fix(spectool): pre-fill audio buffer before audio_start() in play mode

Trigger voice and render ahead before starting the audio device to
avoid "Audio buffer not pre-filled" warning and silent playback.

handoff(Claude): spectool play now produces sound correctly.

1 files changed, 5 insertions, 1 deletions

diff --git a/tools/spectool.cc b/tools/spectool.cc
index bd17dfc..c3aebb2 100644
--- a/tools/spectool.cc
+++ b/tools/spectool.cc
@@ -237,7 +237,6 @@ int play_spec(const char* in_path) {
 
   PlatformState platform_state = platform_init(false, 100, 100);
   audio_init();
-  audio_start();
   Spectrogram spec;
   spec.spectral_data_a = spec_data.data();
   spec.spectral_data_b =
@@ -247,6 +246,11 @@ int play_spec(const char* in_path) {
   int spec_id = synth_register_spectrogram(&spec);
   synth_trigger_voice(spec_id, 0.7f, 0.0f);
 
+  // Pre-fill ring buffer before starting audio device
+  const float prefill = audio_get_required_prefill_time();
+  audio_render_ahead(0.0f, prefill);
+
+  audio_start();
   printf("Playing... Press Ctrl+C to exit.\n");
   while (synth_get_active_voice_count() > 0 &&
          !platform_should_close(&platform_state)) {