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 short[] Decode(byte[] adpcm, short[] coefficients, GcAdpcmParameters config = null)
{
config = config ?? new GcAdpcmParameters {
SampleCount = ByteCountToSampleCount(adpcm.Length)
};
var pcm = new short[config.SampleCount];
if (config.SampleCount == 0)
{
return(pcm);
}
int frameCount = config.SampleCount.DivideByRoundUp(SamplesPerFrame);
int currentSample = 0;
int outIndex = 0;
int inIndex = 0;
short hist1 = config.History1;
short hist2 = config.History2;
for (int i = 0; i < frameCount; i++)
{
byte predictorScale = adpcm[inIndex++];
int scale = (1 << GetLowNibble(predictorScale)) * 2048;
int predictor = GetHighNibble(predictorScale);
short coef1 = coefficients[predictor * 2];
short coef2 = coefficients[predictor * 2 + 1];
int samplesToRead = Math.Min(SamplesPerFrame, config.SampleCount - currentSample);
for (int s = 0; s < samplesToRead; s++)
{
int adpcmSample = s % 2 == 0 ? GetHighNibbleSigned(adpcm[inIndex]) : GetLowNibbleSigned(adpcm[inIndex++]);
int distance = scale * adpcmSample;
int predictedSample = coef1 * hist1 + coef2 * hist2;
int correctedSample = predictedSample + distance;
int scaledSample = (correctedSample + 1024) >> 11;
short clampedSample = Clamp16(scaledSample);
hist2 = hist1;
hist1 = clampedSample;
pcm[outIndex++] = clampedSample;
currentSample++;
}
}
return(pcm);
}
