Set the position of a channel.
int Mix_SetPosition(int channel, Sint16 angle, Uint8 distance);
|channel||The mixer channel to position, or MIX_CHANNEL_POST.|
|angle||angle, in degrees. North is 0, and goes clockwise.|
|distance||distance; 0 is the listener, 255 is maxiumum distance away.|
Returns zero if error (no such channel or Mix_RegisterEffect() fails), nonzero if position effect is enabled. Error messages can be retrieved from Mix_GetError().
angle is an integer from 0 to 360, that specifies the location of the sound in relation to the listener.
angle will be reduced as neccesary (540 becomes 180 degrees, -100 becomes 260). Angle 0 is due north, and rotates clockwise as the value increases. For efficiency, the precision of this effect may be limited (angles 1 through 7 might all produce the same effect, 8 through 15 are equal, etc).
distance is an integer between 0 and 255 that specifies the space between the sound and the listener. The larger the number, the further away the sound is. Using 255 does not guarantee that the channel will be removed from the mixing process or be completely silent. For efficiency, the precision of this effect may be limited (distance 0 through 5 might all produce the same effect, 6 through 10 are equal, etc). Setting
distance to 0 unregisters this effect, since the data would be unchanged.
If you need more precise positional audio, consider using OpenAL for spatialized effects instead of SDL_mixer. This is only meant to be a basic effect for simple "3D" games.
If the audio device is configured for mono output, then you won't get any effectiveness from the angle; however, distance attenuation on the channel will still occur. While this effect will function with stereo voices, it makes more sense to use voices with only one channel of sound, so when they are mixed through this effect, the positioning will sound correct. You can convert them to mono through SDL before giving them to the mixer in the first place if you like.
Setting the channel to MIX_CHANNEL_POST registers this as a posteffect, and the positioning will be done to the final mixed stream before passing it on to the audio device.
This is a convenience wrapper over Mix_SetDistance() and Mix_SetPanning().
Note that unlike most SDL and SDL_mixer functions, this function returns zero if there's an error, not on success. We apologize for the API design inconsistency here.
This function is available since SDL_mixer 2.0.0.