FAQ Number 3
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MPEG
MPEG is a set of international standards for audio and video compression. MPEG-4 is the newest MPEG standard, and is designed for delivery of interactive multimedia across networks. As such, it is more than a single codec, and includes specifications for audio, video and interactivity. Windows Media encodes and decodes MPEG4. Quicktime and Realplayer are working on versions which will do the same.
MPEG produces high quality video which can be streamed over networks. Quicktime and Realmedia use the MPEG standards to improve the quality of their files for delivery on the Web.
It is possible to store audio or video in an MPEG format, and to play an MPEG file. This would be NOF's preferred solution, as proper MPEG files are open, non-proprietary, and should be readable by most audio and video player programs and plug-ins. Many/most current web browsers have the capability to play MPEG-1 video without any extra plug-ins.
RealPlayer, Windows Media Player et al support a variety of audio and video formats, including MPEG, and a range of proprietary formats such as AVI.
Digital Audio
Standards for storage and playout may differ. Commonly an archive/library would wish to store (preserve) the highest quality possible - meaning uncompressed - but would deliver using a standard and datarate appropriate to user requirements.
Electronic delivery could then involve compression.
Software which delivers at multiple data rates, according to an Internet user's connection, is now available from Real and Quicktime, amongst others, but the 'master copy' should ordinarily be the 'best available', which would usually mean uncompressed, linear PCM with a sampling rate and quantisation appropriate to the bandwidth and dynamic range of the material. This form of audio is typically held in .WAV files (though there are over 100 registered forms of coded audio that are possible within WAV, including highly compressed).
Within European broadcasting, 16-bit quantisation and 48 kHz sampling are the EBU (European Broadcasting Union) recommendation for broadcast quality audio. The EBU has gone a step further and added metadata to WAV, to add information critical to broadcasting and broadcast archives, forming the "Broadcast Wave Format" standard: BWF.
The actual transfer of analogue material to digital format, especially in bulk or for unique items, is not simple. For European Radio Archives, standardisation and guidance is being developed within EBU Panel 'Future Radio Archives'.
In their public service role, the BBC would be pleased to offer advice to libraries / archives requiring help - providing it is for non-commercial purposes.
A few years ago VRML (Virtual Reality Markup Language) was thought to be the emerging standard for virtual reality. However VRML has failed to gain widescale market acceptance. VRML is now evolving. Its successor X3D will make use of XML to provide the syntax for 3D worlds. The development of X3D is being coordinated by the Web3D Consortium.
A range of browser plugins to render X3D worlds are available, see the Web3D Consortium web site for details.
The requirement that alternative format must be provided if a plug-in is required is intended primarily for accessibility purposes and to ensure that an open format is available if a project makes use of a proprietary format which requires a plugin. In the case of 3D visualisation it is recognised that a textual equivalent will probably not be appropriate and since X3D is an open standard which is currently accessible primarily through use of browser plugins, the use of these plugins is acceptable.
Realvideo
It is suggested that all projects work from a format that can be re-digitised from easily e.g. for video DV or DV Cam. Media, particularly video will need to be redigitised for delivery as technology advances. An equally important issue is probably the copyright and making sure thatall footage is covered by "blood chits" which hands over all the rights to the projects.
Although the use of Realvideo is not particularly recommended, we accept that in some cases the use of proprietary or non-standard formats may be the most appropriate solution. However, where proprietary standards are used, the project must explore a migration strategy that will enable a transition to open standards to be made in the future.
With regard to Real, if you do use this you should check that the stringent conditions which encoding with Real imply are suitable for both the project and the programme.
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Last Modified 13-July-2004
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