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• The most efficient way to generate mp4 video containing looped boomerang-alike video file ?

  29 juillet 2019, par B. Palka

  I’ve developed an Android app that allows user to create boomerang-alike mp4 video. This video consists of 10 still images being played back and forth quite fast. I know that such video (boomerang effect) can be easily looped from single video file while playing it, but I really need to create a mp4 video that would essentially contain already prepared boomerang video. The output video can be downloaded and played by user on any external player (over which obviously I don’t have any control).

  For that purpose currently I create a video from images in a loop. The loop starts from 1st picture and goes to 10th picture with 0.25 sec delay between frames, then goes back from 10th to 1st including delay. And there is 5 of those loops, which essentialy means creating a single video from 5 * 10 * 2 = 100 images. I know it’s kinda ridiculous, so the time that it takes to prepare this video is riduculous as well (around 1:40 min).

  What solution could you recommend assuming that the output video really has to consist of 5 loops back-and-forth ? I’ve thought about creating single loop video (20 pictures) and then create final output video by concatenating it 5 times. But could it be any good ? I’m trying to find an efficient yet understandable for a beginner Android programmer way.

• Moviepy write_videofile changes number of video and audio frames even after using 'rawvideo' as the codec parameter

  14 mars 2019, par Jaideep Sagar

  I am using moviepy (Python) to read video and audio frames of a video and after making some changes I am writing them back to a videofile, say new.avi, to preserve the changes, or to avoid compression, I am using codec= ’rawvideo’ in write_videofile function. But when I read the video and audio frames back, the number of video and audio frames are different than when they were when written, they are usually increased.
  Can anybody tell me the reason, ? is it because of the ffmpeg used or some other reason ? Does it happen always or there is some problem in my machine ? Thank you :-)

• How to cleanup data to reuse ffmpeg.wasm instance

  24 avril, par rickyz

  I have multiple files that I am trying to process back to back using ffmpeg.wasm. I have noticed that after around 150 runs, a memory issue comes up : RuntimeError: memory access out of bounds. I tried doing cleanup using ffmpeg.deleteFile() on both the input and output files after every run, but that didn't make a difference. Is there something I am missing that will allow me to reuse the ffmpeg instance as many times as I want ?

  


  If I can avoid it, I do not want to have to call ffmpeg.terminate() after each use since loading ffmpeg for the next use takes a long time ( .5 secs on my test machine).

  


  Note : I am using the updated ffmpeg.wasm v0.12+ in a browser setting