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• OpenCV+ffmpeg : Set max_analyze_duration ?

  3 avril 2013, par Christian Jonassen

  import sys
  
  import cv
  
  
  
  video = "http://192.168.1.15:8000/video.mjpg" # from motion
  
  capture = cv.CaptureFromFile(video)
  
  print capture
  
  cv.NamedWindow('Stream', 1 )
  
  
  
  while True:
  
    frame = cv.QueryFrame(capture)
  
  
  
    if frame is None:
  
      print "No frame, exiting program"
  
      break
  
    else:
  
      cv.ShowImage('Stream', frame)
  
      cv.WaitKey(20)

  , which sort of works. Meaning that after a while, I get

  Using network protocols without global network initialization. Please use avformat_network_init(), this will become mandatory later.
  
  Using network protocols without global network initialization. Please use avformat_network_init(), this will become mandatory later.
  
  [mjpeg @ 0xb46720] max_analyze_duration reached
  
  [mjpeg @ 0xb46720] Estimating duration from bitrate, this may be inaccurate
  
  Using network protocols without global network initialization. Please use avformat_network_init(), this will become mandatory later.
  
  Using network protocols without global network initialization. Please use avformat_network_init(), this will become mandatory later.
  
  [mjpeg @ 0xb46720] max_analyze_duration reached
  
  [mjpeg @ 0xb46720] Estimating duration from bitrate, this may be inaccurate
  
  <capture 0x7f0aed25c630="0x7f0aed25c630">
  
  </capture>

  The stream then works fine (it's a bit speedy in the start).

  It makes sense : FFMPEG finds the stream mysterious, and therefore analyzes it for the maximum duration, which makes the buffer full, and hence the speediness at the start. Now, is there a way I can (without recompiling FFMPEG) set max_analyze_duration, or otherwise pass some hints to FFMPEG so that it doesn't analyse the stream until max_analyze_duration has passed ?

  The stream is from the motion program : an MJPEG stream of 10 FPS with 640x480.

• How Do I Convert a yuv420 Video File to 16-bit (using ffmpeg) ?

  1er novembre 2022, par IanMurphy

  As the title says, my video file has 12-bit depth and I want to convert it to 16-bit. I dont care which yuv pixel format, as long as its 16 bit. I have installed ffmpeg and I can't figure out what combination of arguments to use to convert it. The video file is very small : 20 frames at 352x288.

  


  This is the command I have been trying, but the file size is the same number of bytes as the original :

  


  ffmpeg -video_size 352x288 -pixel_format yuv420p -sample_fmt s16 -i inpput.yuv output.yuv


  


  If there is another way to do this without ffmpeg, I am open to any suggestions. Thanks in advance !

  


• Superimpose audio track on plot animation

  17 février 2023, par Antoine101

  I plot a matrix in a standard matplotlib figure with imshow. Each matrix is the result of a signal processing calculation on a time signal snapshot (0.2s). I plot each snapshot one after the other (the signal is several seconds long) in a loop and record the animation with FFMPegWriter, setting the FPS so that it matches real time. The output is an MP4 file.

  


  Now, I'd like to add a soundtrack on top of it, of the time signal that was used to calculate the matrices.

  


  How would you do that ? I scrolled a lot but didn't find any suitable solution.
Any idea of libraries or packages ?

  


  Many thanks in advance.