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• Fetching movies' frames via ffmpeg and feed it to vlfeat's sift

  16 novembre 2012, par Karl

  I am going to develop a program that uses ffmpeg and vlfeat on a linux server.

  My task is simply : get some frames from a movie file and feed these frames to vlfeat's sift.

  I am reading through some documents regarding using ffmpeg in c development, mainly here and here. As stated in the site, "There is not much "web based" official documentation for using these libraries." And some tutorials there might be a little outdated. I also read around that the API might differ from version to version. So I would like to ask for the following :

  1. Is it safe to follow this tutorial for the current implementation ?

     • If so, given the impression from above, what are some of the things that should be change for the current implementation ? (currently I got ffmpeg-git-c995644)
     • If not, what are the functions to acquire the frames of the movie file in any format ?

  2. For vlfeat side, if I am to feed a movie's image frame from ffmpeg, what kind of conversion is required so that vlfeat's sift implementation can "digest" the movie's image frame ?

• Reliable video decode-(heavy edit)-encode with Mediacodec

  27 mai 2017, par Jason M

  I am building a Android app that does heavy video processing. I have read some background and examples from bigflake as well as the official docs but did not get a final answer. Here is what I would like to do in my app :

  1. Decode a mp4 video into raw yuv frames ;
  2. Edit each frame with a lot of computation, including flipping and cropping, preferably with my existing native C++ ;
  3. Encode the raw frames into another video.

  I am using API22 for robustness since "All video codecs support flexible YUV 4:2:0 buffers since LOLLIPOP_MR1." Unfortunately, when I call

  encoder.getInputImage();

  instead of

  encoder.getInputBuffer();

  I get a null, similar to This post with no answer. Is this a common issue ? Do I have other options to decode-edit-encode a video without either rendering to a Surface or using FFMPEG, which is a headache to build and debug ?

• time_internal : Prefix fallback versions of gmtime_r/localtime_r with ff_

  10 avril 2019, par Martin Storsjö

  time_internal : Prefix fallback versions of gmtime_r/localtime_r with ff_
  Use a macro to redirect calling code from the official name to the
  
  ff_ prefixed one.
  Detecting these functions in configure can be tricky (on mingw, they
  
  are conditionally available depending on posix feature defines).
  
  If configure didn't detect them, but they still are visible at
  
  compile time (due to an unrelated header defining the posix feature
  
  defines), providing the local fallback versions with a prefixed
  
  name is safer.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavutil/time_internal.h