Computationally efficient adaptive bit allocation for encoding method and apparatus with allowance for decoder spectral distortions
Patent 5623577 Issued on April 22, 1997. Estimated Expiration Date: 
April 22, 2014. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
April 22, 2014. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesAudio signal subband encoder Method of compressing an audio signal using adaptive bit allocation taking account of temporal masking Patent #: 5475789 InventorApplicationNo. 190655 filed on 01/28/1994US Classes:704/200.1, Psychoacoustic704/221, Pattern matching vocoders704/226, Noise704/228, Post-transmission704/230QuantizationExaminersPrimary: MacDonald, Allen R.Assistant: Sartori, Michael A. Attorney, Agent or FirmForeign Patent References
International ClassG10L 009/00AbstractThe invention relates in general to low bit-rate encoding and decoding of information such as audio information. More particularly, the invention relates to computationally efficient adaptive bit allocation and quantization of encoded information useful in high-quality low bit-rate coding systems.In audio applications, a digital split-band encoder splits an input signal into frequency subband signals having bandwidths commensurate with the critical bandwidths of the human auditory system, quantizes the subband signals according to values established by an allocation function, and assembles the quantized subband signals into an encoded signal. The allocation function establishes allocation values in accordance with psychoacoustic principles with allowance for decoding synthesis filter bank spectral distortions.In one embodiment, an allocation function establishes allocation values using a psychoacoustic masking threshold generated by estimating the power spectral density (PSD) of the input signal, generating an excitation pattern by applying a basilar-membrane spreading function to the PSD, adjusting the excitation pattern by an amount equal to a sensitivity function which specifies a signal-to-noise ratio (SNR) sufficient to achieve psychoacoustic masking, comparing the level of the adjusted pattern to the threshold of hearing and generating the psychoacoustic masking threshold which is equal to the larger of the two. An allocation function may allow for decoder synthesis filter bank spectral distortions in any of a number of ways such as by adapting the sensitivity function.Other References
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