HOME UDX - Advanced -> Delay

The Advanced → Delay menu allows the user to apply an additional delay to the app's media streams: video, audio and meta. It can be used to sync the output of the HOME UDX to other video sources on the network, or to deal with situations where, for example, the video arriving at the app is not synchronous to the audio.

Before explaining the available controls, it is useful to understand the inherent delay added by the HOME UDX itself, and when the additional delay may be useful.

Please note: If the Maximum Additional Delay in the app configuration is set to zero (0), then no additional delay is available and the Advanced → Delay menu is hidden.

Inherent Delay (App Latency)

Signals passing through a HOME UDX are subject to a delay due to the need to process the signals, this is known as latency. Even when there is no processing enabled, the signals are subject to a delay, due to the need to receiver and send the signals.

• The inherent delay through the UDX is 5 fields (interlaced sources) or 3 frames (progressive sources).

The HOME UDX has been carefully designed to ensure that all signals (video, audio and metadata) remain synchronous with each other. If a process has been applied to the video, for example, which causes additional latency, the audio and metadata streams are delayed to ensure they stay synchronous with the video.

Time-aligning Signals

Sometimes, there are external factors that can cause the one or more of the signals arriving at the UDX receiver to be asynchronous. For example, the video may have been processed by an external device which has added delay to the video, but not to the audio and metadata.

The HOME UDX offers a Delay function where the user is able to add additional delay to any of the receiver's streams individually, to aid realignment.

Additional Delay - Functionality

The inherent delay means that the video stream passing through the app will have a minimum delay of 5 fields (interlaced formats) or 3 frames (progressive formats). An additional delay can then be added of up to 16 fields / frames. Thus, the maximum video delay that can be applied is 21 fields / 19 frames.

By default, when a delay is applied to the video, the audio and meta streams are delayed by the same amount. Audio and/or meta streams can then be offset to the video if required. This offset can be either a positive or negative value.

• If the audio and meta streams have a offset delay of zero (0), they will be delayed by the same duration as the video stream.
• A positive value will add additional delay (stream arrives later) compared to the video stream.
• A negative value will reduce the delay (stream arrives earlier) compared to the video stream.

The table below shows the minimum and maximum delay values. For simplicity, the timings in milliseconds (ms) are rounded to 1 decimal place.

Configuration

To use the Delay function, there are two steps: first, define the maximum additional delay supported by the app; then, once the app is running, set the amount of additional delay (up to the maximum additional delay value).

Initial Configuration

As part of the app configuration, the user is asked to configure a Maximum Additional Delay value, up to 16 Fields / Frames. This sets the maximum additional delay supported by the app which, in turn, defines the amount of App Server memory used to buffer the app's incoming sources (once the app is running).

By setting the maximum additional delay to a lower value, the user can limit the amount of App Server memory reserved by the app. This can be advantageous as, when the user attempts to start the app, the system presents only App Servers with enough available resources and, if a maximum additional delay is specified, then this will include an amount of free memory.

Note that the Maximum Additional Delay control cannot be modified whilst the app is running. If you need to change this value later, then you will need to stop the app and edit the app configuration.

Runtime Controls

Once the app is running, the user can set the amount of additional delay to be applied, for each stream type, up to the Maximum Additional Delay value (defined in the app configuration).

Note that streams passing through the app are delayed by 3 frames (progressive sources) or 5 fields (interlaced sources), this is the minimum delay.

Beneath each control, the amount of delay being applied to that stream is displayed, which includes the inherent 3 frames /  5 fields.