Datashow is an application to display lyrics or other texts in a projector, intended to be used in church's services. It is designed to be simple, flexible and quick to operate

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Functional Specification Draft


Datashow is an application to display lyrics or other texts in a projector, intended to be used in church's services. It have been designed to be simple, flexible and quick to operate.

It runs in any standard Windows PC and supports usign multiple monitors, using a video capture device for showing live video and projecting the text over the live video.

It uses format templates for determinating how some content should be presented, so the user can focus in the content to be presented. This reduces the time needed to prepare a new item to be presented.

Datashow is free software and is available under the terms of GNU General Public License (GPL).

The Three Video Outputs

Datashow can use up to three video outputs, as shown below

Figure 1: The first video output is used by the user to control the application.

Through this first video output the user is able to control what is shown in the other displays, manage the itens in the order of service, edit the text for some item (such as lyrics or the bible verses) or create alerts (for nursery or parking, for example).

Figure 2: The second video output is projected to the congregation.

The second video output is shown to the congregation. It can be composed by live video, text (such as lyrics) and alerts. It is designed for showing pretty graphics, overlaying text and images over live video.

This lead us to a problem. For the public it is good to see live video with only two lines of fancy text each time. But for the musicans or the choir is better to have big text, with high contrast and with the text of the next slide too.

The third video output shows the text with high contrast and big font. It is intended to be shown in monitors for feedback for the musicans. It also include a clock.

Figure 3: The third video output is optional and is used to provide feedback for the choir

Displaying Text

Datashow manages separately the text contents and the text formating. The text contents are managed by the itens of the order of service and the formating by the templates

Itens of the Order of Service

Each text that will be presented is a item in the Order of Service. Examples of itens are lyrics, biblical text, annoucements or prayer requests.

A item of the Order of Service consists in:

The content does not support formating. All formating rules are defined in the template. The content is typed in text-only format, using a blank line for separating each block of text (slides). It can also import or export itens of the service order from/to text files (.txt).

Figure 4: Editing a item in the order of service


The formating rules for displaying text are defined by the templates. Each template defines:

This creates a very flexible mechanism for displaying texts.

In the main output three images are overlayed:

The Figure 5 shows an example of the use of the layers. The light green on the templates are replaced by transparent. In the example, live video is being presented simultaneously with the lyrics (Shout to the Lord!) and with a nursery alert (calling mom with card number 05). Note that the formatting rules for the text are defined in the template, so for displaying a new alert the operator just type the text, without caring about formating or positioning it.

Figure 5: The three layers and the output

Samuel Mello 2005-10-17 Logo