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Compressor

(See the Compressor properties below.)

The Compressor plug-in reduces the dynamic range of a signal by weakening any part of the input signal that is above a pre-defined threshold value. When the signal is loud and above the threshold, the Compressor begins to reduce the signal's gain. When the signal is softer or lower than the threshold value, no gain reduction is applied to the signal.

A ratio factor determines the extent of the dynamic compression when the input is above the threshold. For example, a ratio of 4 means that for every 4 dB the input signal is over the threshold, only 1 dB will be observed in the output signal.

To provide smooth transitions between the areas of gain reduction and no gain reduction, you can specify times for the attack and release properties. The attack time is the time it takes for the gain to be reduced. The release time is the time it takes for the signal to return to normal levels, where gain reduction is no longer applied.

The Compressor plug-in contains a series of properties, many of which can be edited in real-time and can be mapped to specific Game Parameters using RTPCs.

You can use the Compressor plug-in to create a variety of different effects. For example, you could simulate radio communication between game characters by routing a white noise sound and different voice sounds to the same bus and then applying a Compressor Effect on the bus. The compressor properties can be set so that the white noise will increase between gaps in words or phrases and decrease as soon as a voice is heard.

[Caution]Caution

Sounds with a DC offset may alter the results of the compression effect. Make sure to remove the DC offset before applying the Compressor Effect in Wwise.


[Note]Note

The following are some general remarks on Wwise dynamic processing plug-ins:

  • There is no interpolation of ratio control (RTPC parameter) for Compressor, Expander, or Peak Limiter. Changing this parameter during playback may lead to signal discontinuities on very clean signals.

  • Sounds with DC offset may alter results of compression/expansion because the sidechain detection algorithm will be offset considerably. DC offset should be removed prior to use in Wwise.

  • The Compressor, Expander, and Peak limiter are non-linear audio processes. This means that order of processing is important. For example, results will be different if you apply gain before or after the Effect.

  • For the first audio buffers, the processing algorithms are said to be in non-steady state. Because the estimated signal power operated by the side chain has no knowledge of the past, its estimate of signal power may be erroneous for a short period of time (but only if the Compressor is already engaged at the start of the sound). A solution to this (if it's a problem at all) is to start the Compressor with a ratio of 1 and shortly after bring it to the desired value.

  • If the Compressor applies some gain reduction and is suddenly bypassed, a signal discontinuity will be heard. A potential solution is to gradually bring the ratio to 1 prior to bypassing the Effect.

Using Compressor on an Audio Objects bus

Applying a linear Effect, such as the Parametric EQ, to multiple Audio Objects independently is identical to applying it once to a downmix of those objects. Typically, this is not the case with non-linear Effects, such as compression or expansion. However, the Compressor plug-in is a special type of Effect, called an Object Processor. When the Compressor plug-in is inserted on an Audio Objects bus, the result is as follows:

  • The Effect is instantiated only once per bus instance, regardless of how many Audio Objects are routed to the bus.

  • It achieves the compression of multiple Audio Objects together by working on an internal downmix, all while preserving the individual Audio Objects (that is, without mixing them down).

  • The gain reduction is common to all Audio Objects.

  • Compression occurs implicitly in Channel Linked mode. Consequently, the Channel Link option is ignored.

Refer to Using Effects with Audio Objects for further details.

Compressor properties

Interface Element

Description

Name

The name of the Effect instance.

Effect instances are a group of effect property settings. They can be one of two types: custom instances or ShareSets. Custom instances can be used by only one object, whereas ShareSets can be shared across several objects.

(Object Color)

Displays the object's color. Clicking the icon opens the color selector.

Select a color to apply it to the object. When you choose a color for an object, a palette icon appears on the selected square, as well as a yellow triangle in the lower-right corner, as shown.

To inherit the parent object's color, select the square at the far left of the color selector.

Inclusion

Determines whether the element is included in the SoundBanks when they are generated. When selected, the element is included. When unselected, the element is not included.

To optimize your sound design for each platform, you might want to exclude certain elements on certain platforms. By default, this check box applies across all platforms. Use the Link indicator to the left of the check box to unlink the element. Then you can customize the state of the check box per platform.

When this option is unselected, the property and behavior options in the editor become unavailable.

Default value: true

(Show references)

Indicates the number of elements in your project that contain direct references to the object. The icon is displayed in orange when references to the object exist, and in gray when no references exist.

Selecting the button opens the Reference View with the object's name in the References to: field.

Notes

Additional information about the Effect.

Metering

Indicates the name of the object currently being metered.

Allows you to browse for other objects to meter.

[Note]Note

The metering interface elements only appear in the Effect Editor for Effects that include VU meters.

Sets the display of the Effect Editor's selected tabs. By default, there is one panel displaying only one selected tab. You can, however, click a splitter button to split the panel into two, either side by side or one on top of the other, for two different tabs. The currently selected option is highlighted with a background color.

[Note]Note

You cannot display the same tab in both panels. If you select the tab that is currently displayed in the other panel, then the other panel will automatically display another tab.

Threshold

The level of the input signal above which the compressor will begin to apply gain reduction.

Default value: 0

Range: -96.3 to 0

Ratio

The relationship between the input signal and the output signal above a threshold value. This value defines the slope of the output signal above the threshold.

A ratio of 4:1 indicates that for every 4 dB the input signal is above the threshold, only 1 dB will be included in the output signal.

Default value: 10

Range: 1 to 50

Attack time

The amount of time it takes the Compressor to apply the gain reduction as the input level rises above the threshold.

[Note]Note

If the Attack time is set to 0, then there is no output.

Default value: 0.1

Range: 0 to 2

Units: s

Release Time

The amount of time it takes the Compressor to remove the gain reduction as the input level falls below the threshold.

Default value: 0.1

Range: 0 to 2

Units: s

Output Gain

The amount of gain applied to the output signal after the dynamic compression that makes up for potential gain losses.

Default value: 0

Range: -24 to 24

Units: dB

Process LFE

Determines whether the Effect is processed in the LFE channel or not. When selected, the Effect is processed in the LFE channel. When unselected, the LFE channel will be unaffected.

Default value: true

Channel Link

Applies the same gain reduction to all channels. This is implemented by taking the RMS power in the signal of all channels. The threshold is set by scaling the power in dB for the number of channels that are linked.

If this option is not selected, no information is shared between channels, and the Effect is applied on a per-channel basis.

This option is ignored when running on an Object-Based configuration.

Default value: true

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