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Old 01-29-09, 10:13 AM   #1
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Default VdpVideoSurfaceGetBitsYCbCr speed

I realise that by its entire nature VdpVideoSurfaceGetBitsYCbCr is going to be pretty slow, but are there any hints on maximising it's performance?

It's pegging a single core of my AMD 5000+ trying to call this on a 1080p24 video - does that sound about right?
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Old 01-29-09, 11:11 AM   #2
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Default Re: VdpVideoSurfaceGetBitsYCbCr speed

Are you actually experiencing bad performance using this API (i.e. it takes an unexpectedly long time to operate), or just that the CPU usage is high?

The download process has to do the following:

a) Wait for the GPU to complete any previous rendering commands to the surface that you're downloading (which may include decoding video), since VDPAU functions mostly just send commands to the GPU and don't wait for them.

b) Actually perform the download of the data

Hence, overall execution time can include the time taken for the GPU to execute other operations besides the download.

Also, the wait-for-everything-to-download code on the CPU probably busy waits for at least some of the time, so just because CPU usage is high doesn't mean that the CPU is working hard, just doing nothing waiting for the GPU to finish.

I'm not sure right now if the busy wait implementation could be improved so as to not use CPU. I'll keep it in the back of my mind to look at this.
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