Telephone (application)

Telephone is a softphone for macOS developed by 64 Characters. It uses Session Initiation Protocol for communication. Telephone is distributed as free software under the GPL-3.0-or-later license.

Audio codecs

 * Speex/8000 (narrowband), Speex/16000 (wideband), and Speex/32000 (ultra-wideband)
 * Opus
 * G.711 family codec (PCMA, PCMU)
 * G.722
 * iLBC
 * GSM