static int AdpcmMsExpandNibble(ref MsAdpcmState channel, int nibble)
{
int nibbleSign = nibble - (((nibble & 0x08) != 0) ? 0x10 : 0);
int predictor = ((channel.sample1 * channel.coeff1) + (channel.sample2 * channel.coeff2)) / 256 + (nibbleSign * channel.delta);
if (predictor < -32768)
{
predictor = -32768;
}
else if (predictor > 32767)
{
predictor = 32767;
}
channel.sample2 = channel.sample1;
channel.sample1 = predictor;
channel.delta = (adaptationTable[nibble] * channel.delta) / 256;
if (channel.delta < 16)
{
channel.delta = 16;
}
return(predictor);
}
// Convert buffer containing MS-ADPCM wav data to a 16-bit signed PCM buffer
internal static byte[] ConvertMsAdpcmToPcm(byte[] buffer, int offset, int count, int channels, int blockAlignment)
{
MsAdpcmState channel0 = new MsAdpcmState();
MsAdpcmState channel1 = new MsAdpcmState();
int blockPredictor;
int sampleCountFullBlock = ((blockAlignment / channels) - 7) * 2 + 2;
int sampleCountLastBlock = 0;
if ((count % blockAlignment) > 0)
{
sampleCountLastBlock = (((count % blockAlignment) / channels) - 7) * 2 + 2;
}
int sampleCount = ((count / blockAlignment) * sampleCountFullBlock) + sampleCountLastBlock;
var samples = new byte[sampleCount * sizeof(short) * channels];
int sampleOffset = 0;
bool stereo = channels == 2;
while (count > 0)
{
int blockSize = blockAlignment;
if (count < blockSize)
{
blockSize = count;
}
count -= blockAlignment;
int totalSamples = ((blockSize / channels) - 7) * 2 + 2;
if (totalSamples < 2)
{
break;
}
int offsetStart = offset;
blockPredictor = buffer[offset];
++offset;
if (blockPredictor > 6)
{
blockPredictor = 6;
}
channel0.coeff1 = adaptationCoeff1[blockPredictor];
channel0.coeff2 = adaptationCoeff2[blockPredictor];
if (stereo)
{
blockPredictor = buffer[offset];
++offset;
if (blockPredictor > 6)
{
blockPredictor = 6;
}
channel1.coeff1 = adaptationCoeff1[blockPredictor];
channel1.coeff2 = adaptationCoeff2[blockPredictor];
}
channel0.delta = buffer[offset];
channel0.delta |= buffer[offset + 1] << 8;
if ((channel0.delta & 0x8000) != 0)
{
channel0.delta -= 0x10000;
}
offset += 2;
if (stereo)
{
channel1.delta = buffer[offset];
channel1.delta |= buffer[offset + 1] << 8;
if ((channel1.delta & 0x8000) != 0)
{
channel1.delta -= 0x10000;
}
offset += 2;
}
channel0.sample1 = buffer[offset];
channel0.sample1 |= buffer[offset + 1] << 8;
if ((channel0.sample1 & 0x8000) != 0)
{
channel0.sample1 -= 0x10000;
}
offset += 2;
if (stereo)
{
channel1.sample1 = buffer[offset];
channel1.sample1 |= buffer[offset + 1] << 8;
if ((channel1.sample1 & 0x8000) != 0)
{
channel1.sample1 -= 0x10000;
}
offset += 2;
}
channel0.sample2 = buffer[offset];
channel0.sample2 |= buffer[offset + 1] << 8;
if ((channel0.sample2 & 0x8000) != 0)
{
channel0.sample2 -= 0x10000;
}
offset += 2;
if (stereo)
{
channel1.sample2 = buffer[offset];
channel1.sample2 |= buffer[offset + 1] << 8;
if ((channel1.sample2 & 0x8000) != 0)
{
channel1.sample2 -= 0x10000;
}
offset += 2;
}
if (stereo)
{
samples[sampleOffset] = (byte)channel0.sample2;
samples[sampleOffset + 1] = (byte)(channel0.sample2 >> 8);
samples[sampleOffset + 2] = (byte)channel1.sample2;
samples[sampleOffset + 3] = (byte)(channel1.sample2 >> 8);
samples[sampleOffset + 4] = (byte)channel0.sample1;
samples[sampleOffset + 5] = (byte)(channel0.sample1 >> 8);
samples[sampleOffset + 6] = (byte)channel1.sample1;
samples[sampleOffset + 7] = (byte)(channel1.sample1 >> 8);
sampleOffset += 8;
}
else
{
samples[sampleOffset] = (byte)channel0.sample2;
samples[sampleOffset + 1] = (byte)(channel0.sample2 >> 8);
samples[sampleOffset + 2] = (byte)channel0.sample1;
samples[sampleOffset + 3] = (byte)(channel0.sample1 >> 8);
sampleOffset += 4;
}
blockSize -= (offset - offsetStart);
if (stereo)
{
for (int i = 0; i < blockSize; ++i)
{
int nibbles = buffer[offset];
int sample = AdpcmMsExpandNibble(ref channel0, nibbles >> 4);
samples[sampleOffset] = (byte)sample;
samples[sampleOffset + 1] = (byte)(sample >> 8);
sample = AdpcmMsExpandNibble(ref channel1, nibbles & 0x0f);
samples[sampleOffset + 2] = (byte)sample;
samples[sampleOffset + 3] = (byte)(sample >> 8);
sampleOffset += 4;
++offset;
}
}
else
{
for (int i = 0; i < blockSize; ++i)
{
int nibbles = buffer[offset];
int sample = AdpcmMsExpandNibble(ref channel0, nibbles >> 4);
samples[sampleOffset] = (byte)sample;
samples[sampleOffset + 1] = (byte)(sample >> 8);
sample = AdpcmMsExpandNibble(ref channel0, nibbles & 0x0f);
samples[sampleOffset + 2] = (byte)sample;
samples[sampleOffset + 3] = (byte)(sample >> 8);
sampleOffset += 4;
++offset;
}
}
}
return(samples);
}