[FFmpeg-user] Filter video using libavfilter is longer than input video

Roger Pau Monné roger.pau at entel.upc.edu
Sun Apr 17 21:24:18 CEST 2011


Thanks for your quick reply, I think I'm doing something wrong in the
filter, because if I execute ffmpeg -i INPUT -vf null OUTPUT the
duration of the video is the same, but if I insert my filter, the
duration of the video is increased.

I would like to add the filter to FFmpeg, but I'm still working on the
decoder to extract the mark. Since input and output videos are not
synchronized (marked video seems to start later) I cannot recover the
mark correctly because there is a difference between input videos
(I've based my recover filter on the overlay filter, I will try to
clean the code and send it tomorrow).

2011/4/17 Stefano Sabatini <stefano.sabatini-lala at poste.it>:
> On date Sunday 2011-04-17 20:38:43 +0200, Roger Pau Monné encoded:
>> Hello,
>> I'm trying to develop a new filter using the avfilter API, but it
>> seems to add some frames at the beginning of the video, so input and
>> output videos don't have the same duration (for example if I use an
>> input video of duration 00:01:41.60 the output video has a duration of
>> 00:01:41.64). I don't know if there is a problem with my filter, I
>> don't think I'm adding any frames, but it's the first time I use it,
>> so I'm attaching the filter I'm working on to see if anyone knows what
>> the problem might be.
>> Thanks, Roger.
> Hi,
> from some quick tests it looks a problem related to transcoding, so
> not necessarily libavfilter-specific.
> BTW if you want to integrate the filter into FFmpeg you're welcome to
> post it on ffmpeg-devel, I see there are some simplifications which
> can be done.
> --
> ffmpeg-user random tip #11
> One minute of video silence with ffmpeg:
> ffmpeg -t 60 -s qcif -f rawvideo -pix_fmt rgb24 -r 25 -i /dev/zero \
>    -y silence.mpeg
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