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Functional Specifications of Codecs

Objective

FUNCODE deals with the techno-economic considerations of codec technology related to the IBC Reference Configuration. The generic service aspects are also treated.

FUNCODE seeks to contribute to standardisation activities through RACE consensus and the Common Functional Specifications. The project will also act as a market interface, particularly in the field of digital image coding and transmission.
The main aim of the research was to investigate the technoeconomic aspects of codec technology with reference to the integrated broadband communications (IBC) reference configuration. The generic service aspects were also considered. The research dealt with:
the compression of information (coding) as a means of reducing the bit rate transmission cost;
the location of codecs, when their initial cost is too high for them to be located in terminals;
the tradeoff between transmission cost, loss of service quality and service interoperability;
the impact of variable bit rate (VBR) transmission.

The research resulted in the following conclusions:
video codecs should be located in the terminal;
one possibility for overcoming the worsening situation regarding interoperability between video standards is to develop one common picture transmission standard based on a descriptive programming language for picture coding.
Technical Approach

Being a systems project, FUNCODE does not produce hardware or software, but detailed analytical studies of codec technology in relation to the IBC. Results are recorded in deliverables available to all RACE actors.

Most of the project objectives can be achieved through detailed analytical work. Computer methods will be used for both modelling and assessment. Subjective quality assessment may also be involved.

FUNCODE actively contributes to the common functional specifications (ie E223, E224, J100, J210, J225, J255, J260, J263, J264, J265), and acts as chairman of STG5.1.

To focus on the key issues, project work has been sub- divided into workpackages dealing with inter-operability, coding vs service, codec location and codec evolution.

Key Issues

- Compression of information (coding) as a means of reducing the bit-rate transmission cost.
- The location of the codecs, when their initial cost is too high for them to be located in terminals.
- Trade off between transmission cost, loss of service quality and service inter-operability.
- The impact of variable bit rate (VBR) transmission.

Achievements

The project has produced a number of deliverables which are kept constantly under review and in some instances, re-issued every year.

The deliverable covering IBC scenarios in the light of activities in CCITT SG XVIII concludes with rather exact recommendations on the type of video codecs that shall be developed for different services.

In addressing the issue as to where video codecs should be located, the overall conclusion is that these should be placed in the terminal. This is also the obvious place for minimising transmission requirements in all parts of the network. In introductory phases sharing of codecs could be an economic alternative however.

The project has recognised one possibility to overcome the worsening situation regarding inter-operability between video standards. This is to develop one common picture transmission standard based on a descriptive programming language for picture coding. The decoding algorithm for this would be transmitted along with the coded picture information. This solution overcomes the problem of transcoding, which otherwise can only be solved by complete decoding followed by coding with the new method.

In the deliverable Codec Evolution 1990-2010, FUNCODE gives its view that there will be a large increase in the demand for and use of, moving picture and video information, for foreseen applications but also in completely new areas.

The project has reported on the performance and costs of codecs for some important audio visual services. Amongst the conclusions are that technology for low cost domestic videotelephones will be available before 1995, that the economic interest of codecs will not decrease at the advent of low cost broadband networks. The most strategic components will be cameras and displays.

Expected Impact

The project will influence codec development, the IBC Functional Reference Model and international standardisation activities.

Coordinator

Televerket
Address

123 86 Farsta
Sweden

Participants (5)

BRITISH TELECOM PLC (BT)
United Kingdom
Matra Communication
France
PTT Netherlands Research
Netherlands
Philips Kommunikations Industrie AG
Germany
Address
Thurn-und-taxis-straße 10
90411 Nürnberg
Telefonica de Espana
Spain