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• vdpau : common support for managing the VdpDecoder in avcodec

  4 octobre 2014, par Rémi Denis-Courmont

  vdpau : common support for managing the VdpDecoder in avcodec
  Using the not so new init and uninit callbacks, avcodec can now take
  
  care of creating and destroying the VDPAU decoder instance.
  The application is still responsible for creating the VDPAU device
  
  and allocating video surfaces - this is necessary to keep video
  
  surfaces on the GPU all the way to the output. But the application
  
  will no longer needs to care about any codec-specific aspects.
  Signed-off-by : Anton Khirnov <anton@khirnov.net>
  

  • [DBH] libavcodec/vdpau.c
  • [DBH] libavcodec/vdpau_internal.h

• How to catch a FFMPEG exception with subprocess ?

  13 mai 2022, par Faindirnomainzein

  I'm doing some work on subtitles and some videos have 1 subtitle track, others have 2 subtitle tracks. For those that have 2, I use the 2nd one (index = 1). I'm trying to automate it with python.

  


  For files with with 2 subtitle tracks, I use :

  


  


  -vf "subtitles='file.mkv':si=1

  


  


  and for those with 1 subtitle track, I use :

  


  


  -vf "subtitles='file.mkv':si=0

  


  


  I'm using this code :

  


  for mkv in all_mkvs:
    try:
      subprocess.call(f'ffmpeg -i ... -vf "subtitles='file.mkv':si=1 ...')
    except:
      subprocess.call(f'ffmpeg -i ... -vf "subtitles='file.mkv':si=0 ...')


  


  But it doesn't seem to care about the exception and just ends the loop whenever it meets a file with 1 subtitle and gives me the error anyway.

  


  Press [q] to stop, [?] for help
[Parsed_subtitles_0 @ 0000011af4912880] Shaper: FriBidi 1.0.10 (SIMPLE) HarfBuzz-ng 2.7.2 (COMPLEX)
[Parsed_subtitles_0 @ 0000011af4912880] Unable to locate subtitle stream in ./test/349.mkv
[AVFilterGraph @ 0000011af623d880] Error initializing filter 'subtitles' with args './test/349.mkv:si=1'
Error reinitializing filters!
Failed to inject frame into filter network: Operation not permitted
Error while processing the decoded data for stream #0:3
Conversion failed!


  


  As you can see in the error message above, it says : "Error initializing filter .... si=1" because it should be si=0 in the case of that specific file, which is why I added the exception, but it doesn't seem to care about it.

  


  

  


  So I'm trying to catch that error and say "ok, in that case, let's do si=0 instead".

  


• Video editing : faded speedup/slowdown with free software

  25 octobre 2013, par Valio

  I would like to do "faded" speedups or slowdowns within videos.
  To illustrate what I mean here's a short clip of what I call "faded slowdown"

  So in a scene running at normal speed, there is a timeframe where the video slows down (or speeds up) and then runs again at normal speed. However the speed does not drop from 1 to e.g. 0.2 in a millisecond, but there's a smooth transition inbetween (I'm not certain if linear or not).

  I guess my video edtiting/cutting terminology is entirely flawed ; don't hesitate to correct it.

  1. Is anyone aware of a free software (*) video editor that offers such functionality ?
  2. Has anyone tried to implement it themself ? I guess it's not really that hard by using a script that generates necessary calls for ffmpeg or the like.

  over at least one second.
  the have one scene that runs at normal speed and at some point has a short slowdown or speedup. Basically we have one scene that gets
  I have not done any experiments yet, but
  If my terminology is confusing an exa

  (* as in free speech)