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• how to make work opencv with FFMPEG driver

  14 janvier 2021, par user3313834

  I have a camera on my linuxbox it is working well :

  


  # $ ls -al /dev/video*
# crw-rw----+ 1 root video 81, 0 janv.  8 16:13 /dev/video0
# crw-rw----+ 1 root video 81, 1 janv.  8 16:13 /dev/video1
# $ groups
# adm cdrom sudo dip video plugdev lpadmin lxd sambashare docker libvirt


  


  From python with cv2 it work well with the default driver CAP_V4L2

  


  >>> from pathlib import Path
>>> import cv2
>>> print(cv2.VideoCapture(0, apiPreference=cv2.cv2.CAP_V4L2).isOpened())
True
>>>


  


  I would like to access it with the FFMPEG driver (no success) :

  


  >>> print(cv2.VideoCapture(0, apiPreference=cv2.CAP_FFMPEG).isOpened())
False
>>>


  


  From Python side the opencv look like to have the FFMPEG Driver :

  


    >>> cv2.__version__
  '4.4.0'
  >>> info = cv2.getBuildInformation()
  >>> video, parallel = info.index('Video'), info.index('Parallel')
  >>> print(info[video:parallel])
  Video I/O:
       DC1394:                      NO
       FFMPEG:                      YES
         avcodec:                   YES (58.109.100)
         avformat:                  YES (58.61.100)
         avutil:                    YES (56.60.100)
         swscale:                   YES (5.8.100)
         avresample:                NO
       GStreamer:                   NO
       v4l/v4l2:                    YES (linux/videodev2.h)
  >>>


  


  From Linux side look ok too :

  


  $ dpkg -l |grep -i opencv
ii  libopencv-core4.2:amd64                    4.2.0+dfsg-5                          amd64        computer vision core library
ii  libopencv-imgcodecs4.2:amd64               4.2.0+dfsg-5                          amd64        computer vision Image Codecs library
ii  libopencv-imgproc4.2:amd64                 4.2.0+dfsg-5                          amd64        computer vision Image Processing library
ii  libopencv-videoio4.2:amd64                 4.2.0+dfsg-5                          amd64        computer vision Video I/O library

$ dpkg -l |grep -i ffm
ii  ffmpeg                                     7:4.2.4-1ubuntu0.1                    amd64        Tools for transcoding, streaming and playing of multimedia files
ii  gstreamer1.0-libav:amd64                   1.16.2-2                              amd64        ffmpeg plugin for GStreamer
ii  libavcodec-extra:amd64                     7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library with extra codecs (metapackage)
ii  libavcodec-extra58:amd64                   7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library with additional de/encoders for audio/video codecs
ii  libavdevice58:amd64                        7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library for handling input and output devices - runtime files
ii  libavfilter7:amd64                         7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library containing media filters - runtime files
ii  libavformat58:amd64                        7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library with (de)muxers for multimedia containers - runtime files
ii  libavresample4:amd64                       7:4.2.4-1ubuntu0.1                    amd64        FFmpeg compatibility library for resampling - runtime files
ii  libavutil56:amd64                          7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library with functions for simplifying programming - runtime files
ii  libffmpegthumbnailer4v5                    2.1.1-0.2build2                       amd64        shared library for ffmpegthumbnailer
ii  libpostproc55:amd64                        7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library for post processing - runtime files
ii  libswresample3:amd64                       7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library for audio resampling, rematrixing etc. - runtime files
ii  libswscale5:amd64                          7:4.2.4-1ubuntu0.1                    amd64        FFmpeg library for image scaling and various conversions - runtime files
$


  


• ffmpeg encoded video don't work on mplayer

  15 septembre 2022, par Turgut

  I've made a C/C++ program that encodes a video. It takes several input videos with presumably different fpses, then encodes them as a single video with a different single fps. For example you can give 2 videos with fpses 30 and 60 respectively then set output fps to 120. This works fine under normal circumstances.

  


  However when ran through mplayer on a different pc then mine, it says the following :

  


  

  

As seen here it says that audio is at 30 while video is at 15. Normally I would just shrug this off however it works on any other video player on the same computer. So I would assume that mplayer is at fault and shrug it off, but it works on my computer's mplayer.


  


  Is this about my video encoding ? Do I need to change the header of the video ? Here is how I set the time :

  


  AVStream* st;&#xA;st->time_base =  av_d2q(1 / fps, std::numeric_limits<int>::max());&#xA;&#xA;</int>

  


  What could be the problem ?

  


• When Kxmovie plays .rm format file, the audio does not work fine

  6 septembre 2016, par Bruce Jordan Wang

  I used third party video player KxMovie to play video in my app, the video streams fluently but the audio keeps on-and-off in a regular way, how to solve it ? What’s the possible reason for this problem ?

  Parameters about the .rm format video :