The Audio Mixer

Welcome to the eighth progress report on the development of the Gameboy Advance version of Payback. If you haven't read the earlier reports then you'll find them here. A lot of improvements have been made to the game over the last month or so - in particular, the audio mixer has been heavily optimised so that it takes just 3.4% CPU to play a 4 channel MOD at 24 KHz - a 32% improvement on the old version's 4.5% CPU usage. This is with less than 2K of IWRAM usage - it could be reduced to as little as 3.2% at the expense of 1.5K of IWRAM (a 41% improvement over the original).

As far as I know, Payback's mixer is the fastest out there - it's between 3 and 6 times faster than any of the competing mixers I've been able to get performance figures for, and it also uses a lot less IWRAM. This means that the game can have more sound effects playing at once, at a higher quality, with a better frame rate than would otherwise be possible. We're considering making it available for other developers to license - if you're a developer and this is something you'd be interested in then let us know. [We have now decided to make these routines available for developers - see the Apex Audio System page.]

More Levels

This month, we've also been compacting the ROM to make room for more cities. We managed to shave off about 700K by compressing the map layout and routing data (getting a ratio of about 4:1), which allowed us to fit another 3 cities on the cartridge. This brings the total number of maps to 11, which is equivalent to about 1.6 million square metres for the player to explore.

We've also rejigged the menu screens and added a "bloom" effect. This makes bright pixels appear to "dazzle" the viewer by bleeding out into surrounding pixels. This is an effect that is only starting to be seen in the latest PC software (3D Mark 2003, for example) and, to the best of my knowledge, has never been done on the GBA before. We've also reworked the pause screen so that it flies around the frozen action. It's pretty cool to see an explosion and its shockwave frozen in time, Matrix style - as shown in the video clip included with this report. A subtler version of the bloom effect is also used here which makes the fireballs look even better.

The game's controls are now fully configurable and will be automatically saved on the cartridge if you change them. Last but not least, I should also mention the multiple language support - the GBA version of the game currently supports English, German, French, Spanish and Italian. This may not be a final list as we do have more translations available but it's a question of whether they can be squeezed onto the cartridge.

What Now?

Right now we're concentrating mainly on fixing the last few bugs and then we'll add save game support. (We're doing this last since there are lots of different methods for saving data on a cartridge and we'd like to get an idea of the manufacturing costs of each before deciding which method to use.)

I've also recorded a short new video clip of the pause mode which you can download using the link on the right. Note that it was recorded on an emulator which does cause some visual glitches and degrade performance slightly. [Next month's report is now available here.]

Please feel free to email us with any questions, suggestions or enquiries. We do not yet have a publisher for the GBA version of Payback. For general information about Payback, please click here.