mvPlaySpeed(3dm)					      mvPlaySpeed(3dm)

NAME    [Toc]    [Back]

     mvSetPlaySpeed, mvGetPlaySpeed, mvGetCurrentDirection - Control rate of
     playback for a movie instance

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/moviefile.h>
     #include <dmedia/movieplay.h>


     void mvSetPlaySpeed(MVid movieId, double newPlaySpeed);

     double mvGetPlaySpeed(MVid	movieId);

     MVdirection mvGetCurrentDirection(MVid movieId);

DESCRIPTION    [Toc]    [Back]

     mvSetPlaySpeed(3dm) changes the movie play	speed, expressed as a fraction
     of	the movie's natural image frame	rate.  This frame rate is stored in
     the movie file (SGI and QuickTime only) and it may	be determined by
     calling mvGetImageRate(3dm).  For example,	if you call
     mvSetPlaySpeed(3dm) with a	value of 2.0, the movie	plays twice as fast as
     it	normally would.

     For movies	with audio, the	Movie Playback Library attempts	to resample
     the audio to match	the requested playback speed.  This changes the	pitch
     of	the audio.  Be aware that the current implementation uses software
     techniques	to perform audio resampling; thus, changing the	speed of
     playback for a movie with an audio	sound-track will consume more
     processor time.

     If	you specify a negative value for newplayspeed, the movie plays in
     reverse.  You should use mvGetCurrentDirection(3dm) to determine the
     direction the movie is actually playing, because the swinging loop	mode
     may cause the movie to play in a direction	other than that	indicated by
     the sign of the current speed. See	mvPlayLoop(3dm)	for details.

     The default movie speed is	always 1.0.

     mvGetPlaySpeed(3dm) returns the current play speed.

     The results of mvSetPlaySpeed(3dm)	depend on whether or not the movie is
     playing every frame (see mvSetPlayEveryFrame(3dm)).  If the movie is not
     playing every frame, then mvSetPlaySpeed(3dm) acts	as described above.
     If	the movie is playing every frame, then mvSetPlaySpeed(3dm) will	have
     no	effect.

     You may call these	functions for a	specified movie	instance regardless of
     whether or	not the	movie is playing.





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mvPlaySpeed(3dm)					      mvPlaySpeed(3dm)

NOTES    [Toc]    [Back]

     The method	the Movie Playback Library uses	to resample audio for variable
     speed playback does not perform any filtering.  Thus, the pitch-shifted
     audio may have aliasing artifacts.

SEE ALSO    [Toc]    [Back]

     mvBindOpenGLWindow(3dm), mvIntro(3dm), mvPlay(3dm), mvPlayLoop(3mv),
     mvSetPlayEveryFrame(3dm).


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