// Dst must be large enough to accept up to 512 samples (1024 for stereo)
private static unsafe void DecodeChunk(ContentStream stream, short *dst, ref Chunk c, bool stereo)
{
uint rem = c.FrameCount * (stereo ? 2u : 1);
if (c.Type == SMALL_TYPE)
{
// Local accumulators
short acc1 = c.Channel1, acc2 = c.Channel2;
// Read in 8 deltas at a time, and accumulate them
for (uint si = 0; si < rem; si += 8)
{
if (stereo)
{
dst[si] = (short)(acc1 + stream.ReadSByte());
dst[si + 1] = (short)(acc2 + stream.ReadSByte());
dst[si + 2] = (short)(dst[si] + stream.ReadSByte());
dst[si + 3] = (short)(dst[si + 1] + stream.ReadSByte());
dst[si + 4] = (short)(dst[si + 2] + stream.ReadSByte());
dst[si + 5] = (short)(dst[si + 3] + stream.ReadSByte());
dst[si + 6] = (short)(dst[si + 4] + stream.ReadSByte());
dst[si + 7] = (short)(dst[si + 5] + stream.ReadSByte());
acc1 = dst[si + 6];
acc2 = dst[si + 7];
}
else // mono
{
dst[si] = (short)(acc1 + stream.ReadSByte());
dst[si + 1] = (short)(dst[si] + stream.ReadSByte());
dst[si + 2] = (short)(dst[si + 1] + stream.ReadSByte());
dst[si + 3] = (short)(dst[si + 2] + stream.ReadSByte());
dst[si + 4] = (short)(dst[si + 3] + stream.ReadSByte());
dst[si + 5] = (short)(dst[si + 4] + stream.ReadSByte());
dst[si + 6] = (short)(dst[si + 5] + stream.ReadSByte());
dst[si + 7] = (short)(dst[si + 6] + stream.ReadSByte());
acc1 = dst[si + 7];
}
}
}
else if (c.Type == MED_TYPE)
{
// Local accumulators
short acc1 = c.Channel1, acc2 = c.Channel2;
// Used to hold the current 8 samples in their packed forms (8 samples in 12 bytes)
byte *tmp = stackalloc byte[12];
// Read/decode/accumulate 8 samples at a time
for (uint si = 0; si < rem; si += 8)
{
// Read the packed samples (12 bytes total, the types dont matter, chosen for brevity)
*((ulong *)tmp) = stream.ReadUInt64();
*((uint *)(tmp + 8)) = stream.ReadUInt32();
// Extract the packed values
int p1 = *((int *)tmp);
int p2 = *((int *)(tmp + 3));
int p3 = *((int *)(tmp + 6));
int p4 = *((int *)(tmp + 9));
// Extract the differences from the packed values (arith. right shift to get 2s compliment)
int d1 = ((p1 & 0xFFF) << 20) >> 20;
int d2 = ((p1 & 0xFFF000) << 8) >> 20;
int d3 = ((p2 & 0xFFF) << 20) >> 20;
int d4 = ((p2 & 0xFFF000) << 8) >> 20;
int d5 = ((p3 & 0xFFF) << 20) >> 20;
int d6 = ((p3 & 0xFFF000) << 8) >> 20;
int d7 = ((p4 & 0xFFF) << 20) >> 20;
int d8 = ((p4 & 0xFFF000) << 8) >> 20;
// Perform the accumulation
if (stereo)
{
dst[si] = (short)(acc1 + d1);
dst[si + 1] = (short)(acc2 + d2);
dst[si + 2] = (short)(dst[si] + d3);
dst[si + 3] = (short)(dst[si + 1] + d4);
dst[si + 4] = (short)(dst[si + 2] + d5);
dst[si + 5] = (short)(dst[si + 3] + d6);
dst[si + 6] = (short)(dst[si + 4] + d7);
dst[si + 7] = (short)(dst[si + 5] + d8);
acc1 = dst[si + 6];
acc2 = dst[si + 7];
}
else // mono
{
dst[si] = (short)(acc1 + d1);
dst[si + 1] = (short)(dst[si] + d2);
dst[si + 2] = (short)(dst[si + 1] + d3);
dst[si + 3] = (short)(dst[si + 2] + d4);
dst[si + 4] = (short)(dst[si + 3] + d5);
dst[si + 5] = (short)(dst[si + 4] + d6);
dst[si + 6] = (short)(dst[si + 5] + d7);
dst[si + 7] = (short)(dst[si + 6] + d8);
acc1 = dst[si + 7];
}
}
}
else // Full samples
{
// Directly read the samples
for (uint si = 0; si < rem; si += 8)
{
dst[si] = stream.ReadInt16();
dst[si + 1] = stream.ReadInt16();
dst[si + 2] = stream.ReadInt16();
dst[si + 3] = stream.ReadInt16();
dst[si + 4] = stream.ReadInt16();
dst[si + 5] = stream.ReadInt16();
dst[si + 6] = stream.ReadInt16();
dst[si + 7] = stream.ReadInt16();
}
}
// Save the channels
if (stereo)
{
c.Channel1 = dst[rem - 2];
c.Channel2 = dst[rem - 1];
}
else
{
c.Channel1 = dst[rem - 1];
}
}
