QuickTime 3 Reference

What Effects Components Do

The basic task of every effect component is very simple. The component is passed zero or more source frames and must produce a single destination frame. The destination frame is the source frame or frames after processing by the effect-rendering algorithm.

The component must provide a set of services that QuickTime can call. These services allow QuickTime (or any other client software that uses your component) to perform actions such as:

Open a connection to your component.
Retrieve information about your effect, particularly descriptions of the parameters your effect can take.
Set the source or sources for the effect.
Set the destination for the effect.
Request that a single frame of the effect is rendered.
Cancel the rendering of a frame.
Close the connection to your component.

Your effect component must be able to service such requests. To do so, it implements a set of standard interface functions that are called through a component dispatch function. Details of these functions are given in the section "The Effect Component Interface" .

The main task of the effect component is to implement the specific algorithm that transforms source frames into a destination frame. You will need to supply versions of your algorithm for each bit depth and pixel format that your component supports. Choosing which bit depths and pixel formats to support, and implementing algorithms for each combination of these, is a significant part of building your effect component.

In addition, your effect component must provide a parameter description that describes the parameters that the effect takes. The parameter description can be used by the software that is calling your component to construct a user interface that allows users to change the value of the parameters sent to your component. This is described in detail in the section "Supplying Parameter Description Information" .