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• 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 ?

• 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 !

  


• Removing / Overlaying logo on mp4 video format with ffmpeg on linux

  13 juillet 2016, par SilverShadow

  I’m trying to remove logo from an .mp4 video format with ffmpeg on linux machine without re-encoding (for preserving the same quality) with the following command :

  ffmpeg -i input.mp4 -vf delogo=x=270:y=190:w=40:h=40 -c:a copy output.mp4

  and it give me the following errors :

  Unrecognized option 'vf'

  then a new error came up :

  Unable to find a suitable output format for 'delogo=x=270:y=190:w=40:h=40'

  ffmpeg always updating and it seems that they change command line arguments alot so any material or tutorial i find online seems to get out-dated quickly

  I review their website documentation but can’t get it to work, I think i’m missing something...?

  so what is the correct command line in linux shell also, how to view or find out exactly the area coordinates to be removed before actually removing logo/overlaying it and keep testing every while

  and how to overlay a solid color in certain area instead of removing logo transparently as well ?