radoslav-orlov: "create lossy copies of lossless tracks" only recognized FLAC, even though ALAC/
WAV/AIFF/DSD are now quality-profile formats. the FLAC knowledge was hardcoded in 3 separate
places (the import path, the Lossy Converter scan, and the fix executor) — exactly how a format
gets added in one spot but not another.
kettui-style fix — one canonical seam both sites route through, instead of 3 more string edits:
- new core/quality/lossless.py: is_lossless_format / is_lossless_audio_path (pure; injects a
codec probe for the ambiguous .m4a/.mp4 — ALAC vs AAC — so the decision stays testable with no
I/O), LOSSLESS_FORMATS (single source of truth, derived-consistent with model.tier_score), and
the lossy_output_would_overwrite_source safety invariant.
- create_lossy_copy + the Lossy Converter scan + repair_worker._fix_missing_lossy_copy all route
through it. SQL pre-filters by candidate extensions, then each file is confirmed (probing .m4a).
- SAFETY: a lossy copy must never be written over its own source — an .m4a ALAC source + AAC
target lands on the same .m4a path, and ffmpeg runs with -y. all three sites now bail on the
overwrite case BEFORE ffmpeg (the existing delete-original guard was too late — the source was
already clobbered). dropped a vestigial mutagen FLAC import; updated FLAC-only UI strings.
19 tests: full seam coverage (formats, the .m4a ALAC/AAC probe branch, candidate extensions, the
overwrite guard), a tier-model consistency test that fails if the lossless set drifts, and import-
site wiring tests — WAV now converts (was rejected), and the .m4a-ALAC+AAC overwrite case proves
ffmpeg NEVER runs. 286 quality/import/repair tests green, ruff clean.
