Patent ID: 8874450
Filing Date: 2014-10-28
Classification: G10L

Abstract:
1. A hierarchical audio coding method, comprising: performing a transient detection on an audio signal of a current frame; when the transient detection is to be a steady-state signal, performing a time-frequency transform on an audio signal to obtain total frequency-domain coefficients; when the transient detection is to be a transient signal, dividing the audio signal into M sub-frames, performing the time-frequency transform on each sub-frame, M groups of frequency-domain coefficients obtained by transformation constituting total frequency-domain coefficients of the current frame, rearranging the total frequency-domain coefficients so that their corresponding coding sub-bands are aligned from low frequencies to high frequencies, wherein, the total frequency-domain coefficients comprise core layer frequency-domain coefficients and extended layer frequency-domain coefficients, the coding sub-bands comprise core layer coding sub-bands and extended layer coding sub-bands, the core layer frequency-domain coefficients constitute several core layer coding sub-bands, and the extended layer frequency-domain coefficients constitute several extended layer coding sub-bands; quantizing and coding amplitude envelope values of the core layer coding sub-bands and the extended layer coding sub-bands, to obtain amplitude envelope quantization indexes and amplitude envelope coded bits of the core layer coding sub-bands and the extended layer coding sub-bands; wherein, if the signal is the steady-state signal, the amplitude envelope values of the core layer coding sub-bands and the extended layer coding sub-bands are jointly quantized, and if the signal is the transient signal, the amplitude envelope values of the core layer coding sub-bands and the extended layer coding sub-bands are separately quantized respectively, and the amplitude envelope quantization indexes of the core layer coding sub-bands and the amplitude envelope quantization indexes of the extended layer coding sub-bands are rearranged respectively; performing a bit allocation on the core layer coding sub-bands according to the amplitude envelope quantization indexes of the core layer coding sub-bands, and then quantizing and coding the core layer frequency-domain coefficients to obtain coded bits of the core layer frequency-domain coefficients; inversely quantizing the above-described frequency-domain coefficients in a core layer which are performed with a vector quantization, and performing a difference calculation between the inversely quantized frequency-domain coefficients and original frequency-domain coefficients, which are obtained after being performed with the time-frequency transform, to obtain core layer residual signals; calculating the amplitude envelope quantization indexes of the core layer residual signals according to bit allocation numbers and the amplitude envelope quantization indexes of the core layer coding sub-bands; performing the bit allocation on coding sub-bands of extended layer coding signals according to the amplitude envelope quantization indexes of the core layer residual signals and the amplitude envelope quantization indexes of the extended layer coding sub-bands, and then quantizing and coding the extended layer coding signals to obtain coded bits of the extended layer coding signals, wherein, the extended layer coding signals are composed of the core layer residual signals and the extended layer frequency-domain coefficients; and multiplexing and packeting the amplitude envelope coded bits of the core layer coding sub-bands and the extended layer coding sub-bands, the coded bits of the core layer frequency-domain coefficients and the coded bits of the extended layer coding signals, and then transmitting to a decoding end.