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• libvpx 0.9.1 and FFmpeg 0.6

  18 juin 2010, par Multimedia Mike — VP8

  Great news : Hot on the heels of FFmpeg’s 0.6 release, the WebM project released version 0.9.1 of their libvpx. I can finally obsolete my last set of instructions on getting FFmpeg-svn working with libvpx 0.9.

  Building libvpx 0.9.1
  Do this to build libvpx 0.9.1 on Unix-like systems :

  • Download libvpx 0.9.1 from http://code.google.com/p/webm/downloads/list
  • Unpack, chdir to the source dir, ’./configure && make && make install’

  libvpx’s build system has been firmed up a bit since version 0.9. It’s now smart enough to install when said target is invoked and it also builds the assembly language optimizations. Be advised that on 32- and 64-bit x86 machines, Yasm must be present (install either from source or through your package manager).

  Building FFmpeg 0.6
  To build the newly-released FFmpeg 0.6 :

  • Install Vorbis through your package manager if you care to encode WebM files with audio ; e.g., ’libvorbis-dev’ is the package you want on Ubuntu
  • Download FFmpeg 0.6 from the project’s download page
  • Configure FFmpeg with at least these options : ./configure --enable-libvpx --enable-libvorbis --enable-pthreads ; the final link step still seems to fail on Linux if the pthreads option is disabled
  • ’make’

  Verifying
  Check this out :

  $ ./ffmpeg -formats 2> /dev/null | grep WebM
    E webm            WebM file format
  $ ./ffmpeg -codecs 2> /dev/null | grep libvpx
  
   DEV    libvpx          libvpx VP8
  

  That means that this FFmpeg binary can mux a WebM file and can both decode and encode VP8 video via libvpx. If you’re wondering why the WebM format does not list a ’D’ indicating the ability to demux a WebM file, that’s because demuxing WebM is handled by the general Matroska demuxer.

  Doing Work
  Encode a WebM file :

  ffmpeg -i <input_file> <output_file.webm>

  FFmpeg just does the right thing when it seems that .webm extension on the output file. It’s almost magical.

  For instant gratification that the encoded file is valid, you can view it immediately using ’ffplay’, if that binary was built (done by default if the right support libraries are present). If ffplay is not present, you can always execute this command line to see some decode operation :

  ffmpeg -i <output_file.webm> -f framecrc -

• Opencv linking to current version of ffmpeg only, Updating ffmpeg version breaks opencv library

  5 octobre 2019, par Amit

  I had manually compiled opencv ver3.2 library on mac system, which had been working fine till now. Recently it seems that i had updated the version for ffmpeg, which is managed by brew package manager, leading to breakage of opencv library looking for libavcodec.57.dylib.

  Upon looking into library path, i found that libavcodec.dylib is symlinked to libavcodec.58.dylib, which is the most probable cause to above problem.

  Now i have two options,
  
   Recompile opencv to link against the latest version of libavcodec
  
   Revert the version of libavcodec to 57

  I am looking for a solution in which opencv works independently of the version of libavcodec and should dynamically link with current installed version of library. I should only be recompiling opencv when it is essentially required, like change in API of libavcodec.

• Capture canvas to video fast as possible

  27 novembre 2019, par Julien Planche

  I write some code about capturing canvas which contains things like videos, images and text, but I capture each frame per frame, using the onseeked event to capture the next frame after seeking the video to the desired frame.
  But it’s taking a long time..
  Do they exist a way to capture canvas faster ? Using GPU acceleration or dedicated software ?
  Thanks a lot