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MF_E_RT_TOO_MANY_CLASSES
MF_E_RT_TOO_MANY_CLASSES reports an MMCSS registration limit for a Media Foundation work queue. The diagnostic subject is the queue-to-class association, not the number of media tracks or codecs in the topology.
Inventory every MMCSS registration that touches the queue
- Log the work-queue identifier, MMCSS class name, task ID, and the API that performs each registration.
- For Media Session topologies, inspect
MF_TOPONODE_WORKQUEUE_MMCSS_CLASSand related work-queue attributes on each source branch. - Do not repeatedly register the same queue under different task classes as a recovery mechanism. Verify the intended scheduling class and balance registration with the corresponding unregister or queue unlock lifecycle.
Media Foundation documents a shared multithreaded queue model in which the platform creates up to one queue per MMCSS task in a process. Topology branches can also be assigned a class before BeginRegisterTopologyWorkQueuesWithMMCSS. This HRESULT is a strong reason to dump the actual class/task mappings and find conflicting or duplicated scheduler policy rather than tuning sample buffers.
Microsoft: shared work queue per MMCSS task · Microsoft: topology work-queue registration · Microsoft: MMCSS work-queue model
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