Visual Accessibility for Color Vision Deficiency in MPEG-21
2003 . 01 ~ current
The vision for MPEG-21 is to define a multimedia framework to enable transparent and augmented use of multimedia resources across different communities as well as a wide range of networks and devices. That is, everyone should be able to easily and equally access any kinds of digital item. In the MPEG-21, user accessibility is an important part of multimedia (or digital item) adaptation.

Specially, MPEG-21 visual accessibility for colored-visual resource of digital item is proposed to give better accessibility of color information to people with color vision deficiency (CVD). We propose an adaptation system for CVD as well as a description of CVD in MPEG-21.

To convey visual information in multimedia contents, color plays an important role as a fundamental visual feature that gives richness to access visual world. Recently, digital multimedia resources with high-quality color are accessible even with wireless personal communication devices such as cellular phone and PDA.

Color visual information works well for people with normal color vision, but not for people with CVD. The use of rich color may even cause people with CVD to misread the true meaning of visual information. Although there is no treatment for the CVD, many still and moving pictures, color documents, and web pages on Internet have been designed without any consideration about the problem.
Figure 1. Procedure of digital item adaptation (DIA)
In MPEG-21, a digital item is composed of resources and descriptions. So MPEG-21 DIA is composed of two modules: resource and description adaptation modules. Upper figure shows DIA procedure in MPEG-21.

As shown in the figure, an engine called 'DIA engine' performs the adaptation for digital item. The adaptation procedure for a digital item is as follows. Firstly, original digital item is delivered from digital item provider to DIA engine. The DIA engine performs the adaptation of the digital item, based on DIA description delivered from the digital item consumer (user). And then the adapted digital item is transferred to the digital item consumer.

In the DIA engine, the description adaptation module adapts description (D in Fig) of the original digital item into a new or modified description (D' in Fig). The resource adaptation module adapts resource (R in Fig) in the original digital item into a new or modified resource (D' in Fig). To do so, the DIA engine needs DIA description containing user characteristics. In result, the DIA engine can provide equivalent accessibility of the digital item to user in any kind of environments.
Table 1. DIA description for CVD
As shown in Table, in TextualDegreeType, 'mild' represents mild CVD (anomalous trichromat). Similarly, 'severe' represents severe CVD (dichromat). NumericalDegreeType expresses mild CVD as the number from 0.0 to 0.9, and severe CVD as the number 1.0 . DIA description containing user's CVD type and severeness is delivered to DIA engine. The DIA engine performs user-optimal adaptation according to the DIA description.