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• ffmpeg change video stream resolution

  10 décembre 2014, par skorpionet

  I have an MKV with a video stream with wrong resolution of 1920x800, but the inside film is 1920x1080 so my main video player, an LG Smart TV, shows a flattened image. I can easily change resolution in container metadata but LG TV ignores this data and read only video stream data.

  First question : only way to change video stream resolution data is scale the video ?

  To scale with ffmpeg I used this command :

  ffmpeg -i input.mkv -map 0 -c:a copy -c:s copy -c:v libx264 -preset slow -crf 17 -vf scale=1920:1080,setdar=16/9 output.mkv

  Now the mkv is fine, my LG TV read it, looks awesome but..... size went from 3,3Gb to 12Gb !!
  Overall bit rate of 3,3Gb video is 2.704 Kbps, 12Gb is 9.829 Kbps. I think that 7000Kbps more are useless, in original video there aren’t info to raise quality.

  Second question : Why this huge size change ? What is my mistake ?

  Best Regards

• Correcting the variable name in an ffmpeg subtitle script

  21 juin 2017, par Steven Foong

  I have 175 mp4 video files and subtitle files with the extension .ass. Unfortunately, my smart TV is not able to read those subtitles. I plan to burn (hardcode) the subtitles into the video.

  I use this command :

  ffmpeg -i orgvideo.mp4 -vf subtitles="subtitle.ass" newvideo.mp4     <br />

  It works. So I plan to use a bash script to automate the process.

  Everything in the script is working but the ffmpeg command line isn’t able to retrieve the subtitle variable.

  After googling around, I found that my file name has special character and space, that causes my script to fail. If the video file name and the subtitle file is simple, then the script should be no problem.

  This is my script :

  for f in *.mp4
  
  do
  
      new="${f%%.mp4} (CHT).mp4"
  
      subtitle="${f%%.mp4}.chi.ass"
  
      < /dev/null ffmpeg -i "$f" -vf subtitles="$subtitle" "$new"
  
  done

  The ffmpeg line is having problems reading the subtitle file variable. Can anyone help ?

• avutil/x86/intmath : remove inline asm implementations for clip functions

  2 juin, par James Almer

  avutil/x86/intmath : remove inline asm implementations for clip functions
  GCC/Clang is smart enough to emit minss/maxss the same way as these functions.
  
  The only theoretical benefit was in x86_32, where x87 floats are used, but the
  
  penalty of making the clipping opaque to the compiler's scheduler plus moving
  
  values from mmx regs to xmm and back will offset any potential speedup.
  
  x86_32 builds targetting anything made in the last two decades and a half
  
  should use -msse -mfp=sse anyway.
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavutil/x86/intmath.h