Get composition time C++

Question

I made my own rtmp server using libav and ffmpeg. I receive as input either an flv file or an rtmp streaming "containing" an flv file. Since I manipulate the flv file and the relative composition time of each frame, I would like to know if there is a way to get this composition time. I thought that given my AVPacket, I could analyze the raw buffer in order to extract the right information since I know that the flv header is 11 bytes and then in the next 16 bytes I should find the composition time. But it doesn't work.

This is a rough example of code:

AVPacket pkt;
AVFormatContext *ifmt_ctx
while(true)
{
    AVStream *in_stream, *out_stream;

    ret = av_read_frame(ifmt_ctx, &pkt);
    //get the composite time
}

Try this: https://stackoverflow.com/questions/6734375/get-current-time-in-milliseconds-using-c-and-boost — U. W., Nov 13 '19 at 14:58
Right you are. Can you get a Hexdump of the 16 Bytes where the time should be? — U. W., Nov 13 '19 at 15:02
Yes, but it looks like it is not the right information I need — Andrea, Nov 13 '19 at 15:29

score 1 · Accepted Answer · answered Nov 13 '19 at 15:44

AVPacket needs to be able to represent the data found in all media formats. Some formats (like mp4 and flv) have a decode_time and a composition_time, other (like transport streams) have a decode_time and a presentation_time. To make it easier for the programmer, AVPacket chose one method to store the information and converts when needed. Luckily its an an easy to convert back:

auto cts = pkt.pts - pkt.dts

Get composition time C++

1 Answers1