RealMedia

RealMedia is a proprietary multimedia container format created by RealNetworks. Its extension is ".rm". It is typically used in conjunction with RealVideo and RealAudio and is used for streaming content over the Internet. Typically these streams are in CBR (constant bitrate), but a container for VBR (variable bitrate) streams, named RMVB (RealMedia variable bitrate), has been developed.

RealMedia
Filename extension
.rm
Developed byRealNetworks
Type of formatmultimedia container format

Support of RealMedia is available in a few multimedia players for different architectures/platforms, including RealPlayer and the Real Alternative codec pack. The open source DAP firmware Rockbox has added support for reading RM containers as of 6 July 2009, although only certain formats used in RM files are playable.

Overview

A RealMedia file consists of a series of chunks that can be of several different types:

  • .RMF: RealMedia file header
  • PROP: File properties header
  • MDPR: Media properties header
  • CONT: Content description header
  • DATA: Data header
  • INDX: Index header

Supported audio formats
  • RealAudio 1.0 (VSELP), IpcJ
  • RealAudio 2.0 (LD-CELP), 28_8
  • AC3, dnet
  • Sipro, sipr
  • Cook, cook
  • ATRAC3, atrc
  • RealAudio Lossless Format, ralf
  • LC-AAC, raac
  • HE-AAC, racp

Supported video formats
  • ClearVideo (from helix spec)
  • H.263, RV10
  • H.263, RV13
  • H.263+, RV20
  • H.264 precursor, RV30
  • H.264 precursor, RV40
  • H.263+ (RV20), RVTR

See also
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