Telos Zephyr Xstream - Manual (Page 184)

USER’S MANUAL
Section 10: APPLICATIONS GUIDE 172
Also note that Layer‐3 has more delay than Layer‐2 which has more delay than AAC. AAC‐LD
follows with G.722 having the shortest delay.
Note that for a given bit rate and sample rate, that AAC offers the best fidelity, followed by
Layer‐3 and AAC‐LD, followed Layer‐2, and finally by G.722.
As a Zephyr Xstream user, you have the best of all worlds. Layer‐2, Layer‐3, and G.722 offer
backwards compatibility with older codecs, while AAC and AAC‐LD allow better quality or
reduced delay.
10.3 Applications Guide
Voice-over applications on a single B channel (1 call)
Good:
Use L3 Dual/Mono Transmit ‐ Far end would use L3 Mono (Zephyr) or L3 Dual/Mono (Zephyr
Xstream) Receive.
Use 32kHz sample rate for best fidelity.
Best Quality:
Use AAC Mono 64 transmit ‐ Far end should use AAC 64 for Receive
Voice-over applications using two B channels (2 calls)
Good:
Use L2 Mono 128 Transmit – Far end should use L2 Receive (Zephyr or Zephyr Xstream) at 48kHz
sample rate.
Better:
Use L3 Mono 128 Transmit – Far end should use L3 (Zephyr Xstream) or L3 Stereo (Zephyr)
Receive.
Use the 32 or 48 kHz sample (both ends must match).
Best:
Use AAC Mono 128 Transmit – Far end should use AAC Receive.
Either 32 or 48 kHz can be used for the sample rate (must match on the both ends).