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fix audiostream cutouts from openal buffer underrun #7456

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fix audiostream cutouts from openal buffer underrun #7456

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e4af84e
fix audiostream cutouts from openal buffer underrun
Goober5000 May 14, 2026
1245546
clang-tidy
Goober5000 May 14, 2026
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24 changes: 19 additions & 5 deletions code/sound/audiostr.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@
#include "sound/ffmpeg/FFmpegWaveFile.h"
#endif

#define MAX_STREAM_BUFFERS 4
constexpr size_t MAX_STREAM_BUFFERS = 8;

// status
#define ASF_FREE 0
Expand Down Expand Up @@ -438,7 +438,7 @@ bool AudioStream::WriteWaveData (uint size, uint *num_bytes_written, int service
const auto alFormat = openal_get_format(m_fileProps.bytes_per_sample * 8, m_fileProps.num_channels);

if ( !service ) {
for (int ib = 0; ib < MAX_STREAM_BUFFERS; ib++) {
for (auto &buffer_id : m_buffer_ids) {
num_bytes_read = m_pwavefile->Read(uncompressed_wave_data, m_cbBufSize);

// if looping then maybe reset wavefile and keep going
Expand All @@ -452,8 +452,8 @@ bool AudioStream::WriteWaveData (uint size, uint *num_bytes_written, int service
m_bReadingDone = 1;
break;
} else if (num_bytes_read > 0) {
OpenAL_ErrorCheck( alBufferData(m_buffer_ids[ib], alFormat, uncompressed_wave_data, num_bytes_read, m_fileProps.sample_rate), { fRtn = false; goto ErrorExit; } );
OpenAL_ErrorCheck( alSourceQueueBuffers(m_source_id, 1, &m_buffer_ids[ib]), { fRtn = false; goto ErrorExit; } );
OpenAL_ErrorCheck( alBufferData(buffer_id, alFormat, uncompressed_wave_data, num_bytes_read, m_fileProps.sample_rate), { fRtn = false; goto ErrorExit; } );
OpenAL_ErrorCheck( alSourceQueueBuffers(m_source_id, 1, &buffer_id), { fRtn = false; goto ErrorExit; } );

*num_bytes_written += num_bytes_read;
}
Expand Down Expand Up @@ -511,7 +511,7 @@ uint AudioStream::GetMaxWriteSize (void)

OpenAL_ErrorCheck( alGetSourcei(m_source_id, AL_BUFFERS_QUEUED, &q), return 0 );

if (!n && (q >= MAX_STREAM_BUFFERS)) //all buffers queued
if (!n && (q >= sz2i(MAX_STREAM_BUFFERS))) //all buffers queued
dwMaxSize = 0;

// nprintf(("Alan","Max write size: %d\n", dwMaxSize));
Expand Down Expand Up @@ -600,6 +600,20 @@ bool AudioStream::ServiceBuffer (void)
m_bPastLimit = true;
}

// Recover from buffer underrun: if the source stopped because the queue drained
// between service ticks, OpenAL will not auto-resume even after WriteWaveData
// queues more buffers. We have to call alSourcePlay again ourselves.
ALint state = AL_PLAYING;
OpenAL_ErrorPrint( alGetSourcei(m_source_id, AL_SOURCE_STATE, &state) );
if (state == AL_STOPPED && m_fPlaying && !m_bReadingDone) {
ALint queued = 0;
OpenAL_ErrorPrint( alGetSourcei(m_source_id, AL_BUFFERS_QUEUED, &queued) );
if (queued > 0) {
nprintf(("Sound", "SOUND => Audiostream underrun, restarting playback\n"));
OpenAL_ErrorPrint( alSourcePlay(m_source_id) );
}
}

if ( PlaybackDone() ) {
if ( m_bDestroy_when_faded == true ) {
SDL_UnlockMutex( write_lock );
Expand Down
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