Telos Zephyr Xstream - Manual (Page 198)

USER’S MANUAL
Section 10: APPLICATIONS GUIDE 186
Remember, if any of the announcer audio from the remote site is returned via the monitor feed,
it will be delayed by the codec link, causing an echo effect. Problem. The answer is to make
sure you have the best possible hybrid with the maximum trans‐hybrid loss, such as a system
that uses ISDN lines. If it has
variable override (caller ducking), you could increase the amount
when these remotes are in progress (or, on some hybrids, you would decrease the setting of the
"duplex" control).
Some users place a downward expander, carefully adjusted to gate the leakage, in the caller
audio path.
Main Program
Output
Telephone
Mix-Minus
Remote
Mix-Minus
Studio Console
Other Sources
for music, etc. Zephyr
Trans-
mission
Path
Phone
Hybrid
REMOTE SITE STUDIO
Diagram showing system set‐up for remotes with delay in the transmission
path and phones taken at the studio. Note that this is the same as required
for satellite links.
Another issue worth considering is the round trip delay. The apparent on‐air response time of
the talent to callers’ comments will be the sum of studio‐to‐remote delay + remote‐to‐studio
delay + talent’s thinking time. For this reason the studio‐to‐remote path will generally use the
G.722 mode, which sacrifices fidelity for delay (after all, the callers need not be in high fidelity).
This round trip delay issue will also affect your choice of remote‐to‐studio coding. If the show
will be 90% talk with just a small amount of music then delay can be minimized by using a mono
mode for this path rather than using one of the slower stereo modes.
Here is where Zephyr Xstream’s AAC‐LD encoding really shines. It gives you high quality
announcer audio with the lowest delay possible. In addition, the reduced delay time will serve
make any leakage less distracting (for more on this see Section 6 ‐ Audio Coding Reference).
Another trick is to use a POTS call (call mode = Phone) for the studio‐to‐remote link, which will
make the delay in that direction very small. Other intermediate tradeoffs are possible, and will
be dependent on your format. Talent thinking time can be significantly reduced by drinking a
strong cup of coffee!
For information on the tradeoff between audio quality and delay, refer to manual Section 6
(Audio Coding Reference)