An observer of the broadcast industry sees encouraging significance in some recent behind-the-scenes developments
by Robin Lanier
THE BARRIERS to better TV sound have seemed so immovable, so final, for so many years that Americans can be forgiven some resignation on the subject. But new forces are at work that promise to up grade TV sound at last.
The problem, now boringly familiar, is a four stage chicken-egg bind. The low quality of sound pickup at TV origination points, mostly major net work stations, has been matched by that of the distribution system (in the past mainly the Bell Sys tem), the local TV stations, and, above all, TV receivers in viewers' homes. Obviously, improving just one link in this chain has little immediate effect, and higher quality has been firmly resisted at each stage, pending improvements in all the others.
But the barriers of origination and distribution are now under heavy attack. As the flow of high fidelity begins to jam up at the local TV station, will the pressure to improve that station rise and will the shock waves reach the receiver in the home so that listenable audio can reach the ear? It seems likely that they will. The forces behind the changes are the commercial industry itself and the Public Broadcasting System in Washington, the national organization of public television stations.
PBS is organizing a distribution system with superlative audio quality, even though it can't be fully used at the receiving end for some time.
In the past, the microphone technique used at the sound pickup point in commercial TV has been based on a single imperative: "Keep the mike out of any possible camera view!" When the norm was a single mike, this rule obviously gave an audio man tough, often insoluble, problems in trying to get even reasonably accurate representation of a musical group. That is being changed by a shift to the multimike techniques that have been common in recording for a long time. Now the audio man can mix his mikes (via a multi-input console) into the final sound in any proportions he wants.
In this way, despite less than optimum positions of the microphones, he can get a balanced sound.
The recording of the audio material is also due for radical change. TV sound traditionally is re corded on a track on the edge of the video tape, via an extra audio head on the video tape recorder.
But the audio gets a tiny track because the picture needs every millimeter of tape it can get. Even the tape is wrong for audio; it is formulated for best response with video signals themselves, the audio being left essentially to fend for itself. Also, the rotating video heads vibrate the tape continuously, producing serious flutter in the audio.
What's the solution? Record the audio on a separate, high-grade audio machine. This "double sys tem" recording has become practical and attractive with the development of effective, comparatively inexpensive systems for keeping the video and audio machines synchronized. The commercial TV networks are using double-system recording only occasionally, on major musical programs and--at ABC, at least-on elaborately produced shows where multitrack capability is advantageous. But the equipment and the skills are there, fully developed and ready for the TV sound revolution. NBC is currently upgrading the audio facilities at its headquarters and can even now deliver high quality sound-in mono or stereo.
Public television stations have often relied on the double system. WGBH-TV in Boston, which originates many top musical programs for the public network, uses thirteen or fourteen mike inputs, mixed down to four channels on tape. These top-grade tapes have in the past been mixed down again to mono before the programs go out for Bell System distribution, but the tapes are ready for any better days that might be coming.
Those better days are also getting a boost from the PBS plan to use satellites for distributing pro grams to the public television stations. Last January the Federal Communications Commission approved a detailed plan for a major satellite transmitter near Washington, with regional transmitters across the country and earth stations at or near all PBS affiliates, for a much cheaper, more flexible, higher-quality program delivery than PBS has had up to now. The $40 million needed to implement it is committed, with various sources contributing. The plan includes a system called DATE (digital audio for television), which will put four top-grade audio channels in digital form alongside the picture. PBS has gone ahead with DATE, even though no local stations can use it yet.
Until TV transmitters and home receivers are equipped for stereo sound, PBS will send along with the DATE signal a mono audio signal on an FM subcarrier. Thanks to the wide bandwidth of satellite links and the high level of equipment and care used at the points of origination, this signal is significantly better than what has been available.
The Bell System itself has not remained dormant during all these developments and has used some experimental equipment in recent simulcasts--transmissions in which the TV audio is sent simultaneously via an FM station. ( New York's Lincoln Center has been a pioneer in this area.) Bell has even toyed with the idea of using DATE.
Although it apparently turned down multichannel audio as too expensive to be justified in the commercial telephone system at this time, it has introduced its own diplexing system for mono TV audio, currently being installed by all three commercial networks and planned for operation early next year. In a diplexing system (DATE is one as well), the audio is put on a separate carrier on the same channel as the video. Video distribution net works have bandwidth that can easily accommodate a high-grade audio signal alongside the video, whereas the standard telephone lines used for TV audio for so many years are limited to 5 kHz, are comparatively noisy, and have little dynamic range.
What is the outlook for getting the better quality through the last two segments of the system-the local TV station and the home receiver? The basic (FM) audio quality of the standard TV transmitter is quite good; and any important change--especially adapting TV transmitters for stereo broad cast-will require comprehensive industry study followed by some sort of FCC standardization.
The Joint Coordinating Industry Committee, made up of representatives of the commercial networks, Bell, the public TV stations, and the manufacturing groups, has been examining television technology for several years to identify those aspects that need improving. The subcommittee on TV sound, chaired by Dan Wells of PBS, has made a number of important recommendations in this area, but it is unlikely that they will be implemented in anything less than five years.
We can only hope that when that does happen, competitive pressures will encourage at least some TV receiver manufacturers to take advantage of the improved audio signal available to home viewers. It would be optimistic to expect real high fidelity from in-cabinet speakers (although considerable improvement is possible), so the sets seeking very high audio quality will probably go to outboard speaker modules. Detector outputs (with the necessary power-line isolation) can also be added at relatively modest cost to provide the owner of a component music system with audio signals comparable to those from an FM tuner.
Meanwhile, you can get sporadic and tantalizing foretastes from simulcasts. Considering the pace at which TV audio is developing, it looks like you won't be waiting too long for the real thing.