void ReadAllocation(IMpegFrame frame, int[] rateTable)
{
var _subBandCount = rateTable.Length;
if (_jsbound > _subBandCount)
{
_jsbound = _subBandCount;
}
Array.Clear(_allocation[0], 0, SBLIMIT);
Array.Clear(_allocation[1], 0, SBLIMIT);
int sb = 0;
for (; sb < _jsbound; sb++)
{
var table = _allocLookupTable[rateTable[sb]];
var bits = table[0];
for (int ch = 0; ch < _channels; ch++)
{
_allocation[ch][sb] = table[frame.ReadBits(bits) + 1];
}
}
for (; sb < _subBandCount; sb++)
{
var table = _allocLookupTable[rateTable[sb]];
_allocation[0][sb] = _allocation[1][sb] = table[frame.ReadBits(table[0]) + 1];
}
}
void ReadSamples(IMpegFrame frame)
{
// load in all the data for this frame (1152 samples in this case)
// NB: we flatten these into output order
for (int ss = 0, idx = 0; ss < SSLIMIT; ss++, idx += SBLIMIT * (_granuleCount - 1))
{
for (int sb = 0; sb < SBLIMIT; sb++, idx++)
{
for (int ch = 0; ch < _channels; ch++)
{
if (ch == 0 || sb < _jsbound)
{
var alloc = _allocation[ch][sb];
if (alloc != 0)
{
if (alloc < 0)
{
// grouping (Layer II only, so we don't have to play with the granule count)
var val = frame.ReadBits(-alloc);
var levels = (1 << (-alloc / 2 + -alloc % 2 - 1)) + 1;
_samples[ch][idx] = val % levels;
val /= levels;
_samples[ch][idx + SBLIMIT] = val % levels;
_samples[ch][idx + SBLIMIT * 2] = val / levels;
}
else
{
// non-grouping
for (int gr = 0; gr < _granuleCount; gr++)
{
_samples[ch][idx + SBLIMIT * gr] = frame.ReadBits(alloc);
}
}
}
else
{
// no energy... zero out the samples
for (int gr = 0; gr < _granuleCount; gr++)
{
_samples[ch][idx + SBLIMIT * gr] = 0;
}
}
}
else
{
// copy chan 0 to chan 1
for (int gr = 0; gr < _granuleCount; gr++)
{
_samples[1][idx + SBLIMIT * gr] = _samples[0][idx + SBLIMIT * gr];
}
}
}
}
}
}
public void AddBits(IMpegFrame frame)
{
var slots = GetSlots(frame);
while (--slots >= 0)
{
var temp = frame.ReadBits(8);
if (temp == -1) throw new System.IO.InvalidDataException("Frame did not have enough bytes!");
_buf[++_end] = (byte)temp;
if (_end == _buf.Length - 1) _end = -1;
}
if (_bitsLeft == 0) _bitsLeft = 8;
}
void ReadScaleFactors(IMpegFrame frame)
{
for (int sb = 0; sb < SBLIMIT; sb++)
{
for (int ch = 0; ch < _channels; ch++)
{
switch (_scfsi[ch][sb])
{
case 0:
// all three
_scalefac[ch][0][sb] = frame.ReadBits(6);
_scalefac[ch][1][sb] = frame.ReadBits(6);
_scalefac[ch][2][sb] = frame.ReadBits(6);
break;
case 1:
// only two (2 = 1)
_scalefac[ch][0][sb] =
_scalefac[ch][1][sb] = frame.ReadBits(6);
_scalefac[ch][2][sb] = frame.ReadBits(6);
break;
case 2:
// only one (3 = 2 = 1)
_scalefac[ch][0][sb] =
_scalefac[ch][1][sb] =
_scalefac[ch][2][sb] = frame.ReadBits(6);
break;
case 3:
// only two (3 = 2)
_scalefac[ch][0][sb] = frame.ReadBits(6);
_scalefac[ch][1][sb] =
_scalefac[ch][2][sb] = frame.ReadBits(6);
break;
default:
// none
_scalefac[ch][0][sb] = 63;
_scalefac[ch][1][sb] = 63;
_scalefac[ch][2][sb] = 63;
break;
}
}
}
}
public bool AddBits(IMpegFrame frame, int overlap)
{
var originalEnd = _end;
var slots = GetSlots(frame);
while (--slots >= 0)
{
var temp = frame.ReadBits(8);
if (temp == -1)
{
throw new System.IO.InvalidDataException("Frame did not have enough bytes!");
}
_buf[++_end] = (byte)temp;
if (_end == _buf.Length - 1)
{
_end = -1;
}
}
_bitsLeft = 8;
if (originalEnd == -1)
{
// it's either the start of the stream or we've reset... only return true if overlap says this frame is enough
return(overlap == 0);
}
else
{
// it's not the start of the stream so calculate _start based on whether we have enough bytes left
// if we have enough bytes, reset start to match overlap
if ((originalEnd + 1 - _start + _buf.Length) % _buf.Length >= overlap)
{
_start = (originalEnd + 1 - overlap + _buf.Length) % _buf.Length;
return(true);
}
// otherwise, just set start to match the start of the frame (we probably skipped a frame)
else
{
_start = originalEnd + overlap;
return(false);
}
}
}
protected override void ReadScaleFactorSelection(IMpegFrame frame, int[][] scfsi, int channels)
{
// we'll never have more than 30 active subbands
for (int sb = 0; sb < 30; sb++)
{
for (int ch = 0; ch < channels; ch++)
{
if (scfsi[ch][sb] == 2)
{
scfsi[ch][sb] = frame.ReadBits(2);
}
}
}
}
void ReadSideInfo(IMpegFrame frame)
{
if (frame.Version == MpegVersion.Version1)
{
// main_data_begin 9
_mainDataBegin = frame.ReadBits(9);
// private_bits 3 or 5
if (frame.ChannelMode == MpegChannelMode.Mono)
{
_privBits = frame.ReadBits(5);
_channels = 1;
}
else
{
_privBits = frame.ReadBits(3);
_channels = 2;
}
for (var ch = 0; ch < _channels; ch++)
{
// scfsi[ch][0...3] 1 x4
_scfsi[ch][0] = frame.ReadBits(1);
_scfsi[ch][1] = frame.ReadBits(1);
_scfsi[ch][2] = frame.ReadBits(1);
_scfsi[ch][3] = frame.ReadBits(1);
}
for (var gr = 0; gr < 2; gr++)
{
for (var ch = 0; ch < _channels; ch++)
{
// part2_3_length[gr][ch] 12
_part23Length[gr][ch] = frame.ReadBits(12);
// big_values[gr][ch] 9
_bigValues[gr][ch] = frame.ReadBits(9);
// global_gain[gr][ch] 8
_globalGain[gr][ch] = GAIN_TAB[frame.ReadBits(8)];
// scalefac_compress[gr][ch] 4
_scalefacCompress[gr][ch] = frame.ReadBits(4);
// blocksplit_flag[gr][ch] 1
_blockSplitFlag[gr][ch] = frame.ReadBits(1) == 1;
if (_blockSplitFlag[gr][ch])
{
// block_type[gr][ch] 2
_blockType[gr][ch] = frame.ReadBits(2);
// switch_point[gr][ch] 1
_mixedBlockFlag[gr][ch] = frame.ReadBits(1) == 1;
// table_select[gr][ch][0..1] 5 x2
_tableSelect[gr][ch][0] = frame.ReadBits(5);
_tableSelect[gr][ch][1] = frame.ReadBits(5);
_tableSelect[gr][ch][2] = 0;
// set the region information
if (_blockType[gr][ch] == 2 && !_mixedBlockFlag[gr][ch])
{
_regionAddress1[gr][ch] = 8;
}
else
{
_regionAddress1[gr][ch] = 7;
}
_regionAddress2[gr][ch] = 20 - _regionAddress1[gr][ch];
// subblock_gain[gr][ch][0..2] 3 x3
_subblockGain[gr][ch][0] = frame.ReadBits(3) * -2f;
_subblockGain[gr][ch][1] = frame.ReadBits(3) * -2f;
_subblockGain[gr][ch][2] = frame.ReadBits(3) * -2f;
}
else
{
// table_select[0..2][gr][ch] 5 x3
_tableSelect[gr][ch][0] = frame.ReadBits(5);
_tableSelect[gr][ch][1] = frame.ReadBits(5);
_tableSelect[gr][ch][2] = frame.ReadBits(5);
// region_address1[gr][ch] 4
_regionAddress1[gr][ch] = frame.ReadBits(4);
// region_address2[gr][ch] 3
_regionAddress2[gr][ch] = frame.ReadBits(3);
// set the block type so it doesn't accidentally carry
_blockType[gr][ch] = 0;
// make subblock gain equal unity
_subblockGain[gr][ch][0] = 0;
_subblockGain[gr][ch][1] = 0;
_subblockGain[gr][ch][2] = 0;
}
// preflag[gr][ch] 1
_preflag[gr][ch] = frame.ReadBits(1);
// scalefac_scale[gr][ch] 1
_scalefacScale[gr][ch] = .5f * (1f + frame.ReadBits(1));
// count1table_select[gr][ch] 1
_count1TableSelect[gr][ch] = frame.ReadBits(1);
}
}
}
else // MPEG 2+
{
// main_data_begin 8
_mainDataBegin = frame.ReadBits(8);
// private_bits 1 or 2
if (frame.ChannelMode == MpegChannelMode.Mono)
{
_privBits = frame.ReadBits(1);
_channels = 1;
}
else
{
_privBits = frame.ReadBits(2);
_channels = 2;
}
for (var gr = 0; gr < 2; gr++)
{
for (var ch = 0; ch < _channels; ch++)
{
// part2_3_length[gr][ch] 12
_part23Length[gr][ch] = frame.ReadBits(12);
// big_values[gr][ch] 9
_bigValues[gr][ch] = frame.ReadBits(9);
// global_gain[gr][ch] 8
_globalGain[gr][ch] = GAIN_TAB[frame.ReadBits(8)];
// scalefac_compress[gr][ch] 9
_scalefacCompress[gr][ch] = frame.ReadBits(9);
// blocksplit_flag[gr][ch] 1
_blockSplitFlag[gr][ch] = frame.ReadBits(1) == 1;
if (_blockSplitFlag[gr][ch])
{
// block_type[gr][ch] 2
_blockType[gr][ch] = frame.ReadBits(2);
// switch_point[gr][ch] 1
_mixedBlockFlag[gr][ch] = frame.ReadBits(1) == 1;
// table_select[gr][ch][0..1] 5 x2
_tableSelect[gr][ch][0] = frame.ReadBits(5);
_tableSelect[gr][ch][1] = frame.ReadBits(5);
_tableSelect[gr][ch][2] = 0;
// set the region information
if (_blockType[gr][ch] == 2 && !_mixedBlockFlag[gr][ch])
{
_regionAddress1[gr][ch] = 8;
}
else
{
_regionAddress1[gr][ch] = 7;
}
_regionAddress2[gr][ch] = 20 - _regionAddress1[gr][ch];
// subblock_gain[gr][ch][0..2] 3 x3
_subblockGain[gr][ch][0] = frame.ReadBits(3) * -2f;
_subblockGain[gr][ch][1] = frame.ReadBits(3) * -2f;
_subblockGain[gr][ch][2] = frame.ReadBits(3) * -2f;
}
else
{
// table_select[0..2][gr][ch] 5 x3
_tableSelect[gr][ch][0] = frame.ReadBits(5);
_tableSelect[gr][ch][1] = frame.ReadBits(5);
_tableSelect[gr][ch][2] = frame.ReadBits(5);
// region_address1[gr][ch] 4
_regionAddress1[gr][ch] = frame.ReadBits(4);
// region_address2[gr][ch] 3
_regionAddress2[gr][ch] = frame.ReadBits(3);
// set the block type so it doesn't accidentally carry
_blockType[gr][ch] = 0;
// make subblock gain equal unity
_subblockGain[gr][ch][0] = 0;
_subblockGain[gr][ch][1] = 0;
_subblockGain[gr][ch][2] = 0;
}
// scalefac_scale[gr][ch] 1
_scalefacScale[gr][ch] = .5f * (1f + frame.ReadBits(1));
// count1table_select[gr][ch] 1
_count1TableSelect[gr][ch] = frame.ReadBits(1);
}
}
}
}