/// <summary>
/// write out the main header
/// </summary>
void writemainheader()
{
// note: this file starttag not actually part of main headers
var tmp = Encoding.ASCII.GetBytes("nut/multimedia container\0");
output.Write(tmp, 0, tmp.Length);
var header = new NutPacket(NutPacket.StartCode.Main, output);
WriteVarU(3, header); // version
WriteVarU(2, header); // stream_count
WriteVarU(65536, header); // max_distance
WriteVarU(2, header); // time_base_count
// timebase is length of single frame, so reversed num+den is intentional
WriteVarU(avparams.fpsden, header); // time_base_num[0]
WriteVarU(avparams.fpsnum, header); // time_base_den[0]
WriteVarU(1, header); // time_base_num[1]
WriteVarU(avparams.samplerate, header); // time_base_den[1]
// frame flag compression is ignored for simplicity
for (int i = 0; i < 255; i++) // not 256 because entry 0x4e is skipped (as it would indicate a startcode)
{
WriteVarU((1 << 12), header); // tmp_flag = FLAG_CODED
WriteVarU(0, header); // tmp_fields
}
// header compression ignored because it's not useful to us
WriteVarU(0, header); // header_count_minus1
// BROADCAST_MODE only useful for realtime transmission clock recovery
WriteVarU(0, header); // main_flags
header.Flush();
}
/// <param name="payload">frame data</param>
/// <param name="payLoadLen">actual length of frame data</param>
/// <param name="pts">presentation timestamp</param>
/// <param name="ptsNum">numerator of timebase</param>
/// <param name="ptsDen">denominator of timebase</param>
/// <param name="ptsIndex">which timestamp base is used, assumed to be also stream number</param>
public NutFrame(byte[] payload, int payLoadLen, ulong pts, ulong ptsNum, ulong ptsDen, int ptsIndex, ReusableBufferPool <byte> pool)
{
_pts = pts;
_ptsNum = ptsNum;
_ptsDen = ptsDen;
_pool = pool;
_data = pool.GetBufferAtLeast(payLoadLen + 2048);
var frame = new MemoryStream(_data);
// create syncpoint
var sync = new NutPacket(NutPacket.StartCode.Syncpoint, frame);
WriteVarU(pts * 2 + (ulong)ptsIndex, sync); // global_key_pts
WriteVarU(1, sync); // back_ptr_div_16, this is wrong
sync.Flush();
var frameHeader = new MemoryStream();
frameHeader.WriteByte(0); // frame_code
// frame_flags = FLAG_CODED, so:
int flags = 0;
flags |= 1 << 0; // FLAG_KEY
if (payLoadLen == 0)
{
flags |= 1 << 1; // FLAG_EOR
}
flags |= 1 << 3; // FLAG_CODED_PTS
flags |= 1 << 4; // FLAG_STREAM_ID
flags |= 1 << 5; // FLAG_SIZE_MSB
flags |= 1 << 6; // FLAG_CHECKSUM
WriteVarU(flags, frameHeader);
WriteVarU(ptsIndex, frameHeader); // stream_id
WriteVarU(pts + 256, frameHeader); // coded_pts = pts + 1 << msb_pts_shift
WriteVarU(payLoadLen, frameHeader); // data_size_msb
var frameHeaderArr = frameHeader.ToArray();
frame.Write(frameHeaderArr, 0, frameHeaderArr.Length);
WriteBe32(NutCRC32(frameHeaderArr), frame); // checksum
frame.Write(payload, 0, payLoadLen);
_actualLength = (int)frame.Position;
}
/// <summary>
/// write out the 1st stream header (audio)
/// </summary>
void writeaudioheader()
{
var header = new NutPacket(NutPacket.StartCode.Stream, output);
WriteVarU(1, header); // stream_id
WriteVarU(1, header); // stream_class = audio
WriteString("\x01\x00\x00\x00", header); // fourcc = 01 00 00 00
WriteVarU(1, header); // time_base_id = 1
WriteVarU(8, header); // msb_pts_shift
WriteVarU(avparams.samplerate, header); // max_pts_distance
WriteVarU(0, header); // decode_delay
WriteVarU(0, header); // stream_flags = none; no FIXED_FPS because we aren't guaranteeing same-size audio chunks
WriteBytes(new byte[0], header); // codec_specific_data
// stream_class = audio
WriteVarU(avparams.samplerate, header); // samplerate_num
WriteVarU(1, header); // samplerate_den
WriteVarU(avparams.channels, header); // channel_count
header.Flush();
}
/// <summary>
/// write out the 0th stream header (video)
/// </summary>
void writevideoheader()
{
var header = new NutPacket(NutPacket.StartCode.Stream, output);
WriteVarU(0, header); // stream_id
WriteVarU(0, header); // stream_class = video
WriteString("BGRA", header); // fourcc = "BGRA"
WriteVarU(0, header); // time_base_id = 0
WriteVarU(8, header); // msb_pts_shift
WriteVarU(1, header); // max_pts_distance
WriteVarU(0, header); // decode_delay
WriteVarU(1, header); // stream_flags = FLAG_FIXED_FPS
WriteBytes(new byte[0], header); // codec_specific_data
// stream_class = video
WriteVarU(avparams.width, header); // width
WriteVarU(avparams.height, header); // height
WriteVarU(1, header); // sample_width
WriteVarU(1, header); // sample_height
WriteVarU(18, header); // colorspace_type = full range rec709 (avisynth's "PC.709")
header.Flush();
}