| | Open Sound System |
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This mixer control type is reserved for future use and it shoud not be used in drivers before its exact usage is defined.
The projected use of this mixer control type is a "virtual joystick" for 3D positioning of sounds. It can be used both for mono and stereo signals. Use with multi channel signals is currently undefined.
The value field has special encoding:
| Bits | Purpose |
value & 0xff) | Volume of the sound source (0 to 100). |
(value >> 8) & 0xff | Distance of the sound source. Value of 0 means inside listener's head and 100 means horizon. Value of 50 means that the sound source is located at the distance of the speakers. |
(value >> 16) & 0xffff | Direction of the sound source in degrees. 0 means ahead. |
The volume/distance field gives the distance of the sound source from the listener. Value of 100 means maximum volume (the sound source is inside the listener's head). Value of 0 means that the sound is almost muted and located near the horizon. Value of 50 means the "nominal" speaker distance.
The Direction field gives the angle (in degrees) to the signal source. Value of 0 means that the signal source is in front of the listener. 90 means right, 180 means back and 270 means left. This field has no effect if the distance field is 100 (inside listener's head).
This control can be used for stereo signals. In this case the direction field will rotate a pair of virtual stereo speakers located +/- 45 degrees in front of the listener. If the direction field is changed these virtual speakers will move so that they are located at direction +/- 45 degrees postition. However this is true only if the distance field is 50 (nominal speaker distance.
When the volume/distance field is close to 100 the stereo signal will become mono because the signal source is inside the listener's head. When the volume/distance field is less than 50 the signal volume will start to fade. In addition the virtual stereo speakers will move closer to each other until at volume/distance level of 0 (horizon) they will join together.