GP32 Vhat Da Heell? (sound)

[fdave]

Gamepark docs:
PCM_S11 Stereo 11,160Hz
PCM_S22 Stereo 22,321Hz
PCM_S44 39,062Hz

Eh?? So S44 actually plays sound at 39062hz on the GP32?

Why on earth...? I'm confused now. Has anyone done anything with sound, I don't know what da hell is going on ere...

 

[mATkEUpON]

Well, if you use a 44100 Hz sound as PCM_S44, you won't really notice the difference...

What is more problematic, is that the sound gets clicky quite easily... Some instructions should be avoided then (GpRectFill), and you have to be careful if you're doing ASM (LDMIAs have a tendency to lock the bus, so the DMA won't feed the sound buffer, and the click).

But then the sound system is easy to use, and you can even mix more channels yourself.

 

[damaki]

PCM_S44 39,062Hz

Eh?? So S44 actually plays sound at 39062hz on the GP32?

It must just be some kind of frame-drop to adjust synch of sound to CPU cycles. I had already heard of such tricks with other portable devices (mp3 player).

 

[sixxie]

The audio is fed with a DMA that is tied to the system clock with a quite limited set of divisors. The speed you set your clocks to determine what sample rates you can use. Use 'srate' to calculate!

 

[fdave]

Well, if you use a 44100 Hz sound as PCM_S44, you won't really notice the difference...

What is more problematic, is that the sound gets clicky quite easily... Some instructions should be avoided then (GpRectFill), and you have to be careful if you're doing ASM (LDMIAs have a tendency to lock the bus, so the DMA won't feed the sound buffer, and the click).

But then the sound system is easy to use, and you can even mix more channels yourself.

Won't notice the difference? It's 12% too low surely?!


Is there any way to force the dma to work? I'm using a lot of ascembler in the CPU core.

I agree the sound system is easy to use, but if it doesn't work properly what's the point

 

[fdave]

The audio is fed with a DMA that is tied to the system clock with a quite limited set of divisors. The speed you set your clocks to determine what sample rates you can use. Use 'srate' to calculate!

Ah right I get you, so is srate a program you can download from somewhere - do you have a link?

Also is there a way to put data in memory which isn't locked by a bit of assembler hammering it?

 

[sixxie]

Ah right I get you, so is srate a program you can download from somewhere - do you have a link?

mr_spiv's site has lots of useful stuff on it. Get srate.zip from here:

http://www.cs.helsinki.fi/u/jikorhon/conde...2/download.html