rmvb The .rmvb filename extension refers to the RealMedia variable bitrate format which is an extension of the RealMedia multimedia container format. RMVB is a proprietary multimedia digital container developed and maintained by RealNetworks, an internet streaming Media Company. It is different from its closely related format .rm in that it was designed for distribution of complete multimedia content, however it does support real-time media streaming. Video and Audio streams can be encoded and packaged into this format and distributed as single files for later playback on compatible devices and software as opposed to file streaming on high bandwidth networks.
mp4 The MP4 file format and the .mp4 filename extension refer to the MPEG-4 part 14 digital multimedia format developed by the Moving Picture Experts Group. It is used as a multimedia container to wrap encoded digital video and audio streams, including subtitles and still images if required. In recent decades, the format has been popularized as one of the main standards for streaming media over the internet and other computer networks and for the digital distribution of large multimedia files. MP4 supports a large number of compression audio codecs allowing files in this format to maintain a relatively small size without discounting playback quality.