Support User Manuals

Telos Zephyr Xstream Two-Way Radio User Manual

Open as PDF

of 381

USER’S MANUAL

Section 10: APPLICATIONS GUIDE 170

10.2 Choosing the Best Transmit Mode for your application

FIDELITY versus CODING METHOD versus DELAY – A quick comparison

Wehavelistedthedifferentmodeshereinapproximateorderofdelay.SeeSection6(Audio

CodingReference)formoreinformationontheQualityandDelayofthevariouscoding

methods.

G.722

Offers7kHzaudiofrequencyresponseatmoderatefidelity.Itoperatesat56‐64kbpsper

channel.Samplerateis16

kHz.Thefrequencyresponseis7.5kHz.G>722wasoriginally

designedfor“enhanced”telephoneapplications.Itiswidelysupportedbyothercodecs.It’s

verylowdelay(lessthan20msec)makesthiscodingmethodverypopularforcueingorfoldback

(IFB)channels.

AAC-LD

AAC‐LDoffersfidelityequivalenttoLayer‐3withverylowdelay(a

bout70msec).Itisan

excellentchoiceforsituationswhereliveinteractionisrequired.

AAC‐LDoffers14kHzaudiofrequencyresponse.

AAC

AACoffersLayer‐2qualityat50%ofthebitrate.Thefidelityofstereoat128kbpsmeetstheITU

(InternationalTelecommunicationsUni

on)criteriafor"IndistinguishableQuality"forstereo

transmission.Thedelayisquitelow,atlessthan1/5thsecond.

AACshouldbeusedwheneveritissupportedatbothends.

Offers15or20kHzaudiofrequencyresponse,at32or48kHzsamplerate,respectively

c

COMPATIBILITY TIP!

Zephyr Xstream supports both 32kHz and 48kHz sample rate for Layer-2 in the following

modes. The majority of Layer-2 codecs deployed in the field (including the Zephyr Classic)

support the 48 kHz sample rate only.

The Layer 2 Mono/Half mode allows operation at 24 kHz sample rate, however the delay is

significantly increased.

Layer-2

L2Mono64&L2Stereo–Offers7.8kHz(at56kbps)or9.8kHz(at64kbps)atmoderatefidelity.

Samplerateis32or48kHz.ItisgenerallypreferredoverG.722formusic,butnotalwaysfor

voice.Sibilancecausesobviousartifacts.Whenthe48kHzsamplerateisused,thedelayis

moderatelylow(1/4seco

ndforstereo,1/10secondformono)howevertheincreased

previous next