ffmpeg avformat example

First, one of the initialization methods.

void Exporty::_InitializeVideoCodecContext( AVFormatContext* avFormatContext,
                                            MEDIA_PARSER::MediaInfo* mediaInfo,
                                            AVCodecContext* avCodecContext ) const
{
    avcodec_get_context_defaults2(avCodecContext, CODEC_TYPE_VIDEO);

    avCodecContext->codec_id = (CodecID)avFormatContext->oformat->video_codec;
    avCodecContext->codec_type = CODEC_TYPE_VIDEO;

    avCodecContext->bit_rate = mediaInfo->GetBitRate();
    X_LOG_INFO( "Detected bit rate: %u\n", mediaInfo->GetBitRate() );

    // Don't need to send this, but might at some point...
    // avCodecContext->gop_size = _videoGopSize;

    avCodecContext->width = mediaInfo->GetFrameWidth();
    avCodecContext->height = mediaInfo->GetFrameHeight();
    X_LOG_INFO( "Resolution: %uX%u", mediaInfo->GetFrameWidth(), mediaInfo->GetFrameHeight() );

    avCodecContext->time_base.num = 1;
    avCodecContext->time_base.den = mediaInfo->GetFrameRate();
    X_LOG_INFO( "Time Base - Numerator: 1, Denomination: %d", mediaInfo->GetFrameRate() );

    avCodecContext->pix_fmt = PIX_FMT_YUV420P;

    // some formats want stream headers to be seperate
    if( !strcmp(avFormatContext->oformat->name, "mp4") ||
        !strcmp(avFormatContext->oformat->name, "mov") ||
        !strcmp(avFormatContext->oformat->name, "3gp") )
        avCodecContext->flags |= CODEC_FLAG_GLOBAL_HEADER;
}


Here is the main part where everything begins... Obviously this is taken out of context... but this is where the ffmpeg calls begin... The above function is called below...

    av_register_all();

    AVFormatContext* formatContext = avformat_alloc_context();
    if( !formatContext )
        X_STHROW( InternalServerError_500, ("Could not allocate AVFormatContext.") );

    formatContext->oformat = av_guess_format(NULL, _ConvertMIMETypeToFileName( _type ).c_str(), NULL);

    if( !formatContext->oformat )
        X_STHROW( InternalServerError_500, ("Could not allocate output format context.") );

    formatContext->oformat->video_codec = CODEC_ID_H264;
    // CODEC_ID_MJPEGCODEC_ID_MJPEG
    // CODEC_ID_MPEG4

    AVStream* videoStream = av_new_stream( formatContext, 1 );
    if( !videoStream )
        X_STHROW( InternalServerError_500, ("Unable to allocate video stream.") );

    _InitializeVideoCodecContext( formatContext, mediaInfo, videoStream->codec );

    av_set_parameters( formatContext, NULL );

    url_open_dyn_buf( &formatContext->pb );

    av_write_header( formatContext );

    _WriteConfigBuffer( videoStream, formatContext, sps );
    _WriteConfigBuffer( videoStream, formatContext, pps );

    for( int i = 0; i < numFramesToExport; i++ )
    {
        lastFrameTS = resultParser->GetFrameTS();

        AVPacket pkt;
        av_init_packet(&pkt);

        pkt.stream_index = videoStream->index;

        XIRef<XMemory> frameBuffer = new XMemory;

        resultParser->GetFrameData( &frameBuffer->Extend( resultParser->GetFrameSize() ),
                                    resultParser->GetFrameSize() );

        pkt.data = frameBuffer->Map();
        pkt.size = frameBuffer->GetDataSize();

        av_write_frame( formatContext, &pkt );

        resultParser->Step();
    }

    av_write_trailer( formatContext );

    uint8_t* fileBytes = NULL;
    int fileSize = url_close_dyn_buf( formatContext->pb, &fileBytes );