Study On Audio Mixing And Its Application In IP Telephone Conference System

IP telephone conference system is composed of the IP telephones and application servers based on kinds of networks. Its main purpose is to make the users in IP conferences obtain the same experiences as in real conferences, such as joining in, leaving and canceling a conference, speaking and speaking with no count limitation. To solve the problem of speaking with no count limitation, audio mixer is used. Audio mixer generates an unique voice for each user with the signals from the IP telephones, thus every user can hear others'voices.Recently, most study of audio mixer mainly focuses on the mixing algorithms, the methods of samples'accumulation. The environment of audio mixing is rarely discussed. In fact, two issues of the mixing in IP conferences need to be solved: one is multi-channel synchronization, with the purpose of ensuring the accuracy of the samples'order; the other is finding a method to solve the problem of samples'accumulation. With the analysis of the simulation results of three typical mixing (accumulation) algorithms, capabilities and conditions of"voltage clamping"in real applications are discussed. Then, an algorithm for multi-channel audio synchronization is proposed, and synchronization will be obtained after 6 comparisons at most. Finally, based on the scheme of audio mixing, an architecture of IP conference system is proposed, which can provide cascade conferences.