The dbx limiter audio object controls the input signal if signal level crosses threshold level. It operates as a RMS Limiter and Peak Limiter.
The below figure displays the panel for dbx Limiter from audio architect (Professional audio tuning and design tool).
The dbx limiter has an optional processing called Peakstop plus processor which further compresses the output signal from RMS limiter. It operates as an RMS limiter during normal operation and when you enable Peakstop plus parameter it acts as a peak limiter.
Use Case: This object can be deployed whenever an audio limiter needs to be introduced in an audio pipeline.
The Dbxlimiter algorithm performs the following operations on the input signal to achieve the signal limiting.
- RMS detection is performed on all channels (each channel has its own RMS detector).
- Any linked channels update their RMS info with the max of the linked channels’ RMS values.
- Compression logic is applied to the RMS values to modify them if in or above the knee.
- Attack/Hold/Release logic is applied to compute the final gain reduction amount (dB).
- The dB gains are converted to linear gains and applied to the audio signal.
- If active for this channel, PeakStop+ sample-wise limiting is applied to the audio signal.
dbxLimiter Properties
Below table describes about the dbx limiter audio object properties and functionality.
| Properties | Description |
| # of Channels | Enter the number of channels. The number of audio channels it can process is configurable in SFD and each channel has its own set of specifications.
The number of audio outputs is the same than the audio inputs. |
| Display Name | Display name of the dbxLimiter audio object in signal flow design. It can be changed based on the intended usage of the object. |
Mode
The dbxLimiter audio object doesn’t support any mode.
Additional Parameters
The dbxLimiter audio object doesn’t have any additional parameters.
Tuning Parameters
| Name | Description | Offset | Type | Unit | Default | Range |
| Threshold | Level of the dbx limiter activation. | 0 | float | dB | 0 | -60.0 to 0.0 |
| Attack time | Time needed to limit signal to the target value. | 4 | float | ms | 10 | 0.1 to 200 |
| Hold Time | Time for which the signal is “held” at threshold even though the input has fallen below threshold. | 8 | float | ms | 0 | 0.0 to 500 |
| Release | The rate at which the release process happens. Release is when the limiter stops compressing/limiting the signal. | 12 | float | dB/s* | 5 | 5.0 to 360.0 |
| Overeasy | The half width of smooth transition band around threshold point. | 16 | float | dB** | 0 | 0 to 100 |
| Peakstop Plus | When this flag is set, Peakstop+ processor gets enabled. | 20 | ULong | NULL | 0 | 0 to 1 |
| Overshoot | In Peak Mode, the output signal will not exceed the level set by overshoot. | 24 | float | dB | 2 | 2 to12 |
| Bypass | When this value is equal one the dbx limiter is transparent. | 28 | ULong | NULL | 0 | 0 to 1 |
| Automode Enable | When this value is equal to one, the dbx limiter algorithm sets the Attack, Hold, and Release parameters in real time based on the incoming signal | 32 | ULong | NULL | 0 | 0 to 1 |
| ChannelLinkId | This parameter indicates the channel that is linked to the current channel. The maximum RMS values of the current and the linked would be considered for the limiting | 36 | ULong | NULL | Channel number | 0 to 255 |
- *Due to the limitation in GTT the unit is kept as ms even though it is actually dB/s.
- **The range used in Audio Architect, the tool used by PRO audio uses a range of only 0 – 10 dB. However, this does not result in any noticeable quality difference to the audio. So, the range of Overeasy has been increased here to a wider range. This can however be changed later based on the requirements of the product teams.
Control Parameters
The dbxLimiter audio object doesn’t have any control parameters.
State Parameters
| Parameter Name | Data Type | Default Value | Range | Description |
| Threshold meter | Float | 0 | 0 to 2 | Indicates the level of the signal after compression |
Native Panel
The dbxLimiter audio object does not support native panel.