SDL info update & Sound paradigms

[njh at cs.monash.edu.au]

On Mon, 4 May 1998, Sam Lantinga wrote:

> (I'm working on about three things at once here...)
> 
> Okay, X11 SDL is rock solid, and no longer uses semaphores by default.

Woo Hoo!  Ok, where can I get it?

> Okay, I've been working on porting code which was given to me... njh... :)

I don't know what you're talking about... :-| (<--- that is my best poker
face!)

> There's a basic problem between my idea of sound mixing and that program.
> SDL uses a periodic callback to mix a relatively small chunk of sound
> (~46 ms worth), while this program queries the audio DMA position at each
> frame, and mixes the next 100 ms or so.
> 
> The problem is, this is completely incompatible with BeOS and Solaris.
> Linux has some hacks to get at the DMA buffer, and Win32 emulates it.

Yeah, but, like these are going to work on linuxppc :-)...

> Is this a very common way to write a mixer?  It makes sense, but is
> tough to implement without emulation on some platforms.

Yeah, it seems that the only really good audio stuff requires practically
direct access to the hardware.  Oh for a decent DSP standard...

> The alternative is to write code that mixes the audio directly, based
> on the state of the application, at the time the audio driver requests
> it, instead of mixing the next frame or two every update.

This would be better, if you can guarantee service.

njh