Patent ID: 7643996

Claim:
A method for using a computer processor to interpolatively code a digitized audio waveform input signal having a first bitrate into a coded audio waveform output signal having a second bitrate lower than said first bitrate, said method comprising the steps of: extracting a slowly evolving waveform from the digitized audio waveform input signal; estimating a dispersion phase of an excitation signal; locking onto a most probable pitch period; quantizing a sequence of gain trajectory correlation values; using the computer processor to transform the extracted slowly evolving waveform, the estimated dispersion phase, the most probable pitch period and the quantized sequence of gain trajectory values into an interpolatively coded audio waveform output signal with said lower bitrate; and outputting said coded audio waveform output signal, wherein said method comprises using the computer processor to execute at least one step selected from the group consisting of: (a) performing an analysis-by-synthesis vector quantization of the dispersion phase such that a linear shift phase residual is minimized; (b) computing a weighted average of a group of adjacent pitch values in order to computer the most probable pitch period; (c) performing spectral and temporal pitch searching in order to compute the most probable pitch period, such that the temporal pitch searching is performed at a different rate than the spectral pitch searching; (d) incorporating temporal weighting in an analysis-by-synthesis vector-quantization of the gain trajectory correlation values; (e) quantizing adjacent gain trajectory correlation values by analysis-by-synthesis vector-quantization without downsampling or interpolation; (f) incorporating switched prediction filtering in an analysis-by-synthesis vector-quantization of the sequence of gain trajectory correlation values; (g) temporal pitch searching with varying segment boundaries.