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• ffmpeg build thumbnail sequence while transcoding

  9 novembre 2018, par Redtopia

  With the goal of improving performance while processing a video file and outputting it into 3 parallel output files, would it be possible to also build a thumbnail sequence as another parallel output or in another process ?

  To create the 3 parallel outputs, I’m following the example on this page : https://trac.ffmpeg.org/wiki/Creating%20multiple%20outputs

  ...and using this example :

  ffmpeg -i input \
  
      -s 1280x720 -acodec … -vcodec … output1 \
  
      -s 640x480  -acodec … -vcodec … output2 \
  
      -s 320x240  -acodec … -vcodec … output3

  My command to generate thumbnails looks like this :

  ffmpeg -f image2 -ss 2 -r "1/3" -s 100x50 ./thumbs/th-%04d.png

  I’m using the ffmpeg 4.1

  What I’m finding is that building a series of thumbnails, say 1 every 10 seconds, can be quite time consuming for large video files, so I’m guessing I could save some processing time if I could build the thumbs at the same time.

• FFMpeg : reencode audio file to have the same codec params as another file [closed]

  11 mars 2023, par EvilOrange

  I need to merge three audio files :

  


  

  • big1

  


  • small1

  


  • big2

  


  


  Codecs in these files may differ (but big1 and big2 which always have the same codec)

  


  small1 is about 20-30 seconds

  


  Now I'm using the following command for that :

  


  ffmpeg -i big1 -i small1 -i big1 -filter_complex concat=n=3:v=0:a=1 -c:a {big1.extension} -vn out.{big1.extension

  


  it's working, but this will require reencoding and it's slow.

  


  I think, that it can be optimized by using concatenation without reencoding : https://trac.ffmpeg.org/wiki/Concatenate

  


  But I need the same codec for all files.

  


  So, now I need the following :

  


  

  1. Get codec information from big1

  


  2. Reencode small1 to the same parameters

  


  3. merge files using concat demuxer without reencoding

  


  


  So, I need a way to get codec information and pass these params to ffmpeg to convert small1.

  


  I'm not tied to ffmpeg, if another linux cmd tool can do the same ( fastly merge three audio files) - it's also acceptable.

  


• HW Accel Transcode Intel Quick Sync Video QSV h264_qsv and CRF Quality

  26 août 2020, par Matt McManis

  I'm having a problem with HW Accel Intel Quick Sync Video and CRF.

  



  It looks like CRF -crf is not compatible with -c:v h264_qsv.

  



  Only Bit Rate -b:v works with -c:v h264_qsv.

  



  ffmpeg -i input.mp4 -c:v h264_qsv -crf 25 -pix_fmt nv12 output.mkv


  



  ---

  



  https://trac.ffmpeg.org/wiki/Hardware/QuickSync

  



  The guide says "ICQ mode (which is similar to crf mode of x264)" -global_quality 25

  



  ffmpeg -i input.mp4 -c:v h264_qsv -global_quality 25 -pix_fmt nv12 output.mkv


  



  But I cannot get it to work. I get the error Selected ratecontrol mode is unsupported.

  



  ---

  



  How do I get either CRF or ICQ to work ?