h264 stream muxing: duration of resulting file is shorter than recording time

Question

I am muxing H264 stream from v4l device to avi container using the approach outlined in the following stackoverflow question

The resulting files are playable, but for (lets say) 30 second recording the resulting file is only 10 seconds length. In other words, once I press 'Start recording' button until I press 'Stop' recording it is 30 seconds that have elapsed but file is only 10 seconds length (as shown in Windows Media player). Muxing starts immediately once I pressed the 'Start recording' button.

Any ideas on how could I approach this problem?

Is the video tripple speed or is is cut but playing in normal speed? — Karol Żygłowicz, May 21 '20 at 10:20
The speed is normal, same as the H264 source - I would say video is cut. — user466540, May 21 '20 at 10:43

score 0 · Answer 1 · answered May 25 '20 at 06:11

The problem was with the fps parameter:

AVStream *pst = avformat_new_stream(fc, 0);
  vi = pst->index;

  AVCodecContext *pcc = pst->codec;
  _M;
  avcodec_get_context_defaults3(pcc, AVMEDIA_TYPE_VIDEO);
  pcc->codec_type = AVMEDIA_TYPE_VIDEO;

  pcc->codec_id = codec_id;
  pcc->bit_rate = br;
  pcc->width = w;
  pcc->height = h;
  pcc->time_base.num = 1;
  int fps = 30; // problem here
  pcc->time_base.den = fps;

As it turned out, H264 stream produces frames with 13 fps. Once I made fps = 13, file duration become aligned with the expected time.

h264 stream muxing: duration of resulting file is shorter than recording time

1 Answers1