#4893: FFmpeg stops outputting frames unexpectedly and indefinitely on "bad"
h264
over UDP stream
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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
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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
itself.
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>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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