Viz Engine Administrator Guide

The volume level of Live Input Channels like SDI, IP or NDI as well as clip channels can be exposed to a Shared Memory Variable. This could be used, for example, to visualize a level meter of an input source.

Any change to the input level is written into a shared memory variable in the System.Map. The naming convention is the following:

AudioLevel.LiveIn0_0 for the first Live Input and the first channel.
AudioLevel.LiveIn0_1 for the first Live Input and the second channel.
AudioLevel.LiveIn1_0 for the second Live Input and the first channel.
AudioLevel.LiveIn1_1 for the second Live Input and the second channel.
AudioLevel.LiveIn5_63 for the sixth Live Input and the sixty fourth channel.
AudioLevel.ClipIn0_0 for the first Clip and the first channel.
etc....

To specify how often these values are updated, you can either specify a fixed value in the Viz configuration file:

############################
SECTION AUDIO_CONFIG
############################
 
## 0: No calculation of VU meter values at all (default), > 0: frequency of frames when calculation happens (every X frame(s)).
AudioLevelMeterUpdateInterval = 2

or you can send a command to change it during runtime:

MAIN*CONFIGURATION*AUDIO*LEVEL_METER_UPDATE_INTERVAL GET / SET

Information: A setting of 0 means to not send values anymore.

Note: That the value you receive is in decibel, which is a logarithmic value between -0 and -120.

A sample script to generate a volume meter:

dim mySrc as string
Sub OnSharedMemoryVariableChanged(map As SharedMemory, mapKey As String)
   dim tmp as array[string]
   dim normal_val as double
   If mapKey.StartsWith("AudioLevel") Then
      dim val = Cdbl(map[mapKey])
      normal_val = calculate(val)
      mapKey.Split("_",tmp)
      dim idx = cInt(tmp[-1])
      if ChildContainerCount >= idx then
           GetChildContainerByIndex(idx).scaling.y = normal_val
      end If
    End If
End Sub
 
function calculate(db as double) as double
    dim myval as double
    calculate = 10 ^(db/20.00)
end function
 
sub OnInitParameters()
    RegisterParameterString("source","Source","LIVE1",20,20,"")
end sub
 
Sub OnParameterChanged(parameterName As String)
    if parameterName = "source" Then
       if mySrc<>"" Then
          system.map.UnregisterChangedCallback("AudioLevel."&mySrc&"_0")
          system.map.UnregisterChangedCallback("AudioLevel."&mySrc&"_1")
       end If
    mySrc = GetParameterString("source")
    system.map.RegisterChangedCallback("AudioLevel."&mySrc&"_0")
    system.map.RegisterChangedCallback("AudioLevel."&mySrc&"_1")
    end If
end Sub

This script generates an input field, that specifies the source (for example, ClipIn0). Any change in the shared memory map for AudioLevel.Clip0_0 or AudioLevel.Clip0_1 (Stereo) is applied to y-scaling of two subcontainers: