When the playback rate is not unity, audio must be resampled in order to play at the new rate. The default resampling affects the pitch of the audio (for example, playing at 2x speed raises the pitch by an octave, 1/2x lowers an octave). If this property is set on the movie, an alternative algorithm is used, which alters the speed without changing the pitch. Since this is more computationally expensive, this property may be silently ignored on some slow CPUs.

This attribute can be read but not written; it must be among the initialization attributes to have any effect. This attribute can be read but not written when the movie has been initialized with QTMovieOpenForPlaybackAttribute set to YES.

Available in Mac OS X v10.4 and later.