[FFmpeg-trac] #8211(avformat:new): ffplay does'nt play mjpeg stream

FFmpeg trac at avcodec.org
Mon Mar 22 22:42:04 EET 2021

#8211: ffplay does'nt play mjpeg stream
             Reporter:  anhsoft      |                    Owner:
                 Type:  enhancement  |                   Status:  new
             Priority:  wish         |                Component:  avformat
              Version:  git-master   |               Resolution:
             Keywords:  rtsp mjpeg   |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  1            |
Changes (by cehoyos):

 * analyzed:  0 => 1


 Sorry for my bad interpretation of the ticket, I had originally found an
 Android binary but no source code!

 The issue is that the restart interval in the attached dump (and according
 to the original description also in the rtp header) is 0x3de (990) for the
 first frame and has similar values between 986 and 1026 for the remaining
 frames. If I force the restart interval for each frame to 0x28 (40) in the
 decoder, the stream plays fine.
 Looking at RFC 2435 I don't see an obvious bug in
 libavformat/rtpdec_jpeg.c and to the best of my knowledge there is no bug
 related to the restart interval in FFmpeg's jpeg decoder indicating that
 in the end, my interpretation may not have been so far off.
 I don't know how this issue can be fixed reliably.
 diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
 index 20f310fd70..9a4c1b8b2b 100644
 --- a/libavcodec/mjpegdec.c
 +++ b/libavcodec/mjpegdec.c
 @@ -1802,6 +1802,7 @@ static int mjpeg_decode_dri(MJpegDecodeContext *s)
      if (get_bits(&s->gb, 16) != 4)
          return AVERROR_INVALIDDATA;
      s->restart_interval = get_bits(&s->gb, 16);
 +s->restart_interval = 40;
      s->restart_count    = 0;
      av_log(s->avctx, AV_LOG_DEBUG, "restart interval: %d\n",

Ticket URL: <https://trac.ffmpeg.org/ticket/8211#comment:18>
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