RMVB is a file format with a variable bitrate developed by RealNetworks. Actually it is an improved version of RM format. It gives greater bandwidth to videos that are difficult to compress. The extension keeps a high video definition. RMVB files are very popular in Asia and they are not supported by all popular players, so the easiest way to playback them is to convert them to another most common format.

F4V is a Flash Video format supported by Adobe Flash Player software and all browsers with flash video playback. The container uses boxes for data storage and it is compatible with h.264 video and AAC audio compression standards. F4V files provide better quality than FLV but need a newer version of Flash (9.0.115 or higher) and a faster processor.