Jeanmougin wrote,
| When you make a copy of a CD with optical cable, SCMS is implemented on
| the MD.
SCMS was implemented on the CD to start, but it was set to allow one gene-
ration of digital copying. Permission to copy does not mean absence of SCMS:
SCMS is the *system* (that's what the second S stands for) and it is imple-
mented on all consumer digital audio media.
[The problem with saying "this doesn't have SCMS" or "there's no SCMS here"
to describe an SCMS-compliant recording that allows copying is that saying
it that way destroys the distinctions among (1) a recording or signal whose
SCMS bits allow one generation of copying, (2) a recording or signal whose
SCMS bits allow unlimited generations of recopying, and (3) a storage format
{such as a .wav or .mp3 file on a hard disk} or a transmission protocol
{such as AES/EBU or an analog signal} that truly does not carry SCMS infor-
mation. Only type #3 can properly be described as "not having SCMS."]
| The copy bit 10 is written and prevents a second generation digital copy.
"10" is the designation for "no further digital copying" on DATs; on MDs it's
actually "01" (in bits 6 and 5 of the segment's status word).
| But is it the MD recorder that puts SCMS protection on the disc or does the
| MD recorder only write the copy bit of the source? In other words, is it
| the digital out of a deck (CD, MD) that sends the SCMS status or is it the
| MD recorder that writes the SCMS status during recording?
Both. (Pardon the anthropomorphisms here, but they do facilitate the expla-
nation.) The source machine reports the SCMS status of whatever it is play-
ing and the destination machine decides how to respond. If the source sends
out "I am playing an SCMS-penultimate recording" in its S/PDIF output, then
the destination machine decides "This signal is SCMS-penultimate, and I obey
SCMS, so I must mark the copy I'm writing as SCMS-final." When you try to
copy an SCMS-final source digitally, it is the destination machine that de-
cides, "This signal is SCMS-final, and I obey SCMS, so I won't record it."
A professional-grade recorder might have logic instead of say, "I'm receiving
an SCMS-final signal, but my switches are set to disobey SCMS and to write
SCMS bits that allow unlimited recopying (or to write SCMS bits that allow
one more generation, or however the switches are set), so that's what I'll
do."
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