m4v M4V is a file format developed by Apple for the iTunes store's content and is very similar to the MP4 file extension. M4V is supported exclusively by Apple devices. Other video formats like MP4 and MOV can be converted to M4V in order to run on Apple devices. The most common difference between the M4V and MP4 formats is that M4V offers DRM-Copyright Protection which prevents the copyright of media content. To play a DRM-protected M4V file the computer needs authorization by opening the iTunes account used for buying the media file. However, if the files are not protected by DRM, the user can just rename the file extension from M4V to MP4 in order for it to be recognized by non-apple devices.
3g2 Originally being developed by a Third Generation Partnership Project II, it's used in the third generation mobile phones, 3g2 is basically used as an audio as well as video file format. It is a relatively similar file format to 3gp with some advancements as well as limitations. Specifically, the 3g2 format is for CDMA based mobile phones rather than GSM-based phones, this format is used in fourth generation phones as well. Basically, it is for video viewing, it is also used for transferring photos and videos through the internet. Based on the standards of MPEG-4, it is developed in the light to play the media and to deliver it through the internet connection over high speed.