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• Trying to trim a video using FFMpeg in Python in a loop using variables as the start frame and end frame

  29 juin 2022, par LearningPython

  I'm writing a program using Python. I need to use FFMpeg as part of a loop within my program. I want FFMpeg to take my video file and create a new output each loop, using variables as the start and end point (as specific frames) How can I do this ? I found some other code online which I think is on the right track but I need some help.

  


  ffmpeg_start = start_sample / 29.97
ffmpeg_end = end_sample / 29.97

import os

path = '/Users/a/Downloads/Video'

for filename in os.listdir(path):
    if filename.endswith(".mp4"):
        command = "ffmpeg -fflags +discardcorrupt -i " + os.path.join(path, filename) + " -c copy -map 0 -ss {ffmpeg_start} -t {ffmpeg_end} -f segment -reset_timestamps 1 " + os.path.join(path, "output%03d.mp4")
        os.system(command)
    else:
        continue


  


  The error I'm currently getting is : "Invalid duration specification for ss : ffmpeg_start"
Thanks in advance !

  


• What is legacyNullReferencePolicy ?

  22 février 2014, par Sugrue

  We are getting mysterious SEHExceptions in our C# application which may be coming from some unmanaged code (FFMPEG). Its not being caught by the try-catch blocks - so we are not certain what is causing it, but it is perhaps due to a null reference.

  I found this on MSDN (SEHException MSDN Page) which says :

  The .NET Framework often encounters unmanaged SEH exceptions that are automatically mapped to managed equivalents. There are two common unmanaged SEH exceptions :
  STATUS_NO_MEMORY exceptions are automatically mapped to the OutOfMemoryException class.
  STATUS_ACCESS_VIOLATION exceptions are automatically mapped as follows :

  If legacyNullReferencePolicy is applied, all access violations are mapped to the NullReferenceException class.

  Now, this bit sounds interesting - if we could set this legacyNullReferencePolicy maybe these mysterious NullReferenceExceptions could be caught and we could find out where they are coming from.

  But I can't find any information online about legacyNullReferencePolicy. What is it ? Where do I set it ?

• FFMPEG : Get the Scene Change Detection value for all frame

  14 novembre 2022, par celacanto

  I'm trying to measure how much a movies is "fast" (more action in the screen and quick scene chances). I don't want just a single value for the movie, but values along the movie to see how the action varies during it. After normalize the frame rate of the movies (10 fps), my idea is to compare each frame with the previous. I'm not only interest if the scene has changed, but also, if there was no cut, how much movement there is. Not only people/object movement but also, camera movement. In summary the paced (I think that the term) of the scenes.

  



  My idea was to use the scene function from ffmpeg as a metric. But looking at the document and examples online I'm thinking I can only use the value of the Scene Change Detection as a threshold to return frames informations, but I can't get ffmpeg to return the value. Is that right ? There is any way I can make it return the value ?