Vector VN8912 Handbuch PDF herunterladen (Seite 56)

Comrex Corporation

APPENDIX BABOUT MIX MINUS

Even the simplest remotes are a two-way process. The remote site must send its

audio to the studio and receive a return feed to monitor the programming. This

return feed may be done over a radio stations regular transmitter (with an AM or

FM radio at the remote), over a special radio link or over a telephone circuit. This

feed may just go to headphones at the remote and also be put on speakers for

any spectators.

The problem comes when there is a time delay in getting audio to and/or from the

studio. In this case, the remote talent hears a delayed version of their voice in the

headphones and finds this very distracting. Even a remote done with simple

equipment or a frequency extender on plain phone lines may have this problem on

a long-distance call. All remotes using ISDN, Switched-56, and POTS codecs will

have delays each way as signals are processed from analog to digital, compressed,

uncompressed, and converted back to analog audio. Some digital compression

schemes, such as G.722, result in shorter delay times, but there will still be a

reverb effect in headphones at the remote site if their audio is sent back from the

studio. In any of these cases, it may not be possible for the remote people to listen

to an off-air or program channel feed.

The solution is

mix-minusmix-minus

mix-minus. A mix-minus feed has a mix of all of the programming

on the radio station (or network)

minusminus

minus the audio from the remote. In other words,

the station or network doesnt send the remote audio back to the remote. At the

remote end, this mix-minus feed is converted back to an air monitor by mixing in

the local audio from the remote. This is easily done on the Vector, with the LOCAL

volume control.

For radio stations, in addition to fixing the time delay problem, using a mix-minus

feed has two other advantages. First, if the station uses a 6-7 second delay to allow

editing of phone calls, pre-delay audio can be sent to the remote site. Second, if

there is a PA system at the remote, they will be able to run the speaker levels higher

with the mix-minus audio. This is because the remote microphone audio is not

running through the stations audio processing, and the levels stay under the

control of the remote operator.

The simplest way to do one mix-minus feed in a typical radio studio is to use the

Audition or second program channel. On many audio consoles, each faders output

may be sent to both Program and Audition. If your board will allow those feeds

simultaneously, just set all of the modules to Program and Audition,

with thewith the

with the

exception of the one carrying the remote audio. Set that one to Program only.exception of the one carrying the remote audio. Set that one to Program only.

exception of the one carrying the remote audio. Set that one to Program only. The

Audition channel will then be a mix of everything on the console except the

remote. That will be your mix-minus which should be sent to the remote site. One

caution  make sure that audio is being sent to and from any telephone modules

you may have in the console. They may have been designed to work with only one

channel at a time  either Program or Audition, but not both. If so, you will have

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