Embedded CELP with adaptive codebooks in enhancement layers and multi-layer gain optimization

International Journal of Electronics and Telecommunications

“…in the G.723.1 coder operating at 5.3 kbit/s [19]. c) multilayer , used in the G.718 coder [6], [12]:…”

“…Target of this paper is to propose algorithms for wideband speech coding at low delay of 1-2 ms. For VoIP applications scalable coders are required, able to switch between several bit rates, due to varying quality of transmission channels [12]. In packet transmission variable rate coder may be applied, where each packet refers to speech signal frame of different duration.…”

“…Optimal sparse excitation was tested using a modified Sphere Decoding algorithm [16]. Finally multilayer sparse excitation was synthesized, based on the ideas expressed in [12] and [15]. The proposed algorithm is scalable and it may be applied also in variable rate and embedded coders.…”

A Novel Approach for Supporting Approximate Representation of Linear Prediction Residuals in Pattern Recognition Tools

“…The standard multipulse algorithm uses a closedloop procedure for computing u(n), once the impulse response h(n) of the all-pole filter 1 A(z) is determined. The reconstructed signalx(n) is obtained by filtering the impulse excitation sequence u(n) with the all-pole filter as reported in Equation (6)…”

“…Therefore, the CELP performance depends on the size of the codebook and on the assumed statistical distribution. Improvements can be obtained using training algorithms for the design of the random codebooks [4,5] and using adaptive codebooks [6]. Second, exhaustive search imposes high computational complexity, which can be reduced using suitable structures of the codebook [7,8].…”