ITU-T coders for wideband, superwideband, and fullband speech communication [Series Editorial]

This section of the magazine presents recent algorithms developed by the ITU to provide high quality coding beyond traditional narrowband telephony. Speech coders can be characterized by their bit rate, quality, complexity, and delay. Typical applications fall into one of two categories, one-way and two-way. The first includes storage applications such as telephone answering systems, streaming, multimedia delivery, and push-to-talk calls. The second includes realtime communications such as two person phone calls and conference calls. In this latter category, if the delay is too large - exceeding 300 ms round-trip - humans have difficulty communicating, while for storage and playback operations delay is not a factor. The complexity of a speech coder is one of the main contributing factors to its cost and energy usage. Complexity is most often measured in terms of memory usage (both RAM and ROM) and the number of instructions executed per second. All applications are sensitive to cost, and many are sensitive to energy usage as well. The desired bit rate is determined by channel capacity or storage capacity, depending on the application.