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VDOM_terminology.md

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Media Sequence Engine Terminology

A set of definitions of terms found in or related to the Media Sequencer Engine (MSE) Virtual Document Object Model (VDOM) tree structure. These are scoped to fit with the way MSE will be used in the first application of this library.

Definition in no particular order (yet!).

View a VDOM tree

The VDOM tree can be viewed and manually editted on any instance of MSE at:

http://mse-host.address.or.ip:8580/app/vdomconfig/vdomconfig.html

Note that the web application must have access to port 8595 for websocket traffic.

Show

/storage/shows/{<uuid>}

As originally intended, a show would be the daily ten o'clock news and contains all the templates that can be used in that show.

An alternative view show can also be used as a larger and more general collection of templates that can be used across several shows, e.g. all news shows done from a particular studio. In this approach, the collection of templates containing a superset of all possible graphical elements for every show of a certain kind, e.g. sports news from studio 3.

A new show may be created for a special event, such as a general election or the Olympics.

Shows and templates are created in MSE via Vizrt Trio.

Template

Shows have elements, master templates and scene information, referred to as the show templates.

Templates are allocated to layers. Each layer has an out template that clear any graphics on that layer. A special template called All_OUT is used to clear all layers and it is recommended that this template is taken at the end of every story. This ensures that the Viz Engine is reset.

Note that, confusingly, this term does not refer to path /storage/templates.

Playlist

/storage/playlists/{<uuid>}

A specific show at a specific date and time has its own playlist. An automation systems must build a playlist before each run of the show. The playlist contains the elements that can be taken within the show. Complex elements (e.g. fullscreens) and elements that are stored externally in the pilot database must be pre-built before the show.

Handlers

/scheduler/<engine_name>

Each Viz Engine has a handler that is a representation of state of that device. This includes the ability to check what (the MSE thinks) the engine is displaying. An automation systems has to create the handlers it intends to use on initialisation, including hostname.

A studio may be configured with more than one Viz Engine. This can be used to:

  • Separate broadcast feed graphics from video walls or other displays;
  • Provide different variants of graphics for different target platforms, for example one for HD TV and one for viewing the stream on a mobile phone.

Profile

/config/profiles/<profile_name>

A profile groups together all the handlers used by a playlist. Typically, an automation system creates itself a single profile within the MSE with its own name, e.g. SOFIE. Commands to take elements are sent via profiles.

Elements

/storage/shows/{<uuid>}/elements/<element_name>
	/storage/playlists/{<uuid>}/elements/<ref_id>
	/external/pilotdb/elements/<element_key>

Elements are the specification of an instance of a master template created by providing the data. For example, a lower third element (bund) contains:

  • a reference to the lower third master template;
  • the name and title fields to be displayed.

Elements can be internal or external.

  • An external element is held in a system called Vizrt Pilot and is completely specified and managed from there, including its template. Pilot is used for large and complex graphical elements. External elements are used for fullscreen graphics and data-rich graphics that can update. Note that in current workflows, the right arrow key is used to navigate between each part of the graphics (continue command).

  • An internal element has its template and data stored within the MSE. Typically, these are used for simple overlays. It is good practice to create a separate element within a show for each instance that is to be used. This allows the elements to be initialized and taken without delay.

(Bad practice would be to create one lower thirds element and keep updating it.)

Commands

POST /config/profile/<profile_name>/<command>

Commands cause the Viz Engine to perform actions, including:

  • take - Show a given graphical element, animating in. This can also be used to update the data in a graphic and, if and only if the data has changed, will run the animation again.
  • out - Hide a graphic, causing the out animation to run.
  • update - Update the contents of a graphic without any animation - not really used.
  • continue - Move to the next state for the graphic. Used for complex fullscreens and controlled by pressing the right arrow key in Mosart. (Also continue_reverse.)
  • cut - cut short a graphic without animating out - not used.
  • initialize, cue, prepare - to be explored.

Initialize and clean commands are available for playlists and shows. These need further investigation.

The body of a command message contains the VDOM path reference to the element that the action is to target.

Layers

Master templates contain layers.

Channels

tbc

Pages

A page is a kind of Trio template. These can be used as a form stylesheet, setting colours and other parameters used in subsequent elements. (tbc)