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• opencv3.1 python VideoCapture black screen

  3 mai 2017, par alex

  i’m trying to use opencv3.1 with python3.5
  following this official)tutorial
  http://docs.opencv.org/3.0-beta/doc/py_tutorials/py_gui/py_video_display/py_video_display.html#display-video

  the camera led is "on" but the window doesn’t show any image (black)

  my current enviroment :
   windows 10
   python 3.5.2 (32bit)
   numpy 1.12.0b1 (32bit) binaries downloaded from : http://www.lfd.uci.edu/ gohlke/pythonlibs/
   opencv 3.1.0 (32bit) binaries downloaded from : http://www.lfd.uci.edu/ gohlke/pythonlibs/

  they seem installed correctly !

  as the tutorial says :

  Note Make sure proper versions of ffmpeg or gstreamer is installed. Sometimes, it is a headache to work with Video Capture mostly due to wrong installation of ffmpeg/gstreamer.

  i’ve no ffmpeg installed !!! so i suppose this is the cause of my problem
  so the questions are :
  1) which version of ffmpeg is needed ?
  2) how install ffmpeg on windows ? it seems a setup doesn’t exist(there is a binary section with a zip file ? how to use it after unzipped ?)
  3) is possible to see(in some way) if the opencv binaries(that i’ve downloaded) were compiled with ffmpeg support(flag ?)

  PS : i’ve tried to add the ffmpeg folder path the the PATH enviroment variable but nothing change

• Compiling FFMPEG with libvpx on Mac OS X

  26 août 2014, par Dalvik

  I’m having hard timed trying to manually compile FFMPEG on my MAC. I’m trying to compile it with —enable-libvpx but keep getting this annoying error :

  ERROR: libvpx decoder version must be >=0.9.1"

  I’m compiling FFMPEG using this guide by ROMAN10 and this link from the FFMPEG official documentation. You can find the build script I’m using in ROMAN’s web page.

  Note : I’m working with HomeBrew because I found it easier and more convenient tool from which I can install all the core packages that ffmpeg requires(yasm,libogg,libvorbis and more).

  In an efforts to solve it I’ve try to fix ffmpeg’s ./configure file and notice that the link to libvpx is as follow :

  enabled libvpx            && {
  
  enabled libvpx_vp8_decoder && { check_lib2 "vpx/vpx_decoder.h vpx/vp8dx.h" vpx_codec_dec_init_ver -lvpx ||
  
                                  die "ERROR: libvpx decoder version must be >=0.9.1"; }
  
  enabled libvpx_vp8_encoder && { check_lib2 "vpx/vpx_encoder.h vpx/vp8cx.h" "vpx_codec_enc_init_ver VP8E_SET_MAX_INTRA_BITRATE_PCT" -lvpx ||
  
                                  die "ERROR: libvpx encoder version must be >=0.9.7"; }
  
  enabled libvpx_vp9_decoder && { check_lib2 "vpx/vpx_decoder.h vpx/vp8dx.h" "vpx_codec_vp9_dx" -lvpx || disable libvpx_vp9_decoder; }
  
  enabled libvpx_vp9_encoder && { check_lib2 "vpx/vpx_encoder.h vpx/vp8cx.h" "vpx_codec_vp9_cx VP9E_SET_AQ_MODE" -lvpx || disable libvpx_vp9_encoder; } }

  You can see that the method check_lib2 receives 2 params - the header path and the function’s name. Unfortunately even when I’m changing the path to a downloaded version of libvpx(which is much newer than 0.9.1) I’m still getting this error. Any help would be much appreciated.

• lavu/riscv : CPU flag for the Zbb extension

  2 octobre 2022, par Rémi Denis-Courmont

  lavu/riscv : CPU flag for the Zbb extension
  Unfortunately, it is common, and will remain so, that the Bit
  
  manipulations are not enabled at compilation time. This is an official
  
  policy for Debian ports in general (though they do not support RISC-V
  
  officially as of yet) to stick to the minimal target baseline, which
  
  does not include the B extension or even its Zbb subset.
  For inline helpers (CPOP, REV8), compiler builtins (CTZ, CLZ) or
  
  even plain C code (MIN, MAX, MINU, MAXU), run-time detection seems
  
  impractical. But at least it can work for the byte-swap DSP functions.
  

  • [DH] libavutil/cpu.c
  • [DH] libavutil/cpu.h
  • [DH] libavutil/riscv/cpu.c
  • [DH] tests/checkasm/checkasm.c