Path: utzoo!utgpu!watmath!iuvax!cica!tut.cis.ohio-state.edu!attctc!ltf
From: ltf@attctc.Dallas.TX.US (Lance Franklin)
Newsgroups: comp.sys.amiga
Subject: Re: Audio Improvements
Message-ID: <9051@attctc.Dallas.TX.US>
Date: 20 Aug 89 05:43:54 GMT
References: <3114@bucsb.UUCP> <1542@convex.UUCP>
Reply-To: ltf@attctc.Dallas.TX.US (Lance Franklin)
Distribution: na
Organization: The Unix(R) Connection BBS, Dallas, Tx
Lines: 33

In article <1542@convex.UUCP> swarren@eugene.UUCP (Steve Warren) writes:
>But 8 bits of resolution means audible quantization noise, which could
>only be improved by increasing the number of bits.  I wish we could get
>16 bit sound on the Amiga, it would really sound great.  But that would
>require significant redesign of the sound chip, and I don't know how it
>could be made compatible with old software.  Maybe a dual-mode design
>that only uses the 8 MSbits of the sound channel for old stuff.

Well, how about adding a "Ham-Mode" for the audio channel...

Let's say, perhaps, that we have a 12 (or more) bit D-A on each channel.
Each byte, when the channel is in this mode, is interpreted thusly:
 
     Bit 7 : Mode bit...when 0, bits 6-0 will be loaded directly into the
             high order 7 bits, with all low-order bits set to zero.
             When set to 1, bits 6-0 are interpreted as a signed 7 bit
             number which is added to the current value of the D-A 

I beleive the scheme is commonly called Delta-Modulation, although I may be
a little off on that...been a while since I've seen the scheme used.

Of course, this setup requires that the data be massaged a bit before it gets
sent to the channel, but that should not be too horrible, since most samples
just get pumped directly from a sample file...just mean adding an extra 
step when creating the file.

Lance

-- 
+-------------------------+ +------------------------------------------+
| Lance T Franklin        | | "And all who heard should see them there,
| ltf@attctc.DALLAS.TX.US | |  And all should cry, Beware!  Beware!
+-------------------------+ +  His flashing eyes, his floating hair!"