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3.7. Inter-operability

The inter-operablity of platform hardware, networks and applications and multimedia formats are a major issue for multimedia users.

Providing networking standards are implemented on each platform, inter-operablity between different platforms can be achieved. It is more difficult to enable applications to use different networks, and to integrate multimedia applications in a modular fashion. Recently bodies like the Interactive Multimedia Association (IMA) and the Multimedia Communications Forum (MMCF) [MCF] have been formed to develop technical solutions to multimedia inter-operablity.

The objectives of the MMCF are to develop :-
End to end networked multimedia communication solutions independent of applications and transport technologies.
Extensible Application Programming Interfaces and protocol infrastructure to support end to end multi-vendor inter-operability. This type of software has been termed 'middleware because it sits between user applications and the complexities of file formats, storage mechanisms, and networks.

The MMCF are developing a reference model for multimedia architecture to allow easy application development for independent software producers.

The IMA has undertaken some work in co-ordinating multimedia file format standardisation. This is a difficult task demonstrated by the large number of formats for audio, images and video.

Audio encoding schemes number about twenty. The most important are based on u-law, A-law and ADPCM coding using 4, 8 or 16 bits per sample:-

Still images come in many formats. Additionally some formats support from 16 to several million colour shades. Common formats include:-

Worldwide there are fifteeen video formats for analogue TV. High Definition TV is close to implementation. Digital video is governed by the CCIR-601 a bit rate of 165 Mbps. Since this is too high for most users a number of compression schemes have been developed, some proprietary, and others as international standards. The key ones are : -

The Digital Audio Video Council is hoping to play the same role in relation to video on demand.

IBM while supporting these efforts have published a proposed LAKES multimedia kernel. IBM hope to license this software to companies developing multimedia applications which will work in a wide variety of environments and networks.

All these efforts are aimed at masking the network type and file format from the users application. If communication hardware suppliers can provide drivers to interface with this 'middleware' and application developers can write to a common interface, the current single platform, single network, single vendor characteristics of much multimedia will disappear.

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