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CDQPrima USERS GUIDE

6-36-3

• Different, high fidelity left and right audio programs

ISO/MPEG Layer III can deliver full duplex, 15 kHz monaural audio

using only one 56 or 64 kb/s ISDN ‘B’ channel. At 112 or 128 kb/s,

transparent 20 kHz monaural audio is possible. Near-transparent 20

kHz audio is possible in joint-stereo mode. In dual mono or stereo

modes, near-transparent 15 kHz audio is obtained.

Although Layer III offers a wider bandwidth than other algorithms at

low bit rates, the inherent drawbacks of this algorithm may outweigh

this benefit. The disadvantages of using Layer III are long coding delay

times and poor cascading ability. In addition, audible artifacts may be

noticeable when using Layer III at lower bit rates, and post-processing

may further degrade the audio.

At 112 or 128 kb/s, the only advantage of using Layer III over

MUSICAM-enhanced Layer II is that Layer III can deliver true stereo

with 15 kHz bandwidth. This makes Layer III ideal for mix auditioning

or other applications where high fidelity and true channel separation

are required, since no sound-stage manipulation is employed. Other

than that, at 112 or 128 kb/s data rates, we recommend using Layer III

only when communication with Layer III-only codecs is required. Even

at 112 or 128 kb/s, digital artifacts may be noticeable, and the delay,

cascading and post-processing limitations are still present.

At bit rates higher than 128 kb/s (not supported with internal terminal

adapters), there is no advantage to using Layer III over MUSICAM or

standard Layer II. Bit rates up to 320 kb/s are supported for

compatibility.

6.1.1.4 MUSICAM and ISO/MPEG Layer II

Recommended applications for MUSICAM-enhanced Layer II:

• Studio-to-transmitter links

• Voice-over

• High-fidelity remotes

• Different audio to two locations

• Highest quality audio over ISDN

• Low delay (single line mode)

The premier coding algorithm used in CDQPrima is MUSICAM,

MUSICAM USA’s enhancement to the ISO/MPEG Layer II encoding

algorithm. MUSICAM offers the best possible combination of fidelity,

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