Support User Manuals

Telos Zephyr Xstream Two-Way Radio User Manual

Open as PDF

of 381

USER’S MANUAL

Section 6: AUDIO CODING REFERENCE 129

t

DEEP TECH NOTE!

While the "Stereo" modes keep the audio separate, the psychoacoustic model assumes the

listener will be hearing both audio channels (i.e. it assumes that audio from one channel may

mask audio on the other channel). For this reason the Mono/Dual mode is preferred when

discrete unrelated material is to be sent down the two channels.

h

HOT TIP!

The when transmitting in the stereo modes, the far end will not receive anything until both

transmission (i.e. ISDN) channels are connected and operating. The decoder will not will not

output anything until this happens. Any data drop outs could cause interruptions of both

audio channels.

If your application requires the ability for the two channels to come and go independently,

such as when they are from independent sites, you must use L3 Mono/Dual for transmit and

the far end must use L3 Mono/Dual receive. Or, you can use G.722. These are the only modes

that support fully independent operation.

Z

ZEPHYR CLASSIC VS. XSTREAM COMPARISON

While the Zephyr Classic supports Dual transmission in Layer-3 as well as G.722, it can only

independently receive in G.722.

• J‐STEREO(JointStereo)modeinAAC,AAC‐LD,andLayer‐3takesadvantage

oftheredundancythatisusuallypresentinstereoprogrammaterial.The

encoderswitchesfromdiscreteL/RtomatrixedL+R/L‐Rdynamically.When

inL+R/L‐Rmode,bitsareallocateddynamicallytothesetwobit‐streams

allowingmax

imumadvantagebetakenadvantageofredundancybetween

thetwochannels.

Sincethe"center‐channel"redundancy,presentinmoststereosources,is

exploitedtoouradvantage,thecompressionratioislowerandtherefore

thequalityishigher,formostmaterial.Forthisreasonwerecommend

usingJ‐stereoundermostcircumstances.

Thebigg

estexceptionswouldbe:

a) Caseswherematerialthathasbeenencodedinasurroundsound

format.

b) Caseswherefinalmixapprovalsofstereosourcematerialarebeing

madeoverthecodedlink.Inthiscase,decisionsabout"stereo

imaging"shouldbemadeindiscretestereowhereasoverallmix

reviewcanbemadeinJ‐stereo.

previous next