DSP Sound processing

Once you know how the sound system works, it is not very difficult to make a simple sound processing routine. All you do is use the Devconnect XBIOS call to connect the DSP between your source and destination devices. So for example, say you wanted to do some real-time processing, you connect the ADC to the DSP IN, and the DSP OUT to the DAC.

Do this with the lines:

Devconnect(3,2,srcclk,prescale,1);
Devconnect(1,8,srcclk,prescale,1);

Or if your an assembler freak:

	move.w	#1,-(sp)
	move.w	prescale,-(sp)
	move.w	srcclk,-(sp)
	move.w	#2,-(sp)
	move.w	#3,-(sp)
	move.w	#139,-(sp)
	trap	#14
	lea	12(sp),sp

	move.w	#1,-(sp)
	move.w	prescale,-(sp)
	move.w	srcclk,-(sp)
	move.w	#8,-(sp)
	move.w	#1,-(sp)
	move.w	#139,-(sp)
	trap	#14
	lea	12(sp),sp

However, if all you do is this, then you will get nothing (unless something has allready used the DSP, in which case it will be unpredictable). Before you actually connect the DSP up, you should have the DSP program which actually does the processing loaded. Use DSP_reserve to reserve some space, and then DSP_LoadProg to load/execute your .LOD file.

The .LOD file will have been written in DSP assembler, with some code to recieve the data, and to transmit the data. I have code for this, which is available here as an LZH, or here is the very simple piece of code here

As I know nothing about actual processing of audio data (to do interesting things like flange, reverb etc.) I will not be covering this side of it. If YOU know something about that, then maybe you could send me some details to me, and I'll include them here...

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Anthony Jacques : jacquesa@zetnet.co.uk