[AD] Sound API

[Ben Davis <bnd25@xxxxxxxxxx>]

Hi,

Elias and I have been discussing Chris's mixer patches on #allegro, and we've 
come to the following conclusion.

The only issue with the patches is the removal of the DirectX mixer. I'm not 
sure the Allegro mixer driver always works. The mixer itself is fine, but the 
hardware interface may be dodgy. For instance, when I tried TeleHack on 
Windows with the DirectX mixer, it worked fine; when I tried it with the 
Allegro mixer, all my audio streams had a large latency (could have been 
anywhere from 0.2 to 0.5 seconds I think, too long ago) and were then 
truncated. Imagine that each sound effect has a little 'window' in time in 
which it can be heard; now delay the sound effect and it will get truncated. 
That's what happened.

However, the reasons for wanting the DirectX mixer removed are sound (no pun 
intended). It differs from the Allegro mixer in certain ways; for example, 
the volume level is different, and I believe left-right panning is processed 
differently too. (How loud should a central sample be in each speaker, 
compared with a sample played in just one speaker? Half? Full? 1/sqrt(2)?)

In all other respects, the mixer changes are great! That's in my opinion, of 
course. The changes have my approval. I've been following Chris's work and he 
definitely knows what he's doing. :)

I would suggest we keep the DirectX mixer for now, but make the Allegro mixer 
the default. Put that in the unstable development version (_IF_ Allegro 4.2 
is just around the corner then wait till 4.3, but wait no longer; otherwise 
add it to 4.1). Get it tested, encourage people to report any problems with 
the Allegro mixer, etc. People can just switch to the DirectX mixer if they 
want to get on with their games without having to downgrade Allegro or wait 
for a fix.

Chris, would you be willing to do new patches that just keep the DirectX mixer 
for emergencies as described? Eric, if there are no objects, will you commit 
such patches when they're available?

Thanks,

Ben