1 files changed, 46 insertions, 0 deletions
diff --git a/src/audio/audio.cc b/src/audio/audio.cc
index d044b00..f5bc4ab 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();
 }
 
@@ -73,12 +97,21 @@ 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;
 
   if (chunk_frames <= 0)
     return;
 
+  static int64_t g_total_render_calls = 0;
+  static int64_t g_total_frames_rendered = 0;
+  const int64_t frames_before = g_ring_buffer.get_total_written() / RING_BUFFER_CHANNELS;
+
   // Keep rendering small chunks until buffer is full enough
   while (true) {
     // First, try to flush any pending samples from previous partial writes
@@ -195,6 +228,19 @@ void audio_render_ahead(float music_time, float dt, float target_fill) {
       }
     }
   }
+
+  // DEBUG: Track actual frames rendered vs expected
+  const int64_t frames_after = g_ring_buffer.get_total_written() / RING_BUFFER_CHANNELS;
+  const int64_t actual_rendered = frames_after - frames_before;
+  g_total_render_calls++;
+  g_total_frames_rendered += actual_rendered;
+
+  if (g_total_render_calls % 600 == 0) {  // Every 10 seconds at 60fps
+    const float expected_frames = g_total_render_calls * (float)(chunk_frames);
+    const float drift_ms = (expected_frames - g_total_frames_rendered) / RING_BUFFER_SAMPLE_RATE * 1000.0f;
+    printf("[RENDER_DRIFT] calls=%lld expect=%.1f actual=%lld drift=%.2fms\n",
+           g_total_render_calls, expected_frames, g_total_frames_rendered, drift_ms);
+  }
 }
 
 float audio_get_playback_time() {