Ekiga

Ekiga (formerly known as GnomeMeeting) is an open-source SoftPhone, video conferencing, and instant messaging application based on the Internet. It supports high-definition audio quality and video up to DVD size and quality. Since it utilizes two major telephony standards (SIP and H.323), it can interoperate with numerous service providers as well as various types of hardware and software. **Key Features** - Modern graphical user interface that is easy to use - Free audio and video calls over the Internet - Free instant messaging over the Internet with online presence support - Audio (and video) calls to landlines and mobile phones, with support for the most cost-effective service providers - High-definition sound (wideband) and video quality up to DVD standards (high frame rate, state-of-the-art codecs, and frame size) - Freedom to choose service providers - SMS messaging to mobile phones if supported by the service provider (e.g., default provider) - Standard telephony features such as call hold, call transfer, call forwarding, and DTMF - Remote and local address book support: remote address book authentication using standard LDAP technology, local address support in Gnome (Evolution) - Multi-platform: Windows and GNU/Linux - Extensive interoperability: Ekiga employs widely adopted telephony protocol standards (SIP and H.323) and has been tested with various softphones, hardphones, PBXs, and service providers

Ekiga is an open-source softphone, video conferencing, and instant messaging application that provides high-definition audio and video calls and messaging services over the internet. It supports SIP and H.323 standards, ensuring interoperability with various service providers and software/hardware.