1.2.3. Codecs

RTP and RTCP data is the payload of a User Datagram Protocol (UDP) packet. Analog signals coming from the an endpoint are converted into the payload of UDP packets by codecs (coders/decoders). The codecs perform compression and decompression on the media streams.

Different types of codecs provide varying sound quality. The bit rate of most narrow-band codecs is in the range 1.2 Kbits/s to 64 Kbits/s. The higher the bit rate the better the sound quality. Some of the most popular codecs are:

• G.711 - Provides a bit rate of 64 Kbits/s.
• G.723.1 - Provides bit rates of either 5.3 or 6.4 Kbits/s. Voice communication using this codec typically exhibits some form of degradation.
• G.729 - Provides a bit rate of 8 Kbits/s. This codec is very popular for voice over frame relay and for V.70 voice and data modems.
• GSM - Provides a bit rate of 13 Kbits.s. This codec is based on a telephony standard defined by the European Telecommunications Standards Institute (ETSI). The 13 Kbits/s bit rate is achieved with little degradation of voice-grade audio.

Click here to contact Telecom Support Resources