Codec was already set to CELT many years ago.
sv_voicecodec
"sv_voicecodec" = "vaudio_celt" ( def. "steam" )
- Specifies which voice codec to use. Valid options are:
vaudio_speex - Legacy Speex codec (lowest quality)
vaudio_celt - Newer CELT codec (22kHz, 22kbps)
vaudio_celt_high - Newer CELT codec, higher bitrate (44kHz, 44kbps)
steam - Use Steam voice API