Self-adaptive grid construction method and device used for bandwidth extended coding

Abstract

The invention relates to a self-adaptive grid construction method and device used for bandwidth extended coding. The method comprises the steps of: S1, based on transient property analysis of input monophonic audio signals, carrying out frequency resolution selection, carrying out self-adaptive multi-resolution filtering on the input monophonic audio signals, and obtaining an optimum time frequency filtering signal; and S2, carrying out transient detection and positioning on each sub-band signal output after the filtering, carrying out self-adaptive grid construction respectively in a frequency direction and a time direction according to the transient property analysis of each sub-band signal and by considering set high frequency band code rates and ear critical frequency band characteristics, and obtaining an optimum time frequency grid under a current code rate. The invention further relates to bandwidth extended coding and decoding methods based on the method. According to the invention, based on audio signal characteristics and high frequency signal available code rate limits, multi-resolution filtering and self-adaptive time frequency grid construction are carried out, and the coding efficiency of high frequency parts of digital audio signals and the sound quality of the high frequency part signals are obviously improved.

Description

technical field [0001] The present invention relates to digital audio codec technology, more specifically, relates to an adaptive grid construction method and device for bandwidth extension coding, and bandwidth extension coding and decoding methods using the method. Background technique [0002] The stereo typical working bit rate of traditional perceptual audio coding technologies (DRA, AAC, MP3, etc.) is 96-128kbps, and the coding quality has obvious subjective perception distortion when it is below 64kbps / stereo. The typical coding bit rate of FM broadcasting application is 48kbps~64kbps / stereo. At this time, the subjective sound quality of traditional sensory audio coding technology can no longer meet the requirements of FM broadcasting. [0003] To this end, a bandwidth extension (BandWidthExtension, BWE for short) coding technique for digital audio signals is proposed. There are many bandwidth extension coding technologies at present, and their performances are also ...

AI Technical Summary

Problems solved by technology

[0007] The bandwidth extension coding technology of 3GPP AMR-WB+ has the following problems: (1) Realizing high-frequency coding in the time domain cannot obtain higher frequency resolution, because this method can be considered as only one high-frequency area division; (2) The starting frequency band of the encoding is fixed and can only be Fs / 4. For the sampling frequency of 48khz, the starting frequency of high-frequency encoding is 12khz; (3) the harmonic signal in the high frequency cannot be accurately recovered; (4) the high frequency The envelope restoration of the signal is not accurate enough

[0008] In addition, there are some bandwidth extension coding techniques. The time-frequency transformation unit uses traditional FFT, and then divides the high frequency into several regions in the frequency domain, and encodes the spectral energy of each region, so each frame can only provide a time-resolved rate multiple frequency resolution

This FFT-based high-frequency reconstruction technology has high frequency-domain resolution but too low time-domain resolution. When a rapidly changing audio signal is input, the high-frequency reconstructed signal cannot track the changes of the original audio signal well.

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