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.

Audio signal encoder/decoder for use in low delay applications, selectively providing aliasing cancellation information while selectively switching between transform coding and celp coding of frames

Abstract: An audio signal encoder includes a transform-domain path which obtains spectral coefficients and noise-shaping information on the basis of a portion of the audio content, and which windows a time-domain representation of the audio content and applies a time-domain-to-frequency-domain conversion. The audio signal decoder includes a CELP path to obtain a code-excitation information and a LPC parameter information. A converter applies a predetermined asymmetric analysis window in both if a current portion is followed by a subsequent portion to be encoded in the transform-domain mode or in the CELP mode. Aliasing cancellation information is selectively provided in the latter case.

Flexible Quantization of Audio and Speech based on the Autoregressive Model

Abstract: We describe a coding scheme based on audio and speech quantization with an adaptive quantizer derived from the autoregressive model under high-rate assumptions The main advantage of this scheme compared to state-of-the-art training-based coders is its flexibility The scheme can adapt in real time to any particular rate and has a computational complexity independent of the rate Experiments indicate that, compared with a non-scalable conventional fixed-rate code-excited linear predictive (CELP) coding scheme, our real time scalable coder with scalar quantization performs at least as well in the constrained entropy case, and has nearly identical performance for the constrained resolution case

Hiding of frame erasure and method for the same

Abstract: PROBLEM TO BE SOLVED: To provide a method of hiding an erased CELP encoding frame which is improved in performance for comparison with an iteration type hiding method. SOLUTION: The decoder for the frame which is subjected to code excitation and CELP encoding by both of an adaptive code book and a fixed code book. The iterative excitation, the smoothing of a pitch gain (gP (i)) of the next good frame and the multi-level articulation classification by the multiple thresholds of the correlation to determine the adaptive code book excitation contribution component subjected to linear interpolation and the fixed ode book excitation contribution component are used.

Automatic Speech Codec Identification with Applications to Tampering Detection of Speech Recordings

Abstract: In this paper we explored many versions of CELP codecs and studied different codebooks they use to encode noisy part of residual. Taking advantage of noise patterns they generated, an algorithm was proposed to detect GSM-AMR,EFR,HR and SILK codecs. Then it’s extended to identify subframe offset to do tampering detection of cellphone speech recordings.

A modified CS-ACELP algorithm for variable-rate speech coding robust in noisy environments

Abstract: This letter deals with a variable bit-rate CS-ACELP speech coder based on new algorithms that are robust in the presence of the background noise typical of wireless communications. The coder presents eight operating modes ranging from 0-8 kbit/s with an average bit-rate of about 4 kbit/s. Subjective and objective comparisons with the recent ITU-T G.729 8 kbit/s standard, used in the discontinuous transmission mode, demonstrate that the proposed coder provides an average bit rate reduction of about 20% maintaining the same algorithmic delay and perceptive quality.