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• Glitchy mp4 File saved with Matplotlib Animation via ffmpeg

  9 janvier 2024, par Jacob Ivanov

  I am attempting to save an .mp4 file using matplotlib.animation to output some simulation results. The relevent section is as follows :

  


  ANI = FuncAnimation(fig, update, init_func = lambda : None, frames = range(0, 21300, 50))
ANI.save("[removed]/anim/v6 256 unforced 0.02.mp4", dpi = 600, fps = 30, writer = 'ffmpeg')


  


  However, it appears that there is some issue in the produced .mp4 file, as when I use macOS Quicktime to view the file, it pauses on certain frames, and restarts later on. It appears to consistently pause on the same frame a few seconds in. In order to check if Quicktime was the problem, I opened some random .mp4 files I found in a family group chat, and did not have this issue.

  


  I also tried viewing this .mp4 file with VLC, which had no issue, and played without any glitches. The Slack media viewer built into the app pauses similar to Quicktime.

  


  The following are all relevant versions :

  


  

  • macOS : 14.2.1 (23C71)

  


  • Python : 3.10.9 via Homebrew

  


  • Matplotlib : 3.6.2

  


  • ffmpeg : 6.1.1

  


  


  If it would help, I can also provide the .mp4 file itself, but I'm not quite sure how to upload it. I will be happy to provide any additional information as well.

  


  Unfortunately, I'm not very familiar with video rendering, but I would appreciate any help anyone could provide. Thank you in advance !

  


• ffmpeg questions

  23 avril 2015, par QuestionGuy

  I have a problem with ffmpeg and I don’t know how to continue. I have 2 computers :

  Client :

  • Run Ubuntu 14.04
  • FFmpeg installed
  • Use c++ language
  • Features : use ffmpeg to encode h264 video data from webcam of client laptop, then real time streaming to server

  Server :

  • Running Windows 7
  • FFmpeg installed
  • Use c++ language (MFC)
  • Features : Get real time data from client and show it on screen.

  I’ve just connected client to server and they can chat text data together, and I don’t have any idea to make real time video work.

  And my questions are :

  1. [Client] How to get video from webcam on laptop (using ffmpeg code), save it to buffer (raw data), encode it and send to server ?

     I use ffmpeg to get video from wc but it save to file. I really don’t want it. Code is :

     ffmpeg -f v4l2 -framerate 25 -video_size 640x480 -i /dev/video0 output.mkv

  2. [Client] How to get raw data from client, decode it and play it ?

     I have an idea to play it by using directshow in MFC.

• WhatsApp video as Gif sharing on Android programatically

  2 novembre 2017, par Razec Luar

  How can i convert a mp4 video file to a WhatsApp gif file (it’s simple showed as gif inside app UI but internally is a specific mp4 format) to be use in android share intent, being recognized as this type of media by whatsapp chat app ???

  I search a lot but i can’t find any information from WhatsApp docs (they don’t have this kind of doc anyway) or any dev with the same problem as i.

  WHAT I HAVE :

  I have discovered that at beginning of whatsapp "gif" mp4 files is present a loop value if you read they on hex editor, all files have this. Remove this value make whatsapp receive as regular video (not sharing as gif).

  How can i add this value using ffmpeg encoding ? (editing my mp4 files manually with this value corrupt the files, maybe i have to fix some mp4 header index that i don’t know yet...)

  
  

  FIRST 80 BYTES in hexadecimal (from beginning to start of "moov" atom from mp4 structure) :

  00 00 00 1C 66 74 79 70 6D 70 34 32 00 00 00 01 6D 70 34 31 6D 70 34 32 69 73 6F 6D 00 00 00 18 62 65 61 6D 01 00 00 00 01 00 00 00 00 00 00 00 05 00 00 00 00 00 00 0C 6C 6F 6F 70 00 00 00 00 00 00 00 08 77 69 64 65 00 00 04 9F 6D 6F 6F 76

  A short mp4 file generated by WhatsApp that internally (at app) was showed as a Gif (with different UI) :

  https://www.dropbox.com/s/kpynmx1bg3z76lz/VID-20171024-WA0009.mp4?dl=0