Convert m4v to pgm

What is the difference between .m4v and .pgm?

Description: The M4V file format is a video container format developed by Apple and is very similar to the MP4 format, with the primary difference being the optional Apple Digital Rights Management (DRM) protection. M4V files are commonly used for TV episodes, movies, and music videos in the iTunes Store. These files can be played on Apple devices such as iPhones, iPads, and iPods, as well as on PCs using iTunes or other compatible media players.; A PGM file is a grayscale image file saved in the portable gray map (PGM) format and encoded with one or two bytes (8 or 16 bits) per pixel. It contains header information and a grid of numbers that represent different shades of gray from black (0) to white (up to 65,536). PGM files are typically stored in ASCII text format, but also have a binary representation.