[FFmpeg-user] non-monotonous DTS in output stream

[cedric.dewijs at telfort.nl]

Hi All,
I am capturing mjpeg frames from my webcam connected to a bananapi, running armbian. The resulting video file is choppy when played with mplayer and VLC, and in the console I see the following messages. The CPU of the bananapi is nowhere near 100%
cedric at bananapi:~/FFmpeg$ ./ffmpeg -f v4l2 -input_format mjpeg -s 1280x720 -i /dev/video0 -c:v copy output.mkv
ffmpeg version N-86245-gcd67ff8 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 5.4.0 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9) 20160609
  configuration: --prefix=/usr --enable-nonfree --enable-gpl --enable-version3 --enable-vdpau --enable-libx264 --enable-libmp3lame --enable-libpulse --enable-libv4l2
  libavutil      55. 63.100 / 55. 63.100
  libavcodec     57. 96.101 / 57. 96.101
  libavformat    57. 72.101 / 57. 72.101
  libavdevice    57.  7.100 / 57.  7.100
  libavfilter     6. 90.100 /  6. 90.100
  libswscale      4.  7.101 /  4.  7.101
  libswresample   2.  8.100 /  2.  8.100
  libpostproc    54.  6.100 / 54.  6.100
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 1488.098843, bitrate: N/A
    Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 1280x720, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
File 'output.mkv' already exists. Overwrite ? [y/N] y
Output #0, matroska, to 'output.mkv':
  Metadata:
    encoder         : Lavf57.72.101
    Stream #0:0: Video: mjpeg (MJPG / 0x47504A4D), yuvj422p(pc, bt470bg/unknown/unknown), 1280x720, q=2-31, 30 fps, 30 tbr, 1k tbn, 1000k tbc
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
[matroska @ 0x1c48860] Non-monotonous DTS in output stream 0:0; previous: 3109, current: 2048; changing to 3109. This may result in incorrect timestamps in the output file.
[matroska @ 0x1c48860] Non-monotonous DTS in output stream 0:0; previous: 3109, current: 2080; changing to 3109. This may result in incorrect timestamps in the output file.
Is there a way to prevent he above errors?
Is there a way to post-process the output file so VLC can play it?
Cheers,
Cedric