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• What ffmpeg arguments will approximate Zoom recording quality [closed]

  25 octobre 2020, par Stan Ivanov

  I've been recording screen sharing presentations using Quicktime on my Mac and it uses x264 format with 60fps. The produced video file is with type MOV and around 2.2GB for 1 hour of presentation. I want to compress it using ffmpeg and I've been doing so using x264 as well. Here are my arguments :

  


  ffmpeg -i '$inputFile' -vcodec "libx264" -crf 32 -vf 'scale=${width}:-2,fps=24' -c:a aac -b:a 128k -preset veryslow -profile:v high -tune stillimage -f mp4 '$outputFile'


  


  I rescale my video to 1600px width to save on space and I also convert the recording to 24fps as I see no need to have the full 60fps available. It's mostly static images as I talk over my screen. This results in about 100MB file using the -profile:v high argument. Otherwise it is around 160MB.

  


  On the other hand Zoom recording for much larger resolutions (4k etc) are around 80MB per 1 hour. Does anyone know what options we can use to approximate this file size and quality ? I know they are using lower quality audio which might explain some of the difference.

  


  But if I increase the -crf 32 argument it starts to degrade quality too much. I am not sure how Zoom achieves it's video quality with high resolutions such as 1080p and 4k with a file size of 80MB while I can't match it using 1600px width.

  


  Edit : I had an idea that I probably don't need all 24 fps in a screen sharing of static content. So I reduced it to 5 fps and that seems to work well for my use case. I wonder if this is what Zoom does ?

  


• avfilter/vidstabtransform : allow negative zoom.

  13 septembre 2013, par Georg Martius

  avfilter/vidstabtransform : allow negative zoom.
  This is useful in addition to crop=black.
  Signed-off-by : Clément Bœsch <clement@stupeflix.com>
  

  • [DH] libavfilter/vf_vidstabtransform.c

• i can not set video duration in Zoom & Pan with Fade In/Out Transition

  4 octobre 2018, par Prashant Godhani

  I am new to ffmpeg. i am doing Zoom & Pan with Fade In/Out Transition on image to make video i used this script, but this is for 4 image and i want to only for single image so i have tried this command :

  ffmpeg -y -loop 1 -i 1.jpg -filter_complex "\
  
  [0:v]setpts=PTS-STARTPTS,scale=w='if(gte(iw/ih,1280/720),-1,1280)':h='if(gte(iw/ih,1280/720),720,-1)',crop=1280:720,setsar=sar=1/1,format=rgba,split=2[stream1out1][stream1out2];\
  
  [stream1out1]trim=duration=1,select=lte(n\,30),split=2[stream1in][stream1out];\
  
  [stream1out2]trim=duration=2,select=lte(n\,60)[stream1];\
  
  [stream1in]fade=t=in:s=0:n=30[stream1fadein];\
  
  [stream1out]fade=t=out:s=0:n=30[stream1fadeout];\
  
  [stream1fadein][stream1][stream1fadeout]concat=n=3:v=1:a=0,scale=1280*5:-1,zoompan=z='min(pzoom+0.002,2)':d=1:x='iw/2-(iw/zoom/2)':s=1280x720 ,format=yuv420p[video]" -map [video] -vsync 2 -async 1 -rc-lookahead 0 -g 0 -profile:v main -level 42 -c:v libx264 -r 30 df.mp4   

  It works fine but it generate 4 second video. So i’m confused about how to set video duration in this command.