mvPlaySpeed(3dm)mvPlaySpeed(3dm)NAME
mvSetPlaySpeed, mvGetPlaySpeed, mvGetCurrentDirection - Control rate of
playback for a movie instance
SYNOPSIS
#include <dmedia/moviefile.h>
#include <dmedia/movieplay.h>
void mvSetPlaySpeed(MVid movieId, double newPlaySpeed);
double mvGetPlaySpeed(MVid movieId);
MVdirection mvGetCurrentDirection(MVid movieId);
DESCRIPTIONmvSetPlaySpeed(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
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 ALSOmvBindOpenGLWindow(3dm), mvIntro(3dm), mvPlay(3dm), mvPlayLoop(3mv),
mvSetPlayEveryFrame(3dm).
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