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• Compiling FFMPEG on CentOS DigitalOcean

  29 juillet 2015, par coder_uk

  I set up a DigitalOcean instance running CentOS 6.5 and successfully followed the guide to compile FFMPEG (https://trac.ffmpeg.org/wiki/CompilationGuide/Centos). Hurrah !

  But of course I realised that by default, DigitalOcean creates a root user and so ffmpeg now lives in /root/bin/ffmpeg. Which isn’t ideal because when I want to exec the ffmpeg bin from nginx, I would have to run nginx as root for it to have permission.

  Questions ...

  1) Long-shot, but presumably if I change the owner of the ffmpeg binary to nginx, it still won’t work, because nginx won’t be able to access the /root folder it is in. Correct ?

  2) I could run nginx as root (’user root’). But this seems like a very bad idea. Correct ?

  3) Which leaves me with the option of creating a new user, and then compiling ffmpeg into its home folder. But : which user ? EC2 creates ’ec2-user’, so should I make my own equivalent for DO ? But then won’t I have to run nginx as that user, else I’ll run into the same problem ?

  Or should I compile ffmpeg into the ’nginx’ home folder, if indeed it has one ? Is that how it is supposed to be done ?

  Since compiling ffmpeg takes ages, I don’t want to keep doing it, and the static files all seem very out of date. Thanks

• FFMPEG Encoding to prores 4444 with alpha doesn't retain original alpha [closed]

  19 mai 2023, par Nick Weeden

  I'm trying to convert an rgba png to prores 4444 with an alpha. When I run the following command it will create prores file with an alpha. But, the alpha is full white, it doesn't retain the values I put in.

  


  ffmpeg -start_number 1001 -r 24.000 - "pngWithAlpha_%06d.png" -c:v prores_ks -profile:v 4 -alpha_bits 16 -y "proresWithAlpha.mov"


  


  I've tried this with both FFMPEG 4.2.2 and 6.0.0 on a linux system, I'm not sure if I'm doing it wrong or if it is a bug.

  


  Looking at this post it seems it should be possible (they're complaining about quality not a fully missing transfer of the alpha).

  


  I would expect it to pass the alpha straight through but it doesn't. I used alpha_extract to copy the alpha in to the rgb to confirm I'm able to read the alpha from the png, which worked. But the alpha was still full white.

  


• ffmpeg zoompan multiple zoomin/zoomout on different areas of big image [closed]

  10 janvier 2024, par LinuxAdmin

  I need to create a video, with zooming in and out different areas of one big square image.
I tried different zoompan examples, but can't do what I want. What I resolved is keeping aspect ratio of square image, setting setsar=ratio='(1/1)' before zoompan and setdar=ratio='(1/1) after.

  


  Video begins with full image (keeping aspect ratio), then zooms in to a sector of image (1sec), stay 1 second, and zoomout back to full size (1sec). I have 40 sectors, all same size. I can iterate every with bash, adding zoompan line for every sector, setting right x/y coordinates.

  


  Please help me evaluate zoompan expression for getting such result.