11.6 BIT RATE CALCULATION FOR DIFFERENT CODECS
VoIP deployment may use multiple codecs in the deployment. Some codecs such as AMR, G.729.1, and G.722 have multiple compression rates. It is required to consider proper mapping of compression rate, payload size, and packets per second. Some codecs may use scalable payload, meaning dropping some of the compressed bits based on the available bit rate. For all these combinations, the variables are payload size, packets per second, and the interface overhead per packet.
Generic VoIP bit rate calculators use voice payload with RTP/UDP/IP. Other interface specific headers are not considered. It is useful to interpret the bit rate calculation up to the network interface. It is also essential to consider many other quality trade-offs and deployment-specific considerations before selecting codec and packet intervals.
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