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• 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()

• Did not locate the video track for seeking

  5 novembre 2018, par Bruce Young

  I using android MediaPlayer to play some audios.It’s works 100% fine with the method seekTo() in some format like m4a(ffmpeg show the media info below) :
  normal is the audio file name

  But when I use other format like matroska,webm,the seekTo()method always fail !(ffmpeg show the media info below)

  seekbad is the audio file name

  Okay,when the seekTo() fail the android studio console show some logs like this :

  11-05 11:07:00.815 763-22357/? E/MatroskaExtractor: Did not locate the video track for seeking

  Than I google the logs and find out the sourcecode in google git :
  https://android.googlesource.com/platform/frameworks/av/+/304ef91624e12661e7e35c2c0c235da84a73e9c0/media/libstagefright/matroska/MatroskaExtractor.cpp

  In MatroskaExtractor.cpp some code like this :

  // Always *search* based on the video track, but finalize based on mTrackNum
  
  if (!pTP) {
  
      ALOGE("Did not locate the video track for seeking");
  
      return;
  
  }

  I do not know why my media file ’Did not locate the video track for seeking’,Does anybody know it,Thanks a lot !

• Combine .dash video and audio segments to .mp4

  11 décembre 2019, par Mike Stevens

  I was able to download some dash video segments (youtube-dl was apparently blocked from downloading the .mpd and just downloading, concatenating as normal) and was hoping to combine/concatenate them so I could watch in VLC, perhaps using ffmpeg. I was able to download the relevant .mpd and .ismc files, so I have all of the DASH video and audio segments, as well as the .mpd and .ismc downloaded and in one folder.

  The video files are labelled as such

  video=869000.dash
  
  video=869000-0.dash
  
  video=869000-600.dash
  
  video=869000-1200.dash

  and the audio in a similar fashion

  audio=96000.dash
  
  audio=96000-0.dash
  
  audio=96000-96225.dash

  Would anyone know of a way to combine all of these into one watchable video file ? AdobeHDS used to work great for combining fragments, and youtube-dl cleary has some sort of method to do it, but neither works with this particular .mpd. I don’t believe concatenate in ffmpeg will work, when I try to do that, it initializes the first .dash file (audio or video), but stops there.

  When I try to put the .mpd file through ffmpeg, it returns "Failed to open an initialization section in playlist 0". I would’ve assumed this initialization was the video=869000.dash file though (which is the one segment file that ffmpeg does recognize) ?