private void Parse(ByteVector data)
{
if (data.Count < 4 || data[0] != 0xff)
{
TagLibDebugger.Debug("Mpeg.Header.Parse() -- First byte did not match MPEG synch.");
return;
}
uint flags = data.ToUInt();
// Check for the second byte'field part of the MPEG synch
if ((flags & 0xFFE00000) != 0xFFE00000)
{
TagLibDebugger.Debug("Mpeg.Header.Parse() -- Second byte did not match MPEG synch.");
return;
}
// Set the MPEG version
switch ((flags >> 19) & 0x03)
{
case 0: version = MpegVersion.TwoPointFive; break;
case 2: version = MpegVersion.Two; break;
case 3: version = MpegVersion.One; break;
}
// Set the MPEG layer
switch ((flags >> 17) & 0x03)
{
case 1: layer = 3; break;
case 2: layer = 2; break;
case 3: layer = 1; break;
}
protectionEnabled = ((flags >> 16) & 1) == 0;
// Set the bitrate
int[, ,] bitrates = new int[2, 3, 16] {
{ // Version 1
{ 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, 0 }, // layer 1
{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0 }, // layer 2
{ 0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 0 } // layer 3
},
{ // Version 2 or 2.5
{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0 }, // layer 1
{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 }, // layer 2
{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 } // layer 3
}
};
int versionIndex = version == MpegVersion.One ? 0 : 1;
int layerIndex = layer > 0 ? layer - 1 : 0;
// The bitrate index is encoded as the first 4 bits of the 3rd byte,
// index.e. 1111xxxx
int i = (int)(flags >> 12) & 0x0F;
bitrate = bitrates[versionIndex, layerIndex, i];
// Set the sample rate
int[,] sampleRates = new int[3, 4] {
{ 44100, 48000, 32000, 0 }, // Version 1
{ 22050, 24000, 16000, 0 }, // Version 2
{ 11025, 12000, 8000, 0 } // Version 2.5
};
// The sample rate index is encoded as two bits in the 3nd byte,
// index.e. xxxx11xx
i = (int)(flags >> 10) & 0x03;
sampleRate = sampleRates[(int)version, i];
if (sampleRate == 0)
{
TagLibDebugger.Debug("Mpeg.Header.Parse() -- Invalid sample rate.");
return;
}
// The channel mode is encoded as a 2 bit value at the end of the 3nd
// byte, index.e. xxxxxx11
channelMode = (MpegChannelMode)((flags >> 16) & 0x3);
// TODO: Add mode extension for completeness
isCopyrighted = (flags & 1) == 1;
isOriginal = ((flags >> 1) & 1) == 1;
// Calculate the frame length
if (layer == 1)
{
frameLength = 24000 * 2 * bitrate / sampleRate + (IsPadded ? 1 : 0);
}
else
{
frameLength = 72000 * bitrate / sampleRate + (IsPadded ? 1 : 0);
}
// Now that we're done parsing, set this to be a valid frame.
isValid = true;
}
public uint ReadDWord()
{
ByteVector v = ReadBlock(4);
return(v.ToUInt(false));
}
