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• How to specify a non default type when calling a FFmpeg library using ctypes

  1er août 2013, par Jim Ramberg

  I am calling an FFMPEG library called avformat_alloc_context() that returns a pointer to type AVFormatContext. The structure AVFormatContext is defined in the avformat library.

  Obviously ; this is not one ctypes default types and results in an error when I try to pass a reference to it to another ffmpeg library further down in my code.

  Is there a way to add in the the classes defined inside of the library ? I read through what documentation I could find online and was not able to find a good answer to this question.

• How to set the value of an arbitrary pixel in ffmpeg ?

  14 mai 2017, par Neb

  I want to modify the rgb value of each pixel inside ffmpeg.

  I need to implement the following function :

  A[x + expr_1][y] = expr_2

  where x and y are the current sampled pixel, A is the input frame whose pixel need to be modified and expr_1, expr_2 are two independent expressions.

  I tried using the geq filter but it seems there no way to set the value of a pixel other than from that currently sampled. For istance, the function p(x,y) only returns the value of the pixel at the specified location, but doesn’t allow to set a value for that pixel. In other word, ffmpeg seems allowing only something like :

  A[x][y] = expr

  Is there a way to tell ffmpeg to set the value of a specific pixel ?

  Thanks for your time.

• How to run a ffmpeg command in python with file paths containing spaces ?

  21 juillet 2023, par tomatochan

  I'm developing a program in Python that requires the use of FFMPEG. In one step, I need to create a video from a text file containing the list of images (path and duration) that need to be assembled to make a video. To do this, I use the following code :

  


  cmd = [ffmpeg, "-y", "-f", "concat", "-safe", "0", "-i", tmp, "-c:v", "libx264", "-r", "25", "-pix_fmt", "yuv420p", out]
subprocess.run(cmd)
# os.system(" ".join(cmd)) # returns same error


  


  What returns the error : The syntax of the file, directory or volume name is incorrect.

  


  I know that paths can be problematic when they contain spaces, and as my username has one, I've taken care to quote the paths in such a way that :

  


  ffmpeg = "C:\Users\John Doe\Documents\ffmpeg\bin\ffmpeg.exe"
tmp = "C:\Users\John Doe\Desktop\path\to\file.txt"
out = "C:\Users\John Doe\Desktop\path\to\video.mp4"


  


  When I print(" ".join(cmd)), this is what I get in my terminal :

  


  "C:\Users\John Doe\Documentsffmpeg\binffmpeg.exe" -y -f concat -safe 0 -i "C:\Users\John Doe\Desktop\path\to\file.txt" -c:v libx264 -r 25 -pix_fmt yuv420p "C:\Users\John Doe\Desktop\path\to\video.mp4"


  


  However, the problem persists.
Has anyone ever had this problem and managed to solve it ?

  


  I've also tried the method where you have to escape the spaces (taking care to replace the \ with / and then the with \ ) but nothing works... The error persists.

  


  For your information, here are the contents of one of my .txt files

  


  file C:\Users\John Doe\Desktop\path\to\image_1.png
duration 0.04
file C:\Users\John Doe\Desktop\path\to\image_2.png
duration 0.04
file C:\Users\John Doe\Desktop\path\toimage_3.png
duration 0.04


  


  When I quote the paths in the .txt files

  


  

  • subprocess gives me the error :
PermissionError: [WinError 5] Access denied

  


  • os.system gives me the error :

  


  


  C:\Users\John' is not recognized as an internal or external command, an executable program or a command file.
The syntax of the file, directory or volume name is incorrect.