fix: keep pcm stream continuous

cai

2026-07-07 a62af4b377643d3b76318ee782763b3833b27456

 src/main.rs

@@ -12,7 +12,7 @@
};

use anyhow::{Context, Result, anyhow};
use audio::{AudioDiagnostics, PcmFrame, load_pre_recorded_frames};
use audio::{AudioDiagnostics, load_pre_recorded_frames};
use base64::{Engine as _, engine::general_purpose};
use futures_util::StreamExt;
use libwebrtc::{
@@ -1343,45 +1343,54 @@
        .trim()
        .to_ascii_lowercase();
    let frames = if format == "pcm_s16le" {
        let frame_alignment_bytes = pcm_s16le_frame_alignment_bytes(
            audio_chunk
        let sample_rate = audio_chunk.sample_rate.unwrap_or(TARGET_SAMPLE_RATE_HZ);
        let channels = audio_chunk
                .channels
                .unwrap_or(u32::from(TARGET_NUM_CHANNELS)),
        )?;
        let (aligned_payload, dropped_tail_bytes) = take_aligned_pcm_payload(
            &mut state.pcm_audio_buffer,
            .unwrap_or(u32::from(TARGET_NUM_CHANNELS));
        if state.pcm_stream_decoder.is_none() {
            state.pcm_stream_decoder = Some(audio::PcmS16leStreamDecoder::new(
                sample_rate,
                channels,
                TARGET_SAMPLE_RATE_HZ,
                TARGET_NUM_CHANNELS,
            )?);
        }
        state.pcm_stream_network_chunk_count =
            state.pcm_stream_network_chunk_count.saturating_add(1);
        let stream_result = state
            .pcm_stream_decoder
            .as_mut()
            .expect("pcm stream decoder initialized")
            .push_bytes(
            &payload,
            frame_alignment_bytes,
                sample_rate,
                channels,
            audio_chunk.last.unwrap_or(false),
        );
        if dropped_tail_bytes > 0 {
            )?;
        if stream_result.dropped_tail_bytes > 0 {
            warn!(
                call_id = %call_id,
                trace_id = %trace_id,
                turn_id = %turn.turn_id,
                chunk_seq = audio_chunk.chunk_seq.unwrap_or_default(),
                dropped_tail_bytes,
                dropped_tail_bytes = stream_result.dropped_tail_bytes,
                "runtime helper stream_audio_pcm_unaligned_tail_dropped"
            );
        }
        if aligned_payload.is_empty() {
        if stream_result.frames.is_empty() {
            warn!(
                call_id = %call_id,
                trace_id = %trace_id,
                turn_id = %turn.turn_id,
                chunk_seq = audio_chunk.chunk_seq.unwrap_or_default(),
                buffered_bytes = state.pcm_audio_buffer.len(),
                "runtime helper stream_audio_pcm_waiting_for_sample_boundary"
                buffered_source_bytes = stream_result.buffered_source_bytes,
                buffered_source_samples = stream_result.buffered_source_samples,
                network_chunk_count = state.pcm_stream_network_chunk_count,
                "runtime helper stream_audio_pcm_waiting_for_20ms_frame"
            );
            return Ok(0);
        }
        pcm_s16le_payload_to_frames(
            &aligned_payload,
            audio_chunk.sample_rate.unwrap_or(TARGET_SAMPLE_RATE_HZ),
            audio_chunk
                .channels
                .unwrap_or(u32::from(TARGET_NUM_CHANNELS)),
        )?
        stream_result.frames
    } else if matches!(format.as_str(), "mp3" | "mpeg" | "wav") {
        state.encoded_audio_buffer.extend_from_slice(&payload);
        match audio::decode_audio_bytes_to_frames(
@@ -1473,6 +1482,34 @@
        sleep_until(pacing_started_at + Duration::from_millis(((index + 1) as u64) * 20)).await;
    }
    if audio_chunk.last.unwrap_or(false) {
        let mut debug_source_path = None;
        let mut debug_pcm_wav_path = None;
        let mut debug_pcm_wav_size_bytes = None;
        if format == "pcm_s16le" {
            if let (Some(debug_dump_dir), Some(decoder)) = (
                bridge_config.audio_debug_dump_dir.as_deref(),
                state.pcm_stream_decoder.as_ref(),
            ) {
                match decoder.write_debug_dump(
                    debug_dump_dir,
                    call_id,
                    &format!("stream-reply-{}", turn.turn_id),
                ) {
                    Ok(debug_dump) => {
                        debug_source_path = debug_dump.debug_source_path;
                        debug_pcm_wav_path = debug_dump.debug_pcm_wav_path;
                        debug_pcm_wav_size_bytes = debug_dump.debug_pcm_wav_size_bytes;
                    }
                    Err(error) => warn!(
                        call_id = %call_id,
                        trace_id = %trace_id,
                        turn_id = %turn.turn_id,
                        error = %safe_error(&error.to_string()),
                        "runtime helper stream_audio_pcm_debug_dump_failed"
                    ),
                }
            }
        }
        emit_activity(
            call_id,
            trace_id,
@@ -1485,94 +1522,17 @@
                "replyPlaybackMode": state.reply_playback_mode.as_str(),
                "format": format.as_str(),
                "chunkSeq": audio_chunk.chunk_seq,
                "networkChunkCount": state.pcm_stream_network_chunk_count,
                "debugSourcePath": debug_source_path,
                "debugPcmWavPath": debug_pcm_wav_path,
                "debugPcmWavSizeBytes": debug_pcm_wav_size_bytes,
                "sampleRate": audio_chunk.sample_rate,
                "channels": audio_chunk.channels,
                "replyTotalAfterVadEndMs": turn_pipeline_started_at.elapsed().as_millis() as u64,
            }),
        );
    }
    Ok(frames.len())
}

fn pcm_s16le_payload_to_frames(
    payload: &[u8],
    sample_rate: u32,
    channels: u32,
) -> Result<Vec<PcmFrame>> {
    audio::pcm_s16le_bytes_to_frames(
        payload,
        sample_rate,
        channels,
        TARGET_SAMPLE_RATE_HZ,
        TARGET_NUM_CHANNELS,
    )
}

fn pcm_s16le_frame_alignment_bytes(channels: u32) -> Result<usize> {
    if channels == 0 {
        return Err(anyhow!("pcm_s16le channel count is zero"));
    }
    let channel_count = usize::try_from(channels)
        .map_err(|_| anyhow!("unsupported pcm_s16le channel count {channels}"))?;
    Ok(2 * channel_count)
}

fn take_aligned_pcm_payload(
    buffer: &mut Vec<u8>,
    payload: &[u8],
    frame_alignment_bytes: usize,
    last: bool,
) -> (Vec<u8>, usize) {
    let alignment = frame_alignment_bytes.max(2);
    buffer.extend_from_slice(payload);
    let aligned_len = buffer.len() - buffer.len() % alignment;
    let aligned_payload = if aligned_len == 0 {
        Vec::new()
    } else {
        buffer.drain(..aligned_len).collect()
    };
    let dropped_tail_bytes = if last && !buffer.is_empty() {
        let dropped = buffer.len();
        buffer.clear();
        dropped
    } else {
        0
    };
    (aligned_payload, dropped_tail_bytes)
}

#[cfg(test)]
mod pcm_stream_tests {
    use super::take_aligned_pcm_payload;

    #[test]
    fn take_aligned_pcm_payload_buffers_split_sample_bytes() {
        let mut buffer = Vec::new();

        let (first, dropped) = take_aligned_pcm_payload(&mut buffer, &[0x01], 2, false);
        assert!(first.is_empty());
        assert_eq!(0, dropped);
        assert_eq!(vec![0x01], buffer);

        let (second, dropped) = take_aligned_pcm_payload(&mut buffer, &[0x02, 0x03], 2, false);
        assert_eq!(vec![0x01, 0x02], second);
        assert_eq!(0, dropped);
        assert_eq!(vec![0x03], buffer);

        let (third, dropped) = take_aligned_pcm_payload(&mut buffer, &[0x04], 2, true);
        assert_eq!(vec![0x03, 0x04], third);
        assert_eq!(0, dropped);
        assert!(buffer.is_empty());
    }

    #[test]
    fn take_aligned_pcm_payload_drops_final_half_sample() {
        let mut buffer = Vec::new();

        let (payload, dropped) =
            take_aligned_pcm_payload(&mut buffer, &[0x01, 0x02, 0x03], 2, true);
        assert_eq!(vec![0x01, 0x02], payload);
        assert_eq!(1, dropped);
        assert!(buffer.is_empty());
    }
}

fn trim_ascii_whitespace(value: &[u8]) -> &[u8] {
@@ -1950,7 +1910,8 @@
    audio_chunk_count: u64,
    device_output_count: u64,
    encoded_audio_buffer: Vec<u8>,
    pcm_audio_buffer: Vec<u8>,
    pcm_stream_decoder: Option<audio::PcmS16leStreamDecoder>,
    pcm_stream_network_chunk_count: u64,
}

impl Default for RuntimeTurnStreamState {
@@ -1964,7 +1925,8 @@
            audio_chunk_count: 0,
            device_output_count: 0,
            encoded_audio_buffer: Vec::new(),
            pcm_audio_buffer: Vec::new(),
            pcm_stream_decoder: None,
            pcm_stream_network_chunk_count: 0,
        }
    }
}