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• piping data into an ffmpeg subprocess. Why does write() get stuck ? [closed]

  12 mai 2024, par Tebyy

  It displays the number of frames at the beginning and shows that there are over 300, but when I count all the frames in the loop, the last one I see is 53, and then it only displays the value of 'ret', which is always true. I'm wondering what could be causing this issue of not reading all the frames, resulting in the file not being closed after reading. From what I've read, 'ret' should return false when there are no more frames to read, but because it's not reading all the frames, this isn't happening. Does anyone have any idea what could be causing this ?

  


  Edit : I solved the problem by adding a Thread. Thanks everyone for the help !

  


  I changed those lines of code :

  


  recogniteAndPushFramesToFfmpeg("video-979257305707693982.mp4", ffmpeg_process)
# In function "recogniteAndPushFramesToFfmpeg"
process.stdin.write(frame)


  


  to these :

  


  ffmpeg_thread = Thread(target=recogniteAndPushFramesToFfmpeg, args=("video-979257305707693982.mp4", ffmpeg_process))
ffmpeg_thread.start()
# In function "recogniteAndPushFramesToFfmpeg"
process.stdin.write(frame.tobytes())


  


  Code :

  


  import subprocess
import cv2

def recogniteAndPushFramesToFfmpeg(video_path, process):
    cap = cv2.VideoCapture(video_path)
    i = 1
    print('Frames:', cap.get(cv2.CAP_PROP_FRAME_COUNT))
    while cap.isOpened():
        ret, frame = cap.read()
        print(ret)
        if not ret:
            break

        process.stdin.write(frame)
        process.stdin.flush()
        print('Frame:', i)
        i += 1

    cap.release()
    process.stdin.close()
    #process.wait()
    return
    

ffmpeg_command = [
    'ffmpeg', '-f', 'rawvideo', '-s:v', '1920x1080', '-r', '60',
    '-i', '-', '-vf', 'setpts=2.5*PTS',
    '-c:v', 'libvpx-vp9', '-g', '60',
    '-f', 'webm', '-'
]
ffmpeg_process = subprocess.Popen(ffmpeg_command, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, bufsize=-1)
recogniteAndPushFramesToFfmpeg("video-979257305707693982.mp4", ffmpeg_process)


  


  Python Logs :

  


  Frames: 328.0
...
True
Frame 50
True
Frame 51
True
Frame 52
True
Frame 53
True


  


  I placed cap.isOpened() in the loop to check if it always returns true, and when I printed it, it always showed true

  


  Link to video : Tested Video

  


• Python moviepy, CompositeVideoClip is Slow and Wierd

  4 mars 2023, par Dan

  I want to add a .mov transparent overlay on top of a .mp4 video, and for that I am using movipy and CompositeVideoClip, but it's too slow.

  


  The speed is 40 it/s when only the video is rendering but when it comes to the overlay it is only 5 it/s. To speed it up I have used use_bgclip=True and now I get 90 it/s but when the overlay comes I still get 5 it/s, and when I use use_bgclip=True there are 2 'bugs' that appears :

  


  

  1. The video freezes after the overlay is done playing.

  


  2. The audio of the video is lost and the overlay sound is the only one left

  


  


  For the two 'bugs', I found a good enough solution, but I want to speed up the process when the overlay comes, because 5 it/s it's way too slow. I have tried to use codec="h264_nvenc" or higher crf but the speed is the same.

  


  Is there a way to speed this up ? (I don't care if I need to use other libraries)

  


  import moviepy.editor as mp
video = mp.VideoFileClip("video.mp4")

overlay = mp.VideoFileClip("overlay.mov", has_mask=True)
overlay = overlay.set_start(5) # start the overlay 5 seconds after the video starts

compose = mp.CompositeVideoClip([video, overlay], use_bgclip=True, size=video.size)
compose = compose.set_duration(video.duration) # fix bug 1
compose = compose.set_audio(video.audio) # fix bug 2 (but I lost the audio from the overlay)

compose.write_videofile("cf15.mp4", codec="libx264", preset="veryfast", ffmpeg_params=["-crf", "15"])

compose.close()
video.close()


  


• How to pause ffmpeg than runs without window ?

  5 février 2015, par Zed Machine

  I’m working on a video converter and I wanted to be able to stop or pause ffmpeg by pressing a button. Googleing I have found a way but it’s not working. basically I Start ffmpeg on a background worker in this way :

  Private Sub bw_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs)
  
  
  
          Dim Proc As New Process
  
  
  
          Proc.StartInfo.UseShellExecute = False
  
          Proc.StartInfo.RedirectStandardError = True
  
          Proc.StartInfo.RedirectStandardOutput = True
  
          Proc.StartInfo.FileName = current_ffmpeg_path
  
          Proc.StartInfo.Arguments = input_params
  
          Proc.StartInfo.CreateNoWindow = True
  
          Proc.Start()
  
  
  
  [do things...]

  then inside a loop I place an if to pause ffmpeg :

  If (pause = 1 Or pause = 2) Then
  
          AppActivate(Proc.Id)
  
          SendKeys.SendWait("^(s)")
  
          SetForegroundWindow(Me)
  
          pause = 0
  
      End If

  but it’s not working.. maybe cause of AppActivate that need a window to work while instead ffmpeg is running without it. There is another way ? maybe not with sendkeys ?