Research And Implementation Of ILBC Codec Algorithm

As the development of network and communication, Internet has found applications in more and more fields. The development of VoIP technology provides efficient means for transmission of voice service via different kinds of data network. By using VoIP, digitalized speech signal is encapsulated in IP packet, and then the packet is transmited over IP network. It is commonly transmitted in terms of bit stream by compression. In order to reduce the bit-rate required for the transmission of speech signal with good speech quality, speech coding at low bit rates has been applied to VoIP. iLBC is one of the low bit rates codec used commonly.The full name of iLBC is Internet Low Bit Rate Codec. It can still provide high-quality voice service even in a poor network environment. In nature, iLBC is a frame-based LPC (Linear predictive coding) method and a kind of development to CELP (Code Excited Linear Predictive Coding). Compared to previous Codec Algorithms such as G.729A and G.723.1, the unique dynamic codebook update technology, enhancement algorithm and packet loss concealment technology of iLBC gives it better performance in application of packet switching network.The main work of this paper is the research of iLBC codec algorithm, and to implete it in embedded platform base on MIPS32 24Kec. The codec is applied to video phone of network TV finally. The specific work is as follows:First, since MIPS32 24Kec is a fixed-point processor, the float-point codec should be converted to fix-point codec. The method used here including Q format transforming and change float-point functions to fixed-point. Then the codec is transplanted to the embedded platform and the performance is tested. Finally, the code is optimized to ensure that the codec can achieve the requirement of real-time video phone.