VideoReader provide wrong number of frames

I want to extract frames from a .mpg video file, and I use VideoReader to read the video file. But the number of frames obtained using this way seems not correct. As shown in the figure, the frame rate and duration of the video are 29.9 FPS and 606s, respective. But the number of frames is 1211, which is obviously not correct. I also tried another .mp4 file, this problem is solved. Does this problem arise from .mpg format? If so, could anyone please tell me how to obtain the correct information from .mpg files?

[Jan]

Maybe the mpg file is damages? Which Matlab version do you use?

[Chenyu Qiao]

Hi Jan, Thank you for your massage. The mpg file can be played normally, I guess the file is not damaged. I also tried transform the mpg file to mp4 file, and the mp4 version can be read by VideoReader correctly. @Jan

[Jan]

Many programs import files even if they contain errors in the header by replacing them with feasable values. So maybe use another software to read the header and compare it with the real number of frames.

[Walter Roberson]

mpg files can be variable frame rate. 29.97 would be the nominal frame rate.