Internet low bitrate codec (iLBC)
Internet Low Bit Rate Codec (iLBC) is a license-free voice codec developed by Global IP Solutions (GIPS) for narrowband voice transmissions in IP networks, for example for Internet telephony, VoIP or audio streaming.
The iLBC codec is specified for two different transmission rates, with the two data packets containing the voice data being encoded after 20 ms and 30 ms respectively. This has the advantage of reducing the data rate, which is 15.2 kbit/s for the 20 ms block and 13.3 kbit/s for the 30 ms block. However, encoding after 30 ms results in a 50% higher delay compared to the shorter blocks.
With a sampling rate of 8 kHz and a sampling depth of 16 bits, which is common in the speech sector, a data rate of 128 kbit/s results. This is compressed to data rates of 15.2 kbit/s and 13.3 kbit/s using block-independent linear predictive coding( LPC). In contrast to other speech codecs, where the speech quality noticeably decreases in case of packet losses, the iLBC codec compensates packet losses in such a way that the speech quality hardly decreases noticeably, which is not least due to the Packet Loss Concealment( PLC). The data blocks are encapsulated and transmitted using the Realtime Transport Protocol( RTP).