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• Black overlay appears when merging a transparent video to another video

  13 juin 2012, par RakeshS

  This is what I have done so far :

  Command to create a transparent PNG image :

  convert -size 640x480 -background transparent -fill blue \
  
  -gravity South label:ROCK image1-0.png

  Command to create a transparent video :

  ffmpeg -loop 1 -f image2 -i image1-0.png -r 20 -vframes 100 \
  
  -vcodec png -pix_fmt bgra mov-1.mov

  (as per this post) - I expect this video to be a transparent video.

  Command to overlay a video with another :

  ffmpeg -i final-video.mov -sameq -ar 44100 \
  
  -vf "movie=mov-1.mov [logo];[in][logo] overlay=0:0 [out]" \
  
  -strict experimental final-video.mov

  Above commands works perfect and I have not faced any problem, but I don't get what I expect which is kinda watermarking effect, I want mov-1.mov to be transparent with final-video.mov.

  Questions :

  1. Is there any way to verify if the generated video is transparent ? other than merging ?
  2. Not sure why the above mov-1.mov is not transparent when it is merged with final-video.mov, any info to solve this problem would be great.

  Please help.

• 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 ?

  


• twinvq : Split VQF-specific part from common TwinVQ decoder core

  4 août 2013, par Kostya Shishkov

  twinvq : Split VQF-specific part from common TwinVQ decoder core
  Signed-off-by : Diego Biurrun <diego@biurrun.de>
  

  • [DBH] libavcodec/Makefile
  • [DBH] libavcodec/twinvq.c
  • [DBH] libavcodec/twinvq.h
  • [DBH] libavcodec/twinvqdec.c