Convert m4v to gsm

What is the difference between .m4v and .gsm?

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 lossy file format used to compress speech in Global Standard for Mobile (GSM) telecommunications. It is very effective for reducing audio file size. However, encoding and decoding audio signals severally is discouraged as the final product will have a lot of noise. Popular with some voice mail software but it is CPU intensive.