Suitable packetization interval for using Constrained Energy Lapped Transform (CELT) CODEC in Bi-directional communication over WLAN 802.11g

Full audio bandwidth with very low algorithmic delay CODEC is state-of-the-art in CODEC technology. This type of CODEC is expected to support full frequency range for human hearing. It will enable future multipurpose audio applications, especially those which require high quality of audio signal with very low delay. A popular choice for this type of CODEC is the Constrained Energy Lapped Transform (CELT) CODEC since it is an open source and royalty free. This study is concerned with the effect of packetization interval for using CELT CODEC in bidirectional communication over WLAN 802.11g with respect to packet loss and end-to-end delay. Possible bitrates used in CELT were also investigated. The result reveals that the commonly default 20 ms. packetization interval is not always suitable for all network conditions. High packetization interval (more than 60 ms) interval are not recommended as packet loss can be quite high and end-to-end delay can exceed the 150 ms. ITU recommended value. Using packetization interval at 30 ms. is recommended, apart from achieving better performance, it allows CODEC bitrate to be varied while packet loss is still acceptable and end-to-end delay is still within the recommended value. A practical application for this study is a synchronous remote music session practice between two persons.