Why gnome-cd is silient: web gossip

[Eric Dunbar]

> > Macintoshes (and many newer pcs) do not have an analog
> > audio cable going from the cd drive to the sound card,
> > which is what Gnome CD Player expects.
> 
> Well, mine does have such cable. Its a factory original MATSHITA CR-585
> (alias: ATAPI 24X). Checking the back of the CD drive let me with
> perplexed thoughts as these is two male plugs back there...
>  One is marked as 'Digital Audio' and has two pins: D and G. It is NOT
> plugged...
>  The other is marked as 'Analog Audio' and has 4 pins: R, G, G and L.
> This one has a cable that connect to a two pins plug on the motherboard
> (!!).

What I suspect (!) is happening is that the audio cable is going
directly to the speakers and not being "digitised" by a DSP (digital
signal processor; converts digital<>audio... used in mobiles/cell
phones). This means the computer offloads _all_ processing of the CD's
data onto the CD-ROM's circuitry -- you may remember back in the day
of crash-prone OS 7/8/9 systems that if you were playing an audio CD
and your computer froze, the audio from the CD would continue, (most
likely) because, although the CPU had come to a grinding halt, it
didn't affect the CD-ROM's music playback!

The "digital audio" is (probably) a digital output of the CD's data
stream, destined for a DSP in a high-end audio system, where it will
be turned into an analogue signal (i.e. noise, or, if it's a good
album, music ;-).

The software "digital audio" setting merely means that the data on the
CD (in the case of a music CD, the digitised music) will be read by
the CD-ROM, and the data stream will be sent through the IDE data
cable through the IDE bus to the computer, where the CPU (G3/4/5, i86,
etc.) will do the heavy lifting.

This what I suspect happens when you play a CD via USB since the music
data will have to be sent as a digital datastream so it could be
output via USB as a digital datastream to be converted to an analogue
signal by the (DSP in the) USB audio gadget (it would be downright
silly to send an audio signal and then convert it again using a DSP...
a lot of excess heat, chips and thus $$$ wasted).

Anyway, this is merely an edumacated guess as to how things work. I
could very easily be totally off base but, to me (given what I know of
DSPs), it seems logical and reasonable.

Eric.