RMVB

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RealMedia Variable Bitrate (RMVB) is a variable bitrate extension of the RealMedia multimedia container format developed by RealNetworks.

As opposed to the more common RealMedia container, which holds streaming media encoded at a constant bit rate, RMVB is typically used for multimedia content stored locally. Files using this format have the file extension ".rmvb".

Allegedly, RealMedia formats typically achieve much more efficient compression than MPEG-4 Part 2 codecs, such as DivX and Xvid^{[citation needed]}, using compression similar to MPEG-4 Part 10 codecs^[1], such as x264. For this reason, they have become noticeably present (though not entirely popular) on file sharing platforms such as BitTorrent, eDonkey and Gnutella. Limited support is available on some media players, generally on the Windows platform, including the proprietary RealPlayer 10 and the open-sourced Media Player Classic, using an appropriate DirectShow filter or Real Alternative. MPlayer and some other programs such as totem are able to play RMVB files in Linux/UNIX-based x86 machines through the use of WIN32 DLLs or native closed-source libraries.

[edit] Identifying characters

The first 4 bytes of the file are ".RMF" (the standard RealMedia format), which is 2E 52 4D 46 in Hex, so the computer system can identify the file more easily.