param Element
[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]
Note
[Deprecated. This API may be removed from future releases of Windows.]
The param element specifies the value of a property on a transition, effect, or other subobject.
Attributes
Parent/Child Information
| Label | Value |
|---|---|
| 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>
Examples
<param name="progress" value="1.0" />
See also