public static byte[] Encode(short[] pcm, short[] coefs, GcAdpcmParameters config = null)
{
config = config ?? new GcAdpcmParameters();
int sampleCount = config.SampleCount == -1 ? pcm.Length : config.SampleCount;
var adpcm = new byte[SampleCountToByteCount(sampleCount)];
/* Execute encoding-predictor for each frame */
var pcmBuffer = new short[2 + SamplesPerFrame];
var adpcmBuffer = new byte[BytesPerFrame];
pcmBuffer[0] = config.History2;
pcmBuffer[1] = config.History1;
int frameCount = sampleCount.DivideByRoundUp(SamplesPerFrame);
var buffers = new AdpcmEncodeBuffers();
for (int frame = 0; frame < frameCount; frame++)
{
int samplesToCopy = Math.Min(sampleCount - frame * SamplesPerFrame, SamplesPerFrame);
Array.Copy(pcm, frame * SamplesPerFrame, pcmBuffer, 2, samplesToCopy);
Array.Clear(pcmBuffer, 2 + samplesToCopy, SamplesPerFrame - samplesToCopy);
DspEncodeFrame(pcmBuffer, SamplesPerFrame, adpcmBuffer, coefs, buffers);
Array.Copy(adpcmBuffer, 0, adpcm, frame * BytesPerFrame, SampleCountToByteCount(samplesToCopy));
pcmBuffer[0] = pcmBuffer[14];
pcmBuffer[1] = pcmBuffer[15];
config.Progress?.ReportAdd(1);
}
return(adpcm);
}
public static void DspEncodeFrame(short[] pcmInOut, int sampleCount, byte[] adpcmOut, short[] coefsIn,
AdpcmEncodeBuffers b = null)
{
b = b ?? new AdpcmEncodeBuffers();
for (int i = 0; i < 8; i++)
{
b.Coefs[i][0] = coefsIn[i * 2];
b.Coefs[i][1] = coefsIn[i * 2 + 1];
}
/* Iterate through each coef set, finding the set with the smallest error */
for (int i = 0; i < 8; i++)
{
DspEncodeCoef(pcmInOut, sampleCount, b.Coefs[i], b.PcmOut[i], b.AdpcmOut[i], out b.Scale[i],
out b.TotalDistance[i]);
}
int bestCoef = 0;
double min = double.MaxValue;
for (int i = 0; i < 8; i++)
{
if (b.TotalDistance[i] < min)
{
min = b.TotalDistance[i];
bestCoef = i;
}
}
/* Write converted samples */
for (int s = 0; s < sampleCount; s++)
{
pcmInOut[s + 2] = (short)b.PcmOut[bestCoef][s + 2];
}
/* Write predictor and scale */
adpcmOut[0] = CombineNibbles(bestCoef, b.Scale[bestCoef]);
/* Zero remaining samples */
for (int s = sampleCount; s < 14; s++)
{
b.AdpcmOut[bestCoef][s] = 0;
}
/* Write output samples */
for (int i = 0; i < 7; i++)
{
adpcmOut[i + 1] = CombineNibbles(b.AdpcmOut[bestCoef][i * 2], b.AdpcmOut[bestCoef][i * 2 + 1]);
}
}
