Audio Delay

Audio and video arriving at inputs in sync maintain sync throughout the system to output or recording. However, you should note that upstream issues can cause video to arrive at system later than the corresponding sound. To mitigate this sort of external problem, the Audio Mixer provides an adjustable Audio Delay feature.

For example, many cameras support simultaneous digital and analog audio output. In-camera processing can delay digital A/V output, resulting in analog audio output actually leading the digital output by a meaningful measure.

Gain

On selected models, and usually for sources set to Mic input type, Gain knobs may appear in the Input Settings tab to allow you to compensate for microphone variances.

Pan

The Audio Configuration panel also provides Pan controls. Pan is a very useful feature; it adjusts placement of sound from source audio channels on the stereo channels comprising the audio mix(es). Using Pan, you can place all or part of channel 1 onto channel 2, and vice versa.

• When Pan is set to the extreme left position for channel 1, its audio is sent exclusively to the first channel for the Input 1 group.

• Centering the Pan 1 knob splits the sound from Input 1 equally onto channels 1 and 2.

• Sliding Pan for channel 1 fully clockwise results in that source only being audible on channel 2.

Pan also modulates the sound levels on the left and right channels so that the overall volume neither rises nor drops as a result of adjustments.

Equalizer

The seven-band equalizer allows you to shape sound to taste, accommodate sources with different acoustic characteristics (say, mismatched mics), minimize feedback or roll off unwanted parts of the audio spectrum.

Enable or disable the Equalizer using the switch beside the label above its control group. The vertical sliders attenuate or boost the tonal range centered on the frequency shown at the top. The effect applied falls off gradually as sound draws closer to neighboring frequencies on either side. Click Reset to return all sliders to 0dB.

Compressor Limiter

The Compressor/Limiter is capable of preventing clipping (see Output and Primary Bus Controls) from unexpected peaks or transients, and making talent sound better than they do in real life, bringing voices, music and other audio sources into an optimal dynamic range. Being able to do this independently for each output too is icing on the cake, especially for Internet streaming, as it ensures correct levels at any time.

Noise Gate

The Audio Mixer’s advanced options panel also include a configurable Noise Gate for each audio source, as well as all outputs. This lets you ensure that unwanted low-level sounds are prevented from inadvertently intruding into the mix.

Busses and Outputs

Consider a very basic audio mixer. Its main audio signal path, from input to output, is properly called the master bus. Sound supplied to one or more inputs is placed on this master bus (in the jargon of audio processing, this is called a send), which ultimately flows to output connectors.

Slightly more advanced mixers often provide more than one send for individual inputs. For example, the sound from all inputs may be sent to the master bus, comprising the master mix. A different mix, sometimes called a sub-mix, might also be created by sending certain signals to a secondary (auxiliary, or Aux) bus.

Let’s summarize what we have learned so far: A send pipes audio signals from an input to a discrete pathway called a bus. Multiple sends can be used to place sound from a given source onto one or more internal busses. What else should we know?

Each audio bus is discrete. Each can be directed along different output paths. And even when the blend of signals it carries is otherwise identical to another bus, it can be processed separately. Thus its levels, equalization, and compressor/limiter settings can be unique.

The Audio Mixer provides four primary audio busses. These are identified in the Audio Mixer as:

• MASTER

• AUX 1, 2 and 3

The Audio Mixer provides controls for each of these busses, allowing you to manage levels and signal processing. It is important to understand the distinction between busses and outputs. Now that we understand the former, let’s consider the latter.

An output may be physical, or virtual (it may involve a connector on the rear panel, or not). For example, audio recorded internally does not require an output connector. Likewise, it may initially be analog or digital.

Sub-Mixes and Mix Minus

At times you may require specially configured audio mixes. For instance – some installations call for sending audio from one or more internal sources (such as a DDR or the Sound player) to a secondary distribution system. Alternatively, you may want a clean output from one or more sources for use apart from the main output mix.

Specialized sub-mixes of this sort are often referred to as mix-minus, since one or more sources are deliberately subtracted from the mix. Mix-minus capabilities can be invaluable for productions like phone-in shows. The remote caller needs to be able to hear the interviewer. Yet - if you simply send the main mix back to him he is forced to endure a late-arriving echo of his own voice. Needless to say, this would be undesirable.

Suppose your interviewer is speaking into a microphone connected to channel 1 of Input 1. The audio from your remote interviewee is routed into Channel 2.

You could easily supply both to your Master bus for your program output needs, but remove channel 1 from Aux 1, and remove channel 2 from Aux 2 to provide mix minuses to send back to both parties.

This approach eliminates annoying echoing, feedback and the like. Meanwhile, both participants can be heard on the main Program output. Also important, independent control and signal processing is provided for each part of the pipeline.

Mix Minus for External Audio Devices

The Routing tab provides 8x8 matrix routing panels for each input, allowing for more sophisticated mixes than the example above. Viz Vectar supports eight channel NDI output, so it’s possible to route a unique mono mix-minus on each of these channels for an Aux bus. Thus, a single NDI a/v output stream can provide all of the mix-minus needed for up to eight external callers.

For clarity, let’s consider a slightly less demanding example. We’ll assume that you have configured Switcher inputs 13-16 to receive audio from four unique remote callers. We can use video MIX 2 to supply Program video to each caller (if the equipment supports video return). We configure AUX 1 as the Audio source for MIX 2, then assign a unique (mono) mix minus to four of its channels to supply return audio for each caller.

• In the Output Configuration panel, assign Aux 1 as the Audio source for MIX 2.

• In the Audio Mixer, open the audio configuration pane for Input 13.

• Access the Routing tab and click the Clear button above the Aux 1 routing matrix.

  

• Check channels 2, 3 and 4 in the column below In 1. This routes sound from the first incoming caller to all Aux 1 output channels except channel 1.

• Open the audio configuration pane Input 14 and, in the Routing tab, clear the Aux 1 matrix.

  

• This time, check channels 1, 3 and 4 in the column below In 1. This routes sound from the second incoming Skype caller to all Aux 1 output channels except channel 2.

• Repeat the steps above for audio inputs 15 and 16, omitting the Aux 1 checkmarks under In 1 for channels 3 and 4, respectively.

That’s it – you’ve got the perfect mix minus configuration for return to four callers, using a single NDI output.