void iRenderer.decodeInitial(iAudioThread decoder)
{
int avail = handle.availableFrames;
if (avail < samplesPerFrame)
{
throw new ApplicationException();
}
int samples = samplesPerFrame;
var span = handle.memoryMap(out int offset, ref samples);
TimeSpan ts = decoder.decodeFrame(span);
handle.memoryCommit(offset, samples);
queue.enqueue(ts);
}
void iRenderer.handlePollResult(iAudioThread decoder, ReadOnlySpan <pollfd> pollHandles)
{
// In mpeg4 sample = what's in the sample rate, frame is much larger unit in the container, after decoding 1 frame can be 1024 samples = 4kb data = 21.33ms of audio.
// In ALSA, frame = what's in sample rate = 4 bytes for stereo, sample = 16 bit in out case, and what mpeg4 calls "frame" ALSA developers call "period".
// This code integrate them two together :-(
ePollResult pollResult = handle.getPollResult(pollHandles, pollHandlesCount);
int encodedFrames = decoder.encodedFrames;
if (pollResult == ePollResult.None || 0 == encodedFrames)
{
// Nothing to do here: either no encoded frames, or no space for decoded ones
return;
}
int alsaAvailableFrames = handle.availableFrames / samplesPerFrame;
if (alsaAvailableFrames <= 0)
{
return;
}
TimeSpan?playedFrame = queue.update(alsaAvailableFrames);
if (playedFrame.HasValue)
{
decoder.updateTimestamp(playedFrame.Value);
}
if (state == eState.Paused)
{
int samples = alsaAvailableFrames * samplesPerFrame;
var span = handle.memoryMap(out int offset, ref samples);
if (0 != samples % samplesPerFrame)
{
throw new ApplicationException($"ALSA mapped { samples } samples, incomplete count of frames");
}
int framesToCommit = samples / samplesPerFrame;
for (int p = 0; p < framesToCommit; p++)
{
span.Slice(p * samplesPerFrame * 2, samplesPerFrame * 2).Fill(0);
queue.enqueueSilence();
}
handle.memoryCommit(offset, samples);
return;
}
int enqueuedFrames = 0;
while (true)
{
int framesToCommit = Math.Min(encodedFrames, alsaAvailableFrames);
if (framesToCommit <= 0)
{
break;
}
int samples = framesToCommit * samplesPerFrame;
var span = handle.memoryMap(out int offset, ref samples);
if (0 != samples % samplesPerFrame)
{
throw new ApplicationException($"ALSA mapped { samples } samples, incomplete count of frames");
}
framesToCommit = samples / samplesPerFrame;
for (int p = 0; p < framesToCommit; p++)
{
TimeSpan ts = decoder.decodeFrame(span.Slice(p * samplesPerFrame * 2));
queue.enqueue(ts);
}
handle.memoryCommit(offset, samples);
alsaAvailableFrames -= framesToCommit;
encodedFrames -= framesToCommit;
enqueuedFrames += framesToCommit;
}
if (0 == enqueuedFrames)
{
Logger.logVerbose("Alsa player is idle: encodedFrames {0}, alsaAvailableFrames {1}, state {2}", encodedFrames, alsaAvailableFrames, handle.state);
return;
}
if (state == eState.Prepared && queue.isFull)
{
handle.start();
state = eState.Playing;
Logger.logInfo("Filled Alsa’s buffer and started audio playback; state {0}", handle.state);
}
/* else if( state == eState.Seek && queue.isFull )
* {
* decoder.seekCompleted();
* } */
// else Logger.logVerbose( "Enqueued {0} to Alsa; state {1}", enqueuedFrames.pluralString( "frame" ), handle.state );
}
