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Viz Engine Administrator Guide

Version 5.0 | Published December 20, 2022 ©

Shared Memory Integration of Channel Volume Levels

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:
images/download/thumbnails/92971044/image2022-3-9_16-33-26.png

images/download/attachments/92971044/image2022-3-9_16-39-26.png