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Telos Zephyr Xstream Two-Way Radio User Manual

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USER’S MANUAL

Section 6: AUDIO CODING REFERENCE 117

Theresultofallthisisthattheresearcherssucceeded.AACprovidesperformancesuperiorto

anyknowncodecatbitratesgreaterthan64kbps,andexcellentperformancerelativetothe

alternativesatbitratesreachingaslowas16kbps.

AndtheresearcherssucceededinachievingtheITUgoal.AACisthefirstcodecsy

stemtofulfill

theITUrequirementsforindistinguishablequalityat128kbps/stereo

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.Ithasapproximately

100%morecodingpowerthanLayer‐2and30%morepowerthantheformerMPEG

performanceleader,Layer‐3.FormoreinformationonAAC,andthetestsofit,seeourwebsite

forapaperonthesubject:www.telos‐systems.com.

ZephyrXstreamisthefirstbroadcastco

dectoincorporatethepowerofAACcoding,resultingin

superiorhigh‐fidelityaudioatlowerbitratesandwithlessdelaythanLayer‐3orLayer‐2.

ItisthemostpowerfulcodingmethodavailableinZephyrXstream,andweparticularlylikeit

becauseitisperfectlymatchedtothebitratesavailableonISDNBR

Ilines.

Itoffers:

• 20kHzmonoorstereoaudiobandwidth.

• SignificantlylessdelaythanLayers2or3.

• Full‐fidelitymonoonasingle56/64kbpschannel.

• CDqualitystereo

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onasingleISDNTelcocircuit.

• Affordable,transparent,audiotransmissionforAM/FMradioor

televisionaudio.

c

COMPTIBILITY TIP!

The Zephyr Xstream cannot receive two J-stereo 64 feeds from the far end (after

all, where would the audio be output?).

When connected to two different sites simultaneously you can receive an audio

feed back from each using G.722 or L3 Dual/Mono.

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Subjective Evaluation of State-of-the-Art Two-Channel Audio Codecs, G. A. Soulodre,

T. Grusec, et al. Journal of the Audio Engineering Society; Vol. 46, #3; March 1998, Pg

164 - 177.

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20kHz bandwidth, >96dB dynamic range... just like a CD. The encoding process can

cause some loss that a trained listener, using carefully-selected program material and

good monitors, could detect. However, most people won’t hear the loss, and there’s no

accepted way to measure it.

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