3 files changed, 48 insertions, 1 deletions
diff --git a/src/audio/audio.cc b/src/audio/audio.cc
index d044b00..a220fbb 100644
--- a/src/audio/audio.cc
+++ b/src/audio/audio.cc
@@ -57,11 +57,35 @@ void audio_init() {
   g_audio_backend->init();
 }
 
+float audio_get_required_prefill_time() {
+  return (float)RING_BUFFER_LOOKAHEAD_MS / 1000.0f;
+}
+
+bool audio_is_prefilled() {
+  const int buffered = g_ring_buffer.available_read();
+  const float buffered_time =
+      (float)buffered / (RING_BUFFER_SAMPLE_RATE * RING_BUFFER_CHANNELS);
+  const float required = audio_get_required_prefill_time();
+  return buffered_time >= (required - 0.001f); // 1ms tolerance
+}
+
 void audio_start() {
   if (g_audio_backend == nullptr) {
     printf("Cannot start: audio not initialized.\n");
     return;
   }
+
+#if !defined(STRIP_ALL)
+  if (!audio_is_prefilled()) {
+    const int buffered = g_ring_buffer.available_read();
+    const float buffered_ms = (float)buffered /
+                              (RING_BUFFER_SAMPLE_RATE * RING_BUFFER_CHANNELS) *
+                              1000.0f;
+    printf("WARNING: Audio buffer not pre-filled (%.1fms < %.1fms)\n",
+           buffered_ms, audio_get_required_prefill_time() * 1000.0f);
+  }
+#endif
+
   g_audio_backend->start();
 }
 
@@ -73,6 +97,12 @@ void audio_render_ahead(float music_time, float dt, float target_fill) {
 
   // Render in small chunks to keep synth time synchronized with tracker
   // Chunk size: one frame's worth of audio (~16.6ms @ 60fps)
+  // TODO(timing): CRITICAL BUG - Truncation here may cause 180ms drift over 63
+  // beats (int) cast loses fractional samples: 0.333 samples/frame * 2560
+  // frames = 853 samples = 27ms But observed drift is 180ms, so this is not the
+  // only source (27ms < 180ms) NOTE: This is NOT a float vs double precision
+  // issue - floats handle <500s times fine See also: tracker.cc BPM timing
+  // calculation
   const int chunk_frames = (int)(dt * RING_BUFFER_SAMPLE_RATE);
   const int chunk_samples = chunk_frames * RING_BUFFER_CHANNELS;
 
diff --git a/src/audio/audio.h b/src/audio/audio.h
index 9d521e6..beb994f 100644
--- a/src/audio/audio.h
+++ b/src/audio/audio.h
@@ -23,6 +23,12 @@ struct SpecHeader {
 void audio_init();
 void audio_start(); // Starts the audio device callback
 
+// Get required pre-fill time (matches ring buffer lookahead)
+float audio_get_required_prefill_time();
+
+// Check if buffer is sufficiently pre-filled
+bool audio_is_prefilled();
+
 // Ring buffer audio rendering (main thread fills buffer)
 // target_fill: Target buffer fill time in seconds (default:
 // RING_BUFFER_LOOKAHEAD_MS/1000)
diff --git a/src/audio/tracker.cc b/src/audio/tracker.cc
index 1c0a9b2..38c814d 100644
--- a/src/audio/tracker.cc
+++ b/src/audio/tracker.cc
@@ -193,7 +193,8 @@ static int get_free_pattern_slot() {
 // sample-accurate timing)
 // volume_mult: Additional volume multiplier (for humanization)
 static void trigger_note_event(const TrackerEvent& event,
-                               int start_offset_samples, float volume_mult = 1.0f) {
+                               int start_offset_samples,
+                               float volume_mult = 1.0f) {
 #if defined(DEBUG_LOG_TRACKER)
   // VALIDATION: Check sample_id bounds
   if (event.sample_id >= g_tracker_samples_count) {
@@ -234,6 +235,16 @@ static void trigger_note_event(const TrackerEvent& event,
 }
 
 void tracker_update(float music_time_sec, float dt_music_sec) {
+  // TODO(timing): CRITICAL BUG - Events trigger ~180ms early over 63 beats @
+  // BPM=90 Observed: Beat 63 snare at 41.82s in WAV, should be at 42.00s (180ms
+  // drift) NOTE: This is NOT a float vs double precision issue - floats handle
+  // <500s times fine Root cause unknown - suspects:
+  //   1. Systematic bias in time calculation (not random accumulation)
+  //   2. Truncation in audio.cc:103 chunk_frames = (int)(dt * sample_rate)
+  //   3. BPM calculation precision below (unit_duration_sec)
+  //   4. Mismatch between tracker time and actual sample rendering
+  // See also: audio.cc sample rendering truncation
+
   // Unit-less timing: 1 unit = 4 beats (by convention)
   const float BEATS_PER_UNIT = 4.0f;
   const float unit_duration_sec =