Halcyon vs Linphone

Halcyon is a free, pre-1.0 Android softphone built on PJSIP and integrated with Android Telecom. It registers with a PBX over UDP, TCP, or TLS, advertises RFC 8599 push parameters, and supports several SIP identities with an account selected for each call. When server-side push is configured, the registrar sends a data-only FCM message before an incoming INVITE to wake the device. Without push, Halcyon uses a foreground SIP service with permanent TLS registration and the associated battery cost. Its Android ConnectionService handles tel: and sip: calls, including from the lock screen, while Telecom-native routing supports Bluetooth headsets and Android Auto. Listed audio codecs are Opus, G.722, AMR-WB, and G.729; video codecs include VP8, VP9, and arm64 MediaCodec H.264. Media uses SRTP encryption, with ZRTP on the roadmap. Android 8.0 or newer is required; signed APKs are available from GitHub Releases.

Linphone combines VoIP voice and video calling, instant messaging, and videoconferencing in one application. It uses SIP and SIP SIMPLE to interoperate with IP-PBXs, proxies, SBCs, and other SIP systems. Calling features include HD audio and video, call forwarding, concurrent calls, recording, DTMF, and Bluetooth headset support. Its Flexisip or SaaS conferencing option supports meetings with up to 50 participants and screen sharing. Messaging features depend on setup: Flexisip supports group chats, file sharing, read receipts, reactions, voice messages, and ephemeral messages; SIP SIMPLE provides basic one-to-one messaging with third-party accounts. Security features include SIP/TLS, SRTP, SRTP-DTLS, ZRTP, end-to-end encryption for exchanged media, and post-quantum encryption using CRYSTALS-Kyber. Flexisip can be hosted on premises and connected to an existing SIP server for group messaging and videoconferencing. Linphone is open source under GNU GPLv3, with proprietary licensing available for closed-source modifications. The app is available on Android, iOS, Linux, macOS, Windows, and web, with API and self-hosted options. Its free SIP service is for individual users and has no guaranteed support; paid support and maintenance are available by contacting the company.