeg': 'libx264', 'recommended_container': 'mp4', 'recommended_extension': '.mp4', 'codec_type': 'video'},
-    {'name': 'h265', 'ffmpeg': 'libx265', 'recommended_container': 'mp4', 'recommended_extension': '.mp4', 'supports_transcoding': True, 'supports_video': True},
+    {'name': 'h265', 'ffmpeg': 'libx265', 'recommended_container': 'mp4', 'recommended_extension': '.mp4', 'codec_type': 'video'},
-    {'name': 'png', 'ffmpeg': 'png', 'recommended_container': 'ogg', 'recommended_extension': '.png', 'supports_transcoding': False, 'supports_video': True},
+    {'name': 'png', 'ffmpeg': 'png', 'recommended_container': 'ogg', 'recommended_extension': '.png', 'codec_type': 'video'},
-    {'name': 'mjpeg', 'ffmpeg': 'mjpeg', 'recommended_container': 'ogg', 'recommended_extension': '.jpg', 'supports_transcoding': False, 'supports_video': True},
+    {'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
@@ -70,22 +76,6 @@ CODEC_TO_EXTENSION_MAP = {codec['name']: codec['recommended_extension'] for code
 # Map codec name → FFmpeg encoder name
 CODEC_NAME_TO_FFMPEG = {codec['name']: codec['ffmpeg'] for codec in CODEC_INFO}
 
-# ------------------------------------------------------------------------------
-# Video codec support per container (legacy, will be superseded by compatibility matrix)
-# ------------------------------------------------------------------------------
-CONTAINER_VIDEO_CODEC_SUPPORT = {
-    'mp4': ['h264', 'h265', 'vp9', 'av1', 'mpeg4', 'hevc'],
-    'mkv': ['*'],
-    'matroska': ['*'],
-    'ogg': ['theora', 'dirac', 'vp8', 'png', 'mjpeg'],
-    'webm': ['vp8', 'vp9', 'av1'],
-    'mp3': [],
-    'm4a': [],
-    'flac': [],
-    'wav': [],
-    'aac': [],
-}
-
 # ------------------------------------------------------------------------------
 # Compatibility matrix: container → supported audio and video codecs
 # ------------------------------------------------------------------------------
@@ -96,14 +86,13 @@ CONTAINER_VIDEO_CODEC_SUPPORT = {
 #            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': []},
+    '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},
-    'matroska': {'audio': None, 'video': None},
+    'ogg': {'audio': ['opus', 'vorbis', 'flac'], 'video': ['theora', 'vp8', 'png', 'mjpeg']},
-    'ogg': {'audio': ['opus', 'vorbis', 'flac'], 'video': ['theora', 'vp8']},
     'webm': {'audio': ['opus', 'vorbis'], 'video': ['vp8', 'vp9', 'av1']},
-    'flac': {'audio': ['flac'], 'video': []},
+    'flac': {'audio': ['flac'], 'video': ['png', 'mjpeg']},
     'wav': {'audio': ['pcm_s16le'], 'video': []},
     'aac': {'audio': ['aac'], 'video': []},
 }
@@ -132,4 +121,4 @@ def is_video_codec_supported(container: str, video_codec: str) -> bool:
 # ------------------------------------------------------------------------------
 # Default bad characters (for filename sanitization)
 # ------------------------------------------------------------------------------
-DEFAULT_BAD_CHARS = r'!@#№$;:%^&?*(){}[]\/<>+=~`\' '
+DEFAULT_BAD_CHARS = r'!@#№$;:%^&?*(){}[]\/<>+=~`\'|," '

audio_splitter/core.py

@@ -7,9 +7,9 @@ import sys
 from typing import List, Dict, Any
 
 from .constants import (
-    FORMAT_INFO,
+    CONTAINER_NAMES,
     CODEC_TO_EXTENSION_MAP,
-    CODEC_NAME_TO_FFMPEG,   # <-- Add this
+    CODEC_NAME_TO_FFMPEG,
 )
 from .ffmpeg import (
     get_audio_duration,
@@ -23,6 +23,7 @@ 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
@@ -120,7 +121,8 @@ def split_audio(input_file: str, output_directory: str, tracks: List[Dict[str, A
     if output_audio_codec in CODEC_TO_EXTENSION_MAP:
         extension = CODEC_TO_EXTENSION_MAP[output_audio_codec]
     else:
-        extension = FORMAT_INFO.get(output_container, {}).get('ext', '.mkv')
+        container_info = next((c for c in CONTAINER_INFO if c['name'] == output_container), None)
+        extension = container_info['extension'] if container_info else '.mkv'
 
     print(f"Output extension: {extension}")
 
@@ -162,6 +164,14 @@ def split_audio(input_file: str, output_directory: str, tracks: List[Dict[str, A
             else:
                 cover_image_path = None
 
+    # Check if we need special handling (e.g., Opus files need opustags)
+    input_audio_codec = stream_info.get('audio_codec')
+    cover_handler = get_handler(output_container, input_audio_codec)
+    needs_drop = needs_drop_video(output_container, input_audio_codec)
+    if cover_image_path and needs_drop:
+        print(f"Using special handler for {output_container} + {input_audio_codec}")
+        print("Temporarily dropping video for opustags post-processing.")
+
     # --------------------------------------------------------------------------
     # 8. Process each track
     # --------------------------------------------------------------------------
@@ -208,6 +218,11 @@ def split_audio(input_file: str, output_directory: str, tracks: List[Dict[str, A
             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 (cover_image_path 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
+        ffmpeg_cover_path = None if (cover_image_path and needs_drop) else cover_image_path
         cmd = build_ffmpeg_command(
             input_file=input_file,
             start_seconds=start_seconds,
@@ -219,9 +234,9 @@ def split_audio(input_file: str, output_directory: str, tracks: List[Dict[str, A
             video_codec=video_enc,
             subtitle_codec=subtitle_enc,
             metadata=metadata,
-            cover_image_path=cover_image_path,
+            cover_image_path=ffmpeg_cover_path,
             video_quality=getattr(args, 'video_quality', None),
-            drop_video=args.drop_video,
+            drop_video=effective_drop_video,
             drop_subs=args.drop_subs,
         )
 
@@ -235,6 +250,21 @@ def split_audio(input_file: str, output_directory: str, tracks: List[Dict[str, A
             print(result.stderr)
         else:
             print(f"  -> Saved to: {output_path}")
+            # Apply cover image handler if needed
+            if cover_image_path and not args.drop_video and needs_drop:
+                print(f"Applying cover image via {output_container} handler...")
+                if not cover_handler(
+                    input_file=input_file,
+                    cover_image_path=cover_image_path,
+                    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

audio_splitter/ffmpeg.py

@@ -5,7 +5,7 @@ import json
 import subprocess
 from typing import Dict, List, Optional, Tuple
 
-from .constants import FORMAT_INFO
+from .constants import CONTAINER_INFO
 from .utils import format_time
 
 
@@ -159,7 +159,7 @@ 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.
@@ -179,7 +179,7 @@ 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
+    # Normalize common aliases to names used in CONTAINER_INFO
     mapping = {
         'mpeg': 'mp3',
         'mp2': 'mp3',
@@ -187,8 +187,8 @@ def get_container_format(input_file: str) -> Optional[str]:
         'm4a': 'mp4',
         'mov': 'mp4',
         '3gp': 'mp4',
-        'matroska': 'matroska',
+        'matroska': 'mkv',
-        'webm': 'matroska',
+        'webm': 'mkv',
         'ogg': 'ogg',
         'flac': 'flac',
         'wav': 'wav',
@@ -269,6 +269,112 @@ def extract_cover_image(input_file: str, output_path: str) -> bool:
     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')
+    if metadata:
+        for key, value in metadata.items():
+            if value is not None and value != '':
+                cmd.extend(['-metadata', f"{key}={value}"])
+
+
+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:
+        cmd.extend(['-map', '0:a:0', '-map', '0:s?'])
+    elif drop_subs:
+        cmd.extend(['-map', '0:a:0', '-map', '0:v:0'])
+    else:
+        cmd.extend(['-map', '0'])
+
+    if audio_codec and audio_codec != 'copy':
+        cmd.extend(['-c:a', audio_codec])
+    else:
+        cmd.extend(['-c:a', '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')
+
+    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')
+
+
+def _build_format(cmd: List[str], format_opt: Optional[str]) -> None:
+    """Add output format option if specified."""
+    if 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,
@@ -309,93 +415,21 @@ def build_ffmpeg_command(
     """
     cmd = ['ffmpeg']
 
-    # Add cover image as first input if provided
+    _build_inputs(cmd, input_file, cover_image_path)
+    _build_time_options(cmd, start_seconds, duration_seconds)
+    _build_metadata(cmd, metadata)
+
     if cover_image_path:
-        cmd.extend(['-i', cover_image_path])
+        _build_cover_image_mapping(cmd, audio_codec, video_codec, video_quality)
-
-    # Add main input file
-    cmd.extend(['-i', input_file])
-
-    # Time options
-    cmd.extend(['-ss', format_time(start_seconds), '-t', format_time(duration_seconds)])
-
-    # Clear all original metadata.
-    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 and codecs ----------
-    if cover_image_path:
-        # We have two inputs: index 0 = cover image, index 1 = main input
-        # Map audio from main input (index 1) and video from cover image (index 0)
-        cmd.extend(['-map', '1:a:0', '-map', '0:v:0'])
-
-        # Video codec: use user-specified codec if provided, otherwise fallback to png
-        if video_codec and video_codec != 'copy':
-            cmd.extend(['-c:v', video_codec])
     else:
-            cmd.extend(['-c:v', 'png'])
+        _build_standard_mapping(
+            cmd, stream_info, audio_codec, video_codec, subtitle_codec,
+            video_quality, drop_video, drop_subs
+        )
 
-        # Audio codec
+    _build_format(cmd, format_opt)
-        if audio_codec and audio_codec != 'copy':
+    _build_output(cmd, output_path)
-            cmd.extend(['-c:a', audio_codec])
-        else:
-            cmd.extend(['-c:a', 'copy'])
 
-        # Subtitle: we don't copy subtitles when using cover image (they would be from main input)
-        cmd.append('-sn')
-
-        # Video quality if specified
-        if video_quality is not None:
-            cmd.extend(['-q:v', str(video_quality)])
-
-    else:
-        # Standard mapping (no cover image)
-        if drop_video and drop_subs:
-            cmd.extend(['-map', '0:a:0'])
-        elif drop_video:
-            cmd.extend(['-map', '0:a:0', '-map', '0:s?'])
-        elif drop_subs:
-            cmd.extend(['-map', '0:a:0', '-map', '0:v:0'])
-        else:
-            cmd.extend(['-map', '0'])
-
-        # Audio codec
-        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.get('has_video'):
-            if video_codec and video_codec != 'copy':
-                cmd.extend(['-c:v', video_codec])
-                # Add video quality if specified (only when re-encoding)
-                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.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
-    if format_opt:
-        ffmpeg_format = FORMAT_INFO.get(format_opt, {}).get('ffmpeg', format_opt)
-        cmd.extend(['-f', ffmpeg_format])
-
-    cmd.extend(['-y', output_path])
     return cmd
+
+

audio_splitter/formats.py

@@ -4,7 +4,7 @@
 from typing import Dict, Optional
 
 from .constants import (
-    FORMAT_INFO,
+    CONTAINER_NAMES,
     CONTAINER_INFO,
     CODEC_TO_CONTAINER_MAP,
     COMPATIBILITY_MATRIX,
@@ -22,7 +22,7 @@ def determine_default_format(container: Optional[str], codec: Optional[str]) ->
     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:
@@ -33,10 +33,10 @@ def determine_default_format(container: Optional[str], codec: Optional[str]) ->
 
     if codec and codec in CODEC_TO_CONTAINER_MAP:
         fmt = CODEC_TO_CONTAINER_MAP[codec]
-        if fmt in FORMAT_INFO:
+        if fmt in CONTAINER_NAMES:
             return fmt
 
-    if container in FORMAT_INFO:
+    if container in CONTAINER_NAMES:
         return container
 
     return None
@@ -47,7 +47,7 @@ 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
@@ -55,6 +55,10 @@ def determine_output_format(stream_info: Dict, user_format: Optional[str],
       - MP4 (M4A) otherwise
     """
     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:
@@ -63,14 +67,14 @@ def determine_output_format(stream_info: Dict, user_format: Optional[str],
             container = get_container_format(input_file)
             audio_codec = get_audio_codec(input_file)
             fmt = determine_default_format(container, audio_codec)
-            if fmt in FORMAT_INFO:
+            if fmt in CONTAINER_NAMES:
                 return fmt
         except Exception:
             pass
 
     # 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'
@@ -93,23 +97,25 @@ def validate_format_compatibility(
     Raises:
         ValueError: If the combination is incompatible.
     """
-    info = FORMAT_INFO.get(container)
+    info = next((c for c in CONTAINER_INFO if c['name'] == container), None)
     if not info:
         print(f"Warning: Unknown container '{container}'. Proceeding, but may fail.")
         return
 
     # Check if container is audio-only and video is present (unless dropped)
-    if info['audio_only'] and stream_info.get('has_video') and not drop_video:
+    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)."
         )
 
-    # Check if audio codec is supported
+    # Determine actual audio codec for validation
-    if audio_codec and audio_codec != 'copy':
+    # When 'copy' is used, we must still validate the input codec against the container
-        if not is_audio_codec_supported(container, audio_codec):
+    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"Container '{container}' does not support audio codec '{audio_codec}'. "
+                f"Container '{container}' does not support audio codec '{actual_audio_codec}'. "
                 f"Please choose a different container or audio codec."
             )
 
@@ -119,7 +125,11 @@ def validate_format_compatibility(
         if video_codec is None and input_file:
             from .ffmpeg import get_video_codec
             video_codec = get_video_codec(input_file)
-        if video_codec and video_codec != 'copy':
+        # 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}'. "

audio_splitter/handlers.py

@@ -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

web/backend/Dockerfile

@@ -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 \
         && \

web/backend/api/info.py

@@ -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}

web/backend/constants.py

@@ -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},
-}

web/backend/services/splitter.py

@@ -70,21 +70,9 @@ def run_split_task(task_id: str, tracklist: List[TracklistEntry], options: Dict[
 
         from audio_splitter.core import split_audio
 
-        # Detect attached picture and extract if applicable
+        # Cover image handling is now done internally by split_audio()
-        cover_image_path = None
+        # via the handler system (opustags for Opus, ffmpeg for others)
-        if not args.drop_video:
+        args.cover_image = None
-            from audio_splitter.ffmpeg import is_attached_picture, extract_cover_image, get_stream_info
-            input_path_str = str(input_path)
-            stream_info = get_stream_info(input_path_str)
-            if stream_info.get('has_video') and is_attached_picture(input_path_str):
-                cover_image_path = output_dir / 'cover.png'
-                if extract_cover_image(input_path_str, str(cover_image_path)):
-                    print(f"Extracted cover image for task {task_id}")
-                else:
-                    cover_image_path = None
-
-        # Attach cover image to args
-        args.cover_image = str(cover_image_path) if cover_image_path else None
 
         task_manager.update_task_with_progress(
             task_id, progress=10, message="Starting split..."

web/frontend/src/components/OptionsPanel.tsx

@@ -18,6 +18,8 @@ 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)
@@ -91,64 +93,12 @@ export const OptionsPanel: React.FC = () => {
   // --------------------------------------------------------------
   // Filter codec options based on selected container
   // --------------------------------------------------------------
-  const filteredAudioCodecs = useMemo(() => {
+  const { filteredAudioCodecs, filteredVideoCodecs } = useFilterCodecs(compatibility, options.container, codecs)
-    const entry = compatibility?.[options.container || '']
-    if (!entry) return codecs.filter(c => c.supports_transcoding)
-    const audioList = entry.audio
-    if (audioList === null) return codecs.filter(c => c.supports_transcoding)
-    return codecs.filter(c => c.supports_transcoding && audioList.includes(c.name))
-  }, [compatibility, options.container, codecs])
-
-  const filteredVideoCodecs = useMemo(() => {
-    const entry = compatibility?.[options.container || '']
-    if (!entry) return codecs.filter(c => c.supports_video)
-    const videoList = entry.video
-    if (videoList === null) return codecs.filter(c => c.supports_video)
-    return codecs.filter(c => c.supports_video && videoList.includes(c.name))
-  }, [compatibility, options.container, codecs])
 
   // --------------------------------------------------------------
   // Validate compatibility
   // --------------------------------------------------------------
-  useEffect(() => {
+  useFormatValidation(options, hasVideo, compatibility, containers, setFormatError)
-    const selectedContainer = containers.find(c => c.name === options.container)
-    if (selectedContainer?.audio_only && 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])
 
   // --------------------------------------------------------------
   // Handlers

web/frontend/src/hooks/useFilterCodecs.ts

@@ -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 }
+}

web/frontend/src/hooks/useFormatValidation.ts

@@ -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])
+}

web/frontend/src/types/index.ts

@@ -48,7 +48,6 @@ export interface ContainerInfo {
   name: string
   ffmpeg: string
   extension: string
-  audio_only: boolean
   supports_video: boolean
   supports_subs: boolean
 }
@@ -58,8 +57,7 @@ export interface CodecInfo {
   ffmpeg: string
   recommended_container: string
   recommended_extension: string
-  supports_transcoding: boolean
+  codec_type: 'audio' | 'video' | 'subtitle'
-  supports_video: boolean
 }
 
 export interface CompatibilityEntry {