Geminus JPEG Acceleration is Slow

For support of the Geminus screen acceleration feature
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tonystill
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Joined: Sun Feb 23, 2003 6:41 pm

Geminus JPEG Acceleration is Slow

Post by tonystill » Mon May 15, 2006 10:01 pm

I'm using Geminus 1.31 (just the JPEG acceleration feature purchased) on RO 5.11 on a 128MB Iyonix. This is disappointingly slow when used with OHP2.5, being about 50% slower than the RO 5 standard code. Am I missing something?

The timings I've done are on directories of digital photos, most being 8MPix images from a Canon EOS (digital SLR). I am just loading them into OHP as a presentation. All OHP does at this point is to check what pictures are there and produce sprite thumbnails (by redirecting the VDU to a 24-bit colour, 256x192 sprite). The timimng difference is dramatic but in the wrong direction :cry:

The Geminus documentation says that it is not optimised for scaled JPEGs but I guess it shouldn't be significantly slower. Are there any tuning parameters I should be setting? I just have the initial settings (DMA and Accelerate JPEG selected and desktop maximum set to 16MB) and, given that's all I've bought, there does not seem to be anything else to tweak.

Two sample timings for different directories of pictures are: 10.8s (RO5) vs 15.1s (Gem); 26.9s (RO5) vs 37.9s (Gem). Timings done by hand with a stopwatch.

tonystill
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Joined: Sun Feb 23, 2003 6:41 pm

Post by tonystill » Mon May 29, 2006 7:53 pm

Any thoughts on the slow JPEG issue? The Geminus code clearly can accelerate rendering but most of the time I seem to be using scaled images (since my camera produces 8MPix+) so there is little (no?) benefit.

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Post by admin » Wed May 31, 2006 12:27 am

I don't have OHP to test with, but Geminus is very noticably faster* than the OS at rendering one of my test images that is 32M pixels (earth.jpg, thanks Michael!) at 20% in !Thump. I'd suggest that you try the same image in !Thump, !Draw and/or other apps that display scaled JPEGs. Not knowing how OHP works or exactly what it's doing, it's hard to speculate.

*approx 2.5 times faster according to quick measurements.

tonystill
Posts: 20
Joined: Sun Feb 23, 2003 6:41 pm

Post by tonystill » Wed May 31, 2006 10:22 pm

I agree that Geminus is faster under some test conditions - that's why the fact that it is slower with OHP is frustrating and surprising.

What extra info do you need from my first post to investigate? Or do you need access to a copy of OHP? It just uses the OS routines to do JPEG_Plot(File)Scaled. Perhaps if you private mail me, I'll get the author to supply you with whatever detail you need? :-)

My images are generally EXIFs, I presume that makes no difference.

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