Section 9: Technical Details.


9.1) How do I get a faster interrupt timer than the centisecond ones?

For this you require the use of IOC Timer 1, a 2MHz timer unused by RISC OS and claimable by code for use. Details of how to program the timer are available in the IOC datasheets, or you could look for various PD utilities like TimerCtrl that handle the timer for you.

I am informed that the forthcoming Acorn TimeCode system now has laid claim to Timer 1 and that software using it is deprecated. However if the software properly obeys the claiming protocols in RISC OS this, hopefully, shouldn't be a major problem.

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9.2) How can I create Interlaced GIFs on Acorn machines?

Four utilities exist to let you create these. spr2gif will take a sprite and convert it to a gif file. It will interlace and render transparent the gif as well. For the transparency it uses the colour of the first masked pixel it encounters in the sprite - suitable for automated gif image creating. (No need to twiddle with specifying transparency colours.)

The second utility, WebGIF, allows you to add transparency and interlacing to your GIFs as well. Creator, from about v2.00, can create interlaced GIFs. However you have to specify the transparency colour directly. And finally InterGIF not only can create interlaced, transparent GIFs but is capable of creating animated ones as well. On top of these utilities an increasing number of commercial programs can create Interlaced GIFs, Photodesk 2 (as from v2.03) being a prime example.

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