The Get Clip Preferences Action
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The Get Clip Preferences Action 

	#include "ofxImageEffect.h"
	#define kOfxImageEffectActionGetClipPreferences       "OfxImageEffectActionGetClipPreferences"
Arguments

  • handle handle to the instance, cast to an OfxImageEffectHandle ,
  • inArgs is redundant and is set to NULL.
  • outArgs has the following properties which the plugin can set...
    • a set of char * X 1 properties, one for each of the input clips currently attached and the output clip, labelled with "OfxImageClipPropComponents_" post pended with the clip's name. This must be set to one of the component types which the host supports and the effect stated it can accept on that input,
    • a set of char * X 1 properties, one for each of the input clips currently attached and the output clip, labelled with "OfxImageClipPropDepth_" post pended with the clip's name. This must be set to one of the pixel depths both the host and plugin supports,
    • a set of double X 1 properties, one for each of the input clips currently attached and the output clip, labelled with "OfxImageClipPropPAR_" post pended with the clip's name. This is the pixel aspect ratio of the input and output clips. This must be set to a positive non zero double value,
    • kOfxImageEffectPropFrameRate , the frame rate of the output clip, this must be set to a positive non zero double value,
    • kOfxImageClipPropFieldOrder , the fielding of the output clip,
    • kOfxImageEffectPropPreMultiplication , the premultiplication of the output clip,
    • kOfxImageClipPropContinuousSamples , whether the output clip can produce different images at non-frame intervals, defaults to false,
    • kOfxImageEffectFrameVarying , whether the output clip can produces different images at different times, even if all parameters and inputs are constant, defaults to false.

Description

This action allows a plugin to dynamically specify its preferences for input and output clips. Please see Image Effect Clip Preferences for more details on the behaviour. Clip preferences are constant for the duration of an effect, so this action need only be called once per clip, not once per frame.

This should be called once after creation of an instance, each time an input clip is changed, and whenever a parameter named in the kOfxImageEffectPropClipPreferencesSlaveParam has its value changed.

Return Values

  • kOfxStatOK, the action was trapped and at least one of the properties in the outArgs was changed from its default value
  • kOfxStatReplyDefault, the action was not trapped and the host should use the default values
  • kOfxStatErrMemory, in which case the action may be called again after a memory purge
  • kOfxStatFailed, something wrong, but no error code appropriate, plugin to post message
  • kOfxStatErrFatal

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