#8014: Piping mjpeg drops frames
-------------------------------------+-------------------------------------
Reporter: sig | Type: defect
Status: new | Priority: normal
Component: ffmpeg | Version: git-
Keywords: h264 mjpeg | master
pipe dropped frames | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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It seems switching output from jpeg image files to a pipe results in
frames not being outputted to the pipe.
Attached is 100-frames.mp4 which is a video of 100 sequentially numbered
frames.
As expected running the below outputs all 100 frames correctly.
{{{
ffmpeg -i 100-frames.mp4 -f image2 -vcodec mjpeg "out%05d.jpg"
}}}
However running this next command results in only 53 frames being
detected:
{{{
ffmpeg -i 100-frames.mp4 -f image2 -vcodec mjpeg -update 1 pipe:1 | xxd |
grep "ffd8" | wc -l
}}}
This one uses xxd to convert the outputted binary into hex then uses grep
to search for the jpeg start bytes ("ffd8"). Finally wc counts the search
hits and prints the total at the end. So the number output at the end is
the number of JPEGs seen in the stream.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/8014>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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