DIFFERENTIAL-TRANSFORM-CODED EXCITATION FOR SPEECH AND AUDIO CODING

摘要

A method for coding speech is disclosed. This method, called DTCX (Differential-Transform-Coded Excitation), combines in a new way, the best features of time domain techniques such as CELP (Code-Excited Linear Prediction) with the best features of frequency-domain techniques such as TC (Transform coding) while avoiding their respective drawbacks. The invention preserves the principle of error m i n i m i z a t i o n i n t h e perceptually-weighted-speech(/audio) domain which is found in CELP along with techniques such as linear filtering and pitch prediction, yet, it circumvents the complexity of the CELP analysis-by-synthesis approach by using quantization. The invention also takes advantage of the efficient frequency-domain differential-quantization techniques typical of transform coding (TC) such as spectral decimation, flexible bit allocation as well as numerous forms of stored or algebraic vector quantization techniques. In addition, it is the difference between the current and previous spectra which is quantized resulting in enhanced performance in particular for audio coding. Yet unlike TC, the invention is essentially free from framing problems that plague block transforming of continuous processes.