[maemo-developers] Xsp pixel-doubling solutions for Nokia 770?

[From: Arnim Sauerbier]

--- The ever-informative Daniel Stone <daniel.stone at nokia.com> wrote:

> The second, and most important, is portability.  Not only are you tying
> your app to the internet tablets, but you're tying them to the _current
> generation_. ---
> You're turning a portable app (hell, the point of SDL is portability, so
> you can run it anywhere), into one that's dependent on the mixture of X,
> an OMAP display controller supported by omapfb, and an external LCD
> controller also supported by omapfb.  Not only is this setup quite
> unique to the internet tablets (due to the high resolution), but it's
> specific to this line of internet tablets.

Good words - they help illustrate why this discussion is addressing two different things.

It's understandable that any work to optimise performance for existing tablets is not interesting
to employees at nokia who are working on the next generation(s) of tablets.  In addition, anyone
writing an sdl app/game from the ground-up would do well to keep that portability in mind.  Most
existing SDL applications are runnable on tablets thanks precisely to SDL abstraction.

The subject *is* interesting, however, to those of us porting existing* apps to the existing*
devices with a fixed feature-set.  We are faced with the fact that the games are written for
desktop pcs with more performance than the tablets, yet many are nearly fast enough on the current
tablets.

For the second group (to which i belong) there are limited options to getting acceptable
performance.   One is to heavily revamp and optimise each game individually.  Another is to look
at ways in which we can improve speed across the board (Primarily for SDL).

> There are any number of changes we can make in future products (such as
> removing the LCD controller, moving to a purely X driver, using a
> different display setup, whatever) that will torpedo your app.
> You can bypass X and go straight to the framebuffer, but it might not work
> correctly, and that will be your problem.  It's not guaranteed to be
> portable to future internet tablets, let alone other platforms.

If the changes are applied as drop-in replacements for existing sdl libraries, then no.  The
tablet version of the SDL app would use the same SDL calls, perhaps with minor changes.  Future
tablet SDL versions would not use those hacks.  This idea is _not_ hot-air.  The gp2x community
has done exactly that - just one example: 

   http://wiki.gp2x.org/wiki/Paeryn's_SDL  

- a community-developed hardware accelerated version of the SDL library for the GP2X
 
Regarding your portability argument: As things stand today, we already *do* need to make
non-portable changes to get acceptable performance using the existing ITOS.  The best example of
this is the fact that to use pixel-doubling, games using SDL_Flip and partial screen UpdateRect
must be modified to not use SDL_Flip, and update the full 320x240 or 400x240 screen, every frame.
as adequately demonstrated by http://pupnik.de/aliens-1.0.2_Nokia.tgz

I think it bears repeating that this discussion is woefully conflating two seperate topics, and
much of this debate is unnecessary if we keep the seperateness of the two goals in mind, namely:

A) Improving game performance on existing tablets, and
B) Improving game performance on future tablets.

So lets do that.  Let's let the gurus at Nokia work on the "next great thing", and us plebes in
the community work on getting acceptable SDL/game performance for the current tablets.  

Cheers
Arnim Sauerbier

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