Abstract: An audio coding method and apparatus capable of improving efficiency of a MPEG-4 AAC (Moving Picture Expert Group-4 Advanced Audio Coding) process are disclosed. The audio coding method and apparatus reduce the number of calculations of an audio coding algorithm to improve efficiency of an audio coding process. Specifically, the audio coding method and apparatus reduce the number of calculations required for a Psychoacoustic model process of the MPEG-4 AAC algorithm capable of coding an audio signal.

Abstract: There is provided a speech coding/decoding apparatus and method, in which the input speech signals are classified into several classes in accordance with characteristics of the input speech signals and the input speech signals are coded using frame sizes, quantizer structures, and bit assignment methods corresponding to the determined classes, or in which the frame sizes can be adjusted in accordance with network conditions or codec type of a counter part. Therefore, by optimally adjusting the frame size, the quantizer structure, and the bit assignment method in accordance with the characteristics of input speech, it is possible to improve the performance of the speech coding apparatus, and by adjusting the frame size in accordance with the speech codec type of a counter part, it is also possible to reduce the total end-to-end delay.

Abstract: Provided are a speech restoration system and method for concealing packet losses.

Abstract: A wide-band speech coder and a method thereof and a wide-band speech decoder and a method thereof are provided.

Abstract: A transcoder for use between speech codecs using different Code-Excited Linear Prediction (CELP) type and a method therefor are disclosed. The transcoder includes a decoding unit of an input CELP codec, a transcoding filter, a transcoding filter design unit, and an encoding unit of an output CELP codec. By substituting a post-filter and a perceptual weighting filter of a prior art with one transcoding filter, the calculation amount of the transcoder is reduced, and speech quality decoded at a receiving end is improved.