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• How to read .mp4 files in opencv

  9 mai 2016, par Noah

  I am totally newbie in OpenCV, C++. Trying to read an mp4 video but found OpenCV does not support mp4, it only reads avi(I am not sure whether I am write or wrong). After an online research came to know ffmpeg is the best option to convert mp4 to avi for further processing.

  I am using OpenCV 3.0 with visual studio 2012. I saw there is a dll file, opencv_ffmpeg300.dll in OpenCV C:\opencv\build\x86\vc11\bin folder. Is there any way I can use this dll file to read and convert my video ?

  It will be really appreciating if someone can provide me some guidelines, I am lost in the OpenCV world totally.

  For video,

  Video I/O:
  
     Video for Windows:           YES
  
     DC1394 1.x:                  NO
  
     DC1394 2.x:                  NO
  
     FFMPEG:                      YES (prebuilt binaries)
  
       codec:                     YES (ver 55.18.102)
  
       format:                    YES (ver 55.12.100)
  
       util:                      YES (ver 52.38.100)
  
       swscale:                   YES (ver 2.3.100)
  
       resample:                  NO
  
       gentoo-style:              YES
  
     OpenNI:                      NO
  
     OpenNI PrimeSensor Modules:  NO
  
     OpenNI2:                     NO
  
     PvAPI:                       NO
  
     GigEVisionSDK:               NO
  
     DirectShow:                  YES
  
     Media Foundation:            NO
  
     XIMEA:                       NO
  
     Intel PerC:                  NO

• Zooming animation in FFMPEG

  2 novembre 2015, par dmcontador

  I need to make a zooming animation for a video input.

  Making a panning animation is possible with the crop filter with something like this :

  "crop=320:240:max(0\\,min(iw-ow\\,n)):0"

  Where the first two parameters, width and height, are fixed, and the second two parameters, accept frame number n or timestamp t as expression parameters.

  But width and height are evaluated only once (and cannot use n or t), so I cannot crop a size in function of time and then apply a scale filter to the original size.

  I know I can :

  • Change the filter after pulling each frame from the buffersink (I’m not in the command line, I’m using the libraries in my software). I’m doing that already, but no for every frame, only by user request in an online application.
  • Use geq filter to "apply a generic equation to each frame".

  Both approaches seem expensive. Is there another filter or approach I could use ?

  Note that I’m using zeranoe FFMPEG libraries in Windows. I’d rather not develop my own filters or modify FFMPEG source.

• FFMPEG : Get the Scene Change Detection value for all frame

  14 novembre 2022, par celacanto

  I'm trying to measure how much a movies is "fast" (more action in the screen and quick scene chances). I don't want just a single value for the movie, but values along the movie to see how the action varies during it. After normalize the frame rate of the movies (10 fps), my idea is to compare each frame with the previous. I'm not only interest if the scene has changed, but also, if there was no cut, how much movement there is. Not only people/object movement but also, camera movement. In summary the paced (I think that the term) of the scenes.

  



  My idea was to use the scene function from ffmpeg as a metric. But looking at the document and examples online I'm thinking I can only use the value of the Scene Change Detection as a threshold to return frames informations, but I can't get ffmpeg to return the value. Is that right ? There is any way I can make it return the value ?