/// <summary>
/// Decode gain parameters for the coded bands
/// </summary>
/// <param name="block"> the gainblock for the current band </param>
/// <param name="numBands"> amount of coded bands </param>
private int decodeGainControl(GainBlock block, int numBands)
{
int b;
for (b = 0; b <= numBands; b++)
{
block.gBlock[b].numPoints = br.read(3);
int[] level = block.gBlock[b].levCode;
int[] loc = block.gBlock[b].locCode;
for (int j = 0; j < block.gBlock[b].numPoints; j++)
{
level[j] = br.read(4);
loc[j] = br.read(5);
if (j > 0 && loc[j] <= loc[j - 1])
{
return(AT3_ERROR);
}
}
}
// Clear the unused blocks
for (; b < 4; b++)
{
block.gBlock[b].numPoints = 0;
}
return(0);
}
/// <summary>
/// Decode a Sound Unit
/// </summary>
/// <param name="snd"> the channel unit to be used </param>
/// <param name="output"> the decoded samples before IQMF in float representation </param>
/// <param name="channelNum"> channel number </param>
/// <param name="codingMode"> the coding mode (JOINT_STEREO or regular stereo/mono) </param>
private int decodeChannelSoundUnit(ChannelUnit snd, float[] output, int channelNum, int codingMode)
{
int ret;
GainBlock gain1 = snd.gainBlock[snd.gcBlkSwitch];
GainBlock gain2 = snd.gainBlock[1 - snd.gcBlkSwitch];
if (codingMode == JOINT_STEREO && channelNum == 1)
{
if (br.read(2) != 3)
{
Console.WriteLine(string.Format("JS mono Sound Unit id != 3"));
return(AT3_ERROR);
}
}
else
{
if (br.read(6) != 0x28)
{
Console.WriteLine(string.Format("Sound Unit id != 0x28"));
return(AT3_ERROR);
}
}
// number of coded QMF bands
snd.bandsCoded = br.read(2);
ret = decodeGainControl(gain2, snd.bandsCoded);
if (ret != 0)
{
return(ret);
}
snd.numComponents = decodeTonalComponents(snd.components, snd.bandsCoded);
if (snd.numComponents < 0)
{
return(snd.numComponents);
}
int numSubbands = decodeSpectrum(snd.spectrum);
// Merge the decoded spectrum and tonal components
int lastTonal = addTonalComponents(snd.spectrum, snd.numComponents, snd.components);
// calculate number of used MLT/QMF bands according to the amount of coded
// spectral lines
int numBands = (subband_tab[numSubbands] - 1) >> 8;
if (lastTonal >= 0)
{
numBands = max((lastTonal + 256) >> 8, numBands);
}
// Reconstruct time domain samples
for (int band = 0; band < 4; band++)
{
// Perform the IMDCT step without overlapping
if (band <= numBands)
{
imlt(snd.spectrum, band * 256, snd.imdctBuf, 0, (band & 1) != 0);
}
else
{
Arrays.Fill(snd.imdctBuf, 0, 512, 0f);
}
// gain compensation and overlapping
ctx.gaincCtx.gainCompensation(snd.imdctBuf, 0, snd.prevFrame, band * 256, gain1.gBlock[band], gain2.gBlock[band], 256, output, band * 256);
}
// Swap the gain control buffers for the next frame
snd.gcBlkSwitch ^= 1;
return(0);
}