A Look at the AVL Signal Chain

If you asked someone what industry HARMAN Professional Solutions participated in, they would probably say “professional AV.” This is true enough, as far as it goes, but the term “AV” doesn’t really capture everything that is involved. In reality, “professional AV” actually involves audio, video, lighting, control and management technology—a wide breadth of solutions that are related, but for whatever reason are often considered separate, if interconnected things.

The development of the term “AV” is understandable. Historically, you had your audio system with your mics and amps and speakers, and you had your video system with your source devices and your displays. Lighting was added first in the performance arena, and it then expanded to installation lighting as well. Eventually control was integrated, giving the ability to centralize the control of all of the devices and even automate them. Finally, as installed systems became more sophisticated and enterprise networks became the central information hub, building-wide (or even organization-wide) management of AV systems became standard.

Today, we see AV and lighting being utilized in ways and places that push the limits even more. From giant sports stadiums and theme parks to hotels and churches to evermore technology-enabled schools, office spaces and government facilities, one trend is clear: the boundaries between previous categories are blurring.

The problem is that most people never got away from the term “AV,” with lighting as an add-on and control and management as afterthoughts. We as an industry never shifted from thinking of AV (or, more properly AVL) solutions as three separate systems. Each solution was designed separately, installed separately and controlled separately, with different devices from different manufacturers pieced together by whichever designer was working on the project at the time.

Instead, we should look at AVL as a single, interconnected system that transmits audio and video from source to destination, ties into lighting and is controlled with user interfaces and automation. This is ultimately what users are really looking for: the cohesive experience that the combined systems deliver.

So, let’s look at the AVL system, starting with audio and video sources. A “source” in this context could be a variety of things. It could be something that captures real-life audio or video, such as a microphone or a camera. It could also be an audio or video recording. It could even be an electronically-generated audio or video signal—meaning audio from a keyboard or a video image from a PC running PowerPoint. Some of these devices only output audio, some only output video and some output both. However, all of it ends up in the AVL system.

Once in the system, the audio and video goes through processing. This step ensures that the audio and video signals are optimized and ready for output. This can happen at the beginning or end of the process (or both).

Audio processing is performed using technology called digital signal processing (or DSP). The DSP takes the raw sound from microphones and instruments and processes it to sound its best. It also mixes multiple signals together, providing a single output sound for the speakers. Finally, it optimizes audio outputs to sound great in each and every room. Audio processing includes a variety of different things, but can generally be broke down into audio mixing (mic mixing, ducking, etc.), level adjustment (compressors, limiters, gates, etc.), equalization (graphic, parametric, etc.), and delay (echo, delay, reverb, chorus, etc.). There is also echo cancellation, noise cancellation and a variety of other effects as well.

Video signals also go through processing. Video sources, due to a number of different factors, often output different specialized resolutions or amounts of detail that may not match the optimal specifications of the various displays in the system. The goal of video scaling, then, is to optimize the signal for each display while also allowing the video to be as close to the source signal as possible. The video source outputs at their highest possible resolution. Scaling then adjusts the signal to match the optimal output resolution for every individual display. This scaling accounts for resolution, aspect ratio, frame rate, color space, interlacing, and a variety of other things.

Lighting also has a processing phase. In this step, the lighting designer lays out all of the LED fixtures in the installation. The LED video processor then takes the source video signal, breaks it down and maps individual pixels from the video signal to individual LED diodes in the various fixtures. This allows the video source signal to stretch and be displayed across the entire installation.

Of course, in order for the LED video lighting signals to reach the lighting fixtures (or for the audio and video signals to reach their final output destinations), the signals need to be distributed. While there have been changes throughout the AVL signal chain in recent years, one of the largest shifts for AVL is in the area of distribution. Historically, AVL distribution was performed using dedicated, specially-designed hardware with proprietary architecture. However, today, AVL signals are increasingly deployed over the network. Network distribution of audio, video and lighting signals allows for infinite flexibility using standardized hardware and topologies, and also provides scalability across a facility, campus or the world.

The final stage of the AVL signal chain is output. Audio signals are routed to amplifiers, which boost the signal for output by the speakers. Video signals are routed to displays, such as televisions or projectors, with audio signals typically routed to the displays as well. Lighting signals are obviously routed to LED video lighting fixtures. Of course, there are also architectural lighting fixtures, such as washesgobos and creative moving effects, but these don’t receive signals from AVL distribution, so we can just think of them as self-contained output devices.

As you might have noticed, I have left out an important point: control. After all, an AVL system doesn’t work without someone telling it what to do. This can come either in the form of manual control performed by an operator or through automation. Truly effective systems often combine some form of both. Manual control requires some sort of user interface, with the type of interface designed to meet the unique tasks of the operator. Audio is typically controlled using either a soundboard or some sort of wall controller. For video, control is performed using a keypad or a touch panel. For lighting, it’s a lighting console. Control for the AVL system can even be combined, with audio, video and lighting control all performed using a single interface.

For solutions that don’t need manual control of parts of the AVL system, automation is available to simplify the process. Audio mixing, for example, can be performed by the DSP, responding to volume levels on the attached microphones. Video switching can do the same, with the video matrix switching to an input when it detects that there is a device—such as a portable laptop—connected to that cable. Multiple actions can even be combined together, with the AVL system responding automatically to a single button press on an interface or to some situation in the room itself.

This is the AVL system. All of the parts come together and work together seamlessly, especially when the system is designed to work efficiently together. HARMAN Professional Solutions is actually the largest audio, video, lighting and control manufacturer in the world. We deliver more solutions for more parts of the AVL signal chain for more vertical markets than anyone else, and the result is a wide range of truly integrated AVL solutions using best-in-breed products for the whole signal chain. Our product portfolio has a breadth and a depth that allows system designers to put together solutions that interoperate smoother and perform better. Historically, designers were left to mix and match components from dozens of manufacturers—resulting in a variety of system functionality and reliability issues. While this has been a necessary evil for a long time, the growth of HARMAN into the world’s largest audio, video, lighting and control manufacturer has provided another choice.

Have a question on how audio, video, lighting and control work together? Ask your questions in the comments.

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  1. Ted Striker

    I have an old Crown line 2 amp, and the same type preamp. Surprisingly it has a lot of clean power. My problem is the preamp isn’t working! I could use help finding a PowerLine 2 preamp, but I doubt I could.
    Thank you for all I have learned from your articles.

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