private static void WriteSpectra(BitWriter writer, CriHcaChannel channel, int subFrame)
{
for (int i = 0; i < channel.CodedScaleFactorCount; i++)
{
int resolution = channel.Resolution[i];
int quantizedSpectra = channel.QuantizedSpectra[subFrame][i];
if (resolution == 0)
{
continue;
}
if (resolution < 8)
{
int bits = CriHcaTables.QuantizeSpectrumBits[resolution][quantizedSpectra + 8];
writer.Write(CriHcaTables.QuantizeSpectrumValue[resolution][quantizedSpectra + 8], bits);
}
else if (resolution < 16)
{
int bits = CriHcaTables.QuantizedSpectrumMaxBits[resolution] - 1;
writer.Write(Math.Abs(quantizedSpectra), bits);
if (quantizedSpectra != 0)
{
writer.Write(quantizedSpectra > 0 ? 0 : 1, 1);
}
}
}
}
private static void CalculateGain(CriHcaChannel channel)
{
for (int i = 0; i < channel.CodedScaleFactorCount; i++)
{
channel.Gain[i] = DequantizerScalingTable[channel.ScaleFactors[i]] * QuantizerStepSize[channel.Resolution[i]];
}
}
public CriHcaFrame(HcaInfo hca)
{
Hca = hca;
ChannelType[] channelTypes = GetChannelTypes(hca);
Channels = new CriHcaChannel[hca.ChannelCount];
for (int i = 0; i < Channels.Length; i++)
{
Channels[i] = new CriHcaChannel
{
Type = channelTypes[i],
CodedScaleFactorCount = channelTypes[i] == StereoSecondary
? hca.BaseBandCount
: hca.BaseBandCount + hca.StereoBandCount
};
}
AthCurve = hca.UseAthCurve ? ScaleAthCurve(hca.SampleRate) : new byte[SamplesPerSubFrame];
}
private static void CalculateOptimalDeltaLength(CriHcaChannel channel)
{
bool emptyChannel = true;
for (int i = 0; i < channel.CodedScaleFactorCount; i++)
{
if (channel.ScaleFactors[i] != 0)
{
emptyChannel = false;
break;
}
}
if (emptyChannel)
{
channel.HeaderLengthBits = 3;
channel.ScaleFactorDeltaBits = 0;
return;
}
int minDeltaBits = 6;
int minLength = 3 + 6 * channel.CodedScaleFactorCount;
for (int deltaBits = 1; deltaBits < 6; deltaBits++)
{
int maxDelta = (1 << (deltaBits - 1)) - 1;
int length = 3 + 6;
for (int band = 1; band < channel.CodedScaleFactorCount; band++)
{
int delta = channel.ScaleFactors[band] - channel.ScaleFactors[band - 1];
length += Math.Abs(delta) > maxDelta ? deltaBits + 6 : deltaBits;
}
if (length < minLength)
{
minLength = length;
minDeltaBits = deltaBits;
}
}
channel.HeaderLengthBits = minLength;
channel.ScaleFactorDeltaBits = minDeltaBits;
}
private static bool ReadScaleFactors(CriHcaChannel channel, BitReader reader)
{
channel.ScaleFactorDeltaBits = reader.ReadInt(3);
if (channel.ScaleFactorDeltaBits == 0)
{
Array.Clear(channel.ScaleFactors, 0, channel.ScaleFactors.Length);
return(true);
}
if (channel.ScaleFactorDeltaBits >= 6)
{
for (int i = 0; i < channel.CodedScaleFactorCount; i++)
{
channel.ScaleFactors[i] = reader.ReadInt(6);
}
return(true);
}
return(DeltaDecode(reader, channel.ScaleFactorDeltaBits, 6, channel.CodedScaleFactorCount, channel.ScaleFactors));
}
private static void WriteScaleFactors(BitWriter writer, CriHcaChannel channel)
{
int deltaBits = channel.ScaleFactorDeltaBits;
var scales = channel.ScaleFactors;
writer.Write(deltaBits, 3);
if (deltaBits == 0)
{
return;
}
if (deltaBits == 6)
{
for (int i = 0; i < channel.CodedScaleFactorCount; i++)
{
writer.Write(scales[i], 6);
}
return;
}
writer.Write(scales[0], 6);
int maxDelta = (1 << (deltaBits - 1)) - 1;
int escapeValue = (1 << deltaBits) - 1;
for (int i = 1; i < channel.CodedScaleFactorCount; i++)
{
int delta = scales[i] - scales[i - 1];
if (Math.Abs(delta) > maxDelta)
{
writer.Write(escapeValue, deltaBits);
writer.Write(scales[i], 6);
}
else
{
writer.Write(maxDelta + delta, deltaBits);
}
}
}
