From b464969cd1f5dd4dceb996ad8410e2695ab477c4 Mon Sep 17 00:00:00 2001 From: skal Date: Sun, 15 Feb 2026 14:45:15 +0100 Subject: docs: document audio WAV drift bug investigation Root cause: audio_render_ahead() over-renders by 366ms per 10s, causing progressive timing drift in WAV files. Events appear early in viewer. Findings: - Renders 11,733 extra frames over 40s (331,533 vs 319,800 expected) - Ring buffer accumulates excess audio (~19 frames/iteration) - WAV dump reads exact 533 frames but renders ~552 frames per call - Results in -180ms drift at 60 beats visible in timeline viewer Debug changes: - Added render tracking to audio.cc to measure actual vs expected - Added drift printf to tracker.cc for kick/snare timing analysis - Added WAV sample rate detection to timeline viewer See doc/AUDIO_WAV_DRIFT_BUG.md for complete analysis and proposed fixes. Co-Authored-By: Claude Sonnet 4.5 --- src/audio/tracker.cc | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'src/audio/tracker.cc') diff --git a/src/audio/tracker.cc b/src/audio/tracker.cc index 37f0683..00c31e9 100644 --- a/src/audio/tracker.cc +++ b/src/audio/tracker.cc @@ -324,6 +324,14 @@ void tracker_update(float music_time_sec, float dt_music_sec) { } } + // DEBUG: Track kick/snare timing for drift investigation + if (event.sample_id == 0 || event.sample_id == 1) { // Assuming kick=0, snare=1 + const char* name = (event.sample_id == 0) ? "KICK " : "SNARE"; + const float delta_ms = (event_music_time - music_time_sec) * 1000.0f; + printf("[DRIFT] %s: music=%.4f expect=%.4f delta=%.2fms offset=%d\n", + name, music_time_sec, event_music_time, delta_ms, sample_offset); + } + trigger_note_event(event, sample_offset, volume_mult); active.next_event_idx++; } -- cgit v1.2.3