[GD-Windows] Streaming WAVE audio

[Brian H. <bri...@py...>]

Yes, it's me with a remedial, way-back, old-school question.  However, this 
is because I'm working on WinCE 3.0 (my God, all those WinCE docs that show 
up in MSDN searches now MEAN something!).

Since WinCE/PPC2K lack Direct Sound, I have to do my own audio mixing into 
wave buffers.  Conceptually, this is simple, although some of the 
implementation details were a bit tough to find out (specifically, using a 
thread instead of a callback).

In a nutshell, I'm doing this in the straightforward fashion you'd expect, 
double buffering two audio buffers that are filled periodically.

fill( buffer[ 0 ] );
fill( buffer[ 1  ] );

Under Win32's waveOut interface, you can specify a thread to handle 
messages indicating WOM_DONE, WOM_OPEN, WOM_CLOSE.  This is pretty easy, 
you just CreateThread() and pass the identifier and CALLBACK_FUNCTION to 
waveOut Open.

That much works.

The thread function basically does this:

while ( GetMessage( ... )
{
    if ( msg == WOM_DONE )
    {
       waveOutWrite( nextBuffer );
       fill( bufferThatJustEnded );
    }
}

The above works as well, in that it doesn't crash =)

That's all a streaming WAVE audio subsystem should really need to do.  Of 
course, I do the necessary waveOutPrepareHeader, etc.

I'm doing this in 8-bit, mono, 11KHz format, and the device definitely 
supports it.  In fact, I have this code running on Win2000 just so that I 
can make sure it works on a desktop before moving to a PDA.

So the problem is that I'm getting dropouts and stuttering, echoing, and a 
host of other bad things.  I boosted the thread's priority to highest, and 
I also set my buffers to some arbitrarily huge sizes to see if it was 
underruns to no avail.  I check all the return values.

Everything looks fine.  I timed calls to WOM_DONE handling, and the delta 
times are the expected buffer sizes.  The mixing code is the same for OS X 
and DirectSound and works as expected.  Each buffer is 150ms, more than 
enough time to mix in some stuff (especially on a P3/1000).

So I'm at a loss what else could be causing problems.  Originally I was 
using a CALLBACK_FUNCTION, but that's somewhat problematic for other 
reasons (you can't call waveOutXXX functions within the callback, since 
that can cause a deadlock).

Any suggestions on what else to look for that could be causing problems?

Brian