public void WriteChunk(byte[] chunk, uint timeStamp)
{
if (chunk.Length < 1)
{
return;
}
if (chunk[0] == 0)
{ // Header
if (chunk.Length < 3)
{
return;
}
var bits = (ulong)BitConverterBE.ToUInt16(chunk, 1) << 48;
_aacProfile = BitHelper.Read(ref bits, 5) - 1;
_sampleRateIndex = BitHelper.Read(ref bits, 4);
_channelConfig = BitHelper.Read(ref bits, 4);
if (_aacProfile == 4) // HE-AAC
{
_aacProfile = 1; // Uses LC profile + SBR
}
if (_aacProfile < 0 || _aacProfile > 3)
{
throw new Exception("Unsupported AAC profile.");
}
if (_sampleRateIndex > 12)
{
throw new Exception("Invalid AAC sample rate index.");
}
if (_channelConfig > 6)
{
throw new Exception("Invalid AAC channel configuration.");
}
}
else
{ // Audio data
var dataSize = chunk.Length - 1;
ulong bits = 0;
// Reference: WriteADTSHeader from FAAC's bitstream.c
BitHelper.Write(ref bits, 12, 0xFFF);
BitHelper.Write(ref bits, 1, 0);
BitHelper.Write(ref bits, 2, 0);
BitHelper.Write(ref bits, 1, 1);
BitHelper.Write(ref bits, 2, _aacProfile);
BitHelper.Write(ref bits, 4, _sampleRateIndex);
BitHelper.Write(ref bits, 1, 0);
BitHelper.Write(ref bits, 3, _channelConfig);
BitHelper.Write(ref bits, 1, 0);
BitHelper.Write(ref bits, 1, 0);
BitHelper.Write(ref bits, 1, 0);
BitHelper.Write(ref bits, 1, 0);
BitHelper.Write(ref bits, 13, 7 + dataSize);
BitHelper.Write(ref bits, 11, 0x7FF);
BitHelper.Write(ref bits, 2, 0);
_fs.Write(BitConverterBE.GetBytes(bits), 1, 7);
_fs.Write(chunk, 1, dataSize);
}
}
private void GetFrameSize(byte[] chunk)
{
if (_codecID == 2)
{
// Reference: flv_h263_decode_picture_header from libavcodec's h263.c
if (chunk.Length < 10)
{
return;
}
if (chunk[0] != 0 || chunk[1] != 0)
{
return;
}
var x = BitConverterBE.ToUInt64(chunk, 2);
int format;
if (BitHelper.Read(ref x, 1) != 1)
{
return;
}
BitHelper.Read(ref x, 5);
BitHelper.Read(ref x, 8);
format = BitHelper.Read(ref x, 3);
switch (format)
{
case 0:
_width = BitHelper.Read(ref x, 8);
_height = BitHelper.Read(ref x, 8);
break;
case 1:
_width = BitHelper.Read(ref x, 16);
_height = BitHelper.Read(ref x, 16);
break;
case 2:
_width = 352;
_height = 288;
break;
case 3:
_width = 176;
_height = 144;
break;
case 4:
_width = 128;
_height = 96;
break;
case 5:
_width = 320;
_height = 240;
break;
case 6:
_width = 160;
_height = 120;
break;
default:
return;
}
}
else if (_codecID == 4 || _codecID == 5)
{
// Reference: vp6_parse_header from libavcodec's vp6.c
var skip = _codecID == 4 ? 1 : 4;
if (chunk.Length < skip + 8)
{
return;
}
var x = BitConverterBE.ToUInt64(chunk, skip);
var deltaFrameFlag = BitHelper.Read(ref x, 1);
var quant = BitHelper.Read(ref x, 6);
var separatedCoeffFlag = BitHelper.Read(ref x, 1);
var subVersion = BitHelper.Read(ref x, 5);
var filterHeader = BitHelper.Read(ref x, 2);
var interlacedFlag = BitHelper.Read(ref x, 1);
if (deltaFrameFlag != 0)
{
return;
}
if (separatedCoeffFlag != 0 || filterHeader == 0)
{
BitHelper.Read(ref x, 16);
}
_height = BitHelper.Read(ref x, 8) * 16;
_width = BitHelper.Read(ref x, 8) * 16;
// chunk[0] contains the width and height (4 bits each, respectively) that should
// be cropped off during playback, which will be non-zero if the encoder padded
// the frames to a macroblock boundary. But if you use this adjusted size in the
// AVI header, DirectShow seems to ignore it, and it can cause stride or chroma
// alignment problems with VFW if the width/height aren't multiples of 4.
if (!_isAlphaWriter)
{
var cropX = chunk[0] >> 4;
var cropY = chunk[0] & 0x0F;
if ((cropX != 0 || cropY != 0) && !_isAlphaWriter)
{
_warnings.Add(String.Format("Suggested cropping: {0} pixels from right, {1} pixels from bottom.", cropX, cropY));
}
}
}
}
