Coded data generation or conversion – Digital code to digital code converters
Patent
1995-09-27
1998-03-24
Gaffin, Jeffrey A.
Coded data generation or conversion
Digital code to digital code converters
395 234, H03M 730, H04B 1400, G11B 2010
Patent
active
057317674
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an information encoding method and an information encoding apparatus, an information decoding method and an information decoding apparatus, an information recording medium, and an information transmission method suitable when used in such a system to carry out encoding of input digital data by so called efficient encoding to allow encoded data to undergo transmission, recording, reproducing and decoding thus to obtain reproduced signals.
BACKGROUND ART
Hitherto, various efficient encoding techniques for audio signals or speech signals, etc. are known. For example, there can be enumerated a Sub Band Coding (SBC), which is the non-blocking frequency division system, for dividing an audio signal, etc. on the time base into signal components in a plurality of frequency bands without carrying out blocking to encode them, a blocking frequency band division system so called a transform encoding for transforming (spectrum-transforming) a signal on the time base into a signal on the frequency base thereafter to divide it into signal components in a plurality of frequency bands to encode them every respective bands. Moreover, an efficient encoding technique in which the Sub Band Coding (SBC) and the transform encoding described above are combined is also proposed. In this case, for example, band division is carried out by the Sub Band Coding thereafter to spectrum-transform signals every respective bands into signals on the frequency base to encode these spectrum-transformed signals every respective bands.
Here, as a band division filter used in the above-described Sub Band Coding, there is, e.g., QMF filter. This QMF filter is described in Digital coding of speech in subbands, R. E. Crochiere, Bell Syst. Tech. J. Vol. 55, No. 8 1976.
Moreover, in the literature "Polyphase Quadrature filters-A new subband coding technique, Joseph H. Rothweiler, ICASSP 83 BOSTON, filter division technique of equal bandwidth is described.
Further, as the above-described spectrum transform processing, there is, e.g., such a spectrum transform processing to carry out blocking of an input audio signal every predetermined unit time (frame) to carry out, every respective blocks, Discrete Fourier Transform (DFT), Discrete Cosine Transform (DCT), or Modified DCT (MDCT), etc. to thereby transform signals on the time base into signals on the frequency base. The above-mentioned MDCT is described in the literature "Subband/Transform Coding Using Filter Bank Designs Based on Time Domain Aliasing Cancellation, J. P. Princen, A. B. Bradley, Univ. of Surrey, Royal Melbourne Inst. of Tech. ICASSP 1987.
By quantizing signals divided every bands by filter or spectrum transform processing in this way, it is possible to control bands where quantizing noises are produced. Thus, it is possible to carry out more efficient encoding from a viewpoint of the hearing sense by making use of the property such as so called masking effect, etc. In addition, if there is employed an approach to carry out, prior to implementation of quantization, normalization, every respective bands, e.g., by the maximum value of the absolute values of signal components in corresponding bands, further more efficient encoding can be carried out.
Here, there are many instances where as frequency division width in the case where respective frequency components subjected to frequency division are quantized, e.g., bandwidths in which the hearing sense characteristic of the human being is taken into consideration are used. Namely, there are instances where an audio signal is divided into signal components in plural (e.g., 25) bands by bandwidths generally called critical bands such that according as frequency shifts to higher frequency band side, bandwidths are broader. Moreover, in encoding data every respective bands at this time, a predetermined bit allocation is carried out every respective bands, or adaptive bit allocation is carried out every respective bands to carry out quantization. For example, in quantizing coefficient data obtained a
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Heddle Robert
Tsutsui Kyoya
Gaffin Jeffrey A.
Jean-Pierre Peguy
Sony Corporation
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