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• Extract individual frames as a buffer from a video

  30 août 2022, par mgo

  I'm trying to process a video using tensorflow in node.js (i.e. on the server - I don't have a web page). I need to process each frame in the video individually. I see some people are using ffmpeg to generate individual image files from the video but that seems wasteful as it creates files on the filesystem. I would prefer to grab each frame as a base64 string in memory. I've got this working using OpenCV4Node but am wondering if there are any lighter weight solutions. Is anyone already doing this ? Any help would be appreciated :-)

  


• Why is accessing these particular videos with ffmpeg far slower than usual ?

  8 novembre 2017, par user779159

  If I run ffmpeg -ss $TIME -i $URL -frames:v 1 -filter:v $FILTER file.jpg -v trace to get a screenshot of a video from a remote website, it normally runs quite quickly. But videos from a different website are taking much longer to run.

  All videos from one particular website are very slow. I’ve compared two videos that are 3-4MB, one from a website where ffmpeg works almost instantly (0.5 seconds) and another from a website where it works terribly slowly (15 seconds).

  Here’s the trace output for the slow video http://pastebin.pl/view/raw/4df9fb06. And here’s trace output for the fast video http://pastebin.pl/view/raw/4b590932.

  Can you identify any reason why one video is so much slower compared to all the other videos ? The ffmpeg command I ran is the one from above and the same for both videos. How can I speed this up ?

  The slow video downloads a few seconds slower than the fast video, but I don’t think the ffmpeg command should be showing such a major difference between the two files.

• FFMpeg ZeroMQ Filter stops working after a short while

  22 septembre 2017, par Casper Alant

  I run FFMpeg as follows :

  #!/bin/bash
  
  fc="[1]scale=iw/2:ih/2 [pip]; [pip] zmq=bind_address=tcp\\\://127.0.0.1\\\:1235,[0]overlay=x=0:y=0"
  
  ffmpeg -v verbose -re -y -i test.mkv -i test2.mkv -filter_complex "$fc" -f mpegts -codec:v libx264 -preset ultrafast resultzmq.mp4

  I then start a Python 3 app to send zmq commands to FFMpeg :

  import zmq
  
  import time
  
  import sys
  
  from  multiprocessing import Process
  
  
  
  context = zmq.Context()
  
  port = "1235"
  
  print("Connecting to server with port {}".format(port))
  
  socket = context.socket(zmq.REQ)
  
  socket.connect("tcp://localhost:{}".format(port))
  
  for request in range (20):
  
      print("Sending request ", request, "...")
  
      socket.send_string("Parsed_overlay_2 x 200")
  
      message = socket.recv()
  
      print("Received reply ", request, "[", message, "]")
  
      time.sleep (1)

  Which runs fine up until about 40 seconds when I get this from Ffmpeg (it stops getting the command) :

  frame=  918 fps= 24 q=19.0 size=   12192kB time=00:00:38.82 bitrate=2572.6kbits
  
  frame=  931 fps= 24 q=19.0 size=   12402kB time=00:00:39.30 bitrate=2585.1kbits
  
  [Parsed_zmq_1 @ 0x56185e089220] Processing command #8 target:Parsed_overlay_2 command:x arg:200
  
  [Parsed_zmq_1 @ 0x56185e089220] Sending command reply for command #8:
  
  0 Success
  
  frame=  938 fps= 24 q=19.0 size=   12516kB time=00:00:39.82 bitrate=2574.1kbits/frame=  952 fps= 24 q=19.0 size=   12752kB time=00:00:40.33 bitrate=2590.0kbits/[Parsed_zmq_1 @ 0x56185e089220] Processing command #9 target:Parsed_overlay_2 command:x arg:200
  
  [Parsed_zmq_1 @ 0x56185e089220] Sending command reply for command #9:
  
  0 Success
  
  frame=  963 fps= 24 q=19.0 size=   12932kB time=00:00:40.81 bitrate=2595.6kbits
  
  frame=  976 fps= 24 q=19.0 size=   13121kB time=00:00:41.31 bitrate=2601.4kbits
  
  frame=  992 fps= 24 q=19.0 size=   13434kB time=00:00:41.84 bitrate=2629.9kbits
  
  frame= 1002 fps= 24 q=18.0 size=   13582kB time=00:00:42.34 bitrate=2627.2kbits

  and this from the Python 3 client :

  Sending request  8 ...
  
  Received reply  8 [ b'0 Success' ]
  
  Sending request  9 ...
  
  Received reply  9 [ b'0 Success' ]
  
  Sending request  10 ...

  The disconnect always happens at the same time, no matter when I start the Python client. If I start it after 40 seconds, it won’t send any commands at all.

  On my actual application, the same thing happens but at about 60 seconds.

  I tried setting up a simple Python server/client and the problem does not occur. So I assume the problem must have something to do with FFMpeg and its zmq plugin ?

  If you would like to test this yourself, just make sure test.mkv and test2.mkv is some video longer than 1 minute.

  I would really appreciate any assistance !