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• How to fetch both live video frame and timestamp from ffmpeg to python on Windows

  8 mai 2018, par vijiboy

  Searching for an alternative as OpenCV would not provide timestamps for live camera stream (on Windows), which are required in my computer vision algorithm, I found ffmpeg and this excellent article https://zulko.github.io/blog/2013/09/27/read-and-write-video-frames-in-python-using-ffmpeg/
  The solution uses ffmpeg, accessing its standard output (stdout) stream. I extended it to read the standard error (stderr) stream as well.

  Working up the python code on windows, while I received the video frames from ffmpeg stdout, but the stderr freezes after delivering the showinfo videofilter details (timestamp) for first frame.

  I recollected seeing on ffmpeg forum somewhere that the video filters like showinfo are bypassed when redirected. Is this why the following code does not work as expected ?

  Expected : It should write video frames to disk as well as print timestamp details.
  Actual : It writes video files but does not get the timestamp (showinfo) details.

  Here’s the code I tried :

  import subprocess as sp
  
  import numpy
  
  import cv2
  
  
  
  command = [ 'ffmpeg', 
  
              '-i', 'e:\sample.wmv',
  
              '-pix_fmt', 'rgb24',
  
              '-vcodec', 'rawvideo',
  
              '-vf', 'showinfo', # video filter - showinfo will provide frame timestamps
  
              '-an','-sn', #-an, -sn disables audio and sub-title processing respectively
  
              '-f', 'image2pipe', '-'] # we need to output to a pipe
  
  
  
  pipe = sp.Popen(command, stdout = sp.PIPE, stderr = sp.PIPE) # TODO someone on ffmpeg forum said video filters (e.g. showinfo) are bypassed when stdout is redirected to pipes??? 
  
  
  
  for i in range(10):
  
      raw_image = pipe.stdout.read(1280*720*3)
  
      img_info = pipe.stderr.read(244) # 244 characters is the current output of showinfo video filter
  
      print "showinfo output", img_info
  
      image1 =  numpy.fromstring(raw_image, dtype='uint8')
  
      image2 = image1.reshape((720,1280,3))  
  
  
  
      # write video frame to file just to verify
  
      videoFrameName = 'Video_Frame{0}.png'.format(i)
  
      cv2.imwrite(videoFrameName,image2)
  
  
  
      # throw away the data in the pipe's buffer.
  
      pipe.stdout.flush()
  
      pipe.stderr.flush()

  So how to still get the frame timestamps from ffmpeg into python code so that it can be used in my computer vision algorithm...

• FFMPEG split into two frames with BGR convertion instead of RGB | OpenVino

  26 avril 2020, par Mayur Kanojiya

  

  



  I don't know why this happen because when i pass the normal frames directly, it didnot split into two frames but when i do some post-processing to count the person at 2nd person it flips into 2 frames.

  



  I think flush called or i missed one frame in loop :/

  



  So my question is that How can this is possible as i am directly feeding my frames ?

  



  I used following ffmpeg command to pipe with python.

  



  

  • ffmpeg -v warning -f rawvideo -pixel_format bgr24 -video_size 768x432 -framerate 24 -i - http://0.0.0.0:3004/fac.ffm

  


  


• Error using pipe ffmpeg

  10 décembre 2016, par user3381786

  i am using ffmpeg to record video, but it doesn’t work..

      byte[] texBytes = tex.EncodeToPNG();//get byte[]
  
      proc = new System.Diagnostics.Process();
  
      proc.StartInfo.FileName = "ffmpeg.exe";
  
      proc.StartInfo.Arguments = " -y -r 30 -f rawvideo -codec rawvideo -s 512x512 -pixel_format rgba -i pipe:0 -vf \"transpose = 1\" -r 30 -threads 8 -c:v libx264 -preset slow -crf 18 -pix_fmt yuv420p test2.mp4";
  
      proc.StartInfo.CreateNoWindow = true;
  
      proc.StartInfo.UseShellExecute = false;
  
      proc.StartInfo.RedirectStandardError = true;
  
      proc.StartInfo.RedirectStandardInput = true;
  
      proc.Start();
  
  
  
      MemoryStream ms = new MemoryStream(texBytes);
  
      ms.WriteTo(proc.StandardInput.BaseStream);
  
      ms.Flush();
  
      ms.Close();

  the output file "test2.mp4" is only 1KB. Any problems in my codes ?
  thank you in advance.