private static void ReadSpectra(BitReader reader, Channel channel)
{
int[] values = channel.SpectraValuesBuffer;
Array.Clear(channel.QuantizedSpectra, 0, channel.QuantizedSpectra.Length);
int maxHuffPrecision = Tables.MaxHuffPrecision(channel.Config.HighSampleRate);
for (int i = 0; i < channel.CodedQuantUnits; i++)
{
int subbandCount = Tables.QuantUnitToCoeffCount[i];
int precision = channel.Precisions[i] + 1;
if (precision <= maxHuffPrecision)
{
HuffmanCodebook huff = Tables.HuffmanSpectrum[channel.CodebookSet[i]][precision][Tables.QuantUnitToCodebookIndex[i]];
int groupCount = subbandCount >> huff.ValueCountPower;
for (int j = 0; j < groupCount; j++)
{
values[j] = ReadHuffmanValue(huff, reader);
}
DecodeHuffmanValues(channel.QuantizedSpectra, Tables.QuantUnitToCoeffIndex[i], subbandCount, huff, values);
}
else
{
int subbandIndex = Tables.QuantUnitToCoeffIndex[i];
for (int j = subbandIndex; j < Tables.QuantUnitToCoeffIndex[i + 1]; j++)
{
channel.QuantizedSpectra[j] = reader.ReadSignedInt(precision);
}
}
}
}
private static void ReadVlcDeltaOffsetWithBaseline(BitReader reader, Channel channel, int[] baseline, int baselineLength)
{
int[] sf = channel.ScaleFactors;
int baseValue = reader.ReadOffsetBinary(5, BitReader.OffsetBias.Negative);
int bitLength = reader.ReadInt(2) + 1;
HuffmanCodebook codebook = Tables.HuffmanScaleFactorsUnsigned[bitLength];
int unitCount = Math.Min(channel.Block.ExtensionUnit, baselineLength);
sf[0] = reader.ReadInt(bitLength);
for (int i = 1; i < unitCount; i++)
{
int delta = Unpack.ReadHuffmanValue(codebook, reader);
sf[i] = (sf[i - 1] + delta) & (codebook.ValueMax - 1);
}
for (int i = 0; i < unitCount; i++)
{
sf[i] += baseValue + baseline[i];
}
for (int i = unitCount; i < channel.Block.ExtensionUnit; i++)
{
sf[i] = reader.ReadInt(5);
}
}
public static int ReadHuffmanValue(HuffmanCodebook huff, BitReader reader, bool signed = false)
{
int code = reader.PeekInt(huff.MaxBitSize);
byte value = huff.Lookup[code];
int bits = huff.Bits[value];
reader.Position += bits;
return(signed ? Bit.SignExtend32(value, huff.ValueBits) : value);
}
private static void ReadVlcDistanceToBaseline(BitReader reader, Channel channel, int[] baseline, int baselineLength)
{
int[] sf = channel.ScaleFactors;
int bitLength = reader.ReadInt(2) + 2;
HuffmanCodebook codebook = Tables.HuffmanScaleFactorsSigned[bitLength];
int unitCount = Math.Min(channel.Block.ExtensionUnit, baselineLength);
for (int i = 0; i < unitCount; i++)
{
int distance = Unpack.ReadHuffmanValue(codebook, reader, true);
sf[i] = (baseline[i] + distance) & 31;
}
for (int i = unitCount; i < channel.Block.ExtensionUnit; i++)
{
sf[i] = reader.ReadInt(5);
}
}
private static void ReadVlcDeltaOffset(BitReader reader, Channel channel)
{
int weightIndex = reader.ReadInt(3);
byte[] weights = ScaleFactorWeights[weightIndex];
int[] sf = channel.ScaleFactors;
int baseValue = reader.ReadInt(5);
int bitLength = reader.ReadInt(2) + 3;
HuffmanCodebook codebook = Tables.HuffmanScaleFactorsUnsigned[bitLength];
sf[0] = reader.ReadInt(bitLength);
for (int i = 1; i < channel.Block.ExtensionUnit; i++)
{
int delta = Unpack.ReadHuffmanValue(codebook, reader);
sf[i] = (sf[i - 1] + delta) & (codebook.ValueMax - 1);
}
for (int i = 0; i < channel.Block.ExtensionUnit; i++)
{
sf[i] += baseValue - weights[i];
}
}
private static void DecodeHuffmanValues(int[] spectrum, int index, int bandCount, HuffmanCodebook huff, int[] values)
{
int valueCount = bandCount >> huff.ValueCountPower;
int mask = (1 << huff.ValueBits) - 1;
for (int i = 0; i < valueCount; i++)
{
int value = values[i];
for (int j = 0; j < huff.ValueCount; j++)
{
spectrum[index++] = Bit.SignExtend32(value & mask, huff.ValueBits);
value >>= huff.ValueBits;
}
}
}