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• How to record a video and create a file every 1 minute and without stopping media recorder as stopping and starting causing delay

  7 January 2021, by Karsh Soni

  I want to develop a functionality where i have to start recording or say start continuous recording for more than 5 hours and for every minute i want to create a video file so that i want to store files of a video every minute without any delay or missing any frame.

  


  Right now to create a file i need to stop the media recorder and which leads to stopping and starting media recorder and it ends up losing 1.5 to 3 seconds of delay based on devices where i want to minimize the delay as negligible as possible.

  


  I am getting callbacks or frames for each second but if i would try to save those bitmaps and then try to convert them into video it might work with 5FPS. but with 30 or 60FPS its not performing as continuous frames wouldn't let me write to files efficiently. even though that is being done in background.

  


  Please let me know if you know any alternate solution or any solution that can help me achieve it.

  


• ffmpeg movies won't play in windows media player

  10 January 2015, by kjgregory

  I am trying to save some fairly simple matplotlib animations as movies in python. I’ve installed ffmpeg, but I don’t really know much about movie encoding and all of the other threads are way over my level of understanding. I’ve tried several different codecs and they all have the same problem.

  My problem is that my movies save and I can view them with VLC player, but not with windows media player. My friend seems to be able to play them too, but I’m not sure what hes using. Anyway, I was hoping someone could break it down for me in a simple way and tell me how to encode my movies so that they are playable on the broadest number of systems.

  Since I know someone is going to ask, here is my setup:
  Windows 7,
  matplotlib v1.4.2,
  python 2.7.9 32-bit,
  ffmpeg v. N-68625-g1728659

  Below is my code:
  the output of the print statements is:

  (7,30,3)

  96

          fig = plt.figure()
  
          ims = []
  
          metadata=dict(artist="SeaWizard",title=(self.codename.capitalize()+" "+self.typename.lower()+" sequence"))
  
          Writer = animation.writers['ffmpeg']
  
          writer = Writer(fps=60,metadata=metadata)
  
          dims = (np.shape(self.__baseimg)[0],np.shape(self.__baseimg)[1],3)
  
          prevdata = np.zeros(dims,np.uint8)
  
  
  
          for i in range(len(self.bright1)):
  
              data = self.__getimg(i)
  
              steps = int(self.speed[i]/5)
  
              for n in range(steps):
  
                  combdata = np.log((n*(data/steps) + (steps-n)*(prevdata/steps))+1)/np.log(self.__imgmax)
  
                  im = plt.imshow(combdata)
  
                  ims.append([im])
  
              prevdata = data
  
  
  
          print np.shape(combdata)
  
          print len(ims)
  
  
  
          anim = animation.ArtistAnimation(fig,ims,interval=16)
  
          anim.save('SeaWizardSimulation.mp4',writer=writer, extra_args=['-vcodec', 'lib264'])
  
          plt.show()

• How to play video Media Source Extensions when the audio start is delayed? Or how to fix it with ffmpeg?

  11 December 2020, by sheodox

  I have a video that I'm splitting the individual video/audio streams out then dashing with MP4Box, then I'm playing them with Media Source Extensions and appending byte ranges to video/audio source buffers from the MPD files. It's all working nicely, but one video I have has audio that is delayed by about 1.1 second. I couldn't get it to sync up and the audio would always play ahead of the video.

  


  Currently I'm trying to set the audioBuffer.timestampOffset = 1.1 and that gets it to sync up perfectly. The issue I'm running into now though is the video refuses to play unless the audio source buffer has data. So the video stalls right away. If I skip a few seconds in (past the offset) everything works because both video/audio are buffered.

  


  Is there a way to get around this? Either make it play without the audio loaded, somehow fill the audio buffer with silence (can I generate something with the Web Audio API)? Add silence to the audio file in ffmpeg? Something else?

  


  I first tried adding a delay in ffmpeg with ffmpeg -i video.mkv -map 0:a:0 -acodec aac -af "adelay=1.1s:all=true" out.aac but nothing seemed to change. Was I doing something wrong? Is there a better way to demux audio while keeping the exact same timing as when it was in the container with the video so I don't have to worry about delays/offsets at all?