DRAGONS: Rendering is excessively slow on older devices

[dwatteau]

This is with the British PS1 version of Blazing Dragons, with latest Git HEAD of ScummVM.

On any modern computer, rendering is fine.

But on some older devices, such as my PS3 (2006) or my PowerBook G4 (2005), character animation is really slow, and the fans go quite crazy. That's a bit strange for a 2D PS1 game. Just making a character walk a bit makes the game go to very few FPS, and CPU usage seems way higher than with most other 90s 2D games inside ScummVM.

In comparison:

• The Curse of Monkey Island on the same devices doesn't have this problem (I'm trying to compare Blazing Dragons with a similar game).
• Rendering is also OK if I use the official PS1 emulator on the PS3, or PCSX on the PowerBook. So, the rendering is actually faster and less power-hungry with a real emulator than with ScummVM.

The Crystal Dynamics/Illusions credits and the intro video appear to run as expected, though. It looks like that there's a framerate sub-optimization when character animation happens?

Enabling/disabling V-Sync appears to have no effect. On the PowerBook, it was maybe a bit better with OpenGL than with SDL, but not much.

I'm at your disposal if something can be done to help profiling the bottleneck.