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mcma-backend/app/infrastructure/metadata/cover_extractor.py
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Senko-san 0bb752f582
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feat: cover-art pipeline (§1D)
Resolve, store and serve album cover art.

Sources (tag-first, mirroring enrichment): embedded artwork extracted
offline via mutagen (ID3 APIC / FLAC+OGG Picture / MP4 covr), then Cover
Art Archive by release-group MBID as a network fallback. Resolution runs
inside MetadataEnrichmentService after album resolution, only when the
album has no cover yet (idempotent, never overwrites), and is best-effort
so a cover failure never affects enrichment status.

- CoverArt value object + CoverArtExtractor/CoverArtProvider ports
- MutagenCoverExtractor + CoverArtArchiveClient adapters
- AcoustID parser now captures release_group_mbid
- Covers stored via FileStorage at covers/{album_id}.{ext} (local + S3)
- AlbumRepository.set_cover_path
- Serve real covers: GET /api/v1/albums|tracks/{id}/cover (StreamUser,
  ?token=), Subsonic getCoverArt (placeholder fallback)
- has_cover flag on AlbumOut/TrackOut
- coverart_enabled / coverart_base_url settings
- tests: cover resolution units + release_group parse + DB-backed
  test_cover_api.py (139 green via make test-api)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-13 12:10:05 +03:00

112 lines
3.8 KiB
Python

"""MutagenCoverExtractor — pulls embedded cover art from a local audio file.
The offline-first cover source (mirrors the tag pre-pass): a well-tagged file
often already carries front-cover artwork (ID3 ``APIC``, FLAC/OGG picture
blocks, MP4 ``covr``). We read it without any network call. Parsing is blocking,
so it runs in a worker thread. Any failure degrades to ``None`` — never raises.
mutagen ships no type stubs, so its objects are handled as ``Any`` and accessed
defensively (``getattr``) — the format zoo doesn't fit one static shape anyway.
"""
import base64
from pathlib import Path
from typing import Any
import anyio
from mutagen import File as MutagenFile # type: ignore[attr-defined]
from mutagen.flac import Picture
from mutagen.mp4 import MP4Cover
from app.core.logging import get_logger
from app.domain.entities.cover import CoverArt
log = get_logger(__name__)
# MP4 cover format flag → MIME (mutagen exposes an int, not a content type).
_MP4_FORMATS: dict[int, str] = {
MP4Cover.FORMAT_JPEG: "image/jpeg",
MP4Cover.FORMAT_PNG: "image/png",
}
_FRONT_COVER = 3 # APIC/Picture "type" value for the front cover
class MutagenCoverExtractor:
"""Implements :class:`app.domain.ports.CoverArtExtractor`."""
async def extract(self, path: Path) -> CoverArt | None:
try:
return await anyio.to_thread.run_sync(self._extract_sync, path)
except Exception:
log.warning("cover_extract_failed", path=str(path))
return None
def _extract_sync(self, path: Path) -> CoverArt | None:
audio: Any = MutagenFile(str(path))
if audio is None:
return None
# FLAC / OGG-FLAC: typed picture blocks on the file object.
pictures = getattr(audio, "pictures", None)
if pictures:
cover = _from_picture(_front_or_first(pictures))
if cover is not None:
return cover
tags = audio.tags
if tags is None:
return None
# MP3 / anything with ID3 frames: APIC frames keyed as "APIC:...".
apics = [frame for frame in tags.values() if frame.__class__.__name__ == "APIC"]
if apics:
cover = _from_picture(_front_or_first(apics))
if cover is not None:
return cover
get = getattr(tags, "get", None)
if get is None:
return None
# MP4 / M4A: "covr" atom holds a list of MP4Cover (a bytes subclass).
covr = get("covr")
if covr:
mp4_cover = covr[0]
content_type = _MP4_FORMATS.get(getattr(mp4_cover, "imageformat", -1), "image/jpeg")
return CoverArt(data=bytes(mp4_cover), content_type=content_type)
# OGG Vorbis: base64 picture block in METADATA_BLOCK_PICTURE.
block = get("metadata_block_picture")
if block:
cover = _from_picture(_decode_vorbis_picture(block[0]))
if cover is not None:
return cover
return None
def _from_picture(picture: Any) -> CoverArt | None:
"""Build a :class:`CoverArt` from a mutagen picture/APIC frame, or ``None``."""
if picture is None:
return None
data = getattr(picture, "data", None)
if not data:
return None
mime = getattr(picture, "mime", None) or "image/jpeg"
return CoverArt(data=bytes(data), content_type=str(mime))
def _front_or_first(pictures: list[Any]) -> Any:
"""Prefer the front-cover picture (type 3), else the first available."""
for pic in pictures:
if getattr(pic, "type", None) == _FRONT_COVER:
return pic
return pictures[0] if pictures else None
def _decode_vorbis_picture(encoded: str) -> Any:
try:
return Picture(base64.b64decode(encoded)) # type: ignore[no-untyped-call]
except Exception:
return None