Basic Concepts

QLab is designed around the principle of simple pieces. Through the organization of simple pieces you can achieve flexible, sophisticated designs.

Cues

Cues are the fundamental building blocks of QLab. They are an atomic unit of action. The particular action that a cue performs is determined by its type. For example, a Sound Cue will play a sound file, a Start Cue will start other cues, and a Stop Cue will stop other cues.

The set of available cue types is determined by what QLab Plugins were loaded when the application was launched.

The specific details of cue operations are described in the Cue documentation.

Cue lists

Cue lists are ordered collections of cues. All cues are in one and only one cue list. You may organize the order in which cues will be run by reordering their position in the cue list. Each cue list keeps track of its current playback position. Starting, or “firing”, a cue list advances this playback position. When the playback position reaches the end of the cue list, firing the cue list will cause no more actions until the playback position is reset.

Cue sequences

Understanding the behavior of cue sequences is centrally important to the effective use of QLab.

Every cue in QLab has a parameter called “autocontinue”. When a cue list is fired, the cue at the current playback position is started. If the autocontinue parameter of this cue is enabled, the subsequent cue is also fired. This process is repeated until a cue is reached for which autocontinue is disabled. A consecutive series of autocontinued cues is called a cue sequence.

Cue sequences are an important concept because they allow you to create a number of actions which will all occur after firing a cue list a single time. Conceptually, a cue sequence is like a series of dominoes: knocking over the first domino will cause all the dominoes to fall until a gap between dominoes is reached. Stopping any cue in the cue sequence is like introducing a gap into the series of dominoes; the playback of the sequence will halt at the stopped cue.

Playback position

Each cue list has only one playback position. You may select any cue in the list to make it the current playback position (including cues in the middle of a cue sequence). When a cue list is fired the playback position is automatically advanced to the beginning of the next sequence.

While a cue list has only one playback position, it may have many active cue sequences. In other words, many different series of dominoes may be falling within a cue list at any given time. Do not confuse the “currently falling domino” in a cue sequence with the playback position of the cue list.