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• Changing gamma_r & g in video filter eq (ffmpeg) causes decrease in vmaf score ?

  14 août 2019, par Billo Binder

  I am using ffmpeg video filter

  -vf eq=contrast=1.1:brightness=0:saturation=1:gamma=1:gamma_r=0.99:gamma_g=0.98:gamma_b=1.1

  to reduce red & green colors in a video. But this causes reduction in vmaf scores but increase in ssim scores and I don’t understand why ?

  Original Scores :

  • aggregateVMAF="98.0557"
  • aggregateSSIM="0.977389"
  • aggregateMS_SSIM="0.982315"
  • poolMethod="mean".

  Modified scores :

  • aggregateVMAF="87.0124"
  • aggregateSSIM="0.991839"
  • aggregateMS_SSIM="0.984841"
  • poolMethod="mean".

  Also eq=contrast=1.1 causes boost in vmaf score.

  How do i interpret this...i mean can i ignore change in vmaf as ssim is high ?

  Original Score i got using video filter at default :

  -vf eq=contrast=1.1:brightness=0:saturation=1:gamma=1:gamma_r=1:gamma_g=1:gamma_b=1

  Other Details :

  Distorted 720p video was upscaled using :

  ffmpeg -i dist.mkv -map 0:0 -map 0:1 -vf scale=1920x1080:flags=lanczos -c:v h264_nvenc -preset lossless -profile:v high -level 4.1 -crf 0 -c:a copy output_1080p.mkv

  i mean can i discard low vmaf score & finalize the encode because ssim is high ot there is some other filter which will not hamper vmaf score and reduce greenish effect ?

• Resize videos with ffmpeg - Keep aspect ratio

  8 juin 2020, par ColinShark

  I'm trying to write a script for a telegram userbot that can convert any video/animation to a .mp4. I already have it so the script communicates and utilizes the API of cloudconvert.com.

  



  Now my problem lies within the ffmpeg command that I'm passing to CC, as I need to keep videos below 1280 pixels on either side. It doesn't matter if the final video is 720*1280 or 1280*1280 or something completely else, as long as neither of the two sides surpass 1280 pixels.

  



  Here comes the tricky part, I don't want to ruin the aspect ratio and I don't want the video to be upscaled if it's smaller than 1280.

  



  The part of code that is actually relevant is the scale portion.
This following piece will resize a video to maximum 1280 pixels in height, but doesn't take the width into account, it just keeps the ratio.

  



  -vf "scale=min'(1280,iw)':-2"

  



  Now how would I have to either adapt it or change it so it will actually resize depending on which side is greater than 1280 pixels ?

  



  I hope I'm being specific enough and I'm looking forward to your help.

  


• Crop, Resize and Cut all in one command - FFMPEG

  24 septembre 2018, par Sabha

  I am trying to do three tasks with FFMPEG

  1. Crop a video without losing quality

  2. Resize (upscale) the cropped video with good quality

  3. Cut specific part of a the upscaled vided without losing quality

  Here are the command line I use :

  to crop : video og.mp4 to video og1.mp4

  ffmpeg -i og.mp4 -vf "crop=1330:615:22:120" -c:v libx264 -crf 1 -preset veryslow -c:a copy og1.mp4

  to resize : video og1.mp4 (converted above) to video og2.mp4

  ffmpeg -i og1.mp4 -vf scale=1920:-1 -c:v libx264 -crf 1 -preset veryslow -c:a copy og2.mp4

  to cut : video og2.mp4 (converted above) to og3.mp4

  ffmpeg -i og2.mp4 -ss 00:00:08.190 -t 00:00:11.680 -c:v libx264 -crf 1 -preset veryslow -c:a copy og3.mp4

  I want to achieve highest quality of 1920 width video (irrespective of height and size of the file)

  Is there a way to get the above tasks in one command or shorter time with best quality ?

  Also advice if there is a better command or parameters to be used.

  Thanks