Newsgroups: comp.sys.apple2
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From: irsman@iastate.edu (Ian Schmidt)
Subject: Re: Sound
Message-ID: <1992Sep5.230433.13319@news.iastate.edu>
Sender: news@news.iastate.edu (USENET News System)
Organization: Iowa State University, Ames, IA
References: <1992Sep5.223747.17988@mnemosyne.cs.du.edu>
Date: Sat, 5 Sep 1992 23:04:33 GMT
Lines: 53

In article <1992Sep5.223747.17988@mnemosyne.cs.du.edu> cshepher@nyx.cs.du.edu (SSP Guy...) writes:
>
>Hello...
>     I'm writing a simple routine to play a sound, which happens to be
>$4c00 bytes long, by using the DOC Registers in bank $00. The problem is,
>it plays about 1 second of the sound, then stops. I know that the whole
>sound is being uploaded to DOC RAM, so I suspect I'm not setting the
>waveform register right. Any ideas? Ian?

You've come to the right place ;)

There are a couple of things that can cause this...

1) there may be a zero in the sound
2) you aren't setting the bankselect/tablesize/resolution register for the
appropriate oscillator(s) high enough

I'd guess your problem is #2.

The BTR register, DOC registers $C0-$DF, selects the size of the sound, as
well as the resolution of the DOC registers.  For normal tuning, the
size and resolution must be identical.  These are the appropriate values:

%000  =  256 bytes ($100)
%001  =  512 bytes ($200)
%010  = 1024 bytes ($400)
%011  = 2048 bytes ($800)
%100  = 4096 bytes ($1000)
%101  = 8192 bytes ($2000)
%110  =16384 bytes ($4000)
%111  =32768 bytes ($8000)

You use the smallest value greater than or equal to the size of the wave you
play.  For your example (a $4c00 length sound) you'd use the max value of
%111.  To make this into a normally valid BTR register, repeat the value twice
and stick two 0 bits on the left to make it a byte...

%00 xxx xxx

In this case, %00111111 = hex $3F.

Hope this helps (whew)!

>| Chris Shepherd Starving Programmer  | cd119@Cleveland.Freenet.Edu |
>|    Ask me about Impasse //gs        | cshepher@nyx.cs.du.edu      |




-- 
   _IanSchmidt(oINet+irsman@iastate.edu,oBITNET+twbv4@isuvax,$C000,Data)
     Data  dc i'Apple IIgs,Rush,Tiny Toons,Dave Barry,David Letterman'
 "I will choose a path that's clear: I will choose free will" - Neil Peart