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• How to combine a .mp4 video with a .wav audio with an offset in ffmpeg from command line ?

  15 mars 2014, par minder42

  I've got a TV clip in mp4 format containing audio and video, and an WAV audio_commentary track.

  I've been trying to combine them in ffmpeg and then play it online with a flash player (which can only take h264 format)

  What's the best ffmpeg command to accomplish this ? My inputs are MP4 video, WAV audio, and an offset in seconds, the time the audio commentary starts relative to the start of the mp4 video.

  I tried

  ffmpeg -i input_audio.wav -i input_vid.mp4 -vcodec copy output.mp4

  and

  ffmpeg -vcodec copy -ss offset -i input_audio.wav -i input_video.mp4 output.mp4

  nether of these do what I want and output the video in the h264 format that is good for flash players- Is there a way to do this from command line in ffmpeg ?

• 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 ?