al_set_sample_instance_pan
bool al_set_sample_instance_pan(ALLEGRO_SAMPLE_INSTANCE *spl, float val)
Set the pan value on a sample instance. A value of -1.0 means to play the sample only through the left speaker; +1.0 means only through the right speaker; 0.0 means the sample is centre balanced.
A constant sound power level is maintained as the sample is panned from left to right. As a consequence, a pan value of 0.0 will play the sample 3 dB softer than the original level. To disable panning and play a sample at its original level, set the pan value to ALLEGRO_AUDIO_PAN_NONE.
Returns true on success, false on failure. Will fail if the sample instance is attached directly to a voice.
(A sound guy should explain that better; I only implemented it. Also this might be more properly called a balance control than pan. Also we don't attempt anything with more than two channels yet.)
See also: al_get_sample_instance_pan.
Examples: ex_audio_props
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