iLBC

iLBC (Internet Low Bit Rate Codec) is an audio compression format designed for reliable speech transmission over IP networks. It is a narrowband codec intended for real-time communications, operating on 8 kHz sampled audio. iLBC emphasizes low bandwidth usage and robustness to network packet loss, making it suitable for VoIP, video conferencing, and other time-sensitive applications.

The codec was developed by Global IP Solutions (GIPS) and was standardized by the Internet Engineering Task Force (IETF). It is defined for use with the Real-time Transport Protocol (RTP) in RFC 3951, which specifies the payload format and operational details. iLBC has been widely implemented in both open-source and commercial VoIP stacks, and its reference implementations are publicly available.

iLBC provides two bitrate modes, commonly cited as 13.33 kbps and 15.2 kbps. These modes offer different trade-offs between bandwidth efficiency and resilience to packet loss. The encoding is frame-based and includes built-in packet loss concealment to minimize audible artifacts when packets are dropped, helping to preserve intelligibility in lossy networks.

In practical use, iLBC is supported by many VoIP clients, servers, and multimedia communication platforms, where it serves as an effective alternative to higher-bandwidth codecs when network conditions are heterogeneous or constrained. It remains favored in scenarios requiring predictable performance under packet loss, low delay, and compatibility across diverse systems.

Licensing and implementation notes vary by source, but generally, the reference implementation and many third-party libraries provide iLBC under open or permissive licenses, facilitating integration into both open-source and commercial products.