Data storage on CD-Audio -- bad news.

From: Martijn van Buul (
Date: 1999-10-22 15:32:34


I really didn't expect my bitstreams to look as cleanly as they were
burned on my test-CD, but I really dit NOT expect them to be -that-

22.5 KHz square wave: (101010101....):

Looks workable. My discman transforms it into some sort of sinus, 
as expected. I know now that my discman uses 8 times oversampling..

11 KHz square wave (11001100...):


2.2 Khz square wave (11111111110000000000....):

Boy, what an overshoot! Then again, since the lowest spike hardly
reaches 3/4 of maximum, it should be filtered out by an infinite 

A-symmetrical stream #1: (110110110110110):

The rising and falling edges of the signal are not as steap as they
should be. Output level is not at maximum at the first '1'. This 
means that the 0v-passage will be to late. Once amplified, this
means that the 0-pulse is too short. Manageable though.

A-symmetrical stream #2: (001001001001001..):

Yes, that's exactly the opposite as above:) The only reason I included
this pattern was to see if the DAC and/or digital filter of my discman
is symmetrical. It is. The result is exactly the same as above, with
the difference that the 1-pulse is too short now.

A-symmetrical stream #3: (101000):

This one is totaly devastated. It hardly represents the signal it's supposed
to be; there are -0v crossings where there shouldn't have been; the peak
values of the signal follow a strange sinus. I'd be really surprised if
a simple amplifier would be able to correct these errors. Seeing this mess,
I don't think that it will be possible to record different data on the
left- and right channel. This signal is hard enough to repair (if that's
even possible!) -without- any crossover from the other channel.

I will try to build a working amplifier anyway next weekend (If I'll be
able to find some time;), but I wouldn't be surprised if the data rate
needs to be reduced drastically. Furthermore, I don't know if it is only
my discman messing up things like that. I intend to run some tests on
other discmans too, but I don't really expect other results. Furthermore,
what's the use of a scheme that will work on some discmans, but won't at

%s/discman/cd-player/g, if you want - I used the line out..

Kind regards,


    Martijn van Buul - -
		Visit OuterSpace: 3333
	finger for my public key block
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