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• Get frames from a video into a matrix

  19 juin 2019, par Nephilim

  I’m currently trying to implement a compression algorithm(frame prediction) for an assignment. I am not looking for thumbnail files, or even just a shell command to generate something for me. My problem is specifically integrating it with a golang program.

  I just started and I’m already stuck. I’m supposed to get each frame out of a video,divide it into I P and B frames and perform inter-coding(compress the frame itself), then perform intra-coding(between the frames).

  Right now I cannot even get started on the above problems, because I have no idea how to read the video as something I could use in code. Apparently, the only library I can think of is ffmpeg. FFMPEG can get separate frames, apparently even i p and b frames.

  ffmpeg -i <inputfile> -vf '[in]select=eq(pict_type\,B)[out]' b.frames.mp4
</inputfile>

  But this is just another video output, that I do not know how to open.
  What I was thinking of was outputting frames into bitmaps(?), then reading each bitmap separately, to reconstruct three 3D matrixes, of i frames, p frames and b frames. However this seems like quite a feat. Someone, somewhere has definitely tried to parse a video into a 3D matrix and has found a better solution than what I’m thinking of.

  To be concise, I have a video, I need a 3D matrix. The 3D matrix is a matrix of 2D matrixes, which represent a frame in the video. Each point in a 3D matrix is a pixel(or whatever the equivalent is in videos).

  

• Process Multiple Streams using ffmpeg-python

  27 novembre 2019, par C Dorman

  I have a MPEG-2 TS with a stream of video and a steam of KLV metadata. I can use ffmpeg-python to process each of these streams independently. For example, I can get the video stream, process each frames using numpy as shown in the docs. I can also get the data stream and show it in following way (using the library klvdata) :

  process = (
  
      ffmpeg
  
          .input(in_filename)
  
          .output('pipe:', format='data', codec='copy', map='data-re')
  
          .run_async(pipe_stdout=True, pipe_stderr=True)
  
  )
  
  
  
  for packet in klvdata.StreamParser(process.stdout.read()):
  
      packet.structure()
  
  
  
  process.wait()

  How do I do these at the same time ? I need to split the TS data into its streams and process them both, keeping them in sync. ffmpeg by itself can demultiplex the streams into separate files, but how do I handle the streams in python. The KLV has information that I want to show on top of the video stream (recognition boxes).

• Make picture from stream(webcam) by ffmpeg [on hold]

  29 novembre 2018, par SkiF

  I have webcam and I want to store video from it. I need to store just last one hour. Can I limit space or time for ffmpeg out file ?

  Second and the main problem is make pictures every minute. I want make pictures from actual webcam state. with minimal delay.

  Based on my current knowledge I think the best solution is make 3 processes.
  The Fist will capture video for one minute and there will be 60 files with time stamp in name and every minutes ffmpeg will be restarted by script and script remove the oldest file. The Second will share video steam and The Third will take last frame from the newest video file. Maybe some one know better solution for this problem.

  I think bash is the best tool for this problem. Solution is based on c++ or python also welcome.