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• Use ffmpeg as external tool to stream 2 or more different sources via pipeline

  25 février 2021, par StackDOX

  I have an application running on an embedded system. This application has 2 video sources (and, theorically, 1 audio source). Concentrating to the video sources, I have 2 subprocess that computes different frames sets (unrelated each others). I want to send these frames to 2 differents streams.

  


  I would to avoid to write a lot of ffmpeg/libav code. I have ffmpeg compiled for the embeeded system and I can use it as tool. For example, I can write to the stdout the first frames set and pass it to the ffmpeg like this :

  


  ./my_app|ffmpeg -an -i - -vcodec copy -f rtp rtp://"remote_ip

  


  This basically works. But, now i would to send the other one frame set. How to do that ? Theorically I need anoter ffmpeg instance that read from another source that can't be the stdout of "my_app", because is already busy.

  


  ---

  


  I'm thinking to use 2 video files as support. I can record the 2 frames sets into 2 video files and then run 2 ffmpeg instances from these sources. In this case I think I need a way to limit the video files dimensions (like a circular buffer), because 2 streams can become really huge in time. It is a possibility ?
This can sound "weird" to me : I need to record a video source in realtime and stream it via ffmpeg (always in realtime). I don't know if it is a good idea, there are realtime problems for sure :

  


  loop:
my_app --write_into--> video_stream1.mp4 
ffmpeg <--read_from-- video_stream1.mp4

my_app --write_into--> video_stream2.mp4 
ffmpeg <--read_from-- video_stream2.mp4


  


  Have you some suggestion to address this kind of situation ?

  


  many thanks, bye.

  


• Overlay of multiple sources with layer order like CSS z-index

  6 mars 2021, par Basj

  Note : I've already read a few questions/answers about [ffmpeg] overlay, but it did not fully answer this.

  


  Let's say we have five inputs [0] ... [4] that can be images, videos, etc.

  


  I'd like to overlay them in a precise order, a bit like "Photoshop layers" or CSS z-index.

  


  Currently I use ffmpeg with a "recursive" use of overlay like this :

  


     -filter_complex "
        [0]setpts=PTS-STARTPTS[s0];
        [1]setpts=PTS-STARTPTS+3/TB[s1];
        [2]setpts=PTS-STARTPTS+7/TB[s2];
        [3]setpts=PTS-STARTPTS+8/TB[s3];
        [4]setpts=PTS-STARTPTS+9/TB[s4];
        [s0][s1]overlay=enable='between(t,3,13)'[o1];
        [o1][s2]overlay=enable='between(t,7,12)'[o2];
        [o2][s3]overlay=enable='between(t,8,15)'[o3];
        [o3][s4]overlay=enable='between(t,9,12)'[o4];
   "


  


  Question : with ffmpeg, is there a way to do a mixing of different inputs / "layers" :

  


  

  • in a shorter way that this recursive use of overlay

  


  • and such that we can specify the "stack order" of each layer, like with CSS z-index

  


  


   ?

  


  To give a concrete example, how would you modify this command such that :

  


  

  • from 0'00" to 0'10", the layer order (from background to foreground) is 0, 1, 2, 3, 4

  


  • from 0'10" to 0'15", the layer order (from background to foreground) is 2, 3, 1, 4, 0 (i.e. [0] goes to foreground)

  


  


   ?

  


• avfilter/scale_cuda : combine separate CUDA sources

  22 juin 2021, par Timo Rothenpieler

  avfilter/scale_cuda : combine separate CUDA sources
  

  • [DH] libavfilter/Makefile
  • [DH] libavfilter/vf_scale_cuda.c
  • [DH] libavfilter/vf_scale_cuda.cu
  • [DH] libavfilter/vf_scale_cuda_bicubic.cu