Newsgroups: comp.sys.next
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!van-bc!ubc-cs!alberta!edson!news
From: keen@ee.ualberta.ca (Jeff '876393' Keen)
Subject: Re: CD-ROM
Message-ID: <1991Mar29.191343.12787@ee.ualberta.ca>
Sender: news@ee.ualberta.ca
Organization: University of Alberta Electrical Engineering
References: <1991Mar27.120647.1302@sinix.UUCP> <CNH5730.91Mar28141743@maraba.tamu.edu> <1991Mar28.224042.23398@nntp-server.caltech.edu>
Date: Fri, 29 Mar 91 19:13:43 GMT

In article <1991Mar28.224042.23398@nntp-server.caltech.edu> madler@nntp-server.caltech.edu (Mark Adler) writes:
>In article <CNH5730.91Mar28141743@maraba.tamu.edu> cnh5730@maraba.tamu.edu writes:
>>In article <1991Mar27.120647.1302@sinix.UUCP> dhg@sinix.UUCP (David Griffith) writes:
>>   I believe some audio CD players
>>   have digital outputs. Is it possible to feed this into the DSP
>>   port?
>>
>>if you're serious about plugging a CD-ROM into a NeXT, you need to be
>>looking at the ones which have a SCSI interface.
>
>Actually, that's not what he's talking about.  I just bought a CD player
>with a digital output, and I'm trying to find what the format of the
>digital data coming out of the thing is.  The bandwidth is there on the
>DSP serial ports brought to the back of the machine to stuff it in, and
>I intend to do just that.  Does anyone have any leads on what that
>format is?
>
>Mark Adler
>madler@pooh.caltech.edu

I just happen to have somewhere in my files the sony document that specifies
what the format is and another doc which explians the electrical specs. 
Actually when my NeXT came in I was planning to do just this.  Also
somewhere from a radio electronics, I believe, there is a circuit meant to
transform optical out into digital signals and the RCA type digital outs.
I'm pretty sure that this circuit, which involves filtering the raised
cosine pulses and running it through a Sckottky buffer to bring the
levels to TTL, could be used to bring the digital out data directly
into the computer thougha DSP port or possibly even a serial port
if its fast enough (I think its around 1-2M bits/sec but all this is
from memory).  Once it is in the machine you have to use the format
spec to 'synch' with the signal and remove the subcode and all the other
wonderful data they throw in there just for fun (like stopping DAT's from
recording other DAT tapes).  The spec for subcode is not in this doc, it
just explains which bits are subcode and not what data they contain.
If anyone is really interested I can email or post where the doc's can
be found once I find them in my files (they're not that organized).  If 
anyone knows where I can find the subcode format I'd be grateful.

-- 
-----------------------------------------------------
Jeff Keen    University of Alberta
alberta!bode!keen                  
-----------------------------------------------------
