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Old 05-18-11, 01:07 PM   #1
TheSwissKnife
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Default What can be the cause for slow VDPAU VdpPresentationQueueQuerySurfaceStatus?

I am doing some timings to help diagnose stuttering/timing issues with xbmc VDPAU. One such test I use a 1080p video stream of 45fps and a display refresh rate of 59.94Hz. It seems that after the frame appears to have been decoded then time taken to return from a call to vdp_presentation_queue_query_surface_status varies between 2ms to say 20ms, generally one slow followed by one fast alternating. The calls use 0 as the presentation time. Does anyone know what this is call is blocking so long waiting for?

Platform is ION2 with 195.36.24 drivers, which is capable of close to 50fps decoding at 1080p.
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Old 05-19-11, 08:10 AM   #2
TheSwissKnife
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Default Re: What can be the cause for slow VDPAU VdpPresentationQueueQuerySurfaceStatus?

Further info...this is the behaviour with only 2 output surfaces. When surfaces are increased to 4 for example the call returns immediately but with status QUEUED and repeating the call until VISIBLE takes essentially just as long as the previous blocking call. Is there something which prevents more than one presentation per vsync cycle?

EDIT: It seems not as when I force it to play as fast as possible without getting stuck in waits eg due to glXSwapBuffers() I get 45 calls per second succeeding using 24Hz VSYNC. So is this all simply saying that when GPU is busy decoding some new frame it is also not servicing the presentation queue for current?
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Old 05-24-11, 05:19 PM   #3
TheSwissKnife
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Default Re: What can be the cause for slow VDPAU VdpPresentationQueueQuerySurfaceStatus?

Are there no vdpau gurus here. There seems a lack of documentation on this presentation queue stuff so I wonder how we are meant to use it. I will re-phrase the question(s) as follows.

What is it that makes a presentation queue output surface to change from QUEUED to VISIBLE?

What is it that makes a presentation queue output surface to change from VISIBLE to IDLE?
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