feedBack/lib
Byron Gamatos 939c98214b
feat(song-info): publish the playable stem list so stems can preload (fixes the 698ms freeze) (#972)
* feat(song-info): publish the playable stem list, so stems can preload

The stems plugin could only learn its stem list from the highway's WS `ready`,
which arrives once the highway is already up. So it fetched, decoded, and then
handed every stem's PCM to its audio worklet — copying the WHOLE SONG — with the
player already on screen.

For a 4-minute 6-stem pack that is over half a GIGABYTE of memcpy, in one frame,
on the main thread. Measured on a real load: a 698 ms frame, right as the
song-credits card appeared, with the venue video visibly stopping. That is the
"the video pauses when the author appears" report.

GET /api/song/{f}?stems=1 now returns the same list — [{id, url, default}] plus
full_mix_url — so the plugin can start the whole load at `song:loading`, before
the highway (and the venue) is drawn, where a stalled frame costs nothing.
Nothing about the work changes; only WHEN.

Opt-in via the query param so the library's own metadata calls — the hot path —
pay nothing. Deliberately NOT stored in the metadata cache: that is a
fixed-column table, and widening it would mean a schema migration plus a stale
row for every song already scanned, to cache something that is a plain manifest
read on an already-unpacked pack.

The safety property: REST and the WS must publish the SAME list. If they
disagreed the plugin would preload a graph and then throw it away and rebuild —
strictly worse than not preloading. So both now resolve `default` through one
shared helper (stem_default_on, extracted from load_song), and a test rebuilds
the WS's payload from load_song and requires the REST helper to produce the
identical list, rather than pinning either against a snapshot.

Also pinned: the mixdown is lifted OUT of the stem list (spec 5.3 — `full` is
not a layer; listing it beside the instruments would play the whole song on top
of the stems) while staying reachable as full_mix_url, a single-`full` pack keeps
it as its only playable stem, and an unreadable pack yields an empty list rather
than failing the request. Full suite 2608 passed.

Consumed by feedBack-plugin-stems (preloadSong).

* fix(song-info): call load_song for the stem payload — do not reimplement it

CodeRabbit caught a real bug, and it would have hit most real libraries.

load_song() falls back to the DEPRECATED `original_audio:` key when a pack has no
reserved `full` stem — which is every pack written before feedpak 1.15.0. My
payload rebuilt the full-mix rule from extract_meta and returned None for those:
REST would say "no full mix" while the WS said there was one.

Worse than a wrong field: the plugin would preload a graph WITHOUT the pristine
mix and — because the stem signature still matched — never rebuild. Unity
playback would silently downgrade to the lossy stem recombination.

That is exactly the drift this PR claims to prevent, and my test had a hole: I
only covered packs that carry a `full` stem.

So stop reimplementing. The payload now calls load_song, whose LoadedSloppak
already carries the partitioned stems and the resolved full mix, and builds the
URLs exactly as ws_highway does. Drift is now impossible by construction rather
than by agreement. extract_meta is reverted to its original shape (it never
needed to change), and the shared stem_default_on helper stays as the one place
`default: off` is resolved.

Tests rewritten to compare against load_song — the WS's own function — for a
reserved-`full` pack, a LEGACY original_audio pack (the case that was broken), and
a single-`full` pack. Also documents the `?stems=1` contract in CHANGELOG.md.
Full suite green.
2026-07-15 00:36:13 +02:00
..
routers feat(song-info): publish the playable stem list so stems can preload (fixes the 698ms freeze) (#972) 2026-07-15 00:36:13 +02:00
acoustid_match.py feat(enrichment): AcoustID audio-fingerprint identification (opt-in) (#759) 2026-07-05 00:17:43 +02:00
appconfig.py refactor(server): extract /api/tunings into routers/tunings.py + lib/appconfig.py (R3) (#858) 2026-07-11 01:43:19 +02:00
appstate.py refactor(server): carve the library scanner into lib/scan.py (R3b) (#901) 2026-07-12 01:26:02 +02:00
audio_effects_db.py refactor(server): extract AudioEffectsMappingDB into lib/audio_effects_db.py (R3) (#831) 2026-07-10 14:30:05 +02:00
audio.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
builtin_content.py refactor(server): carve builtin-content seeding into lib/builtin_content.py (R3b) (#900) 2026-07-12 00:50:50 +02:00
demo_mode.py fix(demo): the janitor re-entry guard actually works now (#902) (#909) 2026-07-12 11:30:53 +02:00
diagnostics_bundle.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
diagnostics_hardware.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
diagnostics_redact.py fix(tests): isolate plugin routes modules + redact .feedpak filenames (#736) 2026-07-03 13:01:07 +02:00
dlc_paths.py perf(paths): resolve the library root once, not on every path check (#966) 2026-07-14 19:48:39 +02:00
drums.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
enrichment.py fix(sloppak): the full mix is a stem — drop the invented original_audio key (#946) 2026-07-13 12:22:42 -04:00
env_compat.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
gp2midi.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
gp2notation.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
gp2rs_gpx.py feat(gp_autosync): piecewise time-warp helpers + refine_sync onset pass (#787) 2026-07-05 20:08:19 +02:00
gp2rs.py fix(gp2rs): write beat times at 6-decimal precision so imported tempo matches Guitar Pro (#819) 2026-07-10 13:12:10 +02:00
gp8_audio_sync.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
gp_autosync.py fix(gp_autosync): slope-constrained DTW steps — stop path collapse on riff-based songs (#791) 2026-07-05 23:12:31 +02:00
jsonc.py feat(core): read .jsonc data files (strip C-style comments) (feedpak-spec §8) 2026-06-20 14:10:04 -07:00
library_registry.py refactor(server): extract library + collections routes + the provider registry (R3) (#866) 2026-07-11 14:56:12 +02:00
logging_setup.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
loosefolder.py Improve wording in terminology cleanup 2026-06-16 19:43:45 +01:00
lyrics_transcribe.py fix: remote transcription posts to /transcribe, not /align (stem-splitter#17) (#959) 2026-07-14 01:58:24 -04:00
mb_match.py feat(enrichment): alias-aware scoring — auto-confirm non-Latin-primary artists (#772) 2026-07-05 01:11:38 +02:00
metadata_db.py feat(library): effective genre falls back to MusicBrainz enrichment (#949) 2026-07-13 16:53:06 +02:00
midi_import.py feat(drums): capture velocities alongside times in unmapped-percussion reporting (#808) 2026-07-07 23:58:49 +02:00
notation_lift.py fix: correctly import and notate multi-staff (piano/keys) tracks from GP8 (#692) 2026-07-02 08:40:20 +02:00
notation.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
progression.py Improve wording in terminology cleanup 2026-06-16 19:43:45 +01:00
reqfields.py refactor(server): extract the playlists routes into routers/playlists.py (R3) (#841) 2026-07-10 19:58:09 +02:00
safepath.py perf(paths): resolve the library root once, not on every path check (#966) 2026-07-14 19:48:39 +02:00
scan_worker.py refactor(server): extract MetadataDB into lib/metadata_db.py (R3) (#830) 2026-07-10 14:18:59 +02:00
scan.py refactor(server): carve the library scanner into lib/scan.py (R3b) (#901) 2026-07-12 01:26:02 +02:00
sloppak.py feat(song-info): publish the playable stem list so stems can preload (fixes the 698ms freeze) (#972) 2026-07-15 00:36:13 +02:00
song_score.py Clean release snapshot 2026-06-16 18:47:13 +02:00
song.py fix(gp-import): correct bass string count, lead/rhythm roles, preview note count (#601) 2026-06-26 18:58:35 +02:00
songmeta.py library: opt-in gap-fill — write confirmed missing metadata into the pack (R4a) (#724) 2026-07-02 20:52:11 +02:00
tailwind_rebuild.py fix(tailwind): stop the dev server rewriting a tracked file (#911) (#918) 2026-07-12 13:25:16 +02:00
tones.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
tunings.py Harden freqs_to_midis against NaN/Inf; badges read exact tuningMidis 2026-07-12 15:24:39 -05:00
vocal_pitch.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
wem_decode.py rename: slopsmith → feedBack, byron → got-feedBack (#537) 2026-06-23 11:03:01 +02:00
xp.py Clean release snapshot 2026-06-16 18:47:13 +02:00