Posted on by Debanka

Matrix Mixer

The Matrix Mixer audio object is used to calculate weighted output audio based on a combination of input audio. In addition to this, the object also supports delay of input channels.

Use Case: The Matrix Mixer takes in a configurable number of input and output channels. Each output of this object is a weighted sum of all the input channels. Any input can get summed into any output with or without a delay.

Matrix Mixer Properties

Below table describes about the Matrix Mixer audio object properties and functionality.

Properties Description
# of Audio In Number of input channels.

  • Range: 1 to 254
  • Default: 2
# of Audio Out Number of output channels.

  • Range: 1 to 254
  • Default: 2
Display Name Display the name of the Matrix Mixer audio object in signal flow design. It can be changed based on the intended usage of the object.
Object Mode Matrix Mixer object operates in one of the following two modes.

  • Linear
  • dB

This object supports DelayMatrixMixer function.

Mode

The Matrix Mixer object supports two different modes of operation.

Mode Description
Linear (Default) In this mode, the gain values (channel weights) are configurable on a linear scale in the range -10 to +10.
dB In this mode, the gain values are configurable in decibels in the range between -128 dB to 20 dB and these decibel values are converted to linear values by xAF by the formula given below before multiplying with input channel samples.

Gain = 10gain_db/20 

Additional Parameters

The Matrix Mixer audio object can be configured with the following additional parameter:

Parameter Descriptions
No Ramp = 0,

Ramp with mute cycle = 1,

Ramp without mute cycle = 2

 The mixer also has three ramping types that can be configured through an additional number of parameters:

  • No Ramp: This exposes variables for each input and output in the GTT for tuning purposes.
    No Ramp is the default configuration.
  • Ramp With Mute Cycle: In this mode, first audio outputs are ramped down and then a new coefficient is applied to ramp up with the new coefficients (i.e. a complete mute cycle). The time taken to ramp from the old to the new coefficients is tunable from GTT. The ramp time can be set in milliseconds. Presently, the object supports only linear ramping in this mode.
  • Ramp without mute cycle: This mode supports ramping. Ramp up or down is decided based on the difference between current gain and old gain. Based on ramp shape and ramp time delta is calculated and ramping is applied towards new coefficient (i.e. ramping without mute cycle). The time taken to ramp from old to new coefficients and ramping shape are tunable from GTT.
    The ramp time can be set in milliseconds, for every millisecond there would be a dB change. It supports three types of ramping shapes.

    • Linear
    • Exponential
    • Jump (No ramping)

In the SFD, you can set the number of input and output channels. These channels do not need to be identical. The mode and ramping type are also configurable in the SFD.

In the GTT, the Matrix Mixer exposes variables for tuning, for each input and output channel. You can modify these to change the weights used to scale the input channels. In the ramp modes, additional ramp time and control variables are exposed as explained above
Single Subblock Tuning The object has an additional configuration variable “Single Subblock Tuning” to enable or disable it. On enabling it, allows contiguous memory allocation and the gain values can be tuned as single subblock.

By Default, Single Subblock Tuning is disabled.
Max Delay

The object has an additional configuration variable “Max Delay”.

  • If the “Max Delay” set to 0, then it functions as the legacy Matrix Mixer audio object.
  • If the value of “Max Delay” is greater than 0, then it functions as a DelayMatrixMixer.

Range: The value ranges from 0 to 500000 samples.

By default, it is set to 0 samples.

Ramp with mute cycle and Ramp without mute cycle types are not supported when Max delay is greater than 0.

There is no native panel for DelayMatrixMixer

Tuning Parameters

The GTT can read or write into parameter memory using tuning command respectively. The memory stores a value per output channel that has a gain value to be multiplied by per input channel based on the mode. These parameters are tunable. Assuming the object is composed of NIn input channel and Nout output channels, the description will look as follows (depending on gain type).

For No Ramp mode

Parameter memory for “No Ramp” mode with Linear Gain

Linear Gain
Sub-block ID

(Single Subblock tuning : Disabled)

 Sub-block ID

(Single Subblock tuning : Enabled)

 Name Type Unit Min Max Default Value Description
0 0 float -10 10 0 NIn gain inputs for Ch0 output
1 0 NIn gain inputs for Ch1 output
… 0 …
Nout-1 0 NIn gain inputs for ChNout-1 output

 Parameter memory for “No Ramp” mode with Logarithmic Gain

Logarithmic Gain
Sub-block ID

(Single Subblock tuning : Disabled)

 Sub-block ID

(Single Subblock tuning : Enabled)

 Name Type Unit Min Max Default Value Description
0 0 float dB -128 dB 20 dB -128 dB NIn gain inputs for Ch0 output
1 0 NIn gain inputs for Ch1 output
… 0 …
Nout-1 0 NIn gain inputs for ChNout-1 output

For Ramp with mute cycle mode

It has an additional ramp time configurable parameter.

Parameter memory for “Ramp with mute cycle” mode ramping with Linear Gain

Linear Gain
Sub-block ID

(Single Subblock tuning : Disabled)

 Sub-block ID

(Single Subblock tuning : Enabled)

 Name Type Unit Min Max Default Value Description
0 0 float -10 10 0 NIn gain inputs for Ch0 output
1 0 NIn gain inputs for Ch1 output
… 0 …
Nout-1 0 NIn gain inputs for ChNout-1 output
Nout 1 Ramp Time float ms 0 5000 500 The time it takes for the ramp to complete. This value is split in half between muting and unmuting stages of the output signal.

Parameter memory for “Ramp with mute cycle” mode ramping with Logarithmic Gain

Logarithmic Gain
Sub-block ID

(Single Subblock tuning : Disabled)

 Sub-block ID

(Single Subblock tuning : Enabled)

 Name Type Unit Min Max. Default Value Description
0 0 float dB -128 dB 20 dB -128 dB NIn gain inputs for Ch0 output
1 0 NIn gain inputs for Ch1 output
… 0 …
Nout-1 0 NIn gain inputs for ChNout-1 output
Nout 1 Ramp Time float ms 0 5000 500 The time it takes for the ramp to complete. This value is split in half between muting and unmuting stages of the output signal.

For “Rampwithout mute cycle” mode

It has an additional ramp characteristics parameters which are ramp down time, ramp up time, ramp down shape and ramp up shape.

Parameter memory for “Ramp without mute cycle” mode ramping with Linear Gain

Linear gain
Sub-block ID

(Single Subblock tuning : Disabled)

 Sub-block ID

(Single Subblock tuning : Enabled)

 Name Type Unit Min Max Default Value Description
0 0 float -10 10 0 NIn gain inputs for Ch0 output
1 0 NIn gain inputs for Ch1 output
… 0 …
Nout-1 0 NIn gain inputs for ChNout-1 output
Nout 1 Ramp down Time float ms 0 5000 500 The time it takes for the ramp to complete.
Nout 1 Ramp up time float ms 0 5000 500 The time it takes for the ramp to complete.
Nout 1 Ramp down shape Int 0 2 1 Ramping shape, it can be jump (0), linear (1) and exponential (2).
Nout 1 Ramp up shape int 0 2 1 Ramping shape, it can be jump (0), linear (1) and exponential (2).

Parameter memory for “Ramp without mute cycle” mode ramping with Logarithmic Gain

Logarithmic Gain
Sub-block ID

(Single Subblock tuning : Disabled)

 Sub-block ID

(Single Subblock tuning : Enabled)

 Name Type Unit Min Max Default Value Description
0 0 float dB -128 dB 20 dB -128 dB NIn gain inputs for Ch0 output
1 0 NIn gain inputs for Ch1 output
… 0 …
Nout-1 0 NIn gain inputs for ChNout-1 output
Nout 1 Ramp down time float ms 0 5000 500 The time it takes for the ramp to complete
Nout 1 Ramp up time float ms 0 5000 500 The time it takes for the ramp to complete
Nout 1 Ramp down shape int 0 2 1 Ramping shape, it can be jump (0), linear (1) and exponential (2).
Nout 1 Ramp up shape int 0 2 1 Ramping shape, it can be jump (0), linear (1) and exponential (2).

DelayMatrixMixer

The object functions as DelayMatrixMixer with Delay Pool when the additional configuration variable “Max Delay “ is set to more than 0 samples. A “Delay” tuning parameter is added in addition to the gain parameter for each input channel. The delay buffer (of length Max Delay) is shared by all the channels. Therefore, the available delay for each channel depends on the delay values configured for the other channels. The input channels are multiplied with the channel weights and are applied with delay configured and summed at the output channel. 

Parameter Description Range Default
Delay Delay to be applied across each channel. 0 to Max Delay(samples) 0
Gain Gain to be applied across each channel Linear : -10 to +10

dB : -128 dB to 20 dB

 Linear : 0

dB : -128 dB

Control Interface

There are no control parameters available for Matrix Mixer audio object.