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.

Multipulse excitation codebook design and fast search methods for CELP speech coding

Abstract: Presents an efficient method for multipurpose excitation coding using direct vector quantization. This method is then extended to the design of the excitation codebook for a CELP (code excited linear predictive) coder. For the best excitation-vector search at low data rates, an approach combining direct vector quantization and an analysis-by-synthesis procedure is used. Computer simulation results for a 4.8 kb/s speech coder based on the new excitation codebook are presented. >

Fast search algorithm of adaptive code-book for speech coding

Abstract: Code Excited Linear Prediction(CELP) can provide high voice quality at low bit rates,but it has high computational complexity.Adaptive code-book search plays an important role in most CELP by replacing long-term prediction.In this paper a new adaptive code-book search algorithm is applied for the conventional algorithm of 4.8 kbp FS1016 and the new algorithm can significantly simplify the computation of code-book search.

Hybrid MELP/CELP coding at bit rates from 6.4 to 2.4 kb/s

Abstract: This paper describes extensions of the 4 kb/s hybrid MELP/CELP coder, up to 6.4 kb/s and down to 2.4 kb/s. The baseline 4 kb/s coder uses three coding modes: MELP in strongly voiced speech frames, CELP with pitch prediction in weakly voiced frames, and CELP with stochastic excitation in unvoiced frames. To minimize switching artifacts between parametric MELP and waveform CELP coding, an alignment phase is encoded in MELP and zero-phase equalization is applied to the CELP target signal. The 6.4 kb/s extension uses the same three modes as the 4 kb/s coder, with improved MELP and CELP coders. The 2.4 kb/s extension uses only two modes: MELP for voiced frames and CELP synthesis with random excitation for unvoiced frames. The alignment phase is encoded in MELP frames for all bit rates so that time synchrony with input speech is always maintained. Alignment phase and zero-phase equalization enable smooth switching between coders at different bit rates. The hybrid MELP/CELP coding structure leads to coders that perform better at a given bit rate than MELP or CELP separately, and better than or equivalent to higher bit-rate ITU standards. Formal subjective tests show that for all-but-one tested conditions, the 6.4 kb/s hybrid coder is better than 8 kb/s G.729 and the 2.4 kb/s coder is equivalent to, or better than, 6.4 kb/s G.729 Annex D.

Improvement to vector quantizing coder

Abstract: A signal vector quantizing coder (CELP) is provided with an adaptive codebook originally loaded with preselected codewords. The codebook is split into a fixed contents portion and a fixed length adaptive contents portion. During coding operations, the codewords dynamically selected for coding the coder input signal are shifted into the fixed length adaptive codebook section for codebook contents updating purposes.

Speech decoding method and apparatus

Abstract: PROBLEM TO BE SOLVED: To reproduce a high quality speech with a small data amount in speech coding and decoding for performing compression coding of a speech signal to a digital signal. SOLUTION: In a code-excited linear prediction (CELP) speech coding, a noise level of the speech in a concerning coding period is evaluated by using a code or coding result of at least one of spectrum information, power information, and pitch information, and various excitation codebooks 19 and 20 are used in response to an evaluation result. COPYRIGHT: (C)2006,JPO&NCIPI