ScheduledFrameCompleted always displays late

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Jonas Geduldig

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  • Joined: Tue Jun 17, 2014 7:04 pm

ScheduledFrameCompleted always displays late

PostTue Jun 27, 2017 4:43 pm

I'm using a 4K Extreme set to 720p 5994 and the 10.9.0 driver. Inside my ScheduledFrameCompleted method the time spent processing the next frame is always about 0.2 ms. So, I would expect the BMDOutputFrameCompletionResult argument to always be bmdOutputFrameCompleted. Instead it is always bmdOutputFrameDisplayedLate. To confirm, I print the elapsed time between calls to ScheduledFrameCompleted. The elapsed time is always 33 ms, double the expected 16.6 ms.

CPU utilization is under 1%. Any suggestions what could cause the late frames?
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Jonas Geduldig

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Re: ScheduledFrameCompleted always displays late

PostWed Jun 28, 2017 1:53 pm

I fixed this issue after looking through the LoopThroughWithOpenGLCompositing example. I noticed that before starting the frame scheduling with StartScheduledPlayback the example project pre-loads the ring buffer.
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Nicholas Gill

Blackmagic Design

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Re: ScheduledFrameCompleted always displays late

PostWed Jul 12, 2017 3:46 am

Hi Jonas,

Glad to hear the issue was resolved.

Informationally, the minimum number of frames required for preroll varies based on the device in use - 4K architecture devices require a minimum of two frames provided for preroll, while pre-4K architecture devices will require a minimum of three frames.

Cheers,

-nick
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Jonas Geduldig

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Re: ScheduledFrameCompleted always displays late

PostWed Jul 12, 2017 2:35 pm

Hi Nick -- Thank you for those specs on pre-loading frames.
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Steinar H. Gunderson

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Re: ScheduledFrameCompleted always displays late

PostThu Jul 20, 2017 5:21 pm

What does it actually mean in practice when a frame is “displayed late”? Does it mean the card duplicated one frame and showed this one the next? Does that mean the next frame will be dropped, or that the latency increases?

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