Code-excited linear prediction

About: Code-excited linear prediction is a research topic. Over the lifetime, 2025 publications have been published within this topic receiving 28633 citations. The topic is also known as: CELP.

Flexible and scalable combined innovation codebook for use in CELP coder and decoder

Abstract: In a CELP coder, a combined innovation codebook coding device comprises a pre-quantizer of a first, adaptive-codebook excitation residual, and a CELP innovation-codebook search module responsive to a second excitation residual produced from the first, adaptive-codebook excitation residual. In a CELP decoder, a combined innovation codebook comprises a de-quantizer of pre-quantized coding parameters into a first excitation contribution, and a CELP innovation-codebook structure responsive to CELP innovation-codebook parameters to produce a second excitation contribution.

Speech compression exploiting linear prediction coefficients codebook and hamming correction code algorithm

Abstract: In this paper, a replacement algorithm for Linear Prediction Coefficients (LPC) along with Hamming Correction Code based Compressor (HCDC) algorithms are investigated for speech compression. We started with an CELP system with order 12 and with Discrete Cosine Transform (DCT) based residual excitation. Forty coefficients with transmission rate of 5.14 kbps were first used. For each frame of the testing signals we applied a multistage HCDC, we tested the compression performance for parities from 2 to 7, we were able to achieve compression only at parity 4. This rate reduction was made with no compromise in the original CELP signal quality since compression is lossless. The compression approach is based on constructing dynamic reflection coefficients codebook, this codebook is constructed and used simultaneously using a certain store/retrieve threshold. The initial linear prediction codec we used is excited by a discrete cosine transform (DCT) residual, the results were tested using the MOS and SSNR, we had acceptable ranges for the MOS (average 3.6), and small variations of the SSNR (±5 db).

Low bit-rate speech coding using quantization of variable length segments.

Abstract: This paper describes a new segmentation and quantization technique for low bit-rate speech coders. Bit-rate reduction is achieved by combining segmentation and quantization, where a segment consists of one or more adjacent frames. The algorithm for selecting and quantizing segments from a pre-determined number of frames extends the frame-based trellis techniques. It models the input speech as a sequence of variable length segments with the option to interpolate frames in skipped segments. The new algorithm, denoted as Trellis Segmentation-Quantization (TSQ), reduces the bit-rate needed for spectral envelope representation, with only a small degradation in log-spectral distance values. Experimental results show that TSQ achieves a lower spectral distance than alternate frame transmission, matrix quantization and trellis based frame selection and interpolation.

Layered Code-Excited Linear Prediction Speech Encoder and Decoder Having Plural Codebook Contributions in Enhancement Layers Thereof and Methods of Layered CELP Encoding and Decoding

Abstract: A layered code-excited linear prediction (CELP) encoder, an Adaptive Multirate Wideband (AMR-WB) encoder and methods of CELP encoding and decoding. In one embodiment, the encoder includes: (1) a core layer subencoder and (2) at least one enhancement layer subencoder having an adaptive-gain multiplier configured to apply a gain for an adaptive contribution to excitation and a fixed-gain multiplier configured to apply a gain for a fixed contribution to the excitation that is separate from the gain for the adaptive contribution.