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Fix delay in alsa input stream

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badaix 2022-09-07 16:17:47 +02:00
parent 51a9f4b62b
commit f2225c1959
1 changed files with 74 additions and 3 deletions
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77
server/streamreader/alsa_stream.cpp
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@ -160,10 +160,33 @@ void AlsaStream::initAlsa()
if ((err = snd_pcm_hw_params(handle_, hw_params)) < 0)
throw SnapException("Can't set hardware parameters: " + string(snd_strerror(err)));
#if 0 // Period size test code
// snd_pcm_uframes_t period_size;
// if ((err = snd_pcm_hw_params_get_period_size(hw_params, &period_size, nullptr)) < 0)
// LOG(ERROR, LOG_TAG) << "Can't get min period size: " << snd_strerror(err) << "\n";
// else
// LOG(INFO, LOG_TAG) << "Period size: " << period_size << ", " << double(period_size) / double(sampleFormat_.rate()) * 1000. << " ms\n";
// period_size = sampleFormat_.msRate() * chunk_ms_;
// if ((err = snd_pcm_hw_params_set_period_size_near(handle_, hw_params, &period_size, 0)) < 0)
// LOG(ERROR, LOG_TAG) << "Can't set period size: " << snd_strerror(err) << "\n";
// else
// LOG(INFO, LOG_TAG) << "Period size: " << period_size << ", " << double(period_size) / double(sampleFormat_.rate()) * 1000. << " ms\n";
// chunk_ = std::make_unique<msg::PcmChunk>(sampleFormat_, 2*period_size, false);
// LOG(INFO, LOG_TAG) << "Chunk duration: " << chunk_->duration<std::chrono::milliseconds>().count() << "\n";
#endif
snd_pcm_hw_params_free(hw_params);
if ((err = snd_pcm_prepare(handle_)) < 0)
throw SnapException("Can't prepare audio interface for use: " + string(snd_strerror(err)));
if (snd_pcm_state(handle_) == SND_PCM_STATE_PREPARED)
{
if ((err = snd_pcm_start(handle_)) < 0)
throw SnapException("Failed to start PCM: " + string(snd_strerror(err)));
}
}
@ -222,12 +245,60 @@ void AlsaStream::do_read()
nextTick_ = std::chrono::steady_clock::now();
}
auto avail = snd_pcm_avail(handle_);
if (avail >= 0)
{
#if 0 // Some debug code
static long max_avail = 0;
if (avail > max_avail)
{
max_avail = avail;
LOG(INFO, LOG_TAG) << "Max Available: " << avail << ", " << double(avail) / double(sampleFormat_.rate()) * 1000. << " ms\n";
}
static utils::logging::TimeConditional cond(1s);
LOG(INFO, LOG_TAG) << cond << "Available: " << avail << ", " << double(avail) / double(sampleFormat_.rate()) * 1000. << " ms, max: " << double(max_avail) / double(sampleFormat_.rate()) * 1000. << " ms\n";
#endif
// check if enough data is available to read from alsa
if ((static_cast<int32_t>(chunk_->getFrameCount()) > avail))
{
// Calculate when there will be enough data available, add half chunk duration tolerance and try later
auto available = std::chrono::milliseconds(static_cast<size_t>(double(avail) / double(sampleFormat_.rate()) * 1000.));
auto missing = chunk_->duration<std::chrono::milliseconds>() - available;
LOG(INFO, LOG_TAG) << "Not enough data available: " << available.count() << " ms, missing: " << missing.count() << " ms, needed: " << chunk_->duration<std::chrono::milliseconds>().count() << " ms\n";
missing += chunk_->duration<std::chrono::milliseconds>() / 2;
resync(missing);
wait(read_timer_, missing, [this] { do_read(); });
return;
}
// check if there is too much data available, i.e. if we are far behind
else if (avail > static_cast<int32_t>(3*chunk_->getFrameCount()))
{
// Fast forward, by reading and dropping audio frames
// const auto newAvail = static_cast<int32_t>(chunk_->getFrameCount() + static_cast<uint32_t>(chunk_->format.msRate() * 20));
const auto newAvail = 1.5 * chunk_->getFrameCount();
LOG(INFO, LOG_TAG) << "Too many frames available, fast forwarding from " << avail << " frames (" << double(avail) / double(sampleFormat_.rate()) * 1000. << " ms) to " << newAvail << " frames (" << double(newAvail) / double(sampleFormat_.rate()) * 1000. << " ms)\n";
do
{
int count = snd_pcm_readi(handle_, chunk_->payload, std::min(chunk_->getFrameCount(), static_cast<uint32_t>(avail - newAvail)));
if (count <= 0)
{
// some read error happened, just break here, this will be handled properly later in the read loop
break;
}
avail -= count;
LOG(DEBUG, LOG_TAG) << "Read " << count << " frames (" << double(count) / double(sampleFormat_.rate()) * 1000. << " ms), available: " << avail << " frames (" << double(avail) / double(sampleFormat_.rate()) * 1000. << " ms)\n";
}
while (avail > newAvail);
}
}
int toRead = chunk_->payloadSize;
auto duration = chunk_->duration<std::chrono::nanoseconds>();
int len = 0;
do
{
int count = snd_pcm_readi(handle_, chunk_->payload + len, (toRead - len) / chunk_->format.frameSize());
snd_pcm_sframes_t count = snd_pcm_readi(handle_, chunk_->payload + len, (toRead - len) / chunk_->format.frameSize());
if (count == -EAGAIN)
{
LOG(INFO, LOG_TAG) << "No data availabale, playing silence.\n";
@ -292,7 +363,7 @@ void AlsaStream::do_read()
{
// LOG(DEBUG, LOG_TAG) << "Next read: " << std::chrono::duration_cast<std::chrono::milliseconds>(next_read).count() << "\n";
// synchronize reads to an interval of chunk_ms_
wait(read_timer_, nextTick_ - currentTick, [this] { do_read(); });
wait(read_timer_, next_read, [this] { do_read(); });
return;
}
else if (next_read >= -kResyncTolerance)
@ -306,7 +377,7 @@ void AlsaStream::do_read()
// reading chunk_ms_ took longer than chunk_ms_
resync(-next_read);
first_ = true;
wait(read_timer_, nextTick_ - currentTick, [this] { do_read(); });
do_read();
}
lastException_ = "";