Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Patent
1996-01-22
1998-05-26
Tung, Kee M.
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
704230, G10L 900
Patent
active
057583153
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an encoding method, a decoding method, an encoding/decoding method, an encoding apparatus, a decoding apparatus, and an encoding/decoding apparatus suitable when used for dividing an original signal such as audio data, etc. into signals (signal components) in a plurality of frequency bands to carry out encoding/decoding thereof, and more particularly relates to an encoding method, a decoding method, an encoding/decoding method, an encoding apparatus, a decoding apparatus, and an encoding/decoding apparatus such that, in quantizing subband signals obtained after undergone frequency band division, or spectrum signals obtained by orthogonal transform processing, etc., the numbers of bits are dynamically allocated to respective subbands or respective spectrum groups.
BACKGROUND ART
For example, as the technique for encoding audio data, there is so called Sub-Band Coding (SBC) for dividing audio data into data portions in a plurality of frequency bands to encode them.
In accordance with the Sub-Band Coding system, in the case where the numbers of bits for quantizing sub-band signals obtained after undergone frequency band division by the Band Pass Filter (BPF) are allocated, there is conducted a processing to calculate energies of respective sub-bands by using the sub-band signals to allocate the numbers of bits thereto in dependency upon their energies.
Alternatively, apart from the sub-band signals, there is carried out a processing to determine spectrum components (spectrum signals) by the Fast Fourier Transform (FFT), etc. to allocate the numbers of bits by making use of the auditory sense characteristic from those spectrum components (spectrum signals).
Moreover, in the so-called Transform Coding for bundling spectrum components (spectrum signals) obtained after undergone the orthogonal transform processing, etc. by several components so that they are divided into groups to carry out quantization every respective spectrum groups, in the case where the numbers of bits are allocated to respective spectrum groups, a processing for allocating the numbers of bits in dependency upon energies of respective spectrum groups, and a processing for allocating the numbers of bits by making use of the auditory sense characteristic from the spectrum are carried out.
In a manner as described above, the numbers of bits are allocated to respective sub-bands or respective spectrum groups, and sub-band signals or spectrum signals are normalized by scale factors in dependency upon the allocated numbers of bits. Quantization processing is implemented to the signals thus normalized. Then, the sub-band signals or the spectrum signals which have undergone quantization processing are composed into a bit stream for transmission or recording onto the recording medium in accordance with a predetermined format. The bit stream thus composed is outputted.
In this case, in decoding data which has undergone encoding processing in a manner as described above, bit allocation information which is the numbers of bits allocated to the sub-bands or the spectrum groups cannot be determined by inverse operation from the encoded data. For this reason, a format adapted for recording, at the same time, bit allocation information along with scale factors is used.
Further, e.g., in the memory for composition into the bit stream, in composition into the bit stream in accordance with the format determined as described above, there is limitation in capacity for storing the bit allocation information into the memory. For this reason, after upper limit is set with respect to the number of allocation bits, bit allocation to the sub-bands or the spectrum groups is carried out.
For example, in the Precision Adaptive Subband Coding (PASC) system employed in the so-called Digital Compact Cassette (DCC), in allocating the numbers of bits to respective bands obtained after undergone frequency band division, Fourier Transform is used to calculate spectrum components. Then, those spectrum components are used to calculate
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Frommer William S.
Sony Corporation
Tung Kee M.
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