Larry Sherry wrote,
S> If I remember correctly it is the MD recorder that adds the SCMS.
No. An S/PDIF signal has SCMS bits in it. Whatever generates the signal
generates those bits. The recorder decides what to do about them.
John Graham wrote,
G> OK, I think I understand better now.
G> If I make an analogue recording to my hard disk it has no SCMS bits set,
G> or is classed as 'unlimited digital copy'.
Er, no. Depending on your ripping software, usually it will be stored,
regardless of whether the connection from your MD player to your hard disk
was analog or digital, in some format that has no SCMS information at all,
like .wav or .mp3. If later your soundcard generates S/PDIF output from it
to record to CDR or MD, the soundcard will have to think of some way to set
the SCMS bits in the outgoing S/PDIF stream.
G> If I make the same analogue recording to my MD the SCMS bit is set to
G> 'digital copy once'.
Yes. An analog signal converted by the MD recorder's own ADC will be
recorded as SCMS-penultimate.
G> What surprised me was that the 'unlimited digital copy' from was
G> preserved when subsequently copying between MDs.
That's why we call it that. If it weren't preserved, it wouldn't be
unlimited.
G> Why shouldn't someone be allowed to make multiple digital copies of their
G> own analogue sourced material?
Unfortunately, the machinery has no way to tell who holds the copyright on
the material. Analog input can also be used for other people's works.
G> What's missing of course is a genuine MD to MD copy, faster than realtime
G> with track and/or disk name data sent.
There are units that do that.
Back to Larry:
S> Yes it is true that the computer does not set SCMS.
Correct. The soundcard does when it generates an S/PDIF signal to send to
the MD or CDR recorder.
S> But I'm still pretty sure that it is the recorder and not the source that
S> encodes the signal.
No, the soundcard does, or if you're going straight between two audio units
without using a computer, the source unit does. If it doesn't encode a
signal, then what the heck is passing between the two units?
S> So in the case of a CD writer, there will be no problem with SCMS.
Yes, there will, if the signal's SCMS bits are set to `final' and the CD
writer complies with SCMS.
S> But the consumer MD recorders are all designed to add SCMS.
Consumer MD recorders are designed to comply with SCMS. The only time they
"add" it is when the internal ADC receives analog input and converts it to
digital for recording on the MD; it lays it down as SCMS-penultimate data.
S> Think about it.
I did. You did too, but you went about it inside out.
S> If the source encoded the SCMS, you would not be able to make a digital
S> copy in the first place. But you can make one original.
Sorry, Larry, but you're wrong there too. The source does encode SCMS bits,
but it sets them to allow one generation of digital recording.
S> That's because the SCMS is added as the first MD is being "burned".
No, it's because the recorder sees incoming SCMS bits that are set to penul-
timate, so it lays down an SCMS-final track. When that track is played, it
generates an SCMS-final digital signal, which consumer-grade recorders will
not copy.
If the recorder did it all, and the information were not there in the signal,
how could the recorder tell when the signal was coming from a premastered MD,
or an MD track recorded from an analog signal, and know to lay down an
SCMS-final recording, or when the signal was coming from an MD track recorded
from a digital source and know not to copy? How could it know when to mark
the copy for unlimited recopying, if the information is not already there in
the source?
S> But the question that I have is this. Since ATRAC is a lossy technique,
S> would you start to notice the degradation in sound quality on the first
S> copy (second generation) MD? Or would it go undetected to the human ear
S> for several copies of copies??
If you re-ATRAC an already ATRACked recording, most of what is lost in the
second compression is what was extrapolated during the decompression, so
successive ATRACkings have even less effect than the first.
S> Has anyone ever experimented with this?? I know that Eric W. has a
S> recorder that can bypass SCMS.
I once took some SCMS-unlimited material and copied it by digital transfer
out to the thirteenth generation. I could not tell the difference between
the thirteenth and the first. Some people have said that it takes twenty
generations before a difference is apparent.
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