Codecs: The Lifesaver of Many Remotes

February 1, 2001

Codecs: A Complete Remote Studio in a Box

Remote broadcasts for radio stations have always been challenging. It's easy to show up at a location on time. Fancy promotional aids such as prize wheels, large inflatable balloons and logos, vans, trailers and booths make the appearance look great, but getting quality sound on the air is a different story. Are you in range for the remote-pickup transmitter? Will another station be on your frequency and cause interference? Can you park the van in a location where you can put the mast up without fear of trees or powerlines overhead? Can you get the antenna above the roof of the building? These questions are always overlooked when a broadcast is booked. For the engineer, there is always that uneasy feeling when rolling up to a remote broadcast location that the station has never been to before. Sometimes it's just not possible to check out every location prior to a show. Most times, the engineer is able to pull it off, but every now and then, it just won't happen. As a fall back, the station would have to do the broadcast on a telephone line, or worse yet, with a cell phone. Equalizers and frequency extenders have been used to try to make telephone remotes sound better, but they can only do so much.

Codecs to the rescue

Now that we are in the digital age, the solutions have not only become easier, but have become the norm. Codecs (from coder/decoder) are used to convert audio to digital data and send it over telephone lines to be decoded at the studio for broadcast. Complex algorithms are used to compress the amount of data before sending to increase the quality of the audio. With the newest revisions of these codecs, it is possible to get a single channel of audio up to 15kHz in bandwidth over a standard dial-up telephone line, commonly referred to as POTS (plain old telephone service) or PSTN (public switched telephone network) lines. This is amazing when you realize that, by feeding a normal analog signal down the same line, you can only achieve an average of 3.5kHz of bandwidth. Most of the remote broadcast transmitters can only broadcast with a bandwidth of 7.5kHz, which, when you get a good signal, sounds great for voice. As if this weren't enough, not only do you get this quality of audio to the studio, but you also get another channel of equal quality back from the studio to the remote site. This provides a built-in talkback circuit without using expensive two-way radios or running up the cell phone costs.

When even higher quality is needed, such as for stereo music, you can use a codec designed for high-speed ISDN phone circuits. Using MPEG algorithms such as Layer II or Layer III, some of these codecs can send 20kHz stereo audio across the country or across the world. These ISDN codecs are great for stations that want to broadcast live music from any remote location with ISDN service. The down side of these codecs is that the ISDN phone lines are not as readily available and can sometimes take as much as 30 days of lead time for installation. Cost can be an issue as well, especially if it is for a one-time-only show. One advantage to POTS codecs is that standard phone lines are usually already available at most locations and ready to plug in a codec for use.

Opening doors

Codecs have become widely accepted, and sales of units is growing rapidly. More manufacturers are jumping on the technology and putting their systems on the market. To make these units more attractive to the consumer, the manufacturers are coming up with a variety of innovative features to sell. The winners are the radio stations. At first, stations had to choose between POTS or ISDN codecs, and if they had a need for both types of service, they had to purchase two systems, one for each type of line. Newer codecs incorporate the ability to connect to either type of line. Some can select the type of line by plugging in different modules, and some have the ability to interface to either type of line built in. There are even codecs that can now take up to three ISDN lines in one unit to allow feeds to multiple locations simultaneously. The same piece of equipment can now be used for every day remotes and also for the more complex stereo broadcasts when the best quality is needed. This makes setup easier for non-technical staff since they don't have to learn how to use different types of units.

Even though phone lines are just about everywhere, you can still run into occasions where lines aren't available, such as in a park, on the beach, or when you just need to be more mobile. For a news station, the news doesn't always happen in an office building. Up until now, these broadcasts would still require the old RPU transmitter with a mast on the van. Codec manufacturers have addressed this issue, and a few companies have introduced units that can connect to cell phones. Due to the low data rate available on most cell phones, the codec can only connect to the new GSM types of service. As this technology grows, so will the versatility of the broadcast. For truly mobile applications, many offer battery operation, some using lightweight AA batteries.

Compact studios in one box

Today's codecs are packing more and more features into compact and lightweight boxes. Many of the systems on the market now have built-in mixers with multiple inputs. Some are selectable for either microphone or line level inputs. Most are even now incorporating headphone amplifiers with multiple outputs, each with their own volume controls built in.

One of the problems with using codecs, as with any other digital audio system, is a delay factor. It takes time for the audio to be converted to digital, transmitted, then received and decoded again. The amount of time delay varies greatly depending on the method of data compression. Layer III has longer delays than G.722, but it offers a better quality audio. To reduce the delay means to compromise the quality. The delay can make it very difficult for the talent to listen to the radio for his cues and then talk. This is where the return audio link from the studio can help. A mix-minus audio feed can be fed back from the studio to the remote location via the codec. At the remote site, the talent will listen to this audio feed to get his cues. When he begins to talk, he will not hear his voice coming from the studio, nor over the air, but rather will mix his local microphone with the feed from the studio. Many of the codecs on the market have this mix ability built right in. It is especially important when taking a talk radio show on the road. When a seven-second delay is used on the air to edit out obscenities, pre-delay audio can be sent back to the remote location for the talk show host to hear the phone callers and commercial breaks.

Some of these complete studio-in-a-box units even have an output to feed to a sound system at the remote site. When you are having troubles with reception of the radio station inside of a building, or outside of your coverage area, or if the delay is bothering the host, you can take this output from the codec to directly feed your PA sound system to play the station. Just like the headphone outputs, you can mix the audio from the studio with the local sources. This is great to reduce feedback. You can also turn up the station louder at the remote without fear of the on-air audio processing grabbing the audio and causing more feedback. Simply show up to the remote with the codec, a microphone, headphones, amp and speakers, and you're running.

More features

As usual, the more we get, the more we want, and the codec manufacturers are not disappointing us. Some codecs will pass contact closures from a remote site to the studio site. This will allow the talent at the remote to start his own commercial break when he's ready, instead of relying on calling ahead and giving the board operator an outcue for which to listen. Some offer multiple closures to allow the talent to have even more control and interface with computer audio storage systems. Since this is digital technology with no interference noises in the background, the talent can simply mute his microphone at the remote site when he's not on the air, use the remote closures, and run the show from the remote site without the use of a control board operator To be in complete contact, many of the codecs also provide a data channel to connect to a PC. Messages can be typed back and forth between the studio and remote location such as names and locations of phone callers, what song is coming up next, even e-mail messages. This is possible with both the ISDN and POTS lines, without suffering loss of audio quality. On POTS lines, data connections of up to 9.6kb/s can be achieved simultaneously with the audio.

One of the more sophisticated units on the market now even allows control of the remote codec from the studio end, or from yet another location. By connecting a computer to the studio end unit, the board operator can use software to connect to the remote site, turn microphones on and off, adjust levels, and even troubleshoot minor problems. If a microphone is plugged into a line input, the change can be made remotely. This is great for broadcasts where an engineer isn't available, or for church broadcasts where nobody is needed. This same computer can monitor the connection quality of the line on a graph for diagnostics at a later time. There are even some third party companies now writing software to control codecs remotely by computer, and even through the Internet. Many of the codecs can be pre-programmed by the engineer at the studio before sending it out, so that one touch of a button at the remote will set up the parameters properly, and even dial the phone number of the station.

With so many options available, what happens when you need to do a broadcast but can't get an ISDN line, or a good quality connection on a POTS line? This can be the case when sending a reporter overseas to a war zone, or to a less technically advanced nation. You might also be looking to do an interview at a concert with an artist or some of the fans in a crowd where you don't have a phone line. Once again, one of the manufacturers is thinking about this. One of the newest units on the market now has the ability to record and store nearly ten minutes of audio digitally, then send the data back to the studio on a POTS line when available, or at whatever data rate is available. While the broadcast will not be live, it does give the highest quality possible audio with even the poorest quality phone line—giving your station the edge on the competition.

Avoid obsolescence

With features changing rapidly, it's important to shop before buying. Look at what's available, and pick the features you need. To help protect your investment from becoming outdated, manufacturers are building their systems with the ability to be upgraded. Some use plug-in modules, not unlike video games, which will continue to be developed in the future to keep up with technology. Since codecs are basically computers and modems, many are now including RS-232 data ports, which can be connected to computers and even the Internet to allow new revisions and upgrades to be downloaded. I think it's safe to say that we have only scratched the surface of this technology. Codecs are popping up everywhere now—from nightclubs to car dealer broadcasts, to overseas news coverage. They are even being used in emergencies to back up STL links. They are rapidly changing the way we do business, and for the better. With a little imagination, you'll find ways to use them to increase revenue, and make the old dreaded remote broadcasts easier than ever, and as we come up with new ideas, the manufacturers will come up with the solutions.

Steve Fluker is director of engineering of Cox Radio, Orlando.