DVD Demystified

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Chapter 9
receiver or as a separate audio processor. For PCM audio output, the PCM
signal from an audio track is sent directly to the digital audio output. Or
alternatively, the multichannel decoder in the player produces a PCM signal.
In either case, a receiver with a built-in digital-to-analog converter
(DAC) or an outboard digital-to-analog converter is required. Some players
provide separate outputs for multichannel audio and for PCM audio. Other
players have either a switch on the back or a section in the onscreen setup
menu where you can choose between PCM output and multichannel output
(undecoded Dolby Digital, DTS, or MPEG audio). The multichannel output
menu option is usually labeled “AC-3” or “Dolby Digital.”
All NTSC DVD players include a two-channel Dolby Digital decoder, so
they can produce PCM audio from Dolby Digital audio. Most PAL DVD
players include both two-channel Dolby Digital and two-channel MPEG
audio decoders, so they can produce PCM output from either format. Many
players (NTSC and PAL) also provide DTS audio output, but only for connection
to an external DTS decoder. Few players have built-in DTS
decoders.
The digital audio output is also used for PCM audio from a CD. Players
that can play Video CDs also may produce PCM audio output converted
from the MPEG-1 audio signal. Combination laserdisc/DVD players also
use this output for the laserdisc’s PCM audio track (but not the AC-3 track;
see the following).
The direct output from PCM tracks on a DVD is at a 48 or 96 kHz sampling
rate with 16, 20, or 24 bits. The converted PCM output from multichannel
audio tracks is at 48 kHz and up to 24 bits. The PCM output from
a CD is at 44.1 kHz and 16 bits. The PCM output from a laserdisc player is
also at 44.1 kHz and 16 bits. The connected audio component does not need
to be able to handle all these variations, but the more the better. A system
capable of 16 and 20 bits at sampling rates of 48 and 96 kHz is recommended.
Some DVD players are incapable of properly formatting a PCM
signal for output at high sampling rates or bit sizes. If you have an external
system capable of 24 bits or 96 kHz, make sure the player can correctly produce
the digital audio signal. Also be aware that players are required by the
CSS/CPPM license to restrict digital output of 96 kHz audio when the disc
is encrypted. In this case, most players downsample to 48 kHz.
The digital audio output must be connected to a system designed to
accept either PCM digital audio, Dolby Digital (AC-3), or both. Most modern
digital receivers can automatically sense the type of incoming signal.
Some players include a dynamic range control setting (also called midnight
mode) that boosts soft audio and reduces loud sound effects. This setting
should be turned off for best effect with a home theater system, but it