avformat_write_header fails with error "invalid argument - c

Question

I'm trying to write a chunk of a mp4 file to a .ts file, which does not yet exist.
So first I create AVFormatContext this way:
AVOutputFormat *oformat = av_guess_format( NULL,
"mpegts",
"video/x-mpegts" );
AVFormatContext * outFormatContext = NULL;
avformat_alloc_output_context2( &outFormatContext, oformat, NULL, dst_file)
outFormatContext is created and outFormatContext->oformat is set to oformat. Then I open I/O context on outFormatContext:
avio_open(&outFormatContext->pb, dst_file, AVIO_FLAG_WRITE)
avformat_write_header( outFormatContext, NULL );
according to this this is enough for avformat_write_header to work but it fails with error "invalid argument".
What else needs to be done to successfully write the header?

Answer 1

Although it's a little bit late, I hope it would be helpful.
Here is my way to call avformat_write_header, you should have a stream provided to write the header.
AVFormatContext* pOutFormatContext;
AVOutputFormat* avOutputFormat;
if ((avOutputFormat = av_guess_format(NULL, "mp4", "video/mp4")) == NULL) {
cerr << "Could not guess output format" << endl;
return -1;
}
avformat_alloc_output_context2(&pOutFormatContext,
av_guess_format("mp4", NULL, "video/mp4"), NULL, NULL);
if (pOutFormatContext == NULL) {
cerr << "Could not allocate output context" << endl;
return -1;
}
for (int i = 0; i < avFormatContext->nb_streams; i++) {
AVStream* inAVStream = avFormatContext->streams[i];
AVStream* outAVStream = avformat_new_stream(pOutFormatContext, inAVStream->codec->codec);
if (avcodec_copy_context(outAVStream->codec, inAVStream->codec) < 0) {
cerr << "Failed to copy codec context" << endl;
return -1;
}
outAVStream->codec->codec_tag = 0;
if (pOutFormatContext->oformat->flags & AVFMT_GLOBALHEADER) {
outAVStream->codec->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
}
}
avio_open(&pOutFormatContext->pb, "test.mp4", AVIO_FLAG_READ_WRITE);
if (pOutFormatContext->pb == NULL) {
cerr << "Could not open for writing" << endl;
return -1;
}
if (avformat_write_header(pOutFormatContext, NULL) != 0) {
cerr << "Could not write header" << endl;
return -1;
}