RMVB (RealMedia Variable Bitrate) is a digital variable bitrate extension for the RM (RealMedia) container format. Unlike the standard RM format that streams content in CBR (Contant Bitrate), the RMVB, as the name suggests, streams local media in VBR (Variable Bitrate). This file format uses a .rmvb filename extension.
RealNetworks RealPlayer Coud Final Media Player Media Monkey RealTrimmer
FLV (Flash Video) is a video container format developed by Adobe Systems and comes with a .flv filename format. FLV is primarily used to stream audio, video, and text data such as subtitles. It supports MPEG-4 Part 10 (H.264) video codec and AAC sound.
RealPlayer, Apple QuicTime Player
VLC Media Player