Spellings.net support site

[adrianl]

Geminus 1.20 which is mainly a bugfix for the main issues with the acceleration feature that showed up post-release:

- the biggie - redraw cacheing disabling itself over time.This is something
that has probably left a few people nonplussed with the speed increase it can provide, because they haven't seen it working properly.

(In actual fact what's happening is that Geminus wasn't forgetting about old
tasks and eventually everything ends up running with the 'Other apps' settings until the configuration is reapplied using the 'Set' button in !GemConfig. Since the recommend setting for 'Other apps, redraw cacheing' is off, this usually means that redraw cacheing becomes inactive.)

- Inverted sprites in Organiser are now handled correctly (this was the consequence of a small oversight in the sprite cacheing code)

- Acceleration is now fully disabled for all apps in the Demo version when the red cross appears on the Geminus icon bar icon. This allows a fairer comparison, where previously acceleration would still work for apps explicitly mentioned in the GemConfig Settings pane.

- A default configuration is supplied which should both ease setup, and prevent apps such as Filer and Pinboard (which don't really benefit from redraw cacheing) polluting the cache and preventing other apps from gaining the full benefit.


Unfortunately I haven't yet tracked down the problem with O2 when part of its window is obscured and retains stale image data (seen with either page change or scrolling) so that still remains, as does the existing slightly wasteful use of cache memory (perhaps limiting the benefits of redraw cacheing in larger screen modes, though it seems to work fine here for 2048 x 1024).

Since I shall be moving next week, I didn't want to delay the update any longer. There could be a short period when development work ceases whilst I setup elsewhere.


Re possible future plans, I think it's likely that Geminus will include a JPEG acceleration feature in the near future since I have a working JPEG decoder which runs about 3-3.5 times faster than the existing SpriteExtend module and works as a drop in replacement. Some of the required functionality still remains to be implemented, so I can't release it yet but it looks promising and there's a very noticable speed increase even with the old 768 x 512 images that came with my RiscPC (remember them?) so with digital camera images it should help a lot.

Interestingly, on DVD resolution JPEGs the decoder currently runs at 20fps even without DMA screen writing. This is considerably faster than Cino can manage at present, illustrating how poorly the IYONIX's IOP321 matches the MPEG motion compensation algorithm, requiring as it does low-latency transfers of a large number of small blocks of pixels.

As a full-rate Motion-JPEG decoder, however, it shows promise. This format is still used in some AVIs, though more recent files use different codecs, so don't go expecting too much just yet I have implemented the code as a library which has been integrated into Geminus (for JPEG plotting) and Cino (prototype of Motion-JPEG playback).

As a point of interest, the JPEG algorithm is approximately symmetric, encoding being no more computationally demanding than decoding (unlike MPEG which is hugely more expensive to encode well) so it should be possible to implement a JPEG compressor that runs on DVD-resolution video at full rate too, a lump of code that could have quite a few applications on our video-challenged platform.


Finally, have a good Christmas and New Year.

[sedm0784]

I would like the Motion JPEG decoder.

Please can I have it?

[adrianl]

It was running at 20fps 32bpp and 22fps 16bpp on DVD resolution JPEGs when I packed it all up in boxes (now in an Internet Cafe)

[sedm0784]

Don't brag about it. Give it to meeee.