unsafe void decode_metadata()
{
byte x;
int i, id;
//bool first = true;
byte[] FLAC__STREAM_SYNC_STRING = new byte[] { (byte)'f', (byte)'L', (byte)'a', (byte)'C' };
byte[] ID3V2_TAG_ = new byte[] { (byte)'I', (byte)'D', (byte)'3' };
for (i = id = 0; i < 4;)
{
if (_IO.Read(_framesBuffer, 0, 1) == 0)
{
throw new Exception("FLAC stream not found");
}
x = _framesBuffer[0];
if (x == FLAC__STREAM_SYNC_STRING[i])
{
//first = true;
i++;
id = 0;
continue;
}
if (id < 3 && x == ID3V2_TAG_[id])
{
id++;
i = 0;
if (id == 3)
{
if (!skip_bytes(3))
{
throw new Exception("FLAC stream not found");
}
int skip = 0;
for (int j = 0; j < 4; j++)
{
if (0 == _IO.Read(_framesBuffer, 0, 1))
{
throw new Exception("FLAC stream not found");
}
skip <<= 7;
skip |= ((int)_framesBuffer[0] & 0x7f);
}
if (!skip_bytes(skip))
{
throw new Exception("FLAC stream not found");
}
}
continue;
}
id = 0;
if (x == 0xff) /* MAGIC NUMBER for the first 8 frame sync bits */
{
do
{
if (_IO.Read(_framesBuffer, 0, 1) == 0)
{
throw new Exception("FLAC stream not found");
}
x = _framesBuffer[0];
} while (x == 0xff);
if (x >> 2 == 0x3e) /* MAGIC NUMBER for the last 6 sync bits */
{
//_IO.Position -= 2;
// state = frame
throw new Exception("headerless file unsupported");
}
}
throw new Exception("FLAC stream not found");
}
do
{
fill_frames_buffer();
fixed(byte *buf = _framesBuffer)
{
BitReader bitreader = new BitReader(buf, _framesBufferOffset, _framesBufferLength - _framesBufferOffset);
bool is_last = bitreader.readbit() != 0;
MetadataType type = (MetadataType)bitreader.readbits(7);
int len = (int)bitreader.readbits(24);
if (type == MetadataType.StreamInfo)
{
const int FLAC__STREAM_METADATA_STREAMINFO_MIN_BLOCK_SIZE_LEN = 16; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_MAX_BLOCK_SIZE_LEN = 16; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_MIN_FRAME_SIZE_LEN = 24; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_MAX_FRAME_SIZE_LEN = 24; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_SAMPLE_RATE_LEN = 20; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_CHANNELS_LEN = 3; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_BITS_PER_SAMPLE_LEN = 5; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_TOTAL_SAMPLES_LEN = 36; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_MD5SUM_LEN = 128; /* bits */
min_block_size = bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_MIN_BLOCK_SIZE_LEN);
max_block_size = bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_MAX_BLOCK_SIZE_LEN);
min_frame_size = bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_MIN_FRAME_SIZE_LEN);
max_frame_size = bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_MAX_FRAME_SIZE_LEN);
int sample_rate = (int)bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_SAMPLE_RATE_LEN);
int channels = 1 + (int)bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_CHANNELS_LEN);
int bits_per_sample = 1 + (int)bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_BITS_PER_SAMPLE_LEN);
pcm = new AudioPCMConfig(bits_per_sample, channels, sample_rate);
_sampleCount = (long)bitreader.readbits64(FLAC__STREAM_METADATA_STREAMINFO_TOTAL_SAMPLES_LEN);
bitreader.skipbits(FLAC__STREAM_METADATA_STREAMINFO_MD5SUM_LEN);
}
else if (type == MetadataType.Seektable)
{
int num_entries = len / 18;
seek_table = new SeekPoint[num_entries];
for (int e = 0; e < num_entries; e++)
{
seek_table[e].number = bitreader.read_long();
seek_table[e].offset = bitreader.read_long();
seek_table[e].framesize = (int)bitreader.read_ushort();
}
}
if (_framesBufferLength < 4 + len)
{
_IO.Position += 4 + len - _framesBufferLength;
_framesBufferLength = 0;
}
else
{
_framesBufferLength -= 4 + len;
_framesBufferOffset += 4 + len;
}
if (is_last)
{
break;
}
}
} while (true);
first_frame_offset = _IO.Position - _framesBufferLength;
}
unsafe void decode_subframe_constant(BitReader bitreader, FlacFrame frame, int ch)
{
int obits = frame.subframes[ch].obits;
frame.subframes[ch].best.residual[0] = bitreader.readbits_signed(obits);
}
unsafe void decode_subframes(BitReader bitreader, FlacFrame frame)
{
fixed(int *r = residualBuffer, s = samplesBuffer)
for (int ch = 0; ch < PCM.ChannelCount; ch++)
{
// subframe header
uint t1 = bitreader.readbit(); // ?????? == 0
if (t1 != 0)
{
throw new Exception("unsupported subframe coding (ch == " + ch.ToString() + ")");
}
int type_code = (int)bitreader.readbits(6);
frame.subframes[ch].wbits = (int)bitreader.readbit();
if (frame.subframes[ch].wbits != 0)
{
frame.subframes[ch].wbits += (int)bitreader.read_unary();
}
frame.subframes[ch].obits = PCM.BitsPerSample - frame.subframes[ch].wbits;
switch (frame.ch_mode)
{
case ChannelMode.MidSide: frame.subframes[ch].obits += ch; break;
case ChannelMode.LeftSide: frame.subframes[ch].obits += ch; break;
case ChannelMode.RightSide: frame.subframes[ch].obits += 1 - ch; break;
}
frame.subframes[ch].best.type = (SubframeType)type_code;
frame.subframes[ch].best.order = 0;
if ((type_code & (uint)SubframeType.LPC) != 0)
{
frame.subframes[ch].best.order = (type_code - (int)SubframeType.LPC) + 1;
frame.subframes[ch].best.type = SubframeType.LPC;
}
else if ((type_code & (uint)SubframeType.Fixed) != 0)
{
frame.subframes[ch].best.order = (type_code - (int)SubframeType.Fixed);
frame.subframes[ch].best.type = SubframeType.Fixed;
}
frame.subframes[ch].best.residual = r + ch * Flake.MAX_BLOCKSIZE;
frame.subframes[ch].samples = s + ch * Flake.MAX_BLOCKSIZE;
// subframe
switch (frame.subframes[ch].best.type)
{
case SubframeType.Constant:
decode_subframe_constant(bitreader, frame, ch);
break;
case SubframeType.Verbatim:
decode_subframe_verbatim(bitreader, frame, ch);
break;
case SubframeType.Fixed:
decode_subframe_fixed(bitreader, frame, ch);
break;
case SubframeType.LPC:
decode_subframe_lpc(bitreader, frame, ch);
break;
default:
throw new Exception("invalid subframe type");
}
}
}
unsafe void decode_frame_header(BitReader bitreader, FlacFrame frame)
{
int header_start = bitreader.Position;
uint readBits = bitreader.readbits(15);
if (readBits != 0x7FFC)
{
throw new Exception("invalid frame");
}
uint vbs = bitreader.readbit();
frame.bs_code0 = (int)bitreader.readbits(4);
uint sr_code0 = bitreader.readbits(4);
frame.ch_mode = (ChannelMode)bitreader.readbits(4);
uint bps_code = bitreader.readbits(3);
if (Flake.flac_bitdepths[bps_code] != PCM.BitsPerSample)
{
throw new Exception("unsupported bps coding");
}
uint t1 = bitreader.readbit(); // == 0?????
if (t1 != 0)
{
throw new Exception("unsupported frame coding");
}
frame.frame_number = (int)bitreader.read_utf8();
// custom block size
if (frame.bs_code0 == 6)
{
frame.bs_code1 = (int)bitreader.readbits(8);
frame.blocksize = frame.bs_code1 + 1;
}
else if (frame.bs_code0 == 7)
{
frame.bs_code1 = (int)bitreader.readbits(16);
frame.blocksize = frame.bs_code1 + 1;
}
else
{
frame.blocksize = Flake.flac_blocksizes[frame.bs_code0];
}
// custom sample rate
if (sr_code0 < 1 || sr_code0 > 11)
{
// sr_code0 == 12 -> sr == bitreader.readbits(8) * 1000;
// sr_code0 == 13 -> sr == bitreader.readbits(16);
// sr_code0 == 14 -> sr == bitreader.readbits(16) * 10;
throw new Exception("invalid sample rate mode");
}
int frame_channels = (int)frame.ch_mode + 1;
if (frame_channels > 11)
{
throw new Exception("invalid channel mode");
}
if (frame_channels == 2 || frame_channels > 8) // Mid/Left/Right Side Stereo
{
frame_channels = 2;
}
else
{
frame.ch_mode = ChannelMode.NotStereo;
}
if (frame_channels != PCM.ChannelCount)
{
throw new Exception("invalid channel mode");
}
// CRC-8 of frame header
byte crc = do_crc ? crc8.ComputeChecksum(bitreader.Buffer, header_start, bitreader.Position - header_start) : (byte)0;
frame.crc8 = (byte)bitreader.readbits(8);
if (do_crc && frame.crc8 != crc)
{
throw new Exception("header crc mismatch");
}
}