Twinkle is a

free and open-source Free and open-source software (FOSS) is software available under a Software license, license that grants users the right to use, modify, and distribute the software modified or not to everyone free of charge. FOSS is an inclusive umbrella term ...

application for voice communications over

Voice over IP Voice over Internet Protocol (VoIP), also known as IP telephony, is a set of technologies used primarily for voice communication sessions over Internet Protocol (IP) networks, such as the Internet. VoIP enables voice calls to be transmitted as ...

(VoIP) protocol.

Architecture

It is designed for

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

operating systems and uses the Qt toolkit for its graphical user interface. For call signaling it employs the

Session Initiation Protocol The Session Initiation Protocol (SIP) is a signaling protocol used for initiating, maintaining, and terminating communication sessions that include voice, video and messaging applications. SIP is used in Internet telephony, in private IP telepho ...

(SIP). It also features direct IP-to-IP calls. Media streams are transmitted via the

Real-time Transport Protocol The Real-time Transport Protocol (RTP) is a network protocol for delivering audio and video over IP networks. RTP is used in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applic ...

(RTP) which may be encrypted with the

Secure Real-time Transport Protocol The Secure Real-time Transport Protocol (SRTP) is a profile for Real-time Transport Protocol (RTP) intended to provide encryption, message authentication and integrity, and replay attack protection to the RTP data in both unicast and multica ...

(SRTP) and the

ZRTP ZRTP (composed of Z and Real-time Transport Protocol) is a cryptographic key-agreement protocol to negotiate the keys for encryption between two end points in a Voice over IP (VoIP) phone telephony call based on the Real-time Transport Protocol ...

security protocols. Since version 1.3.2 (September 2008), Twinkle supports message exchange and a ''buddy-list'' feature for presence notification, showing the online-status of predefined communications partners (provider-support needed).

Supported audio formats

G.711 G.711 is a narrowband audio codec originally designed for use in telephony that provides toll-quality audio at 64 kbit/s. It is an ITU-T standard (Recommendation) for audio encoding, titled Pulse code modulation (PCM) of voice frequencies ...

A-law: 64 kbit/s payload, 8 kHz sampling rate * G.711 μ-law: 64 kbit/s payload, 8 kHz sampling rate * G.726: 16, 24, 32 or 40 kbit/s payload, 8 kHz sampling rate *

GSM The Global System for Mobile Communications (GSM) is a family of standards to describe the protocols for second-generation (2G) digital cellular networks, as used by mobile devices such as mobile phones and Mobile broadband modem, mobile broadba ...

: 13 kbit/s payload, 8 kHz sampling rate * G.729: 8 kbit/s payload, 8 kHz sampling rate *

iLBC Internet Low Bitrate Codec (iLBC) is a royalty-free narrowband speech audio coding format and an open-source reference implementation (codec), developed by Global IP Solutions (GIPS) formerly Global IP Sound (acquired by Google Inc in 2011). It w ...

: 13.3 or 15.2 kbit/s payload, 8 kHz sampling rate *

Speex {{More citations needed, date=May 2025 The Speex project is an attempt to create a free software speech codec, unencumbered by patent restrictions. Speex is licensed under the BSD License and is used with the Xiph.org Foundation's Ogg containe ...

narrow band: 15.2 kbit/s payload, 8 kHz sampling rate * Speex wide band: 28 kbit/s payload, 16 kHz sampling rate * Speex ultra wide band: 36 kbit/s payload, 32 kHz sampling rate

References

Free VoIP software Cryptographic software Internet privacy software Secure communication Software that uses Qt KDE software {{network-software-stub

Architecture

Supported audio formats

See also

References