Recherche avancée

Sur d’autres sites (7102)

• What is num_ref_idx_l0_active_minus1 ?

  9 février 2017, par Victor.dMdB

  I’m encoding an h264 file and the ouput PPS contains num_ref_idx_l0_active_minus1=3, but I need this to be 0 instead.

  In the ITU-T H.264 spec, it states :

  num_ref_idx_l0_active_minus1 specifies the maximum reference index for
  reference picture list 0 that shall be used to decode the slice.

  But the closest option I can find in libx264 is -refs, but that doesn’t seem to affect it.

  I understand that since this is referring to List 0, it is associated with B-Frames, but there are no specific libx264 parameters relevant to that specific field.

• How to make old 4:3 video content into 16:9 with crop/zoom and slight stretch ?

  9 août 2020, par Daniel Iversen

  I have old video cam footage in 4:3 format that I'd like to have play better on modern 16:9 screens, specifically I'd like to :

  


  

  • Crop/"Zoom" the video "a little" (cutting a tiny bit, maybe 10-15%, of the top and bottom of the video off)

  


  • Stretch the video "a tiny bit" (maybe 10%) - this will of course can ruin the footage so would like to only stretch the video a tiny bit

  


  • Still keep a bit of a border on the sides (since I don't want to stretch or crop the video too much)

  


  


  I'll still keep the original files too, but would like a version that just plays slightly nicer natively in 16:9. And I'd like to use free software like ffmpeg or Handbrake.

  


  I've found guides on how to crop and how to stretch the videos independently but I'm fearing having to re-encode the videos twice loses quality and takes a lot of time, so I'd like to do it all in one go.

  


  Does anyone have any ideas on how to do this ?

  


• As part of my program that I am writing I am using ffmpeg. I am debugging. Why would ffmpeg run slower on a GPU than a CPU when doing mp4 compression ? [closed]

  6 mai 2023, par user875234

  I'm running it on modern equipment with latest drivers. I use it to compress video files, like so :

  


  ffmpeg -i 20230502_200913.mp4 -vcodec libx265 -crf 28 -vf "scale=trunc(iw/10)*2:trunc(ih/10)*2" output.mp4


  


  that command runs in 160 seconds on the CPU. but if I use the GPU, like so :

  


  ffmpeg -hwaccel cuda -i 20230502_200913.mp4 -vcodec libx265 -crf 28 -vf "scale=trunc(iw/10)*2:trunc(ih/10)*2" output.mp4


  


  it actually takes 280 seconds. And again, these are same era CPU and GPU. I can see it uses 100% of the GPU when running on the GPU but only 50% of the CPU when running on the CPU. I expected it to run much faster on the GPU than the CPU.

  


  Am I missing something ?