// GenerateMetrics
public byte[] DecodeFromSymbolBits(byte[] bytSymbolBits)
{
// Normally called with bytSymboBits padded with 16 0 symbols tagged on to "flush" decoder
// Number of Output bytes = (bytSymbolsBits.length - 16)/16
Int32 intMetric = 0;
byte[] bytOutput = new byte[bytSymbolBits.Length / 16 - 1];
Int32 ptrOutput = 0;
Int32 intBitcnt = 0;
Int32[] intMets = new Int32[4];
Int32 intBestmetric = default(Int32);
Int32 intBestState = default(Int32);
Int32 i = default(Int32);
stcState[,] stcState = new stcState[2, 64];
Int32 ptrCurrent = 0;
Int32 ptrNext = 1;
int intSymbolsPtr = 0;
// Initialize starting metrics to prefer 0 state
stcState[ptrCurrent, 0].metric = 0;
for (i = 1; i <= 63; i++) {
stcState[ptrCurrent, i].metric = -999999;
}
stcState[ptrCurrent, 0].path = 0;
for (intBitcnt = 0; intBitcnt <= 8 * bytOutput.Length - 1; intBitcnt++) {
intMets[0] = aryMettab[0, bytSymbolBits[intSymbolsPtr]] + aryMettab[0, bytSymbolBits[intSymbolsPtr + 1]];
// mets[0] = mettab[0][symbols[0]] + mettab[0][symbols[1]];
intMets[1] = aryMettab[0, bytSymbolBits[intSymbolsPtr]] + aryMettab[1, bytSymbolBits[intSymbolsPtr + 1]];
// mets[1] = mettab[0][symbols[0]] + mettab[1][symbols[1]];
intMets[2] = aryMettab[1, bytSymbolBits[intSymbolsPtr]] + aryMettab[0, bytSymbolBits[intSymbolsPtr + 1]];
// mets[2] = mettab[1][symbols[0]] + mettab[0][symbols[1]];
intMets[3] = aryMettab[1, bytSymbolBits[intSymbolsPtr]] + aryMettab[1, bytSymbolBits[intSymbolsPtr + 1]];
// mets[3] = mettab[1][symbols[0]] + mettab[1][symbols[1]];
intSymbolsPtr += 2;
// Do the Butterfly calcs here Implemented as a loop vs Macro
for (i = 0; i <= 31; i++) {
int intM0 = 0;
int intM1 = 0;
int sym = bytBtfIndx[i];
// ACS for 0 branch
intM0 = stcState[ptrCurrent, i].metric + intMets[sym];
intM1 = stcState[ptrCurrent, i + 32].metric + intMets[3 ^ sym];
if (intM0 > intM1) {
stcState[ptrNext, 2 * i].metric = intM0;
stcState[ptrNext, 2 * i].path = stcState[ptrCurrent, i].path << 1;
} else {
stcState[ptrNext, 2 * i].metric = intM1;
stcState[ptrNext, 2 * i].path = (stcState[ptrCurrent, i + 32].path << 1) | Convert.ToUInt32(1);
}
// ACS for 1 branch
intM0 = stcState[ptrCurrent, i].metric + intMets[3 ^ sym];
intM1 = stcState[ptrCurrent, i + 32].metric + intMets[sym];
if (intM0 > intM1) {
stcState[ptrNext, 2 * i + 1].metric = intM0;
stcState[ptrNext, 2 * i + 1].path = stcState[ptrCurrent, i].path << 1;
} else {
stcState[ptrNext, 2 * i + 1].metric = intM1;
stcState[ptrNext, 2 * i + 1].path = (stcState[ptrCurrent, i + 32].path << 1) | Convert.ToUInt32(1);
}
}
// Swap current and next states
if ((intBitcnt & 1) != 0) {
ptrCurrent = 0;
ptrNext = 1;
} else {
ptrCurrent = 1;
ptrNext = 0;
}
if (intBitcnt > bytSymbolBits.Length - 7) {
// In tail, poison non-zero nodes
for (i = 1; i <= 63; i += 2) {
stcState[ptrCurrent, i].metric = -9999999;
}
}
// Produce output every 8 bits once path memory is full
if (((intBitcnt % 8) == 5) & intBitcnt > 32) {
// Find current best path
intBestmetric = stcState[ptrCurrent, 0].metric;
intBestState = 0;
for (i = 1; i <= 63; i++) {
if (stcState[ptrCurrent, i].metric > intBestmetric) {
intBestmetric = stcState[ptrCurrent, i].metric;
intBestState = i;
}
}
//Debug.WriteLine("Beststate:" & intBestState.ToString & " metric=" & stcState(ptrCurrent, intBestState).metric.ToString & " path=" & stcState(ptrCurrent, intBestState).path.ToString)
bytOutput[ptrOutput] = Convert.ToByte(stcState[ptrCurrent, intBestState].path >> 24);
ptrOutput += 1;
}
}
// Output remaining bits from 0 state
if (intBitcnt % 8 != 6) {
stcState[ptrCurrent, 0].path = stcState[ptrCurrent, 0].path << (6 - (intBitcnt % 8));
}
bytOutput[ptrOutput] = Convert.ToByte(stcState[ptrCurrent, 0].path >> 24);
ptrOutput += 1;
bytOutput[ptrOutput] = Convert.ToByte(0xff & stcState[ptrCurrent, 0].path >> 16);
ptrOutput += 1;
bytOutput[ptrOutput] = Convert.ToByte(0xff & stcState[ptrCurrent, 0].path >> 8);
ptrOutput += 1;
bytOutput[ptrOutput] = Convert.ToByte(0xff & stcState[ptrCurrent, 0].path);
intMetric = stcState[ptrCurrent, 0].metric;
return bytOutput;
}
