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• Extract the 0th frame of every second on a live video

  14 avril 2020, par geo-freak

  I have a command to extract the zero-th frame of every second. I got the command from here.

  



  ffmpeg -i input.ts -vf "select=between(mod(n\, 25)\, 0\, 0), setpts=N/24/TB" output-%04d.png


  



  But when I run the above command on live feed, it is extracting more than 100000 frames. The above command is not working on a live recording. Can anyone suggest or help me to extract the very first frame on a live recording ? Thanks in advance.

  



  P.S : For my testing I am running the above command on a tcr video.

  


• fftools/ffmpeg_mux_init : Fix attachment_filename use-after-free

  18 février 2024, par Andreas Rheinhardt

  fftools/ffmpeg_mux_init : Fix attachment_filename use-after-free
  The filename is freed with the OptionsContext and therefore
  
  there will be a use-after-free when reporting the filename
  
  in print_stream_maps(). So create a copy of the string.
  This is a regression since 8aed3911fc454e79697e183660bf30d31334a64b.
  
  fate-lavf-mkv_attachment exhibits it (and reports a random nonsense
  
  filename here), but this does not make the test fail (not even with
  
  valgrind ; only with ASAN, as it aborts on use-after-free).
  Reviewed-by : Anton Khirnov <anton@khirnov.net>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] fftools/ffmpeg.h
  • [DH] fftools/ffmpeg_mux.c
  • [DH] fftools/ffmpeg_mux_init.c

• HTML5 / and live transcoding with FFMPEG

  8 mai 2014, par TooTallNate

  So from my web server, I would like to use FFMPEG to transcode a media file for use with an HTML <audio></audio> or <video></video> tag. Easy enough right ?

  The conversion would need to take place in real-time, when an HTTP client requested the converted file. Ideally the file would be streamed back to the HTTP client as it is being transcoded (and not afterwards at the end, since that would potentially take a while before any data starts being sent back).

  This would be fine, except that in today’s browsers, an HTML5 audio or video tag requests the media file in multiple HTTP requests with the Range header. See this question for details.

  In that question linked above, you can see that Safari requests weird chunks of the file, including the ending few bytes. This poses a problem in that the web server WOULD have to wait for the conversion to finish, in order to deliver the final bytes of the file to conform to the Range request.

  So my question is, is my train of thought right ? Is there a better way to deliver transcoding content to an <audio></audio> or <video></video> tag that wouldn’t involve waiting for the entire conversion to finish ? Thanks in advance !