Speaker-dependent speech coding

Abstract

With the rapid expansion of Internet, it became feasible to have low-cost and secure telephone calls via internet. New digital speech compression standards were developed. Digital speech codecs can be used both in regular telephone networks and Internet based systems. Thereby, for a secure call, speech data are firstly compressed by digital speech codecs, and then, these compressed packages are sent in an encoded way through Data Encryption Standard (3DES) [1], Advanced Encryption Standard (AES) [2] encoding methods. Compressing and encoding processes require high processor performance and they may even require the use of high frequency processors and DSP’s to encode the binary speech data. Current speech coders are speaker independent, i.e., they don’t perform any speaker specific operations. They do not even distinguish between male and female speakers. An interesting way to solve this problem is to send speech after encoding it with a system that is based on a specific user. This system, which can be also called as speaker dependent speech encoding, provides a computationally efficient and relatively secure VoIP call, with high quality and without any encoding compared to the same bit rate standard speech codecs. Despite the disadvantages of requirement of acquiring all the speech characteristics of users and the need for extra data space, it has advantages such as providing secure communication because speech characteristics of the speaker is unknown to other users and the synthesized speech has higher quality compared to a same bit rate LPC compressed speech.