Multimedia transmission over wide-area networks currently only considers the server and network resource constraints and client device capabilities. It is also essential that the accessibility of the multimedia content for different users with diverse capabilities and disabilities be considered. In this paper we develop a transcoding technique to present the multimedia content to suit diverse disabled user groups by using an ability based classification approach. Using ability-based prioritization, the appropriate alternate modalities and quality levels are chosen to replace the inaccessible modalities. The transcoding process allows for refinements to cater to specific types and degrees of impairments. Our performance results illustrate the benefits of the ability-based transcoding approach.