Adaptive digital audio encoding apparatus and a bit allocation m

Details Adaptive digital audio encoding apparatus and a bit allocation m Adaptive digital audio encoding apparatus and a bit allocation m

1994-12-30

1996-07-16

MacDonald, Allen R.

H04H 100, H04B 166

Patent

active

055375103

ABSTRACT:
A novel apparatus, capable of adaptively encoding an input digital audio signal, comprises a subband filtering device for receiving the input digital audio signal and filtering the received digital audio signal, on a subband-by-subband basis; a first estimator for estimating signal-to-mask ratio data, sound pressure levels and masking thresholds for the respective subbands of the digital audio signal; a second estimator for estimating perceptual entropies for the respective frames of the input digital audio signal based on the estimated signal-to-mask ratio data, sound pressure levels and masking thresholds and for deriving a mean and a standard deviation parameters for a frame group including two or more current and previous frames which corresponds to the estimated perceptual entropies; a bit allocation unit for adaptively determining bits for each of the subbands based on the estimated signal-to-mask ratio data, perceptual entropies, and mean and standard deviation parameters and for generating bit allocation information corresponding to the determined bits for each of the subbands; a quantizer for quantizing each of the filtered subbands of the digital audio signal in response to the generated bit allocation information for each of the subbands; and a formatting circuit formatting the quantized audio signal together with the generated bit allocation information.

REFERENCES:
patent: 5040217 (1991-08-01), Branderburg et al.
patent: 5285498 (1994-02-01), Johnston
patent: 5404377 (1995-04-01), Moses
patent: 5469474 (1995-11-01), Kitabatake
patent: 5473631 (1995-12-01), Moses
patent: 5481614 (1996-01-01), Johnston
James D. Johnston "Estimation of Perceptual Entropy Using Noise Masking Criteria", International Conference on Acoustics, Speech and Signal Processing, pp. 2524-2527, Apr. 1988.
Kai-Kuang Ma, "Generalized Optimum Bit Allocation Scheme For Source Compression," Image Processing, 1994 International Conference, pp. 864-868.
Anthony C. Koch and Michael P. Beddoes, "Analysis of Subband Quantization Noise Levels and Shapes", IEEE'1993, pp. 285-288.
James D. Johnston, "Transform Coding of Audio Signals Using Perceptual Noise Criteria," IEEE Journal on Selected Areas in Communications, vol. 6, No. 2, Feb. 1988, pp. 314-323.

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