Quicktime File Format (2012-08-14).pdf

Some Useful Examples and ScenariosCreating an Effect DescriptionThe two kEffectSourceName atoms specify the two sources that this effect will use, in this case 'srcA' and'srcB'. The names correspond to entries in the effect track’s input map.The 'pcnt' parameter atom defines which frames of the effect are shown. This parameter contains a tweenentry, so that the value of this parameter is interpolated as the effect runs . The interpolation of the 'pcnt'parameter causes consecutive frames of the effect to be rendered, creating the push effect.The 'from' parameter determines the direction of the push. This parameter is set from an enumeration list,with 2 being defined as the bottom of the screen.In this example, the source 'srcB' will push in from the bottom, covering the source 'srcA'.The 'pcnt' parameter is normally tweened from 0 to 100, so that the effect renders completely, from 0 to100 percent. In this example, the 'pcnt' parameter is tweened from 25 to 75, so the effect will start 25 percentof the way through (with 'srcB' already partly on screen) and finish 75 percent of the way through (with partof 'srcA' still visible).2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.339