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