param Element
| Microsoft DirectShow 9.0 |
param Element
The param element specifies the value of a property on a transition, effect, or other subobject.
Example
<param name="progress" value="1.0" />
Attributes
Parent/Child Information
| Parent | clip, effect, transition |
| Children | at, linear |
Remarks
The value attribute specifies the value of the property at the start of the transition or effect. Use the at or linear element to specify changing values. If the param element contains no at or linear elements, the value remains constant over the duration of the effect or transition.
- Note A param element inside a clip element cannot contain at or linear elements.
Many transitions support a standard Progress property that ranges from 0 to 1.0, indicating what percentage of the transition is reflected in the output. At Progress = 0.0, the transition is at the beginning of its sequence (entirely the first video image). At Progress = 0.5, the transition is half complete. (For example, in a wipe, at Progress = 0.5 the transition boundary is in the center of the image) At Progress = 1.0, the transition is complete (entirely the second image). By default, transitions go from Progress = 0.0 at the start of the transition to Progress = 1.0 at the end.
Other properties are usually specific to one particular transition or effect. For example, the wipe transition supports a GradientSize property that controls the width of the transition area.
To run a transition backward, set the Progress property to 1.0 at the start of the transition, and use the linear element to change the value to 0.0, as shown in the following example:
<transition clsid="{af279b30-86eb-11d1-81bf-0000f87557db}" start="0" stop="6">
<param name="progress" value="1.0">
<linear time="6" value="0.0" />
</param>
</transition>
See Also