This article outlines how to synchronise multiple screens so that images and videos in a sequence start displaying at the same time.
Enable playback synchronisation
To synchronise multiple screens so that they maintain the same position in a sequence, playback synchronisation must be enabled in sequence settings. To do this:
- Open the Sequence dialog.
- Select the Advanced tab.
- Select the Sync tab.
- Click Synchronise playback with local devices.
When playback synchronisation is enabled, devices will broadcast a slot number and time schedule for a synchronised sequence to progress to the next slot. This ensures that all screens connected to the same sequence display the same slot number.
Alternate content for video walls
Playback synchronisation can be extended to start displaying different items (with the same duration) on different screens at the same time. This opens up new possibilities to construct video walls.
For example, a 2x2 arrangement of screens and devices can be erected to form a large videowall. Different content can be uploaded for each screen to build a complete image.
There are two ways of configuring alternate content to display while maintaining synchronisation: One method uses a base sequence and custom sequences stacked on top (1 for each screen). The other method uses a single sequence with conditions to select the desired content.
Using base sequences
A base sequence makes it easy to define a common sequence containing default items that will synchronise playback across many screens.
For each screen, a custom sequence is created that uses the shared base sequence. The custom sequence is applied to the screen.
To add alternative content for a screen, the corresponding custom sequence is updated to include the alternative content. This will override content in the shared base.
Conditions can be used if it is more convenient to only manage a single sequence containing all the content destined for all the screens.
For example consider a video wall of 2 screens positioned side by side.
- Add identifying data to each screen to use in conditions. For this example, one screen could contain screenPosition=left and the other could contain screenPosition=right in the screen data.
- In each slot of the sequence, stack two items. One item for the left screen, another for the right.
- For each item add a condition to ensure it displays on the correct screen. For this example, items to display on the left screen would use the following condition: screenPosition == "left"
- Playback synchronisation does not take effect until all resources in the sequence have downloaded.
- A slot must contain at least one item to display.
- All items in a slot must have the same duration.
- Do not configure conditions that result in a screen having a different loop duration.
- Do not configure events that will interrupt playback synchronisation.
Technical note: There is no master device controlling the timing. All devices broadcast planned sequence progression information and the most recent received broadcast is used by all devices displaying the same sequence.