Multimedia localization is the most complex form of localization; as it consists of any and all types of multimedia, like audio, video, graphics, software, hardware, apps, etc.
Multimedia localization would be the conversion of any and all forms of multimedia, from a source language into a target language; keeping in mind linguistic, cultural and language nuances in the target market.
When we refer to multimedia localization (as stated above) these days it involves mostly the localization of digital formats. There are experts in this field who specialize in localization of content for multimedia, such as voice over specialists and dubbing experts who are required for the "Localization" aspect of Multimedia Localization. You also have the technical side that has its own experts and specialists, like the subtitling and graphics experts and the QA consultants; all of whom make up a holistic Multimedia Localization team.