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Setting an Audio Context

QuickTime normally sends audio to the default audio output for your system. Channels are automatically mixed-down as needed (when playing multichannel sound through a stereo output, for example).

To direct the audio output of a movie to a particular device, or to set up a channel configuration or assign individual sound tracks to particular channels, create an audio context.

To create an audio context, call QTAudioContextCreateForAudioDevice and pass in the UID of an output device. An audio context reference is returned. Pass that audio context ref either to NewMovieFromProperties, as you would pass in a visual context, or to SetMovieAudioContext, to redirect the output of an existing movie.

Audio contexts are not shareable. If you want to route the output of two or more movies to the same device, call QTAudioContextCreateForAudioDevice once for each movie, passing in the same device UID to get another audio context for the same device. Pass a separate audio context reference to each movie.

You can pass NULL as the UID to QTAudioContextCreateForAudioDevice to create an audio context for the default audio output.

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