Recherche avancée

Sur d’autres sites (8002)

• Calculate VMAF score while encoding a video with FFmpeg

  31 octobre 2024, par user8071576

  I have an ffmpeg version built with VMAF library. I can use it to calculate the VMAF scores of a distorted video against a reference video using commands like this :

  


  ffmpeg -i distorted.mp4 -i original.mp4 -filter_complex "[0:v]scale=640:480:flags=bicubic[main];[main][1:v]libvmaf=model_path=model/vmaf_v0.6.1.json:log_path=log.json" -f null -


  


  Now, I remember there was a way to get VMAF scores while performing regular ffmpeg encoding. How can I do that at the same time ?

  


  I want to encode a video like this, while also calulate the VMAF of the output file :

  


  ffmpeg -i original.mp4 -crf 27 -s 640x480 out.mp4


  


• 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 ?

• FFMPEG - bufsize formula

  31 mars 2023, par Data

  Does anyone know what the formula is for bufsize along with the rate it checks in FFMPEG ?

  


  I can't seem to find any concrete answer to this.

  


  Is it :
bufsize = bitrate / rate
 ?

  


  And should it be using maxrate as opposed to bitrate in the calculation ?

  


  Example on working out the rate at which the checks are done :

  


  bitrate: 700Kbps
maxrate: 700Kbps
bufsize: 70Kb

700Kbps/70Kb = 10 sec


  


  Is that right ?
To me that doesn't sound right because a smaller bufsize should be running the check at a higher rate and 10 seconds seems too long of a gap.

  


  Would the formula need to be inverted ?

  


  Does anyone have an idea on the correct syntax for the formula and units ?