private AdpcmDecoderContext GetAdpcmDecoderContext(long Position, long Size)
{
if (Size == 0)
{
return(null);
}
AdpcmDecoderContext Context = new AdpcmDecoderContext();
Context.Coefficients = new short[Size >> 1];
for (int Offset = 0; Offset < Size; Offset += 2)
{
Context.Coefficients[Offset >> 1] = Memory.ReadInt16(Position + Offset);
}
return(Context);
}
private AdpcmDecoderContext GetAdpcmDecoderContext(long position, long size)
{
if (size == 0)
{
return(null);
}
AdpcmDecoderContext context = new AdpcmDecoderContext();
context.Coefficients = new short[size >> 1];
for (int offset = 0; offset < size; offset += 2)
{
context.Coefficients[offset >> 1] = _memory.ReadInt16(position + offset);
}
return(context);
}
public static int[] Decode(byte[] Buffer, AdpcmDecoderContext Context)
{
int Samples = GetSamplesCountFromSize(Buffer.Length);
int[] Pcm = new int[Samples * 2];
short History0 = Context.History0;
short History1 = Context.History1;
int InputOffset = 0;
int OutputOffset = 0;
while (InputOffset < Buffer.Length)
{
byte Header = Buffer[InputOffset++];
int Scale = 0x800 << (Header & 0xf);
int CoeffIndex = (Header >> 4) & 7;
short Coeff0 = Context.Coefficients[CoeffIndex * 2 + 0];
short Coeff1 = Context.Coefficients[CoeffIndex * 2 + 1];
int FrameSamples = SamplesPerFrame;
if (FrameSamples > Samples)
{
FrameSamples = Samples;
}
int Value = 0;
for (int SampleIndex = 0; SampleIndex < FrameSamples; SampleIndex++)
{
int Sample;
if ((SampleIndex & 1) == 0)
{
Value = Buffer[InputOffset++];
Sample = (Value << 24) >> 28;
}
else
{
Sample = (Value << 28) >> 28;
}
int Prediction = Coeff0 * History0 + Coeff1 * History1;
Sample = (Sample * Scale + Prediction + 0x400) >> 11;
short SaturatedSample = DspUtils.Saturate(Sample);
History1 = History0;
History0 = SaturatedSample;
Pcm[OutputOffset++] = SaturatedSample;
Pcm[OutputOffset++] = SaturatedSample;
}
Samples -= FrameSamples;
}
Context.History0 = History0;
Context.History1 = History1;
return(Pcm);
}
