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- Overview
- ========
-
- 3D7.1 is a custom speaker layout designed by Simon Goodwin at Codemasters[1].
- Typical surround sound setups, like quad, 5.1, 6.1, and 7.1, only produce audio
- on a 2D horizontal plane with no verticality, which means the envelopment of
- "surround" sound is limited to left, right, front, and back panning. Sounds
- that should come from above or below will still only play in 2D since there is
- no height difference in the speaker array.
-
- To work around this, 3D7.1 was designed so that some speakers are placed higher
- than the listener while others are lower, in a particular configuration that
- tries to provide balanced output and maintain some compatibility with existing
- audio content and software. Software that recognizes this setup, or can be
- configured for it, can then take advantage of the height difference and
- increase the perception of verticality for true 3D audio. The result is that
- sounds can be perceived as coming from left, right, front, and back, as well as
- up and down.
-
- [1] http://www.codemasters.com/research/3D_sound_for_3D_games.pdf
-
-
- Hardware Setup
- ==============
-
- Setting up 3D7.1 requires an audio device capable of raw 8-channel or 7.1
- output, along with a 7.1 speaker kit. The speakers should be hooked up to the
- device in the usual way, with front-left and front-right output going to the
- front-left and front-right speakers, etc. The placement of the speakers should
- be set up according to the table below. Azimuth is the horizontal angle in
- degrees, with 0 directly in front and positive values go /left/, and elevation
- is the vertical angle in degrees, with 0 at head level and positive values go
- /up/.
-
- ------------------------------------------------------------
- - Speaker label | Azimuth | Elevation | New label -
- ------------------------------------------------------------
- - Front left | 51 | 24 | Upper front left -
- - Front right | -51 | 24 | Upper front right -
- - Front center | 0 | 0 | Front center -
- - Subwoofer/LFE | N/A | N/A | Subwoofer/LFE -
- - Side left | 129 | -24 | Lower back left -
- - Side right | -129 | -24 | Lower back right -
- - Back left | 180 | 55 | Upper back center -
- - Back right | 0 | -55 | Lower front center -
- ------------------------------------------------------------
-
- Note that this speaker layout *IS NOT* compatible with standard 7.1 content.
- Audio that should be played from the back will come out at the wrong location
- since the back speakers are placed in the lower front and upper back positions.
- However, this speaker layout *IS* more or less compatible with standard 5.1
- content. Though slightly tilted, to a listener sitting a bit further back from
- the center, the front and side speakers will be close enough to their intended
- locations that the output won't be too off.
-
-
- Software Setup
- ==============
-
- To enable 3D7.1 on OpenAL Soft, first make sure the audio device is configured
- for 7.1 output. Then in the alsoft-config utility, under the Renderer tab,
- select the 3D7.1.ambdec preset for the 7.1 Surround decoder configuration. And
- that's it. Any applications using OpenAL Soft can take advantage of fully 3D
- audio, and multi-channel sounds will be properly remixed for the speaker
- layout.
-
- Playback can be improved by (copying and) modifying the 3D7.1.ambdec preset,
- changing the specified speaker distances to match the the real distance (in
- meters) from the center of the speaker array, then enable High Quality Mode in
- alsoft-config. That will improve the quality when the speakers are not all
- equidistant.
-
- Note that care must be taken that the audio device is not treated as a "true"
- 7.1 device by non-3D7.1-capable applications. In particular, the audio server
- should not try to upmix stereo and 5.1 content to "fill out" the back speakers,
- and non-3D7.1 apps should be set to either stereo or 5.1 output.
-
- As such, if your system is capable of it, it may be useful to define a virtual
- 5.1 device that maps the front, side, and LFE channels to the main device for
- output and disables upmixing, then use that virtual 5.1 device for apps that do
- normal stereo or surround sound output, and use the main device for apps that
- understand 3D7.1 output.
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