[FFmpeg-trac] #4893(undetermined:new): FFmpeg stops outputting frames unexpectedly and indefinitely on "bad" h264 over UDP stream

FFmpeg trac at avcodec.org
Mon Oct 19 22:00:16 CEST 2015

#4893: FFmpeg stops outputting frames unexpectedly and indefinitely on "bad" h264
over UDP stream
             Reporter:  superware    |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
              Version:  unspecified  |  undetermined
             Keywords:  udp h264     |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0

Comment (by superware):

 > Sorry, I do not understand what you are trying to report: The file you
 provide contains 390 broken frames and all can be transcoded: If you cut
 400k (10%) from the end, 361 frames are decoded, if you cut 500k from the
 beginning, 358 frames are decoded indicating that the whole file can be
 read. With a file as broken as this one, you cannot expect that you get a
 decodable stream no matter where you cut it. This could be different if
 the stream were recognisable but this is not the case.

 Let me explain from the beginning. I have a "black box" generating live
 h264 over UDP stream, but once in a while, ffmpeg seems to enter a
 situation where it unexpectedly stops outputting frames, without recovery.
 The only solution in that point is to restart playback/ffmpeg, and then,
 the stream is '''immediately''' decoded normally. I'm not an expert in
 this, but it seems the decoder enters a dead-lock-like situation within

 By recording the network stream of that UDP/h264 stream, omitting every
 second packet, this was the only way I could reproduce the described
 "decoder halt" condition. You can see that in some point, the decoder
 stops outputting frames (or "garbage" as you might call it), but it
 doesn't recover. It seems that the same "garbled" stream might briefly
 appear in the middle of a perfectly good stream and render the
 decoder/process inoperable.

 The folks at #ffmpeg-devel suggested I try to reproduce with a file, since
 playing a pcap file might be a bit challenging.

 Thank you for helping out.

Ticket URL: <https://trac.ffmpeg.org/ticket/4893#comment:21>
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