Encoding/decoding method and apparatus using bit allocation as a function of scale factor

• US 5,758,315 A
• Filed: 01/22/1996
• Issued: 05/26/1998
• Est. Priority Date: 05/25/1994
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Mori, Masahito
• Primary Examiner(s): Tung, Kee M.
• Application Number:
  US08/583,080
• Time in Patent Office: 855 Days
• Field of Search: 395/2.38, 395/2.39, 395/2.91-2.95, 704/229, 704/230, 704/500-504
• US Class Current: 704/229
• CPC Class Codes: G10L 19/002 Dynamic bit allocation for perceptual audio coders G10L19/032
• CPC Class Codes: G10L 19/0204 using subband decomposition
• CPC Class Codes: G10L 19/0208 Subband vocoders
• CPC Class Codes: G10L 19/083 the excitation function being an excitation gain G10L25/90 takes precedence

Abstract

At an encoder 1, an input signal delivered to an input terminal 100 is divided into 32 subband signals by an analysis filter bank 101 to determine scale factors indicating magnification which normalizes respective subband signals by a scaling section 102 to determine the numbers of allocation bits of the respective subband signals by a bit allocation section 103 in dependency upon their scale factors to quantize the respective subband signals by the determined numbers of allocation bits by a quantizing section 104 to encode the respective quantized subband signals and the scale factors with respect to the respective subband signals. On the other hand, at a decoder 2, an inverse quantizing section 108 is used to determine the numbers of allocation bits by using scale factors included in the encoded signal with respect to the respective subband signals of the encoded signal to inverse-quantize the subband signals to judge whether or not scale factors are preserved with respect to the respective inverse-quantized subband signals to carry out, for a second time, inverse quantization with respect to the subband signals where no scale factor is preserved so as to preserve scale factors.

Claims

1. An encoding method, comprising the steps of:

dividing an input signal into a plurality of signals, each of the signals being in a preselected frequency band;

calculating a corresponding scale factor for each of the signals;

allocating a number of bits to each of the signals as a function of said corresponding scale factor by ascertaining for said each signal whether no bits have been allocated to a respective signal such that 2 bits are allocated to said respective signal, by ascertaining whether some bits have been allocated to said respective signal such that an additional 1 bit is allocated thereto, and by ascertaining whether a predetermined number of bits has been fully allocated to said respective signal such that no additional bits are allocated thereto;

quantizing each of the signals with the corresponding allocated bits; and

encoding each of the quantized signals and each of the scale factors.

2. The method according to claim 1, wherein each of the signals is a subband signal.

3. The method according to claim 1, wherein each of the signals is a spectrum signal.

4. The method according to claim 1, wherein said calculating step is defined by SF=r^SFid/s+k, wherein SFid is a quantized dynamic range of one of the signals, SF is said corresponding scale factor, and r, s and k are predetermined constants.

5. The method according to claim 1, wherein a variable number of bits are allocated to each of the signals.

6. A decoding method for decoding an encoded signal by dividing an input signal into a plurality of signals, each of the signals being in a preselected frequency band, by calculating a corresponding scale factor for each of the signals, by allocating a number of bits to each of the signals as a function of said corresponding scale factor by ascertaining for said each signal whether no bits have been allocated to a respective signal such that 2 bits are allocated to said respective signal, by ascertaining whether some bits have been allocated to said respective signal such that an additional 1 bit is allocated thereto, and by ascertaining whether a predetermined number of bits has been fully allocated to said respective signal such that no additional bits are allocated therto, by quantizing each of the signals with the corresponding allocated bits, and by encoding each of the quantized signals and each of the scale factors, said decoding method comprising the steps of:

determining how many bits had been allocated to each of the signals as a function of the encoded corresponding scale factor;

inverse-quantizing each of the signals with the corresponding allocated bits;

determining whether each of the scale factors is preserved; and

inverse-quantizing each of the signals if none of the scale factors is preserved, wherein said encoded signal is so decoded that each of the scale factors is preserved.

7. The method according to claim 6, wherein each of the signals is a subband signal.

8. The method according to claim 6, wherein each of the signals is a spectrum signal.

9. An encoding/decoding method, comprising the steps of:

dividing an input signal into a plurality of signals, each of the signals being in a preselected frequency band;

calculating a corresponding scale factor for each of the signals;

allocating a number of bits to each of the signals as a function of said corresponding scale factor by ascertaining for said each signal whether no bits have been allocated to a respective signal such that 2 bits are allocated to said respective signal, by ascertaining whether some bits have been allocated to said respective signal such that an additional 1 bit is allocated thereto, and by ascertaining whether a predetermined number of bits has been fully allocated to said respective signal such that no additional bits are allocated thereto;

quantizing each of the signals with the corresponding allocated bits;

encoding each of the quantized signals and each of the scale factors;

determining how many bits had been allocated to each of the signals as a function of the encoded corresponding scale factor;

inverse-quantizing each of the signals with the corresponding allocated bits;

determining whether each of the scale factors is preserved; and

inverse-quantizing each of the signals if none of the scale factors is preserved, wherein said encoded signal is so decoded that each of the scale factors is preserved.

10. The method according to claim 9, wherein each of the signals is a subband signal.

11. The method according to claim 9, wherein each of the signals is a spectrum signal.

12. The method according to claim 9, wherein said calculating step is defined by SF=r^SFid/s+k, wherein SFid is a quantized dynamic range of one of the signals, SF is said corresponding scale factor, and r, s and k are predetermined constants.

13. The method according to claim 9, wherein a variable number of bits are allocated to each of the signals.

14. Encoding apparatus, comprising:

band dividing means for dividing an input signal into a plurality of signals, each of the signals being in a preselected frequency band;

scaling means for calculating a corresponding scale factor for each of the signals;

bit allocation means for allocating a number of bits to each of the signals as a function of said corresponding scale factor by ascertaining for said each signal whether no bits have been allocated to a respective signal such that said bit allocation means is operative to allocate 2 bits to said respective signal, by ascertaining whether some bits have been allocated to said respective signal such that said bit allocation means is operative to allocate an additional 1 bit thereto, and by ascertaining whether a predetermined number of bits has been fully allocated to said respective signal such that said bit allocation means is operative to allocate no additional bits thereto;

quantizing means for quantizing each of the signals with the corresponding allocated bits; and

formatting means for encoding each of the quantized signals and each of the scale factors, and for outputting thereof.

15. Apparatus according to claim 14, wherein each of the signals is a subband signal.

16. Apparatus according to claim 14, wherein each of the signals is a spectrum signal.

17. Apparatus according to claim 14, wherein said corresponding scale factor is defined by r^SFid/s+k, wherein SFid is a quantized dynamic range of one of the signals, and r, s and k are predetermined constants.

18. Apparatus according to claim 14, wherein a variable number of bits are allocated to each of the signals.

19. Decoding apparatus for decoding an encoded signal, including band dividing means by dividing an input signal into a plurality of signals, each of the signals being in a preselected frequency band, scaling means for calculating a corresponding scale factor for each of the signals, bit allocation means for allocating a number of bits to each of the signals as a function of said corresponding scale factor by ascertaining for said each signal whether no bits have been allocated to a respective signal such that said bit allocation means is operative to allocate 2 bits to said respective signal, by ascertaining whether some bits have been allocated to said respective signal such that said bit allocation means is operative to allocate an additional 1 bit thereto, and by ascertaining whether a predetermined number of bits has been fully allocated to said respective signal such that said bit allocation means is operative to allocate no additional bits thereto, quantizing means for quantizing each of the signals with the corresponding allocated bits, and formatting means for encoding each of the quantized signals and each of the scale factors, and for outputting thereof, said decoding apparatus comprising:

means for determining how many bits had been allocated to each of the signals as a function of the encoded corresponding scale factor;

means for inverse-quantizing each of the signals with the corresponding allocated bits;

means for determining whether each of the scale factors is preserved; and

means for inverse-quantizing each of the signals if none of the scale factors is preserved, wherein said encoded signal is so decoded that each of the scale factors is preserved.

20. Encoding/decoding apparatus, comprising:

band dividing means for dividing an input signal into a plurality of signals, each of the signals being in a preselected frequency band;

scaling means for calculating a corresponding scale factor for each of the signals;

bit allocation means for allocating a number of bits to each of the signals as a function of said corresponding scale factor by ascertaining for said each signal whether no bits have been allocated to a respective signal such that said bit allocation means is operative to allocate 2 bits to said respective signal, by ascertaining whether some bits have been allocated to said respective signal such that said bit allocation means is operative to allocate an additional 1 bit thereto, and by ascertaining whether a predetermined number of bits has been fully allocated to said respective signal such that said bit allocation means is operative to allocate no additional bits thereto;

quantizing means for quantizing each of the signals with the corresponding allocated bits;

formatting means for encoding each of the quantized signals and each of the scale factors, and for outputting thereof;

means for determining how many bits had been allocated to each of the signals as a function of the encoded corresponding scale factor;

means for inverse-quantizing each of the signals with the corresponding allocated bits;

means for determining whether each of the scale factors is preserved; and

means for inverse-quantizing each of the signals if none of the scale factors is preserved, wherein said encoded signal is so decoded that each of the scale factors is preserved.

21. Apparatus according to claim 20, wherein each of the signals is a subband signal.

22. Apparatus according to claim 20, wherein each of the signals is a spectrum signal.

23. Apparatus according to claim 20, wherein said corresponding scale factor is defined by r^SFid/s+k, wherein SFid is a quantized dynamic range of one of the signals, and r, s and k are predetermined constants.

24. Apparatus according to claim 20, wherein a variable number of bits are allocated to each of the signals.