Why .mpeg video file does not work when comes to adding noise (Other file formats like .mpg works better ) ?

I have been trying to add noise (Gaussian) to .mpeg video file but error shows up (File is invalid). Pls let me know reasons of using .mpeg , if not, there is other reasons? Psychtoolbox is helpful for adding noises using .mpeg videos?

while hasFrame(Vptr)
%Read from video file
Img = readFrame(Vptr);

%Add noise to the image
Img = imnoise(Img,'gaussian', 0.6);
%write to video file
writeVideo(Wptr,Img);

[Dinesh Iyer]

I am not sure what Wptr is here. I am assuming that it is a VideoWriter object instance.

VideoWriter supports MPEG-4, AVI, MJ2000. Did you call close(Wptr) after you have completed writing all the video frames you wanted?

MPEG-4 file is H.264 encoded. It should give you the best compression for video quality.

[Priyanka P]

By definitation, Vptr = VideoReader(video.mpeg) and Wptr is VideoWriter obj that writes to other video file. I try using closing VideoWriter but still error shows up "file not vallid"

[Walter Roberson]

"By definitation, Vptr = VideoReader(video.mpeg)"

Please confirm that you have a struct named video that has a field named mpeg that contains the name of a file; or else that you have an object of some kind with a property named mpeg that contains the name of a file; or else that you have an object of some kind with a method named mpeg that takes no arguments, and that the method returns the name of a file.