Multi-rate ILBC using the DCT

While the Internet Low Bit-rate Codec (iLBC) has the advantage of high robustness to packet loss, the capability of multiple-rate coding which is an essential property for Voice over Internet Protocol (VoIP) applications is missing. The variation of the iLBC encoding procedure which yielded rate-flexible result was presented. However, the method used in the encoding procedure was based on an Analysis-by-Synthesis approach to search and quantize the Muti-Pulse (MP)-based start state. Thus, the computational requirements are intensive to implement their framework. In this paper, a different approach for encoding the start state based on utilizing the Discrete Cosine Transform (DCT) is presented. The results show that the new approach can achieve the slightly better performance than the MP-based method without requiring any more computational power.