ExoPlayerBackend was the only backend not overriding the PlayerBackend trait's
set_audio_settings/audio_settings defaults, so the Settings > Audio controls
rendered on Android and silently did nothing — the default returns Ok(()) while
applying nothing, so the failure was invisible.
Rust owns what the values are (canonical 10-band ISO layout, preset curves,
normalization presets); Kotlin owns when the AudioEffect objects exist, since
that needs the live audio session id.
- settings.rs: audio_settings_jni_payload() sanitises (crossfade clamped, band
vector normalised) before serialising, so a malformed vector cannot reach the
Kotlin parser. JSON rather than a wide JNI signature, matching how load()
already passes subtitles — adding a field will not change the signature.
- ExoPlayerBackend: set_audio_settings/audio_settings over JNI; ExoPlayerState
gains the first command-side field (settings are pushed out, never reported).
- JellyTauPlayer.kt: Equalizer, LoudnessEnhancer, and gapless via
pauseAtEndOfMediaItems.
Three details that are easy to get wrong:
- Effects re-attach on onAudioSessionIdChanged. ExoPlayer rebuilds its audio
sink on a format change, which invalidates effects bound to the old session;
without this the EQ silently stops applying mid-queue.
- All effect work is posted to mainHandler rather than run inline. AudioEffect
construction from a player callback can re-enter the player and deadlock —
the same shape as the AutoplayDecision lock-scrutinee bug.
- Device equalizers expose a device-dependent band count (commonly 5) at fixed
centres, so the canonical 10 bands are resampled by nearest centre frequency.
resampleBands() is a pure @JvmStatic function so that mapping is testable
without a device.
Normalization is approximate, not parity: LoudnessEnhancer is a gain stage, not
a true EBU R128 normalizer like MPV's dynaudnorm. Recorded as such rather than
claimed as equivalent.
Crossfade is deliberately excluded — unimplemented on every platform and
blocked on mpv, so building it on Android alone would invert the parity gap.
Tests written first and observed failing (cannot find function
audio_settings_jni_payload) before the implementation: the payload contract is
pinned by tests because a serde rename would otherwise silently break the
Kotlin parser.
Not yet verified on a physical device — AudioEffect availability and band
layouts are device-specific. Requirements matrix marks these rows accordingly,
and flipping the trait default to Err(not_implemented()) is deferred until that
verification lands.
Adds a 10-band graphic equalizer to AudioSettings (enabled flag +
per-band dB gains, normalised to 10 entries and clamped to range).
Presets return gain curves; the settings page gains EQ UI. libmpv
applies the filter on Linux (Android parity pending). Old persisted
settings without EQ fields load as disabled + flat.
Also includes the requirements/traceability/ux-flows doc updates for
this feature and the home long-press routing (UR-058/DR-087).
TRACES: UR-027 | IR-020, DR-030 | UT-079, UT-080, UT-081, UT-082
- Add #[specta::specta] to all 201 #[tauri::command] functions.
- Derive specta::Type on all IPC DTOs (repository/types, settings, player/storage/
download command DTOs, player enums, jellyfin SessionInfo/NowPlayingItem/PlayState,
ThumbnailCacheStats, DownloadInfo, CacheConfig, etc.).
- Replace tauri::generate_handler! with a tauri_specta::Builder + collect_commands!
in lib.rs (exports bindings.ts in debug builds).
Two contract changes required by specta constraints (frontend migration follows):
- specta caps command arity at 10 args: download_item_and_start / download_item /
download_video now take a single request struct (params bundled, body unchanged
via destructuring).
- specta can't parse split serde rename_all: SessionInfo/NowPlayingItem/PlayState
switched to rename_all = "PascalCase" (Jellyfin deserialization preserved; these
now serialize PascalCase to the frontend).
cargo check --lib is clean (0 errors). Frontend migration to bindings.ts is the next step.
dtourolle