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• OpenCV reading from live camera creates a short video that moves quickly

  17 novembre 2022, par user19019404

  I am reading in a live vide stream from a CCTV camera. The camera is set to 5 fps, another is set to 25fps and another to 30fps. Irrespective of the FPS that the camera is set, I can record 5 minutes but end up with a 30 second recorded clip where everyone is running around the scene.

  


  My code is the 'typical' read in video and write video code that you would find online such as (code below simplified for readability) :

  


  import cv2

video = cv2.VideoCapture(live RTSP address of camera)

if (video.isOpened() == False):
    print("Error reading video file")
else:
    frame_width = video.get(cv2.CAP_PROP_FRAME_WIDTH)
    frame_height = video.get(cv2.CAP_PROP_FRAME_HEIGHT)
    frame_fps = video.get(cv2.CAP_PROP_FPS)
    size = (frame_width, frame_height)
    result = cv2.VideoWriter('filename.avi',cv2.VideoWriter_fourcc(*'MJPG'),frame_fps , size)

    while(True):
        ret, frame = video.read()
        if ret == True:
            result.write(frame)
            cv2.imshow('Frame', frame)
        if cv2.waitKey(1) & 0xFF == ord('s'):
            break
        else:
            break
    video.release()
    result.release()
    cv2.destroyAllWindows()
print("The video was successfully saved with new fps")


  


  I have tried playing with the FPS by reading in the FPS from the live camera and using the same FPS in the video write, but all that results is a video that is a fraction of the real time and with people zooming around the scene. So watching a 5 minute smooth video results in a 20 second recorded video with everyone zooming around.

  


  Is this something that I need to fix in the writing of the video or do I need a second pass with ffmpeg to readjust the video ?

  


  Much appreciated

  


  Update, corrected the code above and :
When printing the frames read and the frame written the numbers are the same, showing that each frame that is read is being written (so I am not losing frames along the way thereby writing half the amount of frames).

  


• avutil/opt : Print out numeric values of option constants

  17 septembre 2019, par Soft Works

  avutil/opt : Print out numeric values of option constants
  It's often not obvious how option constants relate to numerical values.
  
  Defaults are sometimes printed as numbers and from/to are always printed as numbers.
  
  Printing the numeric values of options constants avoids this confusion.
  
  It also allows to see which constants are equivalent.
  Before this patch :
    -segment_list_type <int>        E........ set the segment list type (from -1 to 4) (default -1)
  
       flat                         E........ flat format
  
       csv                          E........ csv format
  
       ext                          E........ extended format
  
       ffconcat                     E........ ffconcat format
  
       m3u8                         E........ M3U8 format
  
       hls                          E........ Apple HTTP Live Streaming compatible
  Afterwards :
    -segment_list_type <int>        E........ set the segment list type (from -1 to 4) (default -1)
  
       flat            0            E........ flat format
  
       csv             1            E........ csv format
  
       ext             3            E........ extended format
  
       ffconcat        4            E........ ffconcat format
  
       m3u8            2            E........ M3U8 format
  
       hls             2            E........ Apple HTTP Live Streaming compatible
  Signed-off-by : softworkz <softworkz@hotmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavutil/opt.c

• pyglet's video example application not working

  3 octobre 2020, par C. E.

  I'm trying to get the pyglet video player example to work, but I'm getting the following error :

  


  


  pyglet.media.codecs.ffmpeg.FFmpegException : avformat_open_input in
ffmpeg_open_filename returned an error opening file
/home/ce/Downloads/sample-mp4-file.mp4 Error code : -1094995529

  


  


  I decoded this number, and it turns out that it corresponds to the "INDA" error code in FFMPEG's error.h, which means

  


  


  Invalid data found when processing input

  


  


  The example video that I used can be downloaded here. I tried the mp4 one, the avi one and the webm one. I also tried other files that I have locally. They all work in other video players, and in fact some were created using FFMPEG.

  


  Finally, I used pyglet.media.have_ffmpeg() to make sure that pyglet agrees with me that I have ffmpeg installed.

  


  Originally, I had ffmpeg 3.4 installed globally, i.e. which ffmpeg pointed to a 3.4 binary. I then replaced that binary with a ffmpeg 4.1 binary. However, when I run pyglet.info.dump_ffmpeg() it still say 3.4.8 so I may not have suceeded in trying 4.1. I tried setting os.environ["LD_LIBRARY_PATH"] but it is still printing 3.4.8.

  


  Operating system : Ubuntu 18.04. I have gotten it to work on Ubuntu 20.04. It uses a newer FFMPEG which I suspect is important.

  


  What can I do ?