diff options
Diffstat (limited to 'docs/3D7.1.txt')
| -rw-r--r-- | docs/3D7.1.txt | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/docs/3D7.1.txt b/docs/3D7.1.txt new file mode 100644 index 00000000..1d40bec6 --- /dev/null +++ b/docs/3D7.1.txt @@ -0,0 +1,82 @@ +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. |