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• Get 'location' of video using ffmpeg and regex

  6 février 2014, par Foysal

  I have a metadata text of a video file which is produced by ffmpeg.

  Metadata:
  
      major_brand     : qt  
  
      minor_version   : 0
  
      compatible_brands: qt  
  
      creation_time   : 2011-09-10 21:44:22
  
      model           : iPhone 4
  
      model-deu       : iPhone 4
  
      encoder         : 4.3.5
  
      encoder-deu     : 4.3.5
  
      date            : 2011-09-10T17:44:22-0400
  
      date-deu        : 2011-09-10T17:44:22-0400
  
      location        : +40.7329-073.9864/
  
      location-deu    : +40.7329-073.9864/
  
      make            : Apple
  
      make-deu        : Apple

  What regex i need to write if I want to get the 'location' value from above text. I am using C#.

• matplotlib funcanimation save issue

  20 avril 2015, par Richie Abraham

  I have been trying some animation recently using matplotlib animations. It has been going great, i create an ffmpeg writer and save it as a video file. However i face an issue whenever the function that FuncAnimation calls returns more than one object.

  Below is a small snippet of my code base. When I return both im0 and im1, the video file created only has im1 , although the plt.show command works as expected ( showing both the videos ). If i return just a single im0, then it works as expected. IT also works as expected if i return both im0 and im1 with alpha=0.5.

  Can anyone shed some light on what is happening underneath the hood ?

  fig, ax = plt.subplots(1)
  
  def animate(i):
  
      im0=ax.imshow(np.ma.masked_array(imgl[i][:,:,0], mask=get_blob(i)),cmap='cubehelix')
  
  
  
      im1=ax.imshow(imgl[(i-100)%len(imgl)][:,:,0],cmap='cubehelix')
  
  
  
      return [im1,im0]
  
  
  
  
  
  
  
  ani = animation.FuncAnimation(fig, animate, frames=200,
  
                                interval=10, blit=True,repeat=False)
  
  ani.save('ps.mp4', writer=writer)
  
  plt.show()

• How to stream frames from OpenCV C++ code to Video4Linux or ffmpeg ?

  6 juillet 2022, par usamazf

  I am experimenting with OpenCV to process frames from a video stream. The goal is to fetch a frame from a stream, process it and then put the processed frame to a new / fresh stream.

  


  I have been able to successfully read streams using OpenCV video capture functionality. But do not know how I can create an output stream with the processed frames.

  


  In order to do some basic tests, I created a stream from a local video file using ffmpeg like so :

  


  ffmpeg -i sample.mp4 -v 0 -vcodec mpeg4 -f mpegts \
        "udp://@127.0.0.1:23000?overrun_nonfatal=1&fifo_size=50000000"


  


  And in my C++ code using the VideoCapture functionality of the OpenCV library, I am able to capture the above created stream. A basic layout of what I am trying to achieve is attached below :

  


  cv::VideoCapture capture("udp://@127.0.0.1:23000?overrun_nonfatal=1&fifo_size=50000000", cv::CAP_FFMPEG);

cv::Mat frame;

while (true) 
{
    // use the above stream to capture a frame
    capture >> frame;
    
    // process the frame (not relevant here)
    ...

    // finally, after all the processing is done I 
    // want to put this frame on a new stream say at
    // udp://@127.0.0.1:25000, I don't know how to do
    // this, ideally would like to use Video4Linux but
    // solutions with ffmpeg are appreciated as well
}


  


  As you can see from comment in above code, I don't have any idea how I should even begin handling this, I tried searching for similar questions but all I could find was how to do VideoCapture using streams, nothing related to outputting to a stream.

  


  I am relatively new to this and this might seem like a very basic question to many of you, please do excuse me.