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• Why does my linux ffmpeg output file require running it back through ffmpeg to play on windows

  13 septembre 2020, par Sean Miller

  I am using the following to screen capture a Raspberry Pi display :

  


  /usr/bin/ffmpeg -v quiet -f lavfi -i anullsrc -f x11grab -framerate 30 -video_size 720x480 -i :0.0 -f flv -b:v 1M /home/pi/usbdrv/myfile.avi"


  


  I stop screen capturing by hitting the letter q and ffmpeg exits without error.

  


  I can play it back with mplayer in Linux.

  


  However, when I try to play it back on Windows with the old media player or its newer movie player, they reports it is corrupted. I tried mp4 and mkv fromats as well.

  


  If I run it back through ffmpeg to encode it to a new file, it will play.

  


  Any thoughts why Windows will not play it without running it back through ffmpeg again ?

  


  Thanks,
Sean

  


• VideoCapture() returns None in opencv & install opencv with ffmpeg

  16 décembre 2017, par Wentai Chen

  System : UBUNTU 16.04
  Python version : 3.5

  I would like to use cv2.VideoCapture() function to process my mp4 file. However, when I run the script below, I always get a result of None, so I am not able to continue my work after.

  import cv2
  
  video_cap = cv2.VideoCapture('demo.mp4')
  
  ret,frame = video_cap.read()
  
  print(ret,frame)
  
  
  
  result: False,None

  By searching a lot I realized the problem : opencv is not properly installed with ffmpeg, so that the video function in opencv does not work.

  However I didn’t find a efficient tutorial on how to properly install opencv. I wonder if anyone could help. Thank you !

• My webcam works fine, while using cv2.Videocapture() but while trying to read from hard drive it shows error cap.isOpened() returns false, why ?

  27 septembre 2017, par Hu Yang

  import cv2
  video_capture = cv2.VideoCapture("rtsp ://admin:Trust1986_@10.58.94.47:554/h264/ch1/main/av_stream")
  video_capture.isOpened()

  False

  Other information below here, and ffmpeg I had installed.

    Video I/O:
  
      DC1394 1.x:                  NO
  
      DC1394 2.x:                  NO
  
      FFMPEG:                      NO
  
        avcodec:                   NO
  
        avformat:                  NO
  
        avutil:                    NO
  
        swscale:                   NO
  
        avresample:                NO
  
      GStreamer:                   NO
  
      OpenNI:                      NO
  
      OpenNI PrimeSensor Modules:  NO
  
      OpenNI2:                     NO
  
      PvAPI:                       NO
  
      GigEVisionSDK:               NO
  
      Aravis SDK:                  NO
  
      UniCap:                      NO
  
      UniCap ucil:                 NO
  
      V4L/V4L2:                    NO/NO
  
      XIMEA:                       NO
  
      Xine:                        NO
  
      Intel Media SDK:             NO
  
      gPhoto2:                     NO
  
  
  
  root@ubuntu:/home/face_recognition/opencv/ffmpeg/ffmpeg-3.3.4# ffmpeg -version
  
  ffmpeg version 3.3.4 Copyright (c) 2000-2017 the FFmpeg developers
  
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  
  configuration: 
  
  libavutil      55. 58.100 / 55. 58.100
  
  libavcodec     57. 89.100 / 57. 89.100
  
  libavformat    57. 71.100 / 57. 71.100
  
  libavdevice    57.  6.100 / 57.  6.100
  
  libavfilter     6. 82.100 /  6. 82.100
  
  libswscale      4.  6.100 /  4.  6.100
  
  libswresample   2.  7.100 /  2.  7.100
  
  root@ubuntu:/home/face_recognition/opencv/ffmpeg/ffmpeg-3.3.4# 
  
  root@ubuntu:/home/face_recognition/opencv/ffmpeg/ffmpeg-3.3.4# python3.6m -V
  
  Python 3.6.2
  
  root@ubuntu:/home/face_recognition/opencv/ffmpeg/ffmpeg-3.3.4# pkg-config --modversion opencv  
  
  3.3.0

  what shall I do next step ? Thanks.