mvAudio(3dm)mvAudio(3dm)NAME
mvSetPrimaryAudio, mvGetPrimaryAudio - Set/get the movie instance with
control over the audio hardware
SYNOPSIS
#include <dmedia/moviefile.h>
#include <dmedia/movieplay.h>
void mvSetPrimaryAudio(MVid movieid);
MVid mvGetPrimaryAudio(void);
DESCRIPTIONmvSetPrimaryAudio(3dm) tells the Movie Playback Library to favor a
particular movie's audio sampling rate for playback. The preferred audio
sample rate of a movie is the sample rate of the movie's first audio
track. You may designate a movie as primary regardless of whether or not
it is currently playing.
The default value for the primary audio movie is MV_PRIMARY_AUDIO_NOTSET.
When the primary audio movie is set to something other than
MV_PRIMARY_AUDIO_NOTSET, the movie library will use a "rude" policy for
setting the system audio hardware sampling rate. When this is the case
and whenever the primary audio movie is playing, the Movie Playback
Library will set the audio hardware sampling rate based on the preferred
audio sample rate of the primary audio movie.
When the primary audio movie is MV_PRIMARY_AUDIO_NOTSET, the movie
library use a "polite" policy for setting the system audio hardware
sample rate. The Movie Playback Library opens an output ALport for each
movie that has at least one audio track and is currently bound to a
window (see mvBindOpenGLWindow(3dm)). When the primary audio movie is
MV_PRIMARY_AUDIO_NOTSET and such a movie starts playing (see
mvPlay(3dm)), the Movie Playback Library checks to see if the system has
any other currently open output ALports (see alGetParams(3dm)). These
other ALports could belong to other movies currently opened by the same
process (or process group), movies open in other applications, or other
processes that use output ALports. If there are no other currently open
output ALports, the Movie Playback Library will set the audio hardware
sample based on that movie. If there is at least one other currently open
output ALport, the Movie Playback Library will use linear sample rate
conversion (when necessary) to ensure that the movie's audio will play
using the current audio hardware sampling rate.
The Movie Playback library does not follow this protocol for movies bound
directly to a movie library audio port (MV_PORT_AUDIO) with
mvBindMovieToPorts(3dm) with the ownsRate set to DM_TRUE. When these
movies start playing, a "rude" policy is used. See the section on
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mvAudio(3dm)mvAudio(3dm)
MV_PORT_AUDIO in mvPort(3dm) for details.
Once you designate a primary movie, it owns the audio hardware until you
designate another with a subsequent call to mvSetPrimaryAudio(3dm), or
you close the movie by calling mvClose(3dm). If you close the primary
movie, the primary movie will revert to MV_PRIMARY_AUDIO_NOTSET.
To remove primary audio status from a particular movie, but not assign to
another movie, you may call mvSetPrimaryAudio(3dm) with the value
MV_PRIMARY_AUDIO_NOTSET.
mvGetPrimaryAudio(3dm) returns the movie ID which currently has primary
audio status, or MV_PRIMARY_AUDIO_NOTSET if no movie has primary audio
status.
Only one movie may have primary audio status at any given time.
SEE ALSOalIntro(3dm), alGetDefaults(3dm), alOpenPort(3dm), alSetParams(3dm),
mvBindWindow(3dm), mvIntro(3dm), mvPlay(3dm), mvPort(3dm).
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