Encoding, decoding and compression of audio-type data using reference coefficients located within a band of coefficients

Abstract

An audio type signal is encoded. The signal is first divided into bands. For each band, a yardstick signal element is selected. The yardstick may be the signal element having the largest magnitude in the band, the second largest, closest to the median magnitude, or having some other selected magnitude. This magnitude is used for various purposes, including assigning bits to the different bands, and for establishing reconstruction levels within a band. The magnitude of non yardstick signal elements is also quantized. The encoded signal is also decoded. Apparatus for both encoding and decoding are also disclosed. The location of the yardstick element within its band may also be recorded and encoded, and used for efficiently allocating bits to non-yardstick signal elements. Split bands may be established, such that each split band includes a yardstick signal element and each full band includes a major and a minor yardstick signal element.

Description

RELATED APPLICATION[0001]This is a continuation of application Ser. No. 07 / 879,635 filed on May 7, 1992, now U.S. Pat. No. 5,369,724, which is a continuation-in-part of Ser. No. 07 / 822,247, filed Jan. 17, 1992, now U.S. Pat. No. 5,394,508.[0002]The present invention relates generally to the field of signal processing, and more specifically to data encoding and compression. The invention relates most specifically to a method and an apparatus for the encoding and compression of digital data representing audio signals or signals generally having the characteristics of audio signals.BACKGROUND OF THE INVENTION[0003]Audio signals are ubiquitous. They are transmitted as radio signals and as part of television signals. Other signals, such as speech, share pertinent characteristics with audio signals, such as the importance of spectral domain representations. For many applications, it is beneficial to store and transmit audio type data encoded in a digital form, rather than in an analogue f...

AI Technical Summary

Benefits of technology

[0024]Thus, the several objects of the invention include, to provide a method and apparatus for coding and decoding digital audio-type signals: which permits efficient allocation of bits such that in general, fewer bits are used to specify coefficients of smaller magnitude then are used to specify larger coefficients; which provides for a quantization of the amplitude of the coefficients such that bands including larger coefficients are divided into reconstruction levels differently from bands including only smaller coefficients, such that both smaller and larger coefficients can be specified more accurately than if the same reconstruction levels were used for all coefficients; which permits accurate estimation of the masking level; which permits efficient allocation of bits based on the masking level; which robustly localizes errors to small portions of the digitized data, and, with respect to that data, limits the error to a small, known range; and that minimizes the need to redundantly encode coefficients, all allowing a highly efficient use of available bits.BRIEF DESCRIPTION OF THE INVENTION

Problems solved by technology

However, all such known methods result in either a significant waste of bits, or a significant sacrifice in the precision of quantizing the coefficient values.

The gross estimate (which is an inaccurate estimate) causes two problems: the bit allocation is not accurate; the bits that are allocated are not used efficiently, since the range of values for any given coefficient is not known accurately.

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