#11466: FIFO Muxer: restart_with_keyframe does not work when
drop_pkts_on_overflow
false
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Reporter: Wallboy | Type: defect
Status: new | Priority: normal
Component: avformat | Version: 7.1
Keywords: fifo muxer | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Summary of the bug:
When using the FIFO pseudo-muxer with restart_with_keyframe enabled and
drop_pkts_on_overflow disabled, when FIFO recovers, it does not drop until
the next keyframe and immediately begins sending whatever frametype it
left off on.
How to reproduce:
Start a local RTMP server with ffmpeg so we can mock a disconnect:
{{{
ffmpeg -f flv -listen 1 -i rtmp://127.0.0.1/app/path -f null /dev/null
}}}
Create a test source and output to local RTMP server:
{{{
ffmpeg -loglevel repeat+verbose -re -f lavfi -i
"testsrc=duration=600:size=640x360:rate=30" -c:v libx264 -pix_fmt yuv420p
-f fifo -fifo_format flv -attempt_recovery 1 -restart_with_keyframe 1
-drop_pkts_on_overflow 0 -map 0 -flags +global_header
rtmp://127.0.0.1/app/path
}}}
Then stop the RTMP server (Ctrl+C) so that the FIFO muxer goes into
recovery mode. Then start the RTMP server up again.
When FIFO is able to reconnect, you expect to see "Dropping non-keyframe
packet" messages, but it just ends up sending whatever frame it stopped
on. You'll also see likely see h264 errors at the server side, since it
can't decode these B/P frames it's now receiving.
Of course if you enable drop_pkts_on_overflow, the packets are dropped
until keyframe. However, the documentation seems to imply
restart_with_keyframe doesn't depend on drop_pkts_on_overflow.
It should be allowed to block the encoder while we wait for a reconnect,
and then once resumed, drop until we hit a keyframe, so that RTMP servers
do not receive B/P frames that can't be decoded.
This following line keeps FifoThreadContext->drop_until_keyframe from
being set unless drop_pkts_on_overflow was also set:
https://github.com/FFmpeg/FFmpeg/blob/dc7964a862890d58072ee9ca711b4b38eda5a209/libavformat/fifo.c#L374
--
Ticket URL: <https://trac.ffmpeg.org/ticket/11466>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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