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EddieEdwards
New Participant
April 21, 2015

Does SetMaximumFrameLatency actually work?

Does IDXGIDevice1::SetMaximumFrameLatency actually work in DX11? Specifically on Windows 7 with latest drivers on an R9 290X?

I'm calling SetMaximumFrameLatency(1) right before ovrHmd_AttachToWindow, as the samples do, and it's succeeding (S_OK), but I still need to call ovrHmd_EndFrame three times before anything shows up on the HMD. Doesn't that indicate the latency setting is still at 3? Or am I misunderstanding the purpose of this call? In which case, why does it take three submits before anything appears on the HMD?

    1 reply

    DeanOfTheDriver
    Participant
    April 21, 2015
    The delayed display activation is an artifact of direct mode. The two backbuffers that need to be mapped in GPU in direct mode need to be referenced first so the OS will map them for us. When they're ready we can finally turn on the display. It does not mean you have any additional latency--the built-in DK2 latency tester values should be reporting 0ms latency and the CAPI has calls that can supply these numbers for verification.
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