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Support for USB devices with 48-frame buffers.

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This commit is contained in:
Robin E. R. Davies
2025-08-07 22:23:40 -04:00
parent d5ae144266
commit f607aec6c0
1 changed files with 82 additions and 53 deletions
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src/AlsaDriver.cpp
+82 -53
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@@ -24,6 +24,7 @@
#include "pch.h"
#include "util.hpp"
#include <cmath>
#include "Finally.hpp"
#include <bit>
#include <memory>
@@ -56,6 +57,7 @@ using namespace pipedal;
namespace pipedal
{
#define TRACE_BUFFER_POSITIONS 1
static bool ShouldForceStereoChannels(snd_pcm_t *pcmHandle, snd_pcm_hw_params_t *hwParams, unsigned int channelsMin, unsigned int channelsMax)
{
// The problem: old IC2 drivers seem to return 1-8 channels, but 8 channels is non-functinal. The assumption is that legacy drivers
@@ -245,7 +247,41 @@ namespace pipedal
class AlsaDriverImpl : public AudioDriver
{
private:
void TraceBuffers(size_t framesInBuffers, char code = ' ');
struct BufferTrace
{
uint64_t time;
snd_pcm_sframes_t inAvail;
snd_pcm_sframes_t outAvail;
snd_pcm_sframes_t buffered;
snd_pcm_sframes_t total;
char code;
};
std::vector<BufferTrace> bufferTraces{1000};
size_t bufferTraceIndex = 0;
inline void TraceBufferPositions(size_t framesInBuffer, char code = ' ')
{
#if TRACE_BUFFER_POSITIONS
uint64_t time = std::chrono::duration_cast<std::chrono::microseconds>(std::chrono::steady_clock::now().time_since_epoch()).count();
auto inAvail = snd_pcm_avail_update(this->captureHandle);
auto outAvail = snd_pcm_avail_update(this->playbackHandle);
auto total = inAvail + outAvail + framesInBuffer;
bufferTraces[bufferTraceIndex++] = {
time,
inAvail,
outAvail,
(snd_pcm_sframes_t)framesInBuffer,
(snd_pcm_sframes_t)total,
code};
if (bufferTraceIndex == bufferTraces.size())
{
bufferTraceIndex = 0;
}
#endif
}
std::recursive_mutex restartMutex;
pipedal::CpuUse cpuUse;
@@ -257,8 +293,15 @@ namespace pipedal
#endif
uint32_t sampleRate = 0;
uint32_t bufferSize;
uint32_t numberOfBuffers;
uint32_t bufferSize = 0;
uint32_t numberOfBuffers = 0;
unsigned int capturePeriods = 0;
unsigned int playbackPeriods = 0;
uint32_t captureHardwarePeriodSize = 0;
uint32_t playbackHardwarePeriodSize = 0;
;
int playbackChannels = 0;
int captureChannels = 0;
@@ -357,8 +400,6 @@ namespace pipedal
snd_pcm_t *playbackHandle = nullptr;
snd_pcm_t *captureHandle = nullptr;
unsigned int periods = 0;
snd_pcm_hw_params_t *captureHwParams = nullptr;
snd_pcm_sw_params_t *captureSwParams = nullptr;
snd_pcm_hw_params_t *playbackHwParams = nullptr;
@@ -437,11 +478,14 @@ namespace pipedal
snd_pcm_hw_params_t *hwParams,
snd_pcm_sw_params_t *swParams,
int *channels,
unsigned int *periods)
unsigned int *periods,
unsigned int *hwPeriodSize)
{
int err;
snd_pcm_uframes_t stop_th;
bool isCaptureStream = strcmp(streamType, "capture") == 0;
if ((err = snd_pcm_hw_params_any(handle, hwParams)) < 0)
{
AlsaError(SS("No playback configurations available (" << snd_strerror(err) << ")"));
@@ -513,7 +557,7 @@ namespace pipedal
{
AlsaError(SS("Can't set period size to " << this->bufferSize << " (" << alsa_device_name << "/" << streamType << ")"));
}
this->bufferSize = effectivePeriodSize;
*hwPeriodSize = effectivePeriodSize;
*periods = this->numberOfBuffers;
dir = 0;
@@ -547,7 +591,7 @@ namespace pipedal
snd_pcm_sw_params_current(handle, swParams);
if (handle == this->captureHandle)
if (isCaptureStream)
{
if ((err = snd_pcm_sw_params_set_start_threshold(handle, swParams,
0)) < 0)
@@ -564,7 +608,7 @@ namespace pipedal
}
}
stop_th = *periods * this->bufferSize;
stop_th = *periods * *hwPeriodSize;
if (this->soft_mode)
{
stop_th = (snd_pcm_uframes_t)-1;
@@ -582,13 +626,19 @@ namespace pipedal
AlsaError(SS("Cannot set silence threshold for " << alsa_device_name));
}
if (handle == this->playbackHandle)
if (!isCaptureStream)
{
// For playback, set avail_min to one buffer size to minimize latency
// while ensuring we have enough buffered data to prevent underruns
snd_pcm_uframes_t playback_avail_min = this->bufferSize;
err = snd_pcm_sw_params_set_avail_min(
handle, swParams,
this->bufferSize * (*periods - this->numberOfBuffers + 1));
handle, swParams, playback_avail_min);
}
else
{
err = snd_pcm_sw_params_set_avail_min(
handle, swParams, this->bufferSize);
}
if (err < 0)
{
@@ -636,7 +686,8 @@ namespace pipedal
captureHwParams,
captureSwParams,
&captureChannels,
&this->periods);
&this->capturePeriods,
&this->captureHardwarePeriodSize);
}
if (this->playbackHandle)
{
@@ -647,7 +698,8 @@ namespace pipedal
playbackHwParams,
playbackSwParams,
&playbackChannels,
&this->periods);
&this->playbackPeriods,
&this->playbackHardwarePeriodSize);
}
#ifdef ALSADRIVER_CONFIG_DBG
@@ -1186,8 +1238,8 @@ namespace pipedal
}
captureFrameSize = captureSampleSize * captureChannels;
rawCaptureBuffer.resize(captureFrameSize * bufferSize);
memset(rawCaptureBuffer.data(), 0, captureFrameSize * bufferSize);
rawCaptureBuffer.resize(captureFrameSize * bufferSize * 2);
memset(rawCaptureBuffer.data(), 0, rawCaptureBuffer.size());
AllocateBuffers(captureBuffers, captureChannels);
}
@@ -1401,17 +1453,22 @@ namespace pipedal
{
validate_capture_handle();
memset(rawPlaybackBuffer.data(), 0, playbackFrameSize * bufferSize);
memset(rawPlaybackBuffer.data(), 0, rawPlaybackBuffer.size());
int retry = 0;
while (true)
{
auto avail = snd_pcm_avail(this->playbackHandle);
if (avail < 0)
{
if (avail == -EAGAIN)
{
return;
}
if (++retry >= 5) // kinda sus code. let's make sure we don't spin forever.
{
throw std::runtime_error("Timed out trying to fill the audio output buffer.");
}
int err = snd_pcm_prepare(playbackHandle);
if (err < 0)
{
@@ -1422,8 +1479,9 @@ namespace pipedal
}
if (avail == 0)
break;
if (avail > this->bufferSize)
avail = this->bufferSize;
if (avail * playbackFrameSize > this->rawPlaybackBuffer.size())
this->rawPlaybackBuffer.resize(avail * playbackFrameSize);
ssize_t err = WriteBuffer(playbackHandle, rawPlaybackBuffer.data(), avail);
if (err < 0)
@@ -1439,7 +1497,7 @@ namespace pipedal
try
{
TraceBuffers(framesRead,'w');
TraceBufferPositions(framesRead, 'w');
if (err == -EPIPE)
{
err = snd_pcm_prepare(playback_handle);
@@ -1471,7 +1529,7 @@ namespace pipedal
try
{
TraceBuffers(bufferedFrames,'r');
TraceBufferPositions(bufferedFrames, 'r');
if (err == -EPIPE)
{
@@ -1575,7 +1633,7 @@ namespace pipedal
{
snd_pcm_wait(captureHandle, 1);
}
TraceBuffers(framesRead);
TraceBufferPositions(framesRead);
} while (frames > 0);
return framesRead;
}
@@ -1659,7 +1717,7 @@ namespace pipedal
int err;
if ((err = snd_pcm_start(captureHandle)) < 0)
{
throw PiPedalStateException("Unable to start ALSA capture.");
throw PiPedalStateException(SS("Unable to start ALSA capture. " << snd_strerror(err)));
}
CrashGuardLock crashGuardLock;
@@ -1733,6 +1791,7 @@ namespace pipedal
this->driverHost->OnUnderrun();
recover_from_output_underrun(captureHandle, playbackHandle, err, framesRead);
framesRead = 0;
}
cpuUse.AddSample(ProfileCategory::Write);
}
@@ -2270,36 +2329,6 @@ namespace pipedal
#endif
}
struct BufferTrace
{
snd_pcm_sframes_t inAvail;
snd_pcm_sframes_t outAvail;
snd_pcm_sframes_t buffered;
snd_pcm_sframes_t total;
char code;
};
std::vector<BufferTrace> bufferTraces(1000);
size_t bufferTraceIndex;
void AlsaDriverImpl::TraceBuffers(size_t framesInBuffer,char code)
{
auto inAvail = snd_pcm_avail_update(this->captureHandle);
auto outAvail = snd_pcm_avail_update(this->playbackHandle);
auto total = inAvail + outAvail + framesInBuffer;
bufferTraces[bufferTraceIndex++] = {
inAvail,
outAvail,
(snd_pcm_sframes_t)framesInBuffer,
(snd_pcm_sframes_t)total,
code};
if (bufferTraceIndex == bufferTraces.size())
{
bufferTraceIndex = 0;
}
}
void FreeAlsaGlobals()
{
snd_config_update_free_global(); // to get a clean Valgrind report.