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.
wmv The Windows Media Video (or WMV) file format and its associated .wmv filename extension was first released to the public in 1999. It was a proprietary video stream wrapper developed by Microsoft as part of their ASF multimedia container. As of writing, WMV is no longer considered proprietary, since WMV 9 gained standardization as an open standard in the SMPTE 421M specification as VC-1. WMV supports a combination of both audio and video bit streams compressed using one of Microsoft's associated codecs. Also supported is windows media digital rights management for video content.