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.
avi The AVI file format is one of the most widely used multimedia containers ever devised. AVI, which stands for audio video interleaved, was first introduced to the public by Microsoft in 1992 as part of their 'video for windows' multimedia framework. Being a container format, an AVI file with the .avi filename extension can exist with both video and audio content synchronized for playback. The format can thus be used by authors to edit and encode audio video sequences or just video sequences. The Digital video AVI format exists in two forms, Type 1 and Type 2.