How to add Triggers and Cue Points to a player
An useful feature for DJ applications is the ability to setup Triggers and/or Cue points that will generate one or more events when a predefined position is reached: the main difference between a trigger and a cue point is the fact that a trigger is identified though a unique identification number (for example 0, 1, 2, 1000, 2000, etc.) while a cue point is identified by a mnemonic string of characters containing a custom name (for example "intro start", "mainpart start", "refrain start", etc.): obviously you are free to define your own set of triggers and of cue points identifiers.
You can add as many Triggers and Cue Points you need to a given player using a set of predefined methods.
Triggers
Each time you create a trigger using the
TriggersAdd or
TriggersAddPerc methods, you must provide a
unique identification number that will be used in order to identify the trigger at a later time: each time a trigger is reached during playback, a
TriggerReached event will be generated and you will be able to discriminate the specific trigger through its
nTriggerID parameter: this parameter will match exactly the
unique identification number assigned to the trigger when added through the
TriggersAdd or
TriggersAddPerc methods.
Each single trigger can be enabled/disabled through the
TriggersEnable method and its enabled/disabled state can be obtained through the
TriggersIsEnabled method.
Cue Points
Each time you create a cue point using the
CuePointsAdd method, you must provide a mnemonic string of characters containing a custom name that will be used in order to identify the cue point at a later time: each time a cue point is reached during playback, a
CuePointReached event is generated allowing to discriminate the specific cue point through its
strCuePointName parameter: this parameter will match exactly the custom name assigned to the cue point when added through the
CuePointsAdd method.
The total number of existing cue points can be obtained using the
CuePointsGetCount method; you can obtain/modify the position for an existing cue point, expressed in milliseconds, through the
CuePointsGetPos and
CuePointsSetPos methods.
Each single cue point can be enabled/disabled through the
CuePointsEnable method and its enabled/disabled state can be obtained through the
CuePointsIsEnabled method.
A further feature available for cue points is the capability to save them inside a XML-based file through the
CuePointsSaveToFile method and to retrieve them at a later time using the
CuePointsLoadFromFile method: last but not least, each time a new sound is loaded, the control will automatically search for a XML file containing cue points for that specific file: if for example the loaded sound file should be named
MySong.mp3, the corresponding XML file containing cue points should be named
MySong.cue: when the control will find this specific XML file inside the same folder of the loaded sound it will automatically create the list of cue points.
The XML file, which should always have extension .cue, has a structure like the sample below:
<?xml version="1.0" ?>
<CuePoints>
<CuePoint PosInMs="1000" name="Silence end" />
<CuePoint PosInMs="4200" name="Fading point" />
<CuePoint PosInMs="18000" name="Silence start" />
</CuePoints>
As you can see, each cue point is identified by the name attribute and has a position expressed in milliseconds set into the PosInMs attribute.
A sample of use of Triggers in Visual Basic 6 and Visual C++ 6 can be found inside the following samples installed with the product's setup package:
- Triggers
