🚀 go-pugleaf

In article <1990Dec2.073639.22387@zorch.SF-Bay.ORG>,
xanthian@zorch.SF-Bay.ORG (Kent Paul Dolan) writes:
|> In article <90335.112615AXN100@psuvm.psu.edu> AXN100@psuvm.psu.edu writes:
|> 
|> > I have a Pioneer (sp) 6pack player. On the back there are two pin-outs
|> > for a receiver to take control of the player. I was wondering if there
|> > was anyway for me to use these pin-outs to let my amiga take control
|> > of the CD player; thereby, making it into a CD-ROM jukebox.
|> 
|> I'm no world class expert on CD-ROM, so take this with a grain of salt.
|> 
|> Both digital CD-ROM and audio CDs use binary data on the media, in the
|> sense that it is either on or off, with no intermediate states.

I agree.

|> However, if I understand it right, in audio CDs, it is the _length_ of
|> the "on" area or "off" area along the track, rather than its mere
|> presence (as in the data bit on a digital CD-ROM), that is important,
|> sort of like the zero crossing distance, rather than the amplitude, is
|> the real signal in an FM radio signal, and it is this ability to ignore
|> signal amplitude that lends the audio CD its enhanced sound reproduction
|> ability.

That would not be digital modulation.  Digital modulation varies some
aspect of the medium (for example, its optical diffusion or its local
magnetic field) to precisely represent _numbers_ (often binary).  What you are
describing is Pulse Width Modulation (PWM).  In PWM, the width of the
pulses usually can meaningfully assume any value in a continuous range.  Hence,
PWM is _analog_.  My explanation is not great, but I'm pretty sure of the
essential idea.

Audio CD's are digitally recorded on the medium.  There are many recording
errors, but these are corrected by big CRC's.  I'm not sure, but I think
audio CD's are recorded somewhat similarly to video CD's, because
there are players that play both.  On the other hand, could it be that
the "pick up" is the same, but that the demodulation is different?
Specifically, I'm wondering if the 4 or 5 MHz bandwidth needed for NTSC
TV is obtained from a video disc by some kind of analog recording (perhaps
the kind you described).

|> As a result, there is a profound incompatibility between the data
|> storage signal recovery methods for audio CDs versus digital CD-ROMS,
|> even though the mechanics of reading with a laser and so on are very
|> similar.

I don't know.  I do know that much of the technology from the audio CD's
was adopted for CD-ROM's, allowing the large-scale economies of audio
CD player manufacturing to reduce the costs of the CD-ROM players.

|> If this is right, you can't use a CD player to read digital CD-ROMS
|> without a whole separate signal extraction "mechanism" behind the read
|> laser.
|> 
|> If I'm all wet here, I'm sure someone in the group can correct/expand on
|> this.
|> 
|> None of this says you couldn't let the Amiga work to control the CD
|> player as a CD player, which might be a fun project in itself.
|> 
|> Kent, the man from xanth.
|> <xanthian@Zorch.SF-Bay.ORG> <xanthian@well.sf.ca.us>

Tom