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• ffmpeg and gnu parallel

  16 août 2013, par souvik

  My work would require me to encode a few thousand movies in a few days. Each movie needs to be encoded in 3 different formats. I use ffmpeg to output these formats in parallel with a single read of the input source as detailed here : http://ffmpeg.org/trac/ffmpeg/wiki/Creating%20multiple%20outputs

  In addition, I am using GNU Parallel to encode from multiple video files in parallel. We have four blade servers of different configurations (48, 32, 16 and 16 cores) encoding videos in parallel. Ideally, we should be able to encode 112 videos in parallel.

  However, it seems that encoding completes faster on machines with lesser cores. I have 16 completed encodes on the 16 core servers in around 4 hours, while it takes close to 10 hours for 48 encodes to complete on the 48 core system. What could be the bottleneck ? A typical encode command is as follows :

  ffmpeg -i sample.mpg -y -vcodec libx264 -vprofile baseline -level 30 -acodec libfdk_aac -ab 128k -ac 2 -b:v 500K -threads 1  encoded/sample_enc.mp4

  Any pointers highly appreciated. Thanks !

• 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 ?

  


• 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.