Dolby Laboratories DP570 Specifications download pdf (Page 20)

Standards and Practices for Authoring Dolby

Digital and Dolby E Bitstreams

6 Frequently Asked Questions

Aren’t Dolby Digital and “5.1” the same thing?

No. A stream encoded in Dolby Digital can carry any number of channels, from a

minimum of one mono signal to a maximum of six channels in a 5.1-channel home

theater configuration. In digital television broadcast, Dolby Digital is commonly used

in a two-channel stereo configuration. The flexibility of Dolby Digital as an encoding

technology to carry anywhere from mono to multichannel surround programs makes

it the ideal tool to carry audio in digital media.

Aren’t Surround EX and “6.1” (or even “7.1”) the same thing?

No. Dolby Digital Surround EX

was first introduced to the public with the release of

Star Wars: Episode One—The Phantom Menace. Since then, many more films have

been released in theatres in the Surround EX format. Now, Surround EX is appearing

on DVDs and consumer electronic equipment for use in the home.

The Surround EX format is different from conventional 5.1 in that an extra back

surround channel is added between the left and right surround channels. To maintain

compatibility, this back surround channel is matrix-encoded with the left/right

surround channels to create a stereo-compatible surround signal. Consumers without

Surround EX capability receive stereo surround channels, while those with Surround

EX decoding capability hear three surround channels. The Surround EX format is

only valid on source signals with at least two surround channels.

How do I set up the speakers on my mix stage or production studio for

Dolby Digital or Dolby E authoring?

Since both Dolby Digital and Dolby E are discrete encoding processes (i.e., speaker

channel separation is maintained throughout the process and no channels are

“matrixed”), what is heard on the mix stage is what the consumer will hear at home,

provided the listening environment is properly calibrated. While there is no specific

standard for sound pressure level (SPL) during mastering for DVD or digital

television broadcast, it is important that each speaker is adjusted to deliver the same

SPL at the mixing position. This can be achieved by measuring the SPL with a meter

at the mixing position and making appropriate adjustments while playing pink noise

through each speaker individually. Some mixing stages are set to 85 dB SPL at each

speaker, while others may be set somewhat lower. The important thing is to make

sure that each speaker is set to the same level at the mixing position.

The subwoofer speaker should be calibrated with 10 dB of in-band gain over the

center channel from 25 to 120 Hz when measured with a real-time frequency

analyzer. This would equate to about 91 dBC when measured with a properly

calibrated SPL meter.

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Dolby Laboratories DP570 Specifications Page 20