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• ffmpeg converting video to images while video file is being written

  20 décembre 2018, par user3398227

  Hopefully an easy question for an ffmpeg expert !

  I’m currently converting large (+6GB) mpeg video into an image sequence - which is working well using the below ffmpeg command :

  ffmpeg -i "input.mpeg" -vf - fps=fps=2 -f image2 -qscale 1 -s 1026x768
  "output%6d.jpg"

  however i have to wait for the file to finish being written to disk before i kick off ffmpeg - but this takes a good hour or so to finish writing, but what i’ve noticed is that ffmpeg can start reading the file while its being written to disk - the only snag here is it gets to the end of the file and stops before the file has finished being written...

  Question is, is there a way that ffmpeg can convert to an image sequence at the same pace the video is being written (and not exit out ?)... or know to wait for the next frame to be written from the source. (unfortunately the input doesn’t support streaming, I only get a network drive and file to work off.. ) I thought i read somewhere that ffmpeg can process at the video frame rate but cant seem to find this command for love or money in the doco !!

  Thanks !

• Split a video file into separate video and audio files using a single ffmpeg call ?

  25 novembre 2015, par sdaau

  Background : I would like to use MLT melt to render a project, but I’d like that render to result with separate audio and video files. I’d intend to use melt’s "consumer" avformat which uses ffmpeg’s libraries, so I’m formulating this question as for ffmpeg.

  According to Useful FFmpeg Commands For Converting Audio & Video Files (labnol.org), the following is possible :

  ffmpeg -i video.mp4 -t 00:00:50 -c copy small-1.mp4 -ss 00:00:50 -codec copy small-2.mp4

  ... which slices the "merged" audio+video files into two separate "chunk" files, which are also audio+video files, in a single call ; that’s not what I need.

  Then, ffmpeg Documentation (ffmpeg.org), mentions this :

  ffmpeg -i INPUT -map_channel 0.0.0 OUTPUT_CH0 -map_channel 0.0.1 OUTPUT_CH1

  ... which splits the entire duration of the content of two channels of a stereo audio file, into two mono files ; that’s more like what I need, except I want to split an A+V file into a stereo audio file, and a video file.

  So I tried this with elephantsdream_teaser.ogv :

  ffmpeg -i /tmp/elephantsdream_teaser.ogv \
  
    -map 0.0 -vcodec copy ele.ogv -map 0.1 -acodec copy ele.ogg

  ... but this fails with "Number of stream maps must match number of output streams" (even if zero-size ele.ogv and ele.ogg are created).

  So my question is - is something like this possible with ffmpeg, and if it is, how can I do it ?

• ffmpeg_opt : Set the video VBV parameters only for the video stream from -target

  25 mai 2015, par Michael Niedermayer

  ffmpeg_opt : Set the video VBV parameters only for the video stream from -target
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] ffmpeg_opt.c