Ambisonic decoder configuration presets are provided here for common surround
sound speaker layouts. The presets are prepared to work with OpenAL Soft's high
quality decoder. By default all of the speaker distances within a preset are
set to the same value, which results in no effect from distance compensation.
If this doesn't match your physical speaker setup, it may be worth copying the
preset and modifying the distance values to match (note that modifying the
azimuth and elevation values in the presets will not have any effect; the
specified angles do not change the decoder behavior).

Details of the individual presets are as follows.

square.ambdec
Specifies a basic square speaker setup for Quadraphonic output, with identical
width and depth. Front speakers are placed at +45 and -45 degrees, and back
speakers are placed at +135 and -135 degrees.

rectangle.ambdec
Specifies a narrower speaker setup for Quadraphonic output, with a little less
width but a little more depth over a basic square setup. Front speakers are
placed at +30 and -30 degrees, providing a bit more compatibility for existing
stereo content, with back speakers at +150 and -150 degrees.

itu5.1.ambdec
Specifies a standard ITU 5.0/5.1 setup for 5.1 Surround output. The front-
center speaker is placed directly in front at 0 degrees, with the front-left
and front-right at +30 and -30 degrees, and the surround speakers (side or
back) at +110 and -110 degrees.

hexagon.ambdec
Specifies a flat-front hexagonal speaker setup for 7.1 Surround output. The
front left and right speakers are placed at +30 and -30 degrees, the side
speakers are placed at +90 and -90 degrees, and the back speakers are placed at
+150 and -150 degrees. Although this is for 7.1 output, no front-center speaker
is defined for the decoder, meaning that speaker will be silent for 3D sound
(however it may still be used with AL_SOFT_direct_channels or ALC_EXT_DEDICATED
output). A "proper" 7.1 decoder may be provided in the future, but due to the
nature of the speaker configuration will have trade-offs.

3D7.1.ambdec
Specifies a 3D7.1 speaker setup for 3D7.1 Surround output. Please see
docs/3D7.1.txt for information about speaker placement. Similar to 7.1, the
front-center speaker is not used for 3D sound, but will be used as appropriate
with AL_SOFT_direct_channels or ALC_EXT_DEDICATED.
