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• Simplest way to do do video editing in C++ ?

  23 décembre 2019, par CaptainCodeman

  I have a video file (approx 30,000 frames) and want to do some processing on the individual frames with a C++ program I’ve written.

  The simplest method would be to extract the frames using ffmeg, do the processing, and then encode the video again. However, this would require a few hundred gigabytes of disk space. Is there a way to stream it ?

  Or is there some library that lets me just open a video, alter the frames, and re-encode ?

• Pipe video frames from ffmpeg to numpy array without loading whole movie into memory

  2 mai 2021, par marcman

  I'm not sure whether what I'm asking is feasible or functional, but I'm experimenting with trying to load frames from a video in an ordered, but "on-demand," fashion.

  


  Basically what I have now is to read the entire uncompressed video into a buffer by piping through stdout, e.g. :

  


  H, W = 1080, 1920 # video dimensions
video = '/path/to/video.mp4' # path to video

# ffmpeg command
command = [ "ffmpeg",
            '-i', video,
            '-pix_fmt', 'rgb24',
            '-f', 'rawvideo',
            'pipe:1' ]

# run ffmpeg and load all frames into numpy array (num_frames, H, W, 3)
pipe = subprocess.run(command, stdout=subprocess.PIPE, bufsize=10**8)
video = np.frombuffer(pipe.stdout, dtype=np.uint8).reshape(-1, H, W, 3)

# or alternatively load individual frames in a loop
nb_img = H*W*3 # H * W * 3 channels * 1-byte/channel
for i in range(0, len(pipe.stdout), nb_img):
    img = np.frombuffer(pipe.stdout, dtype=np.uint8, count=nb_img, offset=i).reshape(H, W, 3)


  


  I'm wondering if it's possible to do this same process, in Python, but without first loading the entire video into memory. In my mind, I'm picturing something like :

  


  

  1. open the a buffer

  


  2. seeking to memory locations on demand

  


  3. loading frames to numpy arrays

  


  


  I know there are other libraries, like OpenCV for example, that enable this same sort of behavior, but I'm wondering :

  


  

  • Is it possible to do this operation efficiently using this sort of ffmpeg-pipe-to-numpy-array operation ?

  


  • Does this defeat the speed-up benefit of ffmpeg directly rather than seeking/loading through OpenCV or first extracting frames and then loading individual files ?

  


  


• using file info from txt file to bull trim audio with ffmpeg

  26 juin 2018, par thirtylightbulbs

  I have found how to trim individual audio files with ffmpeg. Is there any way to do it on bulk ? I have thousands of audio files each with different segments that need to be saved separately. The input file, time to start clipping, and duration are all in separate columns, row by row, in a text/excel file.