/// <summary>
/// This callback occurs when the sound device is ready to buffer more frames
/// </summary>
/// <param name="minFrameCount">The minimum amount of frames expected by the audio backend</param>
/// <param name="maxFrameCount">The maximum amount of frames that can be written to the audio backend</param>
private unsafe void WriteCallback(int minFrameCount, int maxFrameCount)
{
int bytesPerFrame = AudioStream.BytesPerFrame;
uint bytesPerSample = (uint)AudioStream.BytesPerSample;
int bufferedFrames = m_Buffer.Length / bytesPerFrame;
long bufferedSamples = m_Buffer.Length / bytesPerSample;
int frameCount = Math.Min(bufferedFrames, maxFrameCount);
if (frameCount == 0)
{
return;
}
SoundIOChannelAreas areas = AudioStream.BeginWrite(ref frameCount);
int channelCount = areas.ChannelCount;
byte[] samples = new byte[frameCount * bytesPerFrame];
m_Buffer.Read(samples, 0, samples.Length);
// This is a huge ugly block of code, but we save
// a significant amount of time over the generic
// loop that handles other channel counts.
// Mono
if (channelCount == 1)
{
SoundIOChannelArea area = areas.GetArea(0);
fixed(byte *srcptr = samples)
{
if (bytesPerSample == 1)
{
for (int frame = 0; frame < frameCount; frame++)
{
((byte *)area.Pointer)[0] = srcptr[frame * bytesPerFrame];
area.Pointer += area.Step;
}
}
else if (bytesPerSample == 2)
{
for (int frame = 0; frame < frameCount; frame++)
{
((short *)area.Pointer)[0] = ((short *)srcptr)[frame * bytesPerFrame >> 1];
area.Pointer += area.Step;
}
}
else if (bytesPerSample == 4)
{
for (int frame = 0; frame < frameCount; frame++)
{
((int *)area.Pointer)[0] = ((int *)srcptr)[frame * bytesPerFrame >> 2];
area.Pointer += area.Step;
}
}
else
{
for (int frame = 0; frame < frameCount; frame++)
{
Unsafe.CopyBlockUnaligned((byte *)area.Pointer, srcptr + (frame * bytesPerFrame), bytesPerSample);
area.Pointer += area.Step;
}
}
}
}
// Stereo
else if (channelCount == 2)
{
SoundIOChannelArea area1 = areas.GetArea(0);
SoundIOChannelArea area2 = areas.GetArea(1);
fixed(byte *srcptr = samples)
{
if (bytesPerSample == 1)
{
for (int frame = 0; frame < frameCount; frame++)
{
// Channel 1
((byte *)area1.Pointer)[0] = srcptr[(frame * bytesPerFrame) + 0];
// Channel 2
((byte *)area2.Pointer)[0] = srcptr[(frame * bytesPerFrame) + 1];
area1.Pointer += area1.Step;
area2.Pointer += area2.Step;
}
}
else if (bytesPerSample == 2)
{
for (int frame = 0; frame < frameCount; frame++)
{
// Channel 1
((short *)area1.Pointer)[0] = ((short *)srcptr)[(frame * bytesPerFrame >> 1) + 0];
// Channel 2
((short *)area2.Pointer)[0] = ((short *)srcptr)[(frame * bytesPerFrame >> 1) + 1];
area1.Pointer += area1.Step;
area2.Pointer += area2.Step;
}
}
else if (bytesPerSample == 4)
{
for (int frame = 0; frame < frameCount; frame++)
{
// Channel 1
((int *)area1.Pointer)[0] = ((int *)srcptr)[(frame * bytesPerFrame >> 2) + 0];
// Channel 2
((int *)area2.Pointer)[0] = ((int *)srcptr)[(frame * bytesPerFrame >> 2) + 1];
area1.Pointer += area1.Step;
area2.Pointer += area2.Step;
}
}
else
{
for (int frame = 0; frame < frameCount; frame++)
{
// Channel 1
Unsafe.CopyBlockUnaligned((byte *)area1.Pointer, srcptr + (frame * bytesPerFrame) + (0 * bytesPerSample), bytesPerSample);
// Channel 2
Unsafe.CopyBlockUnaligned((byte *)area2.Pointer, srcptr + (frame * bytesPerFrame) + (1 * bytesPerSample), bytesPerSample);
area1.Pointer += area1.Step;
area2.Pointer += area2.Step;
}
}
}
}
// Surround
else if (channelCount == 6)
{
SoundIOChannelArea area1 = areas.GetArea(0);
SoundIOChannelArea area2 = areas.GetArea(1);
SoundIOChannelArea area3 = areas.GetArea(2);
SoundIOChannelArea area4 = areas.GetArea(3);
SoundIOChannelArea area5 = areas.GetArea(4);
SoundIOChannelArea area6 = areas.GetArea(5);
fixed(byte *srcptr = samples)
{
if (bytesPerSample == 1)
{
for (int frame = 0; frame < frameCount; frame++)
{
// Channel 1
((byte *)area1.Pointer)[0] = srcptr[(frame * bytesPerFrame) + 0];
// Channel 2
((byte *)area2.Pointer)[0] = srcptr[(frame * bytesPerFrame) + 1];
// Channel 3
((byte *)area3.Pointer)[0] = srcptr[(frame * bytesPerFrame) + 2];
// Channel 4
((byte *)area4.Pointer)[0] = srcptr[(frame * bytesPerFrame) + 3];
// Channel 5
((byte *)area5.Pointer)[0] = srcptr[(frame * bytesPerFrame) + 4];
// Channel 6
((byte *)area6.Pointer)[0] = srcptr[(frame * bytesPerFrame) + 5];
area1.Pointer += area1.Step;
area2.Pointer += area2.Step;
area3.Pointer += area3.Step;
area4.Pointer += area4.Step;
area5.Pointer += area5.Step;
area6.Pointer += area6.Step;
}
}
else if (bytesPerSample == 2)
{
for (int frame = 0; frame < frameCount; frame++)
{
// Channel 1
((short *)area1.Pointer)[0] = ((short *)srcptr)[(frame * bytesPerFrame >> 1) + 0];
// Channel 2
((short *)area2.Pointer)[0] = ((short *)srcptr)[(frame * bytesPerFrame >> 1) + 1];
// Channel 3
((short *)area3.Pointer)[0] = ((short *)srcptr)[(frame * bytesPerFrame >> 1) + 2];
// Channel 4
((short *)area4.Pointer)[0] = ((short *)srcptr)[(frame * bytesPerFrame >> 1) + 3];
// Channel 5
((short *)area5.Pointer)[0] = ((short *)srcptr)[(frame * bytesPerFrame >> 1) + 4];
// Channel 6
((short *)area6.Pointer)[0] = ((short *)srcptr)[(frame * bytesPerFrame >> 1) + 5];
area1.Pointer += area1.Step;
area2.Pointer += area2.Step;
area3.Pointer += area3.Step;
area4.Pointer += area4.Step;
area5.Pointer += area5.Step;
area6.Pointer += area6.Step;
}
}
else if (bytesPerSample == 4)
{
for (int frame = 0; frame < frameCount; frame++)
{
// Channel 1
((int *)area1.Pointer)[0] = ((int *)srcptr)[(frame * bytesPerFrame >> 2) + 0];
// Channel 2
((int *)area2.Pointer)[0] = ((int *)srcptr)[(frame * bytesPerFrame >> 2) + 1];
// Channel 3
((int *)area3.Pointer)[0] = ((int *)srcptr)[(frame * bytesPerFrame >> 2) + 2];
// Channel 4
((int *)area4.Pointer)[0] = ((int *)srcptr)[(frame * bytesPerFrame >> 2) + 3];
// Channel 5
((int *)area5.Pointer)[0] = ((int *)srcptr)[(frame * bytesPerFrame >> 2) + 4];
// Channel 6
((int *)area6.Pointer)[0] = ((int *)srcptr)[(frame * bytesPerFrame >> 2) + 5];
area1.Pointer += area1.Step;
area2.Pointer += area2.Step;
area3.Pointer += area3.Step;
area4.Pointer += area4.Step;
area5.Pointer += area5.Step;
area6.Pointer += area6.Step;
}
}
else
{
for (int frame = 0; frame < frameCount; frame++)
{
// Channel 1
Unsafe.CopyBlockUnaligned((byte *)area1.Pointer, srcptr + (frame * bytesPerFrame) + (0 * bytesPerSample), bytesPerSample);
// Channel 2
Unsafe.CopyBlockUnaligned((byte *)area2.Pointer, srcptr + (frame * bytesPerFrame) + (1 * bytesPerSample), bytesPerSample);
// Channel 3
Unsafe.CopyBlockUnaligned((byte *)area3.Pointer, srcptr + (frame * bytesPerFrame) + (2 * bytesPerSample), bytesPerSample);
// Channel 4
Unsafe.CopyBlockUnaligned((byte *)area4.Pointer, srcptr + (frame * bytesPerFrame) + (3 * bytesPerSample), bytesPerSample);
// Channel 5
Unsafe.CopyBlockUnaligned((byte *)area5.Pointer, srcptr + (frame * bytesPerFrame) + (4 * bytesPerSample), bytesPerSample);
// Channel 6
Unsafe.CopyBlockUnaligned((byte *)area6.Pointer, srcptr + (frame * bytesPerFrame) + (5 * bytesPerSample), bytesPerSample);
area1.Pointer += area1.Step;
area2.Pointer += area2.Step;
area3.Pointer += area3.Step;
area4.Pointer += area4.Step;
area5.Pointer += area5.Step;
area6.Pointer += area6.Step;
}
}
}
}
// Every other channel count
else
{
SoundIOChannelArea[] channels = new SoundIOChannelArea[channelCount];
// Obtain the channel area for each channel
for (int i = 0; i < channelCount; i++)
{
channels[i] = areas.GetArea(i);
}
fixed(byte *srcptr = samples)
{
for (int frame = 0; frame < frameCount; frame++)
{
for (int channel = 0; channel < areas.ChannelCount; channel++)
{
// Copy channel by channel, frame by frame. This is slow!
Unsafe.CopyBlockUnaligned((byte *)channels[channel].Pointer, srcptr + (frame * bytesPerFrame) + (channel * bytesPerSample), bytesPerSample);
channels[channel].Pointer += channels[channel].Step;
}
}
}
}
AudioStream.EndWrite();
UpdateReleasedBuffers(samples.Length);
}