PSP: adjust audio settings for new dimuse WIP

[rsn8887]

In an effort to reduce the audio lag with the new dimuse engine, with @AndywinXp's help, we came across a fix that seems to work for PSP. But the buffer setting is now very small, 16 samples instead of 4096. I don't quite understand why this works without any stuttering, but it seems to work just fine. See also https://bugs.scummvm.org/ticket/13462

The funny thing is that changing samples to 1024 or even 128 seemed to make no change. The change in audio lag only happens at really low samples numbers.

[AndywinXp]

Hold on, we were testing stuff just to see what was reponsible for the lag in this case, but I don't know if that is a good idea. 16 samples of audio buffer size is a low latency tier for professional music recording tasks.

I don't know how the PSP is being able to handle that, but that's probably going to break all the other 100+ engines which are not SCUMM; are you able to test other games both in this engine domain and the others?

[rsn8887]

I will test more. So far I tested only Full Throttle and DOTT.

[rsn8887]

I tested a few more games with this ultra-low samples setting (samples = 16).

Dreamweb, Discworld, and Beneath A Steel Sky CD Talkie. They work with same sound quality as 2.5.1 (in 2.5.1 samples = 4096), no stutters, no crackles. I don't understand it.

[rsn8887]

I found a game that crackles and stutters with samples = 16: Lands of Lore Throne of Chaos. On 2.5.1 it works fine.

So yes, @AndywinXp, you were right this is a no-go.

[rsn8887]

This was an interesting test, but it doesn't work for all games, and it is not good anyways to try and enforce such a small buffer.