RealVideo
Encyclopedia
RealVideo is a suite of proprietary video compression format
s developed by RealNetworks
– the specific format changes with the version. It was first released in 1997 and is at version 10. RealVideo is supported on many platforms, including Windows, Mac, Linux, Solaris, and several mobile phones.
RealVideo is usually paired with RealAudio
and packaged in a RealMedia
(.rm) container. RealMedia is suitable for use as a streaming media
format, that is one which is viewed while it is being sent over the network. Streaming video can be used to watch live television, since it does not require downloading the entire video in advance.
format. At the time, RealNetworks issued a press release saying they had licensed Iterated Systems' ClearVideo technology and were including it as the RealVideo Fractal Codec. However, support for ClearVideo quietly disappeared in the next version of RealVideo.
RealVideo continued to use H.263 until RealVideo 8, when the company switched to a proprietary
video format. RealVideo codecs are identified by four-character codes
. RV10 and RV20 are the H.263-based codecs. RV30 and RV40 are RealNetworks' proprietary codecs. These identifiers have been the source of some confusion, as people may assume that RV10 is RealVideo version 10, when it is actually the first version of RealVideo. RealVideo 10 uses RV40.
RealVideo can be played from a RealMedia file or streamed over the network using the Real Time Streaming Protocol
(RTSP), a standard protocol for streaming media developed by the IETF. However, RealNetworks uses RTSP only to set up and manage the connection. The actual video data is sent with their own proprietary Real Data Transport (RDT) protocol. This tactic has drawn criticism because it made it difficult to use RealVideo with other player and server software. However, the open source
MPlayer
project has now developed software capable of playing the RDT streams.
To facilitate real-time streaming, RealVideo (and RealAudio) normally uses constant bit rate encoding, so that the same amount of data is sent over the network each second. Recently, RealNetworks has introduced a variable bit rate form called RealMedia Variable Bitrate (RMVB
). This allows for better video quality, however this format is less suited for streaming because it is difficult to predict how much network capacity a certain video stream will need. Video with fast motion or rapidly changing scenes will require a higher bit rate. If the bit rate of a video stream increases significantly, it may exceed the speed at which data can be transmitted over the network, leading to an interruption in the video.
RealNetworks says that the RealVideo and RealAudio codecs are not available in source code under the RPSL
license. Source code is available only under RCSL
license for commercial porting to non-supported processors and operating systems. While RealNetworks owns most of the intellectual property for RealVideo and RealAudio, RealNetworks has licensed third party technology for certain aspects of those codecs. RealNetworks claims that it does not have the rights to license that technology under an open source license.
, Macintosh, and Linux
. Several other players exist, including MPlayer
and Real Alternative. Many of these rely on the dynamically linked libraries (DLLs) from the official RealPlayer to play the video, and thus require RealPlayer to be installed (or at least its DLLs, if not the actual player). However, the open source ffmpeg
library (and its DirectShow
counterpart ffdshow
) can play RealVideo and does not require RealPlayer or any parts thereof.
The latest version of RealPlayer that can run on Windows 9x is RealPlayer 8; but this version can be easily modified to play RealPlayer 9 and 10 files, by the manual addition of just three .dll files (codecs and plugins), from Microsoft's free distribution of RealPlayer 10, that aren't included in RealPlayer 8 Basic.
RealNetworks has also developed the open source Helix player, however support for RealVideo in the Helix Project is limited because RealNetworks is still keeping the codecs proprietary.
RealPlayer does not record RealVideo streams, and RealNetworks has advertised this feature to content owners such as broadcasters, film studios, and music labels, as a means of discouraging users from copying video. However, other software exists which can save the streams to files for later viewing. Such copying, known as time-shifting, is legal in most countries.
s. Each video compression format is identified by a four character code
. Below is a list of the video compression formats and the version in which each was introduced:
The newest version of RealPlayer can play any RealVideo file, as can programs using FFmpeg
. Other programs may not support all video compression formats.
Video compression format
A video compression format or a video compression specification is a specification for digitally representing a video as a file or a bitstream. Examples of video compression formats are MPEG-2 Part 2, MPEG-4 Part 2, H.264 , Theora, Dirac, RealVideo RV40, and VP8...
s developed by RealNetworks
RealNetworks
RealNetworks, Inc. is a provider of Internet media delivery software and services based in Downtown Seattle, Washington, United States. The company is the creator of RealAudio, a compressed audio format; RealVideo, a compressed video format; RealPlayer, a media player; RealDownloader, a download...
– the specific format changes with the version. It was first released in 1997 and is at version 10. RealVideo is supported on many platforms, including Windows, Mac, Linux, Solaris, and several mobile phones.
RealVideo is usually paired with RealAudio
RealAudio
RealAudio is a proprietary audio format developed by RealNetworks and first released in April 1995. It uses a variety of audio codecs, ranging from low-bitrate formats that can be used over dialup modems, to high-fidelity formats for music. It can also be used as a streaming audio format, that is...
and packaged in a RealMedia
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....
(.rm) container. RealMedia is suitable for use as a streaming media
Streaming media
Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a streaming provider.The term "presented" is used in this article in a general sense that includes audio or video playback. The name refers to the delivery method of the medium rather...
format, that is one which is viewed while it is being sent over the network. Streaming video can be used to watch live television, since it does not require downloading the entire video in advance.
Technology
The first version of RealVideo was announced in 1997 and was based on the H.263H.263
H.263 is a video compression standard originally designed as a low-bitrate compressed format for videoconferencing. It was developed by the ITU-T Video Coding Experts Group in a project ending in 1995/1996 as one member of the H.26x family of video coding standards in the domain of the ITU-T.H.263...
format. At the time, RealNetworks issued a press release saying they had licensed Iterated Systems' ClearVideo technology and were including it as the RealVideo Fractal Codec. However, support for ClearVideo quietly disappeared in the next version of RealVideo.
RealVideo continued to use H.263 until RealVideo 8, when the company switched to a proprietary
Proprietary software
Proprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering.Complementary...
video format. RealVideo codecs are identified by four-character codes
FourCC
A FourCC is a sequence of four bytes used to uniquely identify data formats.The concept originated in the OSType scheme used in the Macintosh system software and was adopted for the Amiga/Electronic Arts Interchange File Format and derivatives...
. RV10 and RV20 are the H.263-based codecs. RV30 and RV40 are RealNetworks' proprietary codecs. These identifiers have been the source of some confusion, as people may assume that RV10 is RealVideo version 10, when it is actually the first version of RealVideo. RealVideo 10 uses RV40.
RealVideo can be played from a RealMedia file or streamed over the network using the Real Time Streaming Protocol
Real Time Streaming Protocol
The Real Time Streaming Protocol is a network control protocol designed for use in entertainment and communications systems to control streaming media servers. The protocol is used for establishing and controlling media sessions between end points...
(RTSP), a standard protocol for streaming media developed by the IETF. However, RealNetworks uses RTSP only to set up and manage the connection. The actual video data is sent with their own proprietary Real Data Transport (RDT) protocol. This tactic has drawn criticism because it made it difficult to use RealVideo with other player and server software. However, the open source
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
MPlayer
MPlayer
MPlayer is a free and open source media player. The program is available for all major operating systems, including Linux and other Unix-like systems, Microsoft Windows and Mac OS X. Versions for OS/2, Syllable, AmigaOS and MorphOS are also available. The Windows version works, with some minor...
project has now developed software capable of playing the RDT streams.
To facilitate real-time streaming, RealVideo (and RealAudio) normally uses constant bit rate encoding, so that the same amount of data is sent over the network each second. Recently, RealNetworks has introduced a variable bit rate form called RealMedia Variable Bitrate (RMVB
RMVB
RealMedia Variable Bitrate is a variable bitrate extension of the RealMedia multimedia container format developed by RealNetworks....
). This allows for better video quality, however this format is less suited for streaming because it is difficult to predict how much network capacity a certain video stream will need. Video with fast motion or rapidly changing scenes will require a higher bit rate. If the bit rate of a video stream increases significantly, it may exceed the speed at which data can be transmitted over the network, leading to an interruption in the video.
RealNetworks says that the RealVideo and RealAudio codecs are not available in source code under the RPSL
RealNetworks Public Source License
The RealNetworks Public Source License is a software licence. It has been approved as a free software licence by both Free Software Foundation and Open Source Initiative , but it is incompatible with the GPL and the Debian Free Software Guidelines.The RPSL is used by the Helix project.-External...
license. Source code is available only under RCSL
RealNetworks Community Source License
The RealNetworks Community Source License is a software license. Developers pick this license when they do not want to open source their resultant Helix DNA-based application. RCSL has a free R&D license and commercial terms for distribution....
license for commercial porting to non-supported processors and operating systems. While RealNetworks owns most of the intellectual property for RealVideo and RealAudio, RealNetworks has licensed third party technology for certain aspects of those codecs. RealNetworks claims that it does not have the rights to license that technology under an open source license.
RealVideo Players
The official player for RealVideo is RealNetworks RealPlayer SP, currently at version 12, and is available for various platforms including WindowsMicrosoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
, Macintosh, and Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
. Several other players exist, including MPlayer
MPlayer
MPlayer is a free and open source media player. The program is available for all major operating systems, including Linux and other Unix-like systems, Microsoft Windows and Mac OS X. Versions for OS/2, Syllable, AmigaOS and MorphOS are also available. The Windows version works, with some minor...
and Real Alternative. Many of these rely on the dynamically linked libraries (DLLs) from the official RealPlayer to play the video, and thus require RealPlayer to be installed (or at least its DLLs, if not the actual player). However, the open source ffmpeg
FFmpeg
FFmpeg is a free software project that produces libraries and programs for handling multimedia data. The most notable parts of FFmpeg are libavcodec, an audio/video codec library used by several other projects, libavformat, an audio/video container mux and demux library, and the ffmpeg command line...
library (and its DirectShow
DirectShow
DirectShow , codename Quartz, is a multimedia framework and API produced by Microsoft for software developers to perform various operations with media files or streams. It is the replacement for Microsoft's earlier Video for Windows technology...
counterpart ffdshow
Ffdshow
ffdshow is a media decoder and encoder mainly used for the fast and high-quality decoding of video in the MPEG-4 ASP and AVC formats, but it supports numerous other video and audio formats as well...
) can play RealVideo and does not require RealPlayer or any parts thereof.
The latest version of RealPlayer that can run on Windows 9x is RealPlayer 8; but this version can be easily modified to play RealPlayer 9 and 10 files, by the manual addition of just three .dll files (codecs and plugins), from Microsoft's free distribution of RealPlayer 10, that aren't included in RealPlayer 8 Basic.
RealNetworks has also developed the open source Helix player, however support for RealVideo in the Helix Project is limited because RealNetworks is still keeping the codecs proprietary.
RealPlayer does not record RealVideo streams, and RealNetworks has advertised this feature to content owners such as broadcasters, film studios, and music labels, as a means of discouraging users from copying video. However, other software exists which can save the streams to files for later viewing. Such copying, known as time-shifting, is legal in most countries.
Video compression formats and codecs
RealVideo files are compressed using several different video compression formatVideo compression format
A video compression format or a video compression specification is a specification for digitally representing a video as a file or a bitstream. Examples of video compression formats are MPEG-2 Part 2, MPEG-4 Part 2, H.264 , Theora, Dirac, RealVideo RV40, and VP8...
s. Each video compression format is identified by a four character code
FourCC
A FourCC is a sequence of four bytes used to uniquely identify data formats.The concept originated in the OSType scheme used in the Macintosh system software and was adopted for the Amiga/Electronic Arts Interchange File Format and derivatives...
. Below is a list of the video compression formats and the version in which each was introduced:
- rv10, rv13: RealVideo 1.0, based on H.263H.263H.263 is a video compression standard originally designed as a low-bitrate compressed format for videoconferencing. It was developed by the ITU-T Video Coding Experts Group in a project ending in 1995/1996 as one member of the H.26x family of video coding standards in the domain of the ITU-T.H.263...
(included with RealPlayer 5) - rv20: RealVideo G2 and RealVideo G2+SVT, also based on h.263 (included with RealPlayer 6)
- rv30: RealVideo 8, suspected to based largely on an early draft of H.264 (included with RealPlayer 8)
- rv40: RealVideo 9, suspected to be based on H.264 (included with RealPlayer 9)
- rv40: RealVideo 10, aka RV9 EHQ (included with RealPlayer 10). This refers to an improved encoder for the RV9 format that is fully backwards compatible with RV9 players – the format and decoder did not change, only the encoder did. As a result it uses the same FourCCFourCCA FourCC is a sequence of four bytes used to uniquely identify data formats.The concept originated in the OSType scheme used in the Macintosh system software and was adopted for the Amiga/Electronic Arts Interchange File Format and derivatives...
.
The newest version of RealPlayer can play any RealVideo file, as can programs using FFmpeg
FFmpeg
FFmpeg is a free software project that produces libraries and programs for handling multimedia data. The most notable parts of FFmpeg are libavcodec, an audio/video codec library used by several other projects, libavformat, an audio/video container mux and demux library, and the ffmpeg command line...
. Other programs may not support all video compression formats.
External links
- RealVideo 10 codec Product Page
- Helix Community the open source project of all media framework of RealNetworks
- RealMedia Splitter DirectShowDirectShowDirectShow , codename Quartz, is a multimedia framework and API produced by Microsoft for software developers to perform various operations with media files or streams. It is the replacement for Microsoft's earlier Video for Windows technology...
filter by Gabest (guliverkli, sourceforge.net) to split RV40 etc. in .rmvb, .mkv, .dsm, etc. Decoder is not included. - Filter for playing RealNetworks audio/video files using Windows Media Player