private unsafe List<FlacSubFrameData> AllocOuputMemory()
{
if (_destBuffer == null || _destBuffer.Length < (Header.Channels * Header.BlockSize))
_destBuffer = new int[Header.Channels * Header.BlockSize];
if (_residualBuffer == null || _residualBuffer.Length < (Header.Channels * Header.BlockSize))
_residualBuffer = new int[Header.Channels * Header.BlockSize];
var output = new List<FlacSubFrameData>();
for (var c = 0; c < Header.Channels; c++)
{
fixed (int* ptrDestBuffer = _destBuffer, ptrResidualBuffer = _residualBuffer)
{
_handle1 = GCHandle.Alloc(_destBuffer, GCHandleType.Pinned);
_handle2 = GCHandle.Alloc(_residualBuffer, GCHandleType.Pinned);
var data = new FlacSubFrameData
{
DestinationBuffer = _destBuffer.AsMemory(c * Header.BlockSize),
ResidualBuffer = _residualBuffer.AsMemory(c * Header.BlockSize)
};
output.Add(data);
}
}
return output;
}
public static void ProcessResidual(FlacBitReader reader, FlacFrameHeader header, FlacSubFrameData data,
int order, int partitionOrder, FlacResidualCodingMethod codingMethod)
{
data.Content.UpdateSize(partitionOrder);
var isRice2 = codingMethod == FlacResidualCodingMethod.PartitionedRice2;
var riceParameterLength = isRice2 ? 5 : 4;
var escapeCode = isRice2 ? 31 : 15; //11111 : 1111
var partitionCount = 1 << partitionOrder; //2^partitionOrder -> There will be 2^order partitions. -> "order" = partitionOrder in this case
var residualBuffer = data.ResidualBuffer.Span.Slice(order);
for (var p = 0; p < partitionCount; p++)
{
int samplesPerPartition;
if (partitionOrder == 0)
{
samplesPerPartition = header.BlockSize - order;
}
else if (p > 0)
{
samplesPerPartition = header.BlockSize >> partitionOrder;
}
else
{
samplesPerPartition = (header.BlockSize >> partitionOrder) - order;
}
var riceParameter = reader.ReadBits(riceParameterLength);
data.Content.Parameters[p] = (int)riceParameter;
if (riceParameter >= escapeCode)
{
var raw = reader.ReadBits(5); //raw is always 5 bits (see ...(+5))
data.Content.RawBits[p] = (int)raw;
for (var i = 0; i < samplesPerPartition; i++)
{
var sample = reader.ReadBitsSigned((int)raw);
residualBuffer[i] = sample;
}
}
else
{
ReadFlacRiceBlock(reader, samplesPerPartition, (int)riceParameter, residualBuffer);
}
residualBuffer = residualBuffer.Slice(samplesPerPartition);
}
}
