[FFmpeg-trac] #3353(undetermined:new): Transcode to .ts format gives unexpected video start time
FFmpeg
trac at avcodec.org
Mon Jan 27 11:52:01 CET 2014
#3353: Transcode to .ts format gives unexpected video start time
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Reporter: | Owner:
wdelstrother | Status: new
Type: defect | Component:
Priority: normal | undetermined
Version: unspecified | Resolution:
Keywords: mpegts | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Comment (by wdelstrother):
I am not using -f hls, because I don't have a single input file to break
down into segments.
The problem that I am seeing is simply that the start time in the .ts file
is non-zero, when (as far as I can tell) there is no reason why it should
be.
I think I might need to give some more context to what I'm actually trying
to do; in my application, I'm receiving a sequence of 5 second files from
a 3rd party, and I'm using ffmpeg to transcode each one into a .ts file
(with libx264 / aac) with the appropriate start time. I also generate an
m3u8 playlist outside of ffmpeg at run-time so that the 'chunked' video
can be restreamed in near-real-time.
The only way I've found to set the start time of a .ts file was to use the
'initial_offset' option to ssegment (even though I'm only producing a
single segment). So my command line for a single transcode actually looks
something like:
%ffmpeg -loglevel warning -i input.avi -c:a aac -strict -2 -ac 2 -ar 44100
-b:a 128k -c:v libx264 -profile:v main -level:v 4.1 -x264opts keyint=60 -r
30 -b:v 400k -vf scale=426:240 -f ssegment -map 0 -segment_time 100
-initial_offset 100 output%03d.ts
%mv output000.ts output.ts
In that line, I request a start time of 100s, but the start time which is
actually put into the file is a few seconds off from that. When I attempt
to play the video from the playlist, these start time errors result in
discontinuities, so the video jumps and/or hangs.
I recognise that the above is rather convoluted, so I've tried to simplify
the problem for this bug report. Exactly the same problem (the start time
of a .ts file being offset) happens when we just do a simple 'ffmpeg -i
input output.ts', which is why I provided this example.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/3353#comment:4>
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