The official explanation of this service is that Multimedia Class Scheduler Service (MMCSS) enables multimedia applications to ensure that their time-sensitive processing has priority access to CPU resources. This service enables multimedia applications to use CPU as much as possible without refusing to allocate CPU resources to applications with lower priority. MMCSS uses information stored in the registry to identify supported tasks and determine the relative priority of threads that execute these tasks. Each thread that is performing work related to a specific task calls the avsetmmmaxthreadcharacteristics or AvSetMmThreadCharacteristics function to inform MMCSS that it is performing the task. For an example of a program that uses MMCSS, please see exclusive mode streaming, which is the service that makes me bang so high.