The topic: Talent "IFB"
Live television feeds from remote locations require that the reporter have a method of hearing audio from the newscast as well as instructions from the news director in an ear piece. They receive a "mix-minus" feed that has all the newscast audio except their own voice. Traditionally this has been provided by feeding a mix minus feed with interrupt (IFB) to a two-way radio system, cellular telephone system, or the "Pro Channel" audio sub-carrier broadcast in analog NTSC television.

The issue: Analog broadcast shut down
The Pro Channel system for NTSC broadcasts goes away on February 17, 2009 along with the shut down of analog broadcasts. In some markets this will come earlier.

Two-way radio IFB systems have been popular for years. However, they are limited by far too few available channels. Also, coverage is restricted to 15-20 miles from the central transmit/receive site unless a system of repeaters is employed.

Cellular phones are popular because they're inexpensive and one can generally make a connection from just about anywhere in an urban environment. However, as we all know cell phones can drop calls at the most inopportune times. In addition digital cellular service introduces a significant amount of latency that can change in the course of a call. This long and often variable latency can make cell phones unacceptable for IFB purposes.

Other concerns with cellular phones are their high usage during emergencies (blocking) and preemption by emergency personal using the FCC sanctioned Priorty Access Service (PAS). This blocking and preemption often takes place at events that most need to be covered by live news. As was seen in the 9/11 event, cell phones can become nearly unusable during extreme events.

The solution: MSI DIGITAL PROceiver
Modulation Sciences developed some of the first Pro Channel system products. In anticipation of the analog shut down they've developed a means of delivering low latency audio for IFB usage over theDTV broadcast channel. A virtually unlimited number of IFB audio signals could be sent to an equal number of receive locations. The actual number of IFB channels is limited only by the available bits on the Transport Stream. These IFB signals cannot be detected by consumer DTV receivers.

The DIGITAL PROceiver is a specialized ATSC compatible product that can reproduce these audio signals. It would reside in the ENG vehicle connected to a standard broadcast receive antenna. It provides two independent audio outputs so one receiver delivers two IFB's. It's a one RU, half rack width product that runs off vehicle power and provides two balanced analog audio outputs.

With a properly configured encoder and multiplexed system, audio latency can be under 300 milliseconds, an acceptable amount of delay in a live TV environment.

At the studio end the equipment required for two IFB channels is often already built into the existing encoder, requiring only software codes to activate. Sometimes an expansion to the existing multiplexer or the addition of a downstream multiplexer is needed. There would need to be minor configuration changes in the broadcast multiplex to make room in the 19.3Mbit/sec ATSC stream to accommodate the approximately 96 Kbit/sec per audio pair additional payload. The encoder can accept analog or digital audio inputs.

At the ENG truck the existing IFB system would be fed by the new DIGITAL PROceiver. It would require an antenna feed, which is available on most trucks.

This is a cost effective way to provide IFB audio to talent at their remote site with high quality and reliability.

Note: PROceiver and ENG for IFB are marks of Modulation Sciences, Inc.