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• Merge Audio and Video on Uno Platform

  27 mars 2021, par trungnt2910

  I am trying to merge an audio stream and a video stream into a single file, on the Uno Platform, particularly for WebAssembly.
  
I already know that the normal, desktop-only way is by calling ffmpeg, and I also found a C# only way for UWP here.
  
However, the code used Windows.Media.Editing which is not implemented in Uno.
  
I know there is a ffmpeg library port for WASM here, but I don't know how to call it from my Uno web application.

  


  So are there any ways to merge an audio stream and a video stream to a single file, on the Uno platform for WASM ?

  


• Not able to run the final step of running supervisord for plumi

  1er avril 2021, par manic_startup

  on the github page https://github.com/plumi/plumi.app
I am on the final step of Step 6. see below section

  


  =========================

  


  Step 6 : start supervisord
With plumi buildout having finished and ffmpeg installed on our system, it's time to run supervisord :

  


  root@user :/home/plumi.app# ./bin/supervisord

  


  ========================

  


  When I type in the above on CentOS 7 it says "bash : ./bin/supervisord : No such file or directory

  


  I had to change some things in step 5 "Step 5 Install ffmpeg" for the centos section there are two urls in that section pointing to some repos. They did not work so I had to find some other ones on the Internet. The ones I used where.
https://dl.fedoraproject.org/pub/epel/7/x86_64/Packages/e/epel-release-7-13.noarch.rpm

  


  http://ftp.riken.jp/Linux/atrpms/el7-x86_64/atrpms/stable/atrpms-repo-7-7.el7.x86_64.rpm

  


  The first one looks the same but it is different also the only release available was 7-13 so i used that.
The second one is a different url but the file is the same.

  


  also in that section is asks to edit /etc/yum.repos.d/atrpms.repo. It asks to change the base URL to a URL similar to the what is asks when it asked to download from the second repo above. Obviously that url is different now so I changed it to this instead.
http://ftp.riken.jp/Linux/atrpms/el$releasever-$basearch/atrpms/stable/

  


  After this I asks to install ffmpeg this did not work so I used the below guide
https://linuxize.com/post/how-to-install-ffmpeg-on-centos-7/

  


  Then came the section 6 to install supervisord as explained at the start this did not work. Now im stuck !

  


  I have also realised that when I get to the following command in step 4.

  


  ./bin/python bootstrap.py && ./bin/buildout -v

  


  It fails and says "Error : couldn't find distribution for 'hachoir-parser==1.3.4' and bombs out. I have tried to find this file but cant install it and dont know if i even have the correct file. not sure what to do.

  


• Overlay Intro Titles/Video in FFMPEG and fix missing keyframes in one step

  23 juin 2021, par Digicrat

  How can I optimally apply an intro video (replacing the few seconds of video with a potentially missing keyframe, but keep the original audio) in one step ?

  


  I have a batch of input videos and a batch of associated (auto-generated) 'intro' videos to overlay on top of them (in this case, replacing the first 3 seconds of video). This is complicated by the fact that some of the input videos were cut in such a way that the first key frame is missing/corrupted in order to achieve the desired audio start point.

  


  My current working (but slow) two-step process is :

  


  ./ffmpeg.exe -i videoA.mp4 -force_key_frames "expr:gte(t,n_forced*3)" videoA-fixed.mp4

./ffmpeg.exe -i videoA-fixed.mp4 -i intro-videoA.mp4 -filter_complex "[0:0][1:0]overlay=enable='between(t,0,3)'[out]" -shortest -map [out] -map 0:1 -pix_fmt yuv420p -c:a copy -c:v libx264 -crf 18 mergedVideo.mp4


  


  I've tried adding the force_key_frames arguments to the latter command, but ffmpeg doesn't seem to like that. Placing it before the filter_complex yields an error "Stream specifier ':0' in filtergraph description [0:0][1:0]overlay=enable='between(t,0,3)'[out] matches no streams."