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• What is the most efficient way of stacking two videos using ffmpeg ?

  4 octobre 2024, par technical_difficulty

  I want to stack two videos of a talk together vertically using ffmpeg. One shows the presentation (slides) and one shows the speaker. Since I want to do this for several talks, I'd like to do this in a more general way and as efficiently as possible. Most of the time the videos have different resolutions and aspect ratios.

  


  My current workflow is :

  


  


  1. Scale the video with the lower resolution up to match the resolution of the other video :
ffmpeg -i video1.mp4 -s 1920x1080 -c:a copy video1_upscaled.mp4

     


  


  2. Stack the two videos :
ffmpeg -i video1_scaled.mp4 -i video2.mp4 -filter_complex vstack=inputs=2 combined.mp4

     


  


  


  The videos are between one and two hours long and the commands do take a while to complete. Is there any way of saving some time ?

  


  Would it be faster to put black bars/borders around the smaller video instead of scaling it to the size of the other one ? Can the stacking be done in a more efficient way ? Would it help a lot if those two steps were combined into one ?

  


  Some information that might be relevant :

  


  

  • it's always exactly two videos to stack vertically, one above the other

  


  • the quality of the video is not incredibly important, both having the resolution of the video with the lower resolution would be perfectly fine

  


  • disk space is not an issue

  


  • the resolution and aspect ratio of the videos are known (use any for your example)

  


  • both videos have the same audio

  


  • both videos have the exact same length

  


  


• Using ffmpeg to play file on windows, should use directshow to render the decoded frame [on hold]

  22 juillet 2013, par Terry

  I want to write a video file player using ffmpeg(support many format).

  However ffmpeg(/ffplay.exe) using SDL to render the video frame and play the audio sound. I only want to support windows platform. I think the default windows technology/api is more suitalbe for me to render the decoded frame. Do you think so ?

  If so, should I use direct show, or just using direct draw for video frame and direct sound for audio frame.

  If using direct show, I think I need to wrapper a direct show source filter(/splitter), then pass down the decoded video/audio frame data to render filter.

  Please help me which is the best choice ?

• How to convert animated webp to gif in android / java ?

  21 avril 2022, par UHS

  I want to convert the animated webp files to gif file and looking for solution since couple of days but did not get any easy straight solution yet.

  


  I tried ffmpeg but it could not do the job and after looking for solution I found that webp decoder is not implemented in ffmpeg yet.
https://trac.ffmpeg.org/ticket/4907

  


  I also checked libwebp library by google and they also says animated webp is not supported. https://developers.google.com/speed/webp/docs/dwebp

  


  I tried demo of aspose this library also fail to convert animated webp to gif.
https://products.aspose.com/imaging/java/conversion/webp-to-gif/

  


  I think ImageMagick can convert animated webp to gif but do not know how to implement that in my project.
How can I avoid dropouts when using (imagemagick) `mogrify` to convert webp files to animated gif ?

  


  So is there any easy way to convert webp to gif