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• 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 ?

  


• 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 blend filter not work right in android

  15 mai 2018, par tainguyen

  I’m doing my android project which uses blend filter to create uncover down video transition. My test device is Samsung S4 (Android version : 4.4.2)
  this is my command string :

  ffmpeg 
  
  -loop 1 -t 1 -i img001.jpg 
  
  -loop 1 -t 1 -i img002.jpg 
  
  -loop 1 -t 1 -i img003.jpg 
  
  -loop 1 -t 1 -i img004.jpg 
  
  -loop 1 -t 1 -i img005.jpg 
  
  -filter_complex 
  
  "[1:v][0:v]blend=all_expr='if(lte(Y,N*H/24),A,B)'[b1v];
  
  [2:v][1:v]blend=all_expr='if(lte(Y,H*N/24),A,B)'[b2v];
  
  [3:v][2:v]blend=all_expr='if(lte(Y,H*N/24),A,B)'[b3v];
  
  [4:v][3:v]blend=all_expr='if(lte(Y,H*N/24),A,B)'[b4v];
  
  [0:v][b1v][1:v][b2v][2:v][b3v][3:v][b4v]
  
  [4:v]concat=n=9:v=1:a=0,format=yuv420p[v]" -map "[v]" out_cover_top.mp4 -y

  The result video transition is not scroll from the top to the bottom as I want. It break into several parts ( the red arrow show you the top and bottom of an part).
  

  Help me please.