Dolby Laboratories Lake LP4D12, Руководство пользователя

Страница: 61 / 68

Dolby
®
Lake
®
Processor System Manual Connecting Digital Audio Devices
49
Both Primary and Sample Rate Converter clocks produce multiple audio clocks
derived from a base sample rate. The Primary Clock’s base rate is 48 kHz, which also
derives the 96 and 192 kHz clocks.
The Sample Rate Converter Clock’s base rate can either be 44.1 or 48 kHz. If the
Sample Rate Converter Clock’s base rate is chosen to be 44.1, 88.2, and 176.4 kHz
clocks are also derived. If the Sample Rate Converter Clock’s base rate is chosen to
be 48, 96, and 192 kHz clocks are also derived.
In most typical applications, the Sample Rate Converter Clock will be set at a base
rate of 44.1 kHz. A base rate of 48 kHz is provided as an enhancement to allow for
both synchronous (from Primary Clock) and asynchronous (from Sample Rate
Converter Clock) digital audio outputs.
All clocks derived from the Primary and Sample Rate Converter clocks are available
to drive digital audio outputs. The end user can independently choose the desired
sample rate for each digital audio output, as shown on the right side of Figure 7-1.
For example, you can configure AES1, AES2, AES3, and AES4 to provide 96 kHz
AES/EBU outputs to drive digital amplifiers in the sound system, and configure
AES5 to provide a 44.1 kHz output to an onsite video facility for press or broadcast
use.
7.2 Clock Source Priorities
By default, the most appropriate digital clocks are automatically detected. The first
valid clock in the order of the following list is chosen to configure the Primary Clock
as 48/96/192 kHz, and the Sample Rate Converter Clock as 44.1/88.2/176.4 kHz.
1. BNC Word Clock
2. AES1 (In 1+2)
3. AES2 (In 3+4)
4. AES3 (In 5+6)
5. AES4 (In 7+8)
6. S/PDIF
7. Internal Clock (88.2 or 96 kHz; also includes conductor/performer negotiation
for CobraNet
®
at 48 kHz)
If a clock signal is unavailable, or temporarily lost, the automatic detection process
reverts to the internal clock using the same sample rate multiples as that selected for