Specifications

Standards and Practices for Authoring Dolby
®
Digital and Dolby E Bitstreams
5
DBS, etc.). Setting the Dialogue Normalization parameter is crucial to the proper
operation of home decoders and provides three main functions:
1. In multimedia postproduction, the level-matching of dialnorm allows different
content (i.e., titles, short movies, game replays, etc.) to be interspersed,
maintaining the same comfortable listening level in the home. During the digital
broadcast of a television program, dialnorm allows commercials, news breaks,
and the like to be interspersed within the program so that the viewer doesn’t have
to constantly reach for the volume control during breaks.
2. Consumer requirements for home enjoyment of multichannel audio vary widely. Not
everyone who owns a DVD player or receives a digital television broadcast listens in
an ideal home theater environment; for example, many laptop computers offer DVD
players and DTV receivers. The specifications, price, and capabilities of speakers,
amplifiers, DVD players, etc., range from the basic to near-professional. Some care
must be taken so that consumers of multichannel audio programs can be reasonably
assured that the mixer’s intent will be carried through their chosen playback system
to their ears. In addition to level-matching between different program content and
media, dialnorm ensures that the full dynamic range of the program can be
reproduced without clipping the digital-to-analog (D/A) converters. As this level shift
occurs well before the consumer’s volume control knob, the decision on how loud to
listen to a particular program is still up to the consumer.
3. A properly set dialnorm value provides the null band within the dynamic range
profile (see Section 3.5) where the audio level is neither raised nor lowered.
Without a properly set dialnorm parameter, reduced dynamic range listening modes
may not have the intended effect of allowing softer portions of the signal to be
audible while simultaneously reducing the decibel level of explosions, gunshots, or
similar effects that may disturb others in the home.
Typically, consumers of a DVD movie or digital television program set their system’s
playback volume to a comfortable level centered around the level of dialogue within
the program. This comfortable listening level depends on the consumer’s taste and the
intelligibility of the dialogue component. The parameter is called “Dialogue
Normalization” because it uses the knowledge of the dialogue level within a program
to make sure the consumer’s comfortable listening level remains consistent between
programs. This concept is derived from a standard practice in film mixing.
That is not to say that dialogue is required to set the Dialogue Normalization
parameter. In music-only DVDs or television broadcasts, the dialnorm parameter can
be thought of as the average volume level of the program.
Dialogue Normalization, in simple terms, is exactly the same as turning the volume
down a bit on a consumer’s home stereo. However, simply adjusting the volume on a
home stereo provides none of the other advantages of dialnorm: providing a reference
for reduced dynamic range listening conditions, accurate and musical dynamic range
compression, and clipping protection prior to the D/A circuitry.