New submission from Anatoly madRat L.Berenblit <[email protected]>:
FFMPEG some times can not correctly convert mpegts from pipe, but works well
this the same file
In short:
not works ./ffmpeg -y -i - -vcodec copy -acodec copy -f mpegts ~/out.ts <
~/badpipe.ts
works ./ffmpeg -y -i ~/badpipe.ts -vcodec copy -acodec copy -f mpegts
~/out.ts
sample file ftp://upload.ffmpeg.org/incoming/tspipe-bug/badpipe.ts
more detailed description -
ftp://upload.ffmpeg.org/incoming/tspipe-bug/description.txt
patch - ftp://upload.ffmpeg.org/incoming/tspipe-bug/tspipe.patch
----------
files: desc.txt
messages: 13792
priority: normal
status: new
substatus: open
title: av_find_stream_info may generate but data for outputs if input source is
non-seekable
type: bug
________________________________________________
FFmpeg issue tracker <[email protected]>
<https://roundup.ffmpeg.org/issue2636>
________________________________________________
BUG: FFMPEG some times can not correctly convert mpegts from pipe, but works
well this the same file
This issue based on av_find_stream_info precaching.
When this function parse some input stream data (for input format detectoin) it
stores readed packets
in special buffer (AVFormatContext::packet_buffer).
Later (at av_read_packet), if input streams supports seek(files) - stream reset
to seek(0) and parse packets again. For inputs w/o seek,
first packets taking from packe_buffer.
For correct timestamp calculation needed stream info, that is returned by
decoder after packet is added into packe_buffer, and if before returning to
client packets will be fluash and re-read again - behaviour is correct (for 2nd
parse of 1st packet all information (samplerate and etc) is available), but if
seek is not available - for 1st packet at 1st pass - sample rate is invalid and
packets timestamp/duration may be ugly.
This ugly timestamp of 2nd packet ( = timestamp of 1st packet +
1st_packet_duration) crashes some format-outputs.
Solution:
After try_decode_frame update packet_buffer.
Patch is applied.
Sample - badpipe.ts
not works ./ffmpeg -y -i - -vcodec copy -acodec copy -f mpegts ~/out.ts <
~/badpipe.ts
works ./ffmpeg -y -i ~/badpipe.ts -vcodec copy -acodec copy -f mpegts
~/out.ts
