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Normalize audio frame rate in AudioMixer output #1271

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Merged
richiemcilroy merged 2 commits into from
Oct 22, 2025
Merged

Normalize audio frame rate in AudioMixer output #1271

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ac61470
Normalize audio frame rate in AudioMixer output
richiemcilroy Oct 22, 2025
28eabb4
Fix audio frame duration calculation in mixer
richiemcilroy Oct 22, 2025
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12 changes: 10 additions & 2 deletions crates/recording/src/sources/audio_mixer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -322,7 +322,7 @@ impl AudioMixer {

source.buffer_last = Some((
timestamp,
Duration::from_secs_f64(frame.samples() as f64 / frame.rate() as f64),
Duration::from_secs_f64(frame.samples() as f64 / rate as f64),
));
source.buffer.push_back(AudioFrame::new(frame, timestamp));
}
Expand Down Expand Up @@ -400,7 +400,15 @@ impl AudioMixer {

let mut filtered = ffmpeg::frame::Audio::empty();
while self.abuffersink.sink().frame(&mut filtered).is_ok() {
let elapsed = Duration::from_secs_f64(self.samples_out as f64 / filtered.rate() as f64);
let output_rate_i32 = Self::INFO.rate();
let output_rate = output_rate_i32 as f64;

// Downstream encoders assume the mixer outputs at AudioMixer::INFO.rate().
// Normalize the frame metadata so we don't inherit whatever FFmpeg propagated
// from upstream sources (some CoreAudio devices report 16 kHz).
filtered.set_rate(output_rate_i32 as u32);

let elapsed = Duration::from_secs_f64(self.samples_out as f64 / output_rate);
let timestamp = start.instant() + start_timestamp.duration_since(start) + elapsed;

self.samples_out += filtered.samples();
Expand Down
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