How add Data Stream into MXF(using mpeg2video) file with FFmpeg and C/C++ - c++

Question

I'm a little bit stuck here trying create a MXF file
with data stream on it. I have several MXF video files that contain
this standard
**1 Video Stream:
Stream #0:0: Video: mpeg2video (4:2:2), yuv422p(tv, bt709, top first), 1920x1080 [SAR 1:1 DAR 16:9], 50000 kb/s, 29.9
16 audio streams
Audio: pcm_s24le, 48000 Hz, 1 channels, s32 (24 bit), 1152 kb/s
1 Data Stream:
Data: none**
This data stream, contain personal data inside video file. I can
open this stream and data is really there. Is all ok. But, when i try
to create a file exactly like this, everytime i call "avformat_write_header"
it returns an error.
If i do comment the creation of this data streams the video file is succeffully
created.
If i change to "mpegts" with this data stream, the video file is also succeffully
created.
But, i can't use mpets and i need this data stream.
I know that is possible MXF with data stream cause i have this originals files
that have this combination.
So, i know that i missing something in my code.
This is the way i create this Data Stream:
void CFFmpegVideoWriter::addDataStream(EOutputStream *ost, AVFormatContext *oc, AVCodec **codec, enum AVCodecID codec_id)
{
AVCodecParameters *par;
ost->stream = avformat_new_stream(oc, NULL);
if (ost->stream == NULL)
{
fprintf(stderr, "OOooohhh man: avformat_new_stream() failed.\n");
return;
}
par = ost->stream->codecpar;
ost->stream->index = 17;
par->codec_id = AV_CODEC_ID_NONE;
par->codec_type = AVMEDIA_TYPE_DATA;
ost->stream->codec->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
}
the file openning is this:
CFFMpegVideoWriter::CFFMpegVideoWriter(QString outputfilename) : QThread()
{
av_register_all();
avcodec_register_all();
isOpen = false;
shouldClose = false;
frameIndex = 0;
#ifdef __linux__
QByteArray bFilename = outputfilename.toUtf8();
#else
QByteArray bFilename = outputfilename.toLatin1();
#endif
const char* filename = bFilename.data();
codecContext = NULL;
//encontra o formato desejado...
outputFormat = av_guess_format("mp2v", filename, nullptr);
if (!outputFormat)
{
qDebug("Could not find suitable output format\n");
return;
}
//encontra o codec...
codec = avcodec_find_encoder(outputFormat->video_codec);
if (!codec)
{
qDebug( "Codec not found\n");
return;
}
//aloca o contexto do codec...
codecContext = avcodec_alloc_context3(codec);
codecContext->field_order = AV_FIELD_TT;
codecContext->profile = FF_PROFILE_MPEG2_422;
//aloca o contexto do formato...
formatContext = avformat_alloc_context();
formatContext->oformat = outputFormat;
//aloca o contexto da midia de saida...
avformat_alloc_output_context2(&formatContext, NULL, NULL, filename);
if (!formatContext)
{
qDebug("Erro");
return;
}
videoStream.tmp_frame = NULL;
videoStream.swr_ctx = NULL;
//adiciona a stream de video...
if (outputFormat->video_codec != AV_CODEC_ID_NONE)
{
addVideoStream(&videoStream, formatContext, &video_codec, outputFormat->video_codec);
}
//adiciona as 16 streams de audio...
if (outputFormat->audio_codec != AV_CODEC_ID_NONE)
{
for (int i = 0; i < 16; i++)
{
addAudioStream(&audioStream[i], formatContext, &audio_codec, outputFormat->audio_codec);
}
}
addDataStream(&datastream, formatContext, &video_codec, outputFormat->video_codec);
videoStream.sws_ctx = NULL;
for (int i = 0; i < 16; i++)
{
audioStream[i].sws_ctx = NULL;
}
opt = NULL;
//carreca o codec de video para stream de video...
initVideoCodec(formatContext, video_codec, &videoStream, opt);
//carrega o codec de audio para stream de audio...s
for (int i = 0; i < 16; i++)
{
initAudioCodec(formatContext, audio_codec, &audioStream[i], opt);
}
av_dump_format(formatContext, 0, filename, 1);
//abrea o arquivo de saida..
if (!(outputFormat->flags & AVFMT_NOFILE))
{
ret = avio_open(&formatContext->pb, filename, AVIO_FLAG_WRITE);
if (ret < 0)
{
qDebug("Could not open'%s", filename);
return;
}
}
//escreve o cabecalho do arquivo...
ret = avformat_write_header(formatContext, &opt);
if (ret < 0)
{
qDebug("Error occurred when opening output file");
return;
}
isOpen = true;
QThread::start();
}
The code always fails at "avformat_write_header" call.
But if i remove "datastream" or change it to mpegts everything runs fine.
Any ideia of what am i doing wrong here?
Thanks for reading this.
Helmuth

Answer 1

After some long hours trying a lot of solutions i found what was wrong. I had to add a metadata item specifing data type.
In my case, data type was "vbi_vanc_smpte_436M" wich is supported by MXF.
so, i dit with:
av_dict_set(&out_stream->metadata, "data_type", "vbi_vanc_smpte_436M", AV_DICT_IGNORE_SUFFIX);
Then everything works fine.
I hope this can help anyone else with same problem.