Coded data generation or conversion – Digital code to digital code converters – Unnecessary data suppression
Patent
1995-11-17
1997-10-21
Young, Brian K.
Coded data generation or conversion
Digital code to digital code converters
Unnecessary data suppression
341 50, 341 51, 395 292, H03M 730
Patent
active
056801300
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an information encoding method and apparatus for encoding information such as input digital data by high efficiency encoding, an information decoding method and apparatus for decoding encoded information, an information transmission method for transmitting encoded information, and an information recording medium in which encoded information is recorded.
BACKGROUND ART
There exist a variety of high efficiency encoding techniques of audio or speech signals. Examples of these techniques include transform coding in which a frame of digital signals representing the audio signal on the time axis is converted by an orthogonal transform into a block of spectral coefficients representing the audio signal on the frequency axis, and a sub-band coding (SBC) in which the frequency band of the audio signal is divided by a filter bank into a plurality of sub-bands without forming the signal into frames along the time axis prior to coding. There is also known a combination of sub-band coding and transform coding, in which signals representing the audio signal on the time axis are divided into bands by band division and are then transformed into signals on the frequency axis by spectral transform, and frequency components obtained by the spectral transform are encoded each band.
Among the filters for dividing a frequency spectrum into a plurality of equal-width frequency ranges include the quadrature mirror filter (QMF) as discussed in R. E. Crochiere, Digital Coding of Speech in Sub-bands, 55 Bell Syst. Tech. J. No.8 (1978). With the QMF filter, the frequency spectrum of the signal is divided into two equal-width bands. With the QMF, aliasing is not produced when the frequency bands resulting from the division are subsequently combined together.
In "Polyphase Quadrature Filters--A New Subband Coding Technique", Joseph H. Rothweiler ICASSP 83, Boston, there is shown a technique of dividing the frequency spectrum of the signal into equal-width frequency bands. With the present polyphase QMF, the frequency spectrum of the signals can be divided at a time into plural equal-width frequency bands.
There is also known a technique of orthogonal transform including dividing the digital input audio signal into frames of a predetermined time duration, and processing the resulting frames using a discrete Fourier transform (DFT), discrete cosine transform (DCT) and modified DCT for converting the signal from the time axis to the frequency axis. Discussions on MDCT may be found in J. P. Princen and A. B. Bradley, Subband Transform Coding Using Filter Bank Based on Time Domain Aliasing Cancellation", ICASSP 1987.
By quantizing the signals divided on the band basis by the filter or spectrum conversion, it becomes possible to control the band subjected to quantization noise and psychoacoustically more efficient coding may be achieved by utilizing the so-called masking effects. If the signal components are normalized from band to band with the maximum value of the absolute values of the signal components, it becomes possible to effect more efficient coding.
In a technique of quantizing the spectral coefficients resulting from an orthogonal transform, it is known to use sub-bands that take advantage of the psychoacoustic characteristics of the human auditory system. That is, spectral coefficients representing an audio signal on the frequency axis may be divided into a plurality of critical frequency bands, for example 25 critical bands. The width of the critical bands increase with increasing frequency. In such a quantizing system, bits are adaptively allocated among the various critical bands. For example, when applying adaptive bit allocation to the spectral coefficient data resulting from MDCT, the spectral coefficient data generated by the MDCT within each of the critical bands is quantized using an adaptively allocated number of bits.
There are presently known the following two bit allocation techniques. For example, in IEEE Transactions of Acoustics, Speech and Signal Processing, vol. ASSP
REFERENCES:
patent: 4485337 (1984-11-01), Sandusky
patent: 4669120 (1987-05-01), Ono
patent: 4908810 (1990-03-01), Oie
patent: 4972484 (1990-11-01), Theile
patent: 5040217 (1991-08-01), Brandenburg
patent: 5045812 (1991-09-01), Tateishi
patent: 5063550 (1991-11-01), Watari et al.
patent: 5109417 (1992-04-01), Fielder
patent: 5204677 (1993-04-01), Akagiri et al.
patent: 5301205 (1994-04-01), Tsutsui et al.
patent: 5311561 (1994-05-01), Akagiri
patent: 5355430 (1994-10-01), Huff
patent: 5440584 (1995-08-01), Wiese
patent: 5537510 (1996-07-01), Kim
patent: 5581653 (1996-12-01), Todd
Patent Abstract of Japan, vol. 14, No. 525 (P-1132) Nov. 19, 1990 & JP-A-22 20 271 (Pioneer Electronic Corporation) Sep. 3, 1990 *abstract*.
Shimoyoshi Osamu
Sonohara Mito
Tsutsui Kyoya
Kost Jason L. W.
Sony Corporation
Young Brian K.
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