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• merge multiple audio with delay in ffmpeg [duplicate]

  4 août 2019, par Mohammadreza Janipour

  This question already has an answer here :

  • ffmpeg - how to merge multiple audio with time offset into a video ? [closed]
    
    2 answers
    

  I want to use FFMPEG to merege multiple audios in this ffmpeg command :

  -i audio1.mp3 -i audio2.mp3 -i audio3.mp3 -filter_complex amix=inputs=3:duration=first output_audio.mp3

  But i want audio1.mp3 play at start time and audio2.mp3 start after 2 seconds and audio3.mp3 start after 5 seconds.

  What should I do ? Please help me. Thanks

• How to use Python (For example, ffmpeg or moviePy) to split large video to display on multiple screen [on hold]

  27 juillet 2019, par Chen Clarence

  I am trying to find resources to split a very long (1080*15360) video into 8 1080p videos of the same time length. Is there anything that could achieve this, or even better allows control over each pixel（use a function to cover part of my video with a black circle）. Right now I have to brute force it, such as the following, but I’m sure there are much more efficient methods. Thanks in advance !

  cap=cv2.VideoCapture('sample.avi')
  
  #inputs & check for error
  
  numberOfScreens=8
  
  screenArrangement=(1,8)
  
  if (numberOfScreens!=(screenArrangement[0]*screenArrangement[1])):
  
      raise ValueError('The screen arrangement does not match the number of scrrens')
  
      exit(0)
  
  
  
  
  
  currentFrame=0
  
  originalFrames=[]
  
  while(True):
  
      #reading frames
  
      ret,frame=cap.read()
  
      if not ret:
  
          break
  
      height, width, layers = frame.shape
  
      unitHeight=(int)(height/screenArrangement[0])   #reduce this to outside loop
  
      unitWidth=(int)(width/screenArrangement[1])
  
      #cutting frames into desired size
  
      for i in range(screenArrangement[0]):
  
          for j in range(screenArrangement[1]):
  
              try:
  
                  if not os.path.exists('Screen'+str(i*screenArrangement[0]+j+1)):
  
                      os.makedirs('Screen'+str(i*screenArrangement[0]+j+1))
  
                      print('creating directory '+'Screen'+str(i*screenArrangement[0]+j+1))
  
              except OSError:
  
                  print ("Error Creating Directory")
  
              name='./Screen'+str(i*screenArrangement[0]+j+1)+'/frame'+str(currentFrame)+'.png'
  
              cropImg = frame[(i*unitHeight):((i+1)*unitHeight), (j*unitWidth):((j+1)*unitWidth)]
  
              print('creating'+name)
  
              #saving cropeed frames
  
              cv2.imwrite(name, cropImg,[cv2.IMWRITE_PNG_COMPRESSION, 0])
  
      currentFrame+=1
  
  Frames=currentFrame 
  
  
  
  #setting up the writer object
  
  fourcc = cv2.VideoWriter_fourcc(*'XVID')
  
  writer=cv2.VideoWriter('Screen1.avi', fourcc, 30, (unitWidth, unitHeight), True)
  
  #write the video
  
  for i in range(Frames):
  
      img=cv2.imread('./Screen1/frame'+str(i)+'.png')
  
      writer.write(img)
  
  writer.release()
  
  cap.release()
  
  cv2.destroyAllWindows()

• ffmpeg : record/capture stream and do scene detection at the same time

  2 août 2022, par AnodeCathode

  Is it possible to both capture (record) an RTSP stream and capture scene change events using a single ffmpeg command ? I can almost do what I want with :

  



  ffmpeg -i 'rtsp://mystream' \
-map 0:v -map 0:a -c:v copy -c:a copy -f segment \
-segment_time 300 -segment_format matroska -strftime 1 "%Y%m%d%H%M%S_video.mkv" \
-map 0:v -an -filter:v "select='gt(scene,0.1)'" -frames:v 1 "%Y%m%d%H%M%S_scenechange.png"


  



  This gives me nice 300s stream segments saved to disk, and a scene.png when a scene change is detected. However, scene.png only appears when I terminate the process, and when I do, I only get the last scene event. Ideally I'd like to get a new PNG (or even better, a short video clip) anytime a scene change is detected, without interrupting the recording of video.mkv. I'm sure it can be done with pipes and multiple ffmpeg commands, but for simplicity's sake (and mostly my own curiosity at this point), I'd like to see what can be done with just a single process.