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• Using libav (ffmpeg), how to decode a video file directly to a GPU texture ?

  15 janvier 2023, par GaryO

  I'm using ffmpeg's libav to decode video files on Mac. For supported codecs, it says it can use the Mac VideoToolbox framework to hardware-accelerate the decoding.&#xA;Can I get the result of that decode directly as a Metal or CoreVideo buffer or texture, in GPU memory ? My plan is to process it with compute shaders before sending it to the screen and I'd like to maximize framerate by removing CPU<->GPU transfers.

  &#xA;

  Is there an example of doing this anywhere ?

  &#xA;

• Build error caused by missing library arc4random

  25 mai 2016, par Omega1001

  I’m currently working on a Streaming framework, and decided to use ffmpeg to encode and or decode my Video and or Audio.

  So i clicked through https://ffmpeg.org for the api files, and downloaded the statically linked version only to find out it actually contained a .exe (I use Windows in development, but plan on using Linux in production) instead of one or more dll’s and header informations.

  Since i don’t think i can use the ’exe’ as replacement for an dll, i cloned the git source, and tried to compile it myself.

  Then, while compiling i run into this error :

  CC  libavutil/random_seed.o
  
  libavutil/random_seed.c: In function 'av_get_random_seed':
  
  libavutil/random_seed.c:130:12: error: implicit declaration of function 'arc4random' [-Werror=implicit-function-declaration]
  
       return arc4random();
  
              ^
  
  cc1: some warnings being treated as errors
  
  common.mak:60: recipe for target 'libavutil/random_seed.o' failed
  
  make: *** [libavutil/random_seed.o] Error 1

  As far as I can tell, this means that I’m missing the library arc4random, so I started searching for this lib, and found absolutly nothing, besides the fact that this library is somehow Apple related..., but no dll’s and stuff or sources to compile it myself.

  I use cygwin and its GCC to compile on 64-Bit windows 7 Machine.

  Can anyone hint me to some location where I can get this missing library, or some other possibility to get ffmpeg as library into my project ?
  (I would prefer something I can link statically , since this project is meant to be a lib by itself)

  Maybe is there a way I can make use of that downloaded exe of ffmpeg, since i can borrow its headers from the source I cloned from Git ?

  Any Hint appreciated.

  Best Regards,

  Jannik Adam

• Creating an ffmpeg html/php form process and need ffmpeg technical feedback

  7 juin 2016, par dave

  I have decided to create an input form for ffmpeg to go with my video uploader.

  This is for my video uploader plugin for a social site software. Users have told me that they want technical options for videos so they can choose the specific options they want including thumbnail options.

  I have been reading the ffmpeg docs most of the morning as well as watching some videos and i have come up with a rough draft of my form. The videos uploaded will more than likely be non gaming, personal and hobby videos.

  The goal here is to have a form that is easy enough for the non technical user, but technical for those that want the options. So i do plan to have a checkbox which allows the non technical user to skip the technical settings. This will result in a generic ffmpeg command with default settings. If they choose to use the technical specs then it will create a more specific ffmpeg command stream.

  here is what i have so far in the draft.

  select max size options ’50MB’,’100MB’,’200MB’,’500MB’,’650MB’,’750MB’,’1GB’,’2GB’,’3GB’

  input for thumbcapture in seconds maxlength 2 size 2

  input for video in ’mpg’,’wma’,’mov’,’flv’,’mp4’,’avi’,’qt’,’wmv’,’rm’

  option for video size ’200x100’,’320x240’,’560x315’,’640x360’,’853x480’,’1280x720’ not sure if i want to offer a custom slot or not.

  my thought here is that if they do not want the tech version of the form then the codecs will be b:v copy b:a copy (if that is the smart way to do it) or just left out and let ffmpeg decide what is best.

  ===== this is the technical part of the form =======

  select for acodec options copy, mp3, mp1, mp2, dnet, 28_8, wmav2, alac, cook

  select for vcodec option copy, ffv1, ms-cram, mpeg-4, rv40, wmv, xvid, mov, qt, avchd

  select for bitrate audio 32k, 64k, 128k

  select for bitrate video 1000k, 1200k, 1500k

  select for sampling rate 22050, 44100

  input for crf(mp4 out only) size 2 maxlength 2 minval 2 maxval 49

  input for avi quantanizer (avi out only) size 2 maxlength 2 minval 2 maxval 49

  ===== end technical form =====================

  select for video out ’avi’,’mp4’,’flv’

  that is what i have so far. How does that combination on the technical side look to you ffmpeg pros ?

  Any suggestions ? :)