Techniques of optimizing low bit rate sinusoidal transform coding

There are many high performance speech coding algorithms, but most of them using bit rates higher than 5kbps. Expected quality of low bit rate speech coding has not been achieved yet, which is an area of interest for military and security applications. There is still room for improvement for low bit rates. Low bit rate speech coding using sinusoidal transform coding is discussed in this paper. The sinusoidal transform coding (STC) is a frequency domain speech compression technique, which can produce speech of high quality at bit rates below 5kbps.In STC, speech signal are represented by linear combination of sine waves with time-vary amplitudes, phase, and frequencies. STC can produce high quality synthesized speech at low bit rates. This paper focuses on the development of a fully speech coder at 2.4 kbps and 4.8 kbps.