Hardware Reference
In-Depth Information
a user with a PC or dedicated combination audio/data player could access both the audio
and data tracks on the same disc.
The fundamental problem with nonstandard mixed-mode CDs is that if or when an audio
playertriestoplaythedatatrack,theresultisstaticthatcouldconceivablydamagespeak-
ers and possibly hearing if the volume level has been turned up. Various manufacturers
originally addressed this problem in different ways, resulting in a number of confusing
methods for creating these types of discs, some of which still allowed the data tracks to
be accidentally “played” on an audio player. In 1995, Philips and Sony developed the CD
EXTRA specification, as defined in the Blue Book standard. CDs conforming to this spe-
cificationusuallyarereferredtoasCDEXTRA(formerlycalledCDPlusorCDEnhanced
Music) discs and use the multisession technology defined in the CD-ROM XA standard
to separate the audio and data tracks. These are a form of stamped multisession disc. The
audio portion of the disc can consist of up to 98 standard Red Book audio tracks, whereas
the data track typically is composed of XA Mode 2 sectors and can contain video, song
lyrics, still images, or other multimedia content. Such discs can be identified by the CD
EXTRA logo, which is the standard CD-DA logo with a plus sign to the right. Often the
logoormarkingsonthediscpackageareoverlookedorsomewhatobscure,andyoumight
not know that an audio CD contains this extra data until you play it in a computer-based
optical drive.
A CD EXTRA disc normally contains two sessions. Because audio CD players are only
single-session capable, they play only the audio session and ignore the additional session
containing the data. An optical drive in a PC, however, can see both sessions on the disc
and access both the audio and data tracks.
Scarlet Book (SA-CD)
The Scarlet Book defines the official standard for Super Audio CD (SA-CD, also referred
to as SACD) media and drives. It was codeveloped by Philips Electronics and Sony
in 1999. Unlike the original Red Book CD-Audio standard, which samples music at
44.1KHz, Scarlet Book uses Direct Stream Digital encoding with a sampling rate of
2.822MHz—64 times the sampling frequency of Red Book.
Because of the higher sampling rate and the larger disc capacity necessary to store the au-
dio (as well as SA-CD's support for video and text content), you cannot play standard or
dual-layer SA-CD media in a standard CD player or computer's CD or DVD drive. Al-
though standard SA-CD media has a capacity of 4.7GiB (the same as that of single-lay-
er DVD), the formats are not interchangeable. SA-CD contents are copy-protected by a
physicalwatermarkknownasPitSignalProcessing,whichcannotbedetectedbystandard
computer DVD drives, although some high-end BD and DVD set-top boxes can also play
SA-CD media.
