Dynamic Scaling of Encoded Speech Through the Direct Modification of Coded Parameters

In new generation networks like 3G wireless and VoIP, a great deal of emphasis is put on transcoder-free operation (TrFO), where speech remains coded throughout the core network. Any network-based speech processing function must, therefore, operate on the coded parameters directly if the value of TrFO is to be realized. Many of these functions, like echo control, noise reduction, and gain control can be viewed as dynamic amplitude scaling of the speech signal. Given that an intermediate step of decoding/re-encoding is not an option, we present, in this paper, a method for dynamic scaling of speech in the coded-domain directly. We derive expressions for modifying the relevant coded parameters such that the resulting decoded speech would correspond to the desired scaled signal. Experimentally, we use the AMR 12.2 kbps coder, and show that the proposed method results in a signal whose level, as well as speech quality, closely matches the desired scaled signal