The Omnia XII includes an integrated failover engine for switching to your backup system audio (fallback mix) when the preferred mix is not detected.
Configuration includes defining the operational hierarchy between your Preferred Mix and your Fallback Mix. (See Setting up Emergency Playout). In this architecture, the processor uses an advance silence detector to automatically manage your primary and secondary internal audio states.
The Omnia XII failover circuit decides which mix is on-air at any time. The failover occurs between mixes, not inputs. If the level of the preferred mix goes below the set Detect Level for longer than the Trigger Time, then a failover occurs, and the fallback mix is put on air. The failover also occurs if the preferred mix's level drops below the fallback mix's level by more than the Detect Relative Level. This is by design, to support when both mixes carry the same program). Once the primary mix is restored for longer than Return Time, it is put back on-air.
The levels of each of the inputs in each of the mixes are set by the faders in the Preferred Mix and Fallback Mix blocks. Audio corrections to the individual input signals, such as flipping the polarity, swapping the stereo channels, or correcting a level mismatch between the channels, are performed in the Inputs block.
To configure failover audio:
Click the Failover tab in the middle panel of the input controls on the FM/HD Processing page.
Set the Input Mode.
Preferred Only: When a failover occurs, the Preferred Mix remains in use.
Fallback Only: When a failover occurs, the Fallback Mix remains in use.
Failover: When a failover occurs, the system switches from the Preferred Mix to the Fallback Mix.
When set to Failover, the Omnia automatic failover feature is enabled, such that the unit will switch from the preferred mix to the fallback mix when the preferred mix is not detected. The mode can be set to Preferred Only or Fallback Only, to always use one of those respective mixes only.
Set the Trigger Time.
When Failover is enabled, this is the amount of time that will elapse after the failure of audio on the preferred mix before the unit switches to the fallback mix.
For instance, if time is set for 5 seconds and the primary audio source fails, five seconds later the unit will switch to the secondary audio input if that input is active.
Set the Return Time.
This is the amount of time for the fallback mix to continue after the preferred mix is restored and the unit switches back to the preferred mix.
Set the Detect Level.
This sets the absolute silence threshold in dB for the main silence detector. Audio falling below this level is treated as dead air. A recommended baseline is -35 dB to -40 dB. The default is -50 dB. Setting this level too high (for example, - 25 dB) may trigger a failover during quiet speech. Setting this level too low (for example, -60 dB) risks treating background line hiss or studio mic-belle as a valid program signal, keeping a broken link on-air.
Set the Detect Relative Level.
This controls the differential threshold between your operational audio channel levels. It protects against stereo balance and phase protection or side-channel integrity failover. If one side of your stereo pair drops significantly compared to the other, or if a severe phase inversion drops your relative mono sum, this relative detector trips the failover logic even if the absolute dB meters are technically seeing line level.
Failover Considerations
In rare cases, a failover can occur when it should not. This can happen when all of these conditions are present:
1) The valid program audio (the preferred mix input) has one channel silent (or very quiet) for more than the failover trigger time. This occurs in some songs by The Who (and probably The Beatles).
2) The fallback mix input has audio on both channels and the audio is not the same program as the preferred mix.
The comparative failover function looks at both the primary and secondary inputs simultaneously. If the secondary input looks better than the primary (it has both channels while the primary has only one, or it is a lot louder), then it switches to the secondary. The switch when ON takes place after the condition of the secondary being better has persisted for more than the failover time.
The OFF mode failover mechanism is "absolute failover", where it is just looking at the absolute level of the primary input. This mechanism will not react to loss of just one channel. There may be cases where single-channel audio for a while is valid, but if the secondary input has both channels driven, it is more likely the valid signal, and the primary is in error.
Recommendation: If you are feeding the same program to both the primary and secondary inputs, leave this set to ON. If there is a different program on the secondary input, turn it OFF. (It only makes sense to compare the two inputs if they are supposed to have the same thing to begin with).