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From: DJA@cardio.hosp.wisc.edu ()
Newsgroups: alt.cd-rom
Subject: oversampling with audio from CDROM drive?
Date: 21 Feb 1994 14:31:19 GMT
Organization: University of Wisconsion, Cardiology Section
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Technical question on the audio-out capabilities of CD-ROM drives. 

I have installed a Creative Labs Discovery 16 kit in my computer. This kit
includes a Sound Blaster 16 sound/CD-ROM interface card and a 2X CD-ROM drive
(Panasonic/Mitsumi). The card and drive are connected by two cables: a ribbon
cable for transmitting data from the drive to the computer and a 4-wire audio
cable for transmitting analog audio to the sound card circuitry.

When playing an audio CD, the CD-ROM drive/sound card uses zero CPU cycles
except when the user sends a command to start, stop, change tracks, etc. The
digital audio data on the music CD is converted by the CD-ROM drive itself into
an analog signal and is passed to the sound card by the audio cable (and then
in my case, the audio is passed to my stereo system). My question is this - is
there a digital oversampling filter included in the audio circuitry of the
CD-ROM drive? An oversampling filter makes no sense for the data stream coming
off of a data CD-ROM disk, so there would need to be separate circuits for
processing the data streams coming from CD-ROM and audio CD disks. I would
guess that CD-ROM drives incorporate an IC chip set developed for audio CD
players and would therefore have oversampling by default, but I haven't seen
anything to confirm my hunch. The technical data (ha!) accompanying the kit did
not address this issue.