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• Problem using ffmpeg in python to decode video stream to yuv stream and send to a pipe

  30 août 2019, par 瓦达所多阿萨德阿萨德

  This command works nice and fast in shell :

  ffmpeg -c:v h264_cuvid -i ./myvideo.mp4 -f null -pix-fmt yuv420p -

  It was about 13x speed or 300 frames/sec.
  Then I tried to send the yuv stream to pipe and catch it the main process using the following code in python :

  cmd = ['ffmpeg', '-c:v', 'h264_cuvid', '-i', './myvideo.mp4', '-f', 'image2pipe', '-pix_fmt', 'yuv420p', '-']
  
  p = subprocess.Popen(cmd, stdout = subprocess.PIPE, stderr=subprocess.PIPE)
  
  size_Y = int(height * width)
  
  size_UV = int(size_Y / 4)
  
  s = time.time()
  
  Y = p.stdout.read(size_Y)
  
  U = p.stdout.read(size_UV)
  
  V = p.stdout.read(size_UV)
  
  print('read time: ', time.time() - s)

  However, this took seconds to read just one yuv frame. What wronged here ? Im not sure what ffmpeg was sending into the pipe, the yuv planar frames or just the pointers to data planes ?

  the console output :

  [('Number of Frames', 61137), ('FPS', 25.0), ('Frame Shape', (1920, 1080))]
  
  --Number of Frames: 61137
  
  --FPS: 25.0
  
  --Frame Shape: (1920, 1080)
  
  cmd:  ['ffmpeg', '-c:v', 'h264_cuvid', '-i', './myvideo.mp4', '-f', 'image2pipe', '-pix_fmt', 'yuv420p', '-']
  
  read time:  5.251002073287964
  
  1/61137 (0.00%)read time:  2.290238618850708
  
  2/61137 (0.00%)read time:  1.2984871864318848
  
  3/61137 (0.00%)read time:  2.2100613117218018
  
  4/61137 (0.01%)read time:  2.3444178104400635

• Pipe FFMPEG MPEG-DASH livestream to AWS S3

  17 août 2019, par Alexander

  So I’m currently trying to livestream the rendering of a GPU-heavy video (renders about 1fps), encode it to a 30fps MPEG-DASH livestream and output this to AWS S3 so Shaka Player can display the live rendering.

  The first issue is that the livestream keeps looping, it doesn’t stop after the rendering for loop is done.

  I use a python script to pipe the output of the rendering to FFMPEG, and pipe the output of FFMPEG to the aws s3 cli like this :

  p1 = Popen(['ffmpeg', '-y', '-hwaccel', 'cuvid', '-f', 'image2pipe', '-r', '24', '-i', '-', '-c:v', 'h264_nvenc', '-b:v', '5M', '-f', 'dash', '-movflags', 'frag_keyframe+empty_moov', '-'], stdin=PIPE)#, shell=True) #'-method', 'PUT', 'https://example.s3.amazonaws.com/test1/test1.mpd'], stdin=PIPE)
  
  
  
  p2 = Popen(['aws', 's3', 'cp', '-', 's3://example/test1/test1.mpd'], stdin=p1.stdout)
  
  
  
  
  
  #The following commented aws s3 sync command uploads successfully to S3
  
  #but the issue here is that it stops after the syncing is done and its hacky
  
  #p1 = Popen(['ffmpeg', '-y', '-vsync', '0', '-hwaccel', 'cuvid', '-f', 'image2pipe', '-r', '24', '-i', '-', '-c:v', 'h264_nvenc', '-b:v', '5M', '-f', 'dash', '-movflags', 'frag_keyframe+empty_moov', 'test2.mpd'], stdin=PIPE)#, shell=True) #'-method', 'PUT', 'https://teststream.s3.amazonaws.com/test1/test1.mpd'], stdin=PIPE)
  
  #p2 = Popen(['aws', 's3', 'sync', '.', 's3://teststream/test1', '--exclude', '"*"', '--include', '"*.m4s"', '--include', '"*.mpd"'], stdin=PIPE)
  
  
  
  #pseudocode
  
  for ci,(content,contentName) in enumerate(content_loader):
  
      im = renderframe(content)
  
      im.save(p1.stdin, 'PNG')
  
  
  
  p1.stdin.close()
  
  p1.wait()
  
  p2.stdin.close()
  
  p2.wait()

• FFMPEG - Pipe PCM to STDOUT in real-time for Node.js

  20 août 2019, par bloom.510

  I am able to stream realtime PCM data from my system’s loopback driver that I can either encode raw or in WAV format using FFMPEG.

  How can I pipe the PCM to stdout as its being recorded in real-time ?

  I’m batting around in the dark here. So far I’ve tried logging stdout in Node.js, as well as creating a named pipe and listening for changes to it. None of these has returned any output.

  The basic shell command captures the audio :

  ffmpeg -f alsa -i loopout -f s16le -acodec pcm_s16le out.raw

  Using child_process.spawn() in Node.js :

  let ffmpeg = spawn('ffmpeg', [
  
      '-f', 'alsa', '-ac', '2', '-ar', '44100', '-i',
  
      'loopout', '-f', 's16le', '-acodec', 'pcm_s16le', 'out.raw',
  
  ]);

  However :

  // this never logs anything
  
  ffmpeg.stdout.on('data', (data) => {
  
      console.log(data.toString());
  
  });
  
  
  
  // this outputs what you would see in the terminal window
  
  ffmpeg.stderr.on('data', (data) => {
  
      console.log(data.toString());
  
  });

  Is there a way to access a readable stream of this file as its being created ?

  Or perhaps there is a way to stream the PCM to an RTP server and forward it as a buffer over UDP to an Express server ?

  Whatever the methodology is, the ultimate goal is to access it as a stream in Node.js and convert it into an ArrayBuffer.