Abstract:
Provided is a residual signal coding/decoding apparatus and method. The residual signal coding apparatus includes a transformer, a band splitter, a pulse searcher, and a pulse quantizer. The transformer transforms time-domain residual signals into a frequency domain to output transform coefficients. The band splitter splits the transform coefficients into bands to output the transform coefficients. The pulse searcher searches the transform coefficients for the respective bands to select optimal pulses and output parameters of the optimal pulses. The pulse quantizer quantizes the parameters of the optimal pulses.
Abstract:
A post-filtering apparatus and method for speech enhancement in a modified discrete cosine transform (MDCT) domain are disclosed. In the apparatus and method, previous and current MDCT coefficients are used for obtaining a speech spectrum coefficient similar to a real speech spectrum, and a convex function is used for transforming the speech spectrum coefficient and obtaining a post-filter coefficient so that difference can increase in the case where the speech spectrum coefficient is small but decrease in the case where the coefficient is large. Then, the post-filter coefficient is applied to the MDCT coefficient. With this configuration, both the current and previous MDCT values are used, so that it is possible to obtain a spectrum coefficient similar to the real speech spectrum and to obtain a more accurate filter coefficient. Further, the coefficient is adaptively transformed through the convex function, thereby enhancing speech quality.
Abstract:
Disclosed is a packet (frame) loss concealment method and device for a VoIP system, for reducing speech quality degradation caused by packet loss generated when transmitting speech data through a packet network. When a packet loss occur, the speech signal of the lost frame are reconstruct by combing the forward and backward prediction from the good frame before and after the lost frame Thus, speech quality of a speech coder can be improved without any extra delay in packet loss condition.
Abstract:
An apparatus and method of improving the quality of a speech codec are provided. In the method, a first energy of a signal decoded by a core codec is calculated, and a second energy of a signal decoded by a low-band enhancement mode is calculated. Then, when the first energy is less than a first threshold value or less than a product of the second energy and a second threshold value, a size of the decoded signal is scaled. Accordingly, generation of a quantization error with respect to a silence segment is reduced.
Abstract:
Provided are a method and an apparatus for encoding and decoding an audio signal. A method for encoding an audio signal includes receiving a transformed audio signal, dividing the transformed audio signal into a plurality of subbands, performing a first sinusoidal pulse coding operation on the subbands, determining a performance region of a second sinusoidal pulse coding operation among the subbands on the basis of coding information of the first sinusoidal pulse coding operation, and performing the second sinusoidal pulse coding operation on the determined performance region, wherein the first sinusoidal pulse coding operation is performed variably according to the coding information. Accordingly, it is possible to further improve the quality of a synthesized signal by considering the sinusoidal pulse coding of a lower layer when encoding or decoding an audio signal in an upper layer by a layered sinusoidal pulse coding scheme.
Abstract:
Provided is an audio coding apparatus and method that can selectively apply a operation mode of a coding module for stereo or multi-channel representation according to input signal characteristics of each channel, when voice or music signals are transmitted using an audio codec in portable terminals capable of stereo or multi-channel input and output. The audio coding apparatus includes a down-mixer for down-mixing multi-channel audio signals into mono signals; a coder for coding the mono signals; an input channel correlation analyzer for deciding whether to give them stereo effect based on their signal distribution characteristics, and outputting a control signal indicating whether to perform stereo representation process; and a stereo representation unit for performing stereo representation process onto the multi-channel audio signals when the control signal indicating to perform stereo representation process.
Abstract:
Provided are a packet processing apparatus and method used when an output bitstream of an embedded codec is divided into a plurality of packets and transmitted accordingly, and more particularly, an efficient packet processing apparatus and method which can reduce deterioration of sound quality which may occur when a packet required for the reproduction of a voice signal is not received due to different arrival times of a plurality of packets at a receiving end if an output bitstream of an embedded codec is divided into the packets and transmitted accordingly through a path or a plurality of paths. In particular, an apparatus for processing packets of an embedded codec is provided. The apparatus includes a packet reception unit receiving packets, a layer information unit identifying layer information from received packets, a bitstream determination unit using the received packets, and a bitstream generation unit generating a new bitstream. The apparatus is used to provide a voice and multimedia service using an embedded codec in a packet network.
Abstract:
An apparatus and method of improving the quality of a speech codec are provided. In the method, a first energy of a signal decoded by a core codec is calculated, and a second energy of a signal decoded by a low-band enhancement mode is calculated. Then, when the first energy is less than a first threshold value or less than a product of the second energy and a second threshold value, a size of the decoded signal is scaled. Accordingly, generation of a quantization error with respect to a silence segment is reduced.
Abstract:
An apparatus for coding of variable bitrate wideband speech and audio is described. The apparatus utilizes: a) a speech and audio divider for dividing signals inputted to a CODEC into speech or audio signals; b) a narrowband coder for performing narrowband coding, in the case the divided input signals are speech signals; c) a bitrate modifier for modifying a bitrate for coding of low frequency band and a bitrate for coding of a high frequency band, in the case the divided input signals are audio signals; and d) a wideband coder for performing coding by the modified bitrate in the bitrate modifier.
Abstract:
Provided is a highband coding apparatus and method for a wideband coding system. The coding apparatus and method can reduce a pre-echo phenomenon by encoding the highband based on lowband encoding information and Temporal Noise Shaping technique. A highband encoding apparatus includes: a domain converter for converting the domain of an input highband signal into a frequency domain; a linear prediction order determiner for determining a linear prediction order based on the lowband encoding information; a linear prediction analyzer for analyzing a highband signal of the frequency domain based on the determined linear prediction order to thereby generate a linear prediction coefficient; a linear prediction coefficient quantizer for quantizing the linear prediction coefficient based on the lowband encoding information; and a residual signal quantizer for obtaining a residual signal by dequantizing the quantized linear prediction coefficient and quantizing the residual signal.