Implemented using libopus for the Opus codec, same as is used in Discord.
This adds the following cvars:
- `voice_chat` On/Off, triggers self-deafen state on server via weaponprefs
- `voice_mode` Activity/PTT
- `voice_selfmute` On/Off, triggers self-mute state on server via weaponprefs
- `voice_inputamp` -30 to 30, scales input by value in decibels
- `voice_activationthreshold` -30 to 0, if any peak in a frame is higher, activates voice
- `voice_loopback` On/Off, plays back local transcoded voice
- `voice_proximity` On/Off, enables proximity effects for server
- `voice_distanceattenuation_distance` distance in fracunits to scale voice volume over
- `voice_distanceattenuation_factor` distance in logarithmic factor to scale voice volume by distance to. e.g. 0.5 for "half as loud" at or above max distance
- `voice_stereopanning_factor` at 1.0, player voices are panned to left or right speaker, scaling to no effect at 0.0
- `voice_concurrentattenuation_factor` the logarithmic factor to attenuate player voices with concurrent speakers
- `voice_concurrentattenuation_min` the minimum concurrent speakers before global concurrent speaker attenuation
- `voice_concurrentattenuation_max` the maximum concurrent speakers for full global concurrent speaker attenuation
- `voice_servermute` whether voice chat is enabled on this server. visible from MS via bitflag
- `voicevolume` local volume of all voice playback
A Voice Options menu is added with a subset of these options, and Server Options has server mute.
