Transmitter, encoding system and method employing use of a bit allocation unit for subband coding a digital signal

• US 5,367,608 A
• Filed: 10/27/1993
• Issued: 11/22/1994
• Est. Priority Date: 05/14/1990
• Status: Expired due to Term

• Current Assignee: IPG Electronics 503 Limited (Coller IP Capital Limited)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Veldhuis, Raymond N. J., Keesman, Gerrit J.
• Primary Examiner(s): Knepper, David D.
• Application Number:
  US08/144,092
• Time in Patent Office: 391 Days
• Field of Search: 381/29-47, 395/2, 395/2.38, 395/2.39, 395/2.14, 395/2.12
• US Class Current: 704/229
• CPC Class Codes: G06T 9/007 Transform coding, e.g. discrete cosine transform
• CPC Class Codes: H04B 1/667 using a division in frequency subbands for TV signals H04N19/63

Abstract

Transmitter, encoding system and method for subband coding a digital signal. The encoding system includes a splitter unit for dividing the digital signal into subband signals SB₁, . . . , SB_p ; a quantizer unit for quantizing time-equivalent q sample signal blocks of the subband signals; a bit need determining unit and a bit allocation unit. The bit need determining unit determines a bit need b_m which corresponds to the number of bits by which the q samples in a time-equivalent signal block in a subband signal SB_m should be represented, where 1≦m≦P. The bit allocation unit allocates n_m bits to each of the q samples of the time-equivalent signal block of subband signal SB_m on the basis of the bit need b_m and an available bit quantity B, n_m being the number of bits by which the q samples in the time-equivalent signal block of subband signal SB_m will be represented, where 1≦m≦P.

Claims

1. An encoding system for encoding a digital signal having a specific sampling frequency and bandwidth, comprising:

splitter means for dividing the bandwidth of the digital signal into M successive subbands, and generating, in response to the digital signal, P subband signals having reduced sampling frequencies, each of the subband signals being associated with one of the subbands;

quantizing means for quantizing time-equivalent signal blocks of the subband signals, a subband signal SB_m of the subband signals having successive signal blocks which each contain q samples of that subband signal, each sample in a signal block of subband signal SB_m being quantized by n_m bits, where n_m may vary for different signal blocks of subband signal SB_m ;

bit need determining means for determining bit needs for the time-equivalent signal blocks a bit need b_m for a signal block of subband signal SB_m corresponding to the number of bits by which the q samples in that signal block should be represented, where b_m may vary for different signal blocks of subband signal SB_m ; and

bit allocation means for allocating bits to the time-equivalent signal blocks from an available number of bits B, n_m bits being allocated to each of the q samples of a signal block of subband signal SB_m in accordance with at least the bit need b_m for that signal block;

wherein m and P are integers such that 1≦

m≦

p and said bit allocation means is adapted for allocating bits to the time-equivalent signal blocks by performing a routine S₁, which includes the following operations, at least twice;

(a) determining which signal block of the time-equivalent signal blocks has a highest bit need b_j, where b_j denotes the bit need b_m for that signal block and j is an integer, such that 1≦

j≦

P, which denotes the same subband signal which m denotes for that signal block; and

(b1) if bits have not already been allocated to the signal block having the highest bit need b_j, then

(i) allocating a₁ bits to n_j, where n_j denotes the n_m bits allocated to each of the q samples of the signal block having the highest bit need b_j, to arrive at a value for n_j,

(ii) subtracting a₂ from b_j to arrive at a reduced value for b_j, and

(iii) subtracting a₁ ·

q+x from B to arrive at a reduced value for B;

or

(b2) if bits have already been allocated to the signal block having the highest bit need b_j, then

(i) allocating c₁ additional bits to n_j to arrive at an increased value for n_j,

(ii) subtracting c₂ from b_j to arrive at a reduced value for b_j, and

(iii) subtracting c₁ ·

q from B to arrive at a reduced value for B;

wherein q and x are positive integers greater than unity, x being a number of bits necessary to represent a scale factor for the signal block having the highest bit need b_j ;

n_m, n_j, b_m and b_j are variables where n_m and n_j are greater than or equal to zero;

a₁, a₂, c₁ and c₂ are numbers greater than zero, a₁ is greater than c₁ and a₂ is greater than or equal to c₂ ; and

B and M are positive integers.

2. The encoding system as claimed in claim 1, wherein said bit allocation means is further adapted to perform the following operations for at least one of the time-equivalent signal blocks prior to performance of the operations of the routine S₁ :

subtracting A_k1 from b_k, where b_k denotes the bit need b_m for that at least one signal block and k denotes the same subband signal which m denotes for that at least one signal block, to arrive at a reduced value for b_k ;

allocating A_k0 bits to n_k, where n_k is the n_m bits allocated to each of the q samples of that at least one time-equivalent signal block, to arrive at a value for n_k ; and

subtracting A_k0 ·

q+x from B to arrive at a reduced value for B;

where A_k0 and A_k1 are numbers greater than zero, n_k and b_k are variables and k is an integer such that 1≦

k≦

P.

3. The encoding system as claimed in claim 2 wherein A_k0 is equal to a₁ and A_k1 is equal to a₂.

4. The encoding system as claimed in claim 1, wherein said bit allocation means is further adapted for allocating a flag value to at least one of the time-equivalent signal blocks, which flag value indicates that no bits are to be allocated to the q samples in that at least one time-equivalent signal block.

5. The encoding system as claimed in claim 1, wherein characterized a₁ is equal to a₂ and c₁ is equal to c₂.

6. The encoding system as claimed in claim 1 for subband encoding of a single digital signal, such as a mono signal or a left or right signal portion of a stereo signal, wherein P=M.

7. The encoding system as claimed in claim 6, wherein there is one subband signal associated with each subband.

8. The encoding system as claimed in claim 1 for subband encoding of a stereo signal, comprising a left and a right signal portion, wherein P=2M.

9. The encoding system as claimed in claim 6, wherein there are two subband signals associated with each subband.

10. The encoding system as claimed in claim 1, further comprising signal formatting means for assembling into a frame of an output digital signal having successive frames the q samples from time-equivalent signal blocks which have been quantized by said quantizer means, scale factor information being included in the frame in the form of x-bit words representing scale factors associated with the time-equivalent signal blocks for which the q samples are included in the frame.

11. A transmitter comprising an encoding system as claimed in claim 10.

12. The transmitter as claimed in claim 11, wherein the transmitter is adapted for recording the output digital signal in at least an track on a record carrier.

13. The transmitter as claimed in claim 12, wherein the record carrier is a magnetic record carrier.

14. The encoding system as claimed in claim 1 wherein said bit allocation means is further adapted for repeating the operations of the routine S₁ continuously until B has been reduced below c₁ ·

q.

15. The encoding system as claimed in claim 1, wherein said bit allocation means is further adapted for repeating the operations of the routine S₁ continuously until either B has been reduced below c₁ ·

q or the bit need b_m for each of the time-equivalent signal blocks becomes less than or equal to a flag value.

16. The encoding system as claimed in claim 1, wherein said splitter means comprises filter means for dividing the bandwidth of the digital signal into the M subbands and generating in response to the the digital signal P original subband signals having sampling frequencies which are substantially the same as the specific sampling frequency, and sampling means for converting the orignal subband signals into the subband signals having reduced sampling frequencies.

17. A method of encoding a digital signal having a specific sampling frequency and bandwidth, comprising:

dividing the bandwidth of the digital signal into M subbands, and generating, in response to the digital signal, P subband signals having reduced sampling frequencies, each of the subband signals being associated with one of the subbands; and

quantizing time-equivalent signal blocks of the subband signals, a subband signal SB_m of the subband signals having successive signal blocks which each contain q samples of that subband signal, each sample in a signal block of subband signal SB_m being quantized by n_m bits, where n_m may vary for different signal blocks of subband signal SB_m ;

wherein m and P are integers such that 1≦

m≦

P and in order to quantize the time-equivalent signal blocks, the following steps are performed;

determining bit needs for the time-equivalent signal blocks, a bit need b_m for a signal block of subband signal SB_m corresponding to the number of bits by which the q samples in that signal block should be represented, where b_m may vary for different signal blocks of subband signal SB_m ; and

allocating bits to the time-equivalent signal blocks from an available number of bits B, n_m bits being allocated to each of the q samples of a signal block of subband signal SB_m in accordance with at least the bit need b_m for that signal block, the bits being allocated to the time-equivalent signal blocks by performing a routine S₁, which includes the following operations, at least twice;

(a) determining which signal block of the time-equivalent signal blocks has a highest bit need b_j, where b_j denotes the bit need b_m for that signal block and j is an integer, such that 1≦

j≦

P, which denotes the same subband signal which m denotes for that signal block; and

(b2) if bits have not already been allocated to the signal block having the highest bit need b_j, then

(i) allocating a₁ bits to n_j, where n_j denotes the n_m bits allocated to each of the q samples of the signal block having the highest bit need b_j, to arrive at a value for n_j,

(ii) subtracting a₂ from b_j to arrive at a reduced value for b_j, and

(iii) subtracting a₁ ·

q+x from B to arrive at a reduced value for B;

or

(b2) if bits have already been allocated to the signal block having the highest bit need b_j, then

(i) allocating c₁ additional bits to n_j to arrive at an increased value for n_j,

(ii) subtracting c₂ from b_j to arrive at a reduced value for b_j, and

(iii) subtracting c₁ ·

q from B to arrive at a reduced value for B;

wherein q and x are positive integers greater than unity, x being a number of bits necessary to represent a scale factor for the signal block having the highest bit need b_j ;

n_m, n_j, b_m and b_j are variables where n_m and n_j are greater than or equal to zero;

a₁, a₂, c₁, and c₂ are numbers greater than zero, a₁ is greater than c₁ and a₂ is greater than or equal to c₂ ; and

B and M are positive integers.

18. The method as claimed in claim 17 wherein prior to performance of the operations of the routine S₁, the following additional steps are performed for at least one of the time-equivalent signal blocks

subtracting A_k1 from b_k, where b_k denotes the bit need b_m for that at least one signal block and k denotes the same subband signal which m denotes for that at least one signal block, to arrive at a reduced value for b_k ;

allocating A_k0 bits to n_k, where n_k is the n_m bits allocated to each of the q samples of that at least one signal block, to arrive at a value for n_k ; and

subtracting A_k0 ·

q+x from B to arrive at a reduced value of B;

where A_k0 and A_k1 are numbers greater than zero, n_k and b_k are variables and k is an integer such that 1≦

k≦

P.

19. The method as claimed in claim 18, wherein A_k0 is equal to a₁ and A_k1 is equal to a₂.

20. The method as claimed in claim 17, further comprising assigning a flag value to at least one of the time-equivalent signal blocks, said flag value signifying that no bits are to be allocated to the q samples in that at least one time-equivalent signal block.

21. The method as claimed in claim 17, wherein a₁ is equal to a₂ and c₁ is equal to c₂.

22. The method as claimed in claim 17, wherein said the operations of the routine S₁ are continuously repeated until B has been reduced below c₁ ·

q.

23. The method as claimed in claim 17, wherein the operations of the routine S₁ are continuously repeated until either B has been reduced below c₁ ·

q or the bit need b_m for each of the time-equivalent signal blocks becomes less than or equal to a flag value.

24. The method as claimed in claim 17, further comprising assembling into a frame of an output signal having successive frames the q samples from time-equivalent signal blocks which have been quantized, scale factor information being included in the frame in the form of x-bit words representing scale factors associated with the time-equivalent signal blocks for which the q samples are included in the frame.

25. The method as claimed in claim 24, further comprising recording the output digital signal on a record carrier.

26. An encoding system for encoding a digital signal, comprising:

means for dividing the digital signal into a plurality of subband signals, each of the subband signals having a plurality of signal blocks, each containing q samples of that subband signal, where q is a positive integer, which are successive in time, each of the signal blocks of a subband signal being time-equivalent with a corresponding signal block of each of the other subband signals, corresponding signal blocks of the subband signals constituting time-equivalent signal blocks;

means for quantizing each of the q samples of each of the time-equivalent signal blocks with n_m bits, where n_m is a variable greater than or equal to zero which may vary for the time-equivalent signal blocks and/or different signal blocks within the same subband signal and m is a positive integer denoting which one of the subband signals a signal block comes from;

means for determining a bit need b_m for each of the time-equivalent signal blocks, where b_m is a variable which may vary for the time-equivalent signal blocks and/or different signal blocks within the same subband signal, the bit need b_m for each of the time-equivalent signal blocks corresponding to the number of bits by which the q samples in that signal block should be represented; and

bit allocation means for allocating, from an available number of bits B, where B is a positive integer, the n_m bits to each of the q samples of each of the time-equivalent signal blocks in accordance with the bit need b_m for each of the time-equivalent signal blocks, said bit allocation means being adapted to at least twice;

(a) allocate to the signal block of the time-equivalent signal blocks having the bit need b_m which is highest (i) a first number of bits if bits have not already been allocated to that signal block or (ii) an additional second number of bits if bits have already been allocated to that signal block, where the first number is greater than the second number, and

(b) reduce (i) the bit need b_m for the signal block of the time-equivalent signal blocks having the bit need b_m which is highest and (ii) the available number of bits B.

27. The encoding systems as claimed in claim 26, wherein said bit allocation means is adapted to perform the following operations:

(a) determine which signal block of the time-equivalent signal blocks has a highest bit need b_j, where b_j is a variable which denotes the bit need b_m for that signal block and j is an integer which denotes the same subband signal which m denotes for that signal block; and

(b1) if bits have not already been allocated to the signal block having the highest bit need b_j, then

(i) allocate a₁ bits to n_j, where n_j is a variable which denotes the n_m, bits allocated to each of the q samples of the signal block having the highest bit need b_j, to arrive at a value for n_j,

(ii) subtract a₂ from the highest bit need b_j to arrive at a reduced value for b_j, and

(iii) subtract a₁ ·

q+x from B to arrive at a reduced value for B;

or

(b2) if bits have already been allocated to the signal block having the highest bit need b_j, then

(i) allocate c₁ additional bits to n_j to arrive at an increased value for n_j,

(ii) subtract c₂ from the highest bit need b_j to arrive at a reduced value for b_j, and

(iii) subtract c₁ ·

q from B to arrive at a reduced value for B;

where x is an integer greater than unity corresponding to a number of bits necessary to represent a scale factor for the signal block having the highest bit need b_j ; and

a₁, a₂, c₁ and c₂ are numbers greater than zero, where a₁ is greater than c₁ and a₂ is greater than or equal to c₂.

28. The encoding system as claimed in claim 26, wherein said bit allocation means is further adapted to preallocate a predetermined number of bits to at least one of the time-equivalent signal blocks prior to (a) allocating bits to the signal block having the bit need b_m which is the highest and (b) reducing (i) the bit need b_m for the signal block having the bit need b_m which is the highest and (ii) the available number of bits B.

29. The encoding system as claimed in claim 26, wherein said bit allocation means is further adapted to allocate a flag value to at least one of the time-equivalent signal blocks, which flag value indicates that no bits are to be allocated to that signal block.

30. The encoding system as claimed in claim 26, further comprising signal formatting means for assembling into a frame of an output digital signal having successive frames the q samples from the time-equivalent signal blocks which have been quantized, scale factor information being included in the frame in the form of x-bit words representing scale factors associated with the time-equivalent signal blocks for which the q samples are included in the frame.

31. A transmitter, comprising the encoding system claimed in claim 30.

32. The transmitter as claimed in claim 31, further comprising means for recording the output digital signal in at least one track on a record carrier.

33. A transmitter, comprising the encoding system claimed in claim 26.

34. The encoding systems as claimed in claim 26, wherein the subband signals have reduced sampling frequencies as compared to the digital signal.

35. A method for encoding a digital signal, comprising:

dividing the digital signal into a plurality of subband signals, each of the subband signals having a plurality of signal blocks, each containing q samples of that subband signal, where q is a positive integer, which are successive in time, each of the signal blocks of a subband signal being time-equivalent with a corresponding signal block of each of the other subband signals, corresponding signal blocks of the subband signals constituting time-equivalent signal blocks;

quantizing each of the q samples of each of the time-equivalent signal blocks with n_m bits, where n_m is a variable greater than or equal to zero which may vary for the time-equivalent signal blocks and/or different signal blocks within the same subband signal and m is a positive integer denoting which one of the subband signals a signal block comes from;

wherein in order to quantize each of the time-equivalent signal blocks, the following additional steps are performed;

determining a bit need b_m for each of the time-equivalent signal blocks, where b_m is a variable which may vary for the time-equivalent signal blocks and/or different signal blocks within the same subband signal, the bit need b_m for each of the time-equivalent signal blocks corresponding to the number of bits by which the q samples in that signal block should be represented; and

allocating, from an available number of bits B, where B is a positive integer, the n_m bits to each of the q samples of each of the time-equivalent signal blocks in accordance with the bit need b_m for each of the time-equivalent signal blocks by at least twice;

(a) allocating to the signal block of the time-equivalent signal blocks having the bit need b_m which is highest (i) a first number of bits if bits have not already been allocated to that signal block or (ii) an additional second number of bits if bits have already been allocated to that signal block, where the first number is greater than the second number, and

(b) reducing (i) the bit need b_m for the signal block of the time-equivalent signal blocks having the bit need b_m which is highest and (ii) the available number of bits B.

36. The method as claimed in claim 35, wherein allocating the n_m bits to each of the q samples of each of the time-equivalent signal blocks includes the following operations:

(a) determining which signal block of the time-equivalent signal blocks has a highest bit need b_j, where b_j is a variable which denotes the bit need b_m for that signal block and j is an integer which denotes the same subband signal which m denotes for that signal block; and

(b1) if bits have not already been allocated to the signal block having the highest bit need b_j, then

(i) allocating a₁ bits to n_j, where n_j is a variable which denotes the n_m bits allocated to each of the q samples of the signal block having the highest bit need b_j, to arrive at a value for n_j,

(ii) subtracting a₂ from the highest bit need b_j to arrive at a reduced value for b_j, and

(iii) subtracting a₁ ·

q+x from B to arrive at a reduced value for B;

or

(b2) if bits have already been allocated to the signal block having the highest bit need b_j, then

(i) allocating c₁ additional bits to n_j to arrive at an increased value for n_j,

(ii) subtracting c₂ from the highest bit need b_j to arrive at a reduced value for b_j, and

(iii) subtracting c₁ ·

q from B to arrive at a reduced value for B;

where x is an integer greater than unity corresponding to a number of bits necessary to represent a scale factor for the signal block having the highest bit need b_j ; and

a₁, a₂, c₁ and c₂ are numbers greater than zero, where a₁ is greater than c₁ and a₂ is greater than or equal to c₂.

37. The method as claimed in claim 35, further comprising preallocating a predetermined number of bits to at least one of the time-equivalent signal blocks prior to (a) allocating bits to the signal block having the bit need b_m which is the highest and (b) reducing (i) the bit need b_m for the signal block having the bit need b_m which is the highest and (ii) the available number of bits B.

38. The method as claimed in claim 35, further comprising allocating a flag value to at least one of the time-equivalent signal blocks, which flag value indicates that no bits are to be allocated to that signal block.

39. The encoding system as claimed in claim 35, further comprising assembling into a frame of an output digital signal having successive frames the q samples from the time-equivalent signal blocks which have been quantized, scale factor information being included in the frame in the form of x-bit words representing scale factors associated with the time-equivalent signal blocks for which the q samples are included in the frame.

40. A bit allocation device for allocating bits to time-equivalent signal blocks of P subband signals, where P is an integer, each of the time-equivalent signal blocks having q samples, where q is a positive integer, the device comprising:

means for receiving a bit need b_m for each of the time-equivalent signal blocks, where b_m is a variable which may vary for the time-equivalent signal blocks and m is a positive integer denoting which one of the subband signals a time-equivalent signal block comes from, the bit need b_m for a time-equivalent signal block corresponding to the number of bits by which the q samples in that time-equivalent signal block should be represented; and

bit allocation means for allocating, from an available number of bits B, where B is a positive integer, n_m bits to each of the q samples of each of the time-equivalent signal blocks in accordance with the bit need b_m for each of the time-equivalent signal blocks, said bit allocation means being adapted to at least twice;

(a) allocate to the time-equivalent signal block having the bit need b_m which is highest (i) a first number of bits if bits have not already been allocated to that time-equivalent signal block or (ii) an additional second number of bits if bits have already been allocated to that time-equivalent signal block, where the first number is greater than the second number, and

(b) reduce (i) the bit need b_m for the time-equivalent signal block having the bit need b_m which is highest and (ii) the available number of bits B.

41. The device as claimed in claim 40, wherein said bit allocation means is further adapted to preallocate a predetermined number of bits to at least one of the time-equivalent signal blocks prior to (a) allocating bits to the time-equivalent signal block having the bit need b_m which is highest and (b) reducing (i) the bit need b_m for the time-equivalent signal block having the b_m which is highest and (ii) the available number of bits B.

42. The device as claimed in claim 40, wherein said bit allocation means is further adapted for allocating a flag value to at least one of the time-equivalent signal blocks, which flag value indicates that no bits are to be allocated to that time-equivalent signal block.

43. A transmitter comprising the device as claimed in claim 40.

44. The device as claimed in claim 40, wherein said bit allocation means is adapted to perform the following operations in a routine S₁ :

(a) determine which time-equivalent signal block has a highest bit need b_j, where b_j is a variable which denotes the bit need b_m for that time-equivalent signal block and j is an integer which denotes the same subband signal which m denotes for that time-equivalent signal block; and

(b1) if bits have not already been allocated to the time-equivalent signal block having the highest bit need b_j, then

(i) allocate a₁ bits to n_j, where n_j is a variable which denotes the n_m bits allocated to each of the q samples of the time-equivalent signal block having the highest bit need b_j, to arrive at a value for n_j,

(ii) subtract a₂ from the highest bit need b_j to arrive at a reduced value for b_j, and

(iii) subtract a₁ ·

q+x from B to arrive at a reduced value for B;

or

(b2) if bits have already been allocated to the time-equivalent signal block having the highest bit need b_j, then

(i) allocating c₁ additional bits to n_j to arrive at an increased value for n_j,

(ii) subtract c₂ from the highest bit need b_j to arrive at a reduced value for b_j, and

(iii) subtract c₁ ·

q from B to arrive at a reduced value for B;

where x is an integer greater than unity corresponding to a number of bits necessary to represent a scale factor for the time-equivalent signal block having the highest bit need b_j ; and

a₁, a₂, c₁ and c₂ are numbers greater than zero, where a₁ is greater than c₁ and a₂ is greater than or equal to c₂.

45. The device as claimed in claim 44, wherein a₁ is equal to a₂ and c₁ is equal to c₂.

46. The device as claimed in claim 44, wherein said bit allocation means is further adapted for repeating the operations of routine S₁ continuously until B has been reduced below c₁ ·

q.

47. The device as claimed in claim 44, wherein said bit allocation means is further adapted for repeating the operations of routine S₁ continuously until either B has been reduced below c₁ ·

q or the bit need b_m for each of the time-equivalent signal blocks becomes less than or equal to a flag value.

48. The device as claimed in claim 47 wherein A_k0 is equal to a₁ and A_k1 is equal to a₂.

49. The device as claimed in claim 44, wherein said bit allocation means is further adapted to perform the following operations for at least one of the time-equivalent signal blocks prior to performance of the operations of the routine S₁ :

subtracting A_k1 from b_k, where b_k is a variable which denotes the bit need b_m for that at least one time-equivalent signal block and k is an integer which denotes the same subband signal which m denotes for that at least one time-equivalent signal block, to arrive at a reduced value for b_k ;

allocating A_k0 bits to n_k, were n_k is a variable which denotes the n_m bits allocated to each of the q samples of that at least one time-equivalent signal block, to arrive at a value for n_k ; and

subtracting A_k0 ·

q+x from B to arrive at a reduced value for B;

where A_k0 and A_k1 are numbers greater than zero.

50. A method for allocating bits to time-equivalent signal blocks of P subband signals, where P is an integer, each of the time-equivalent signal blocks having q samples, where q is a positive integer, the method comprising:

receiving a bit need b_m for each of the time-equivalent signal blocks, where b_m is a variable which may vary for the time-equivalent signal blocks and m is a positive integer denoting which one of the subband signals a time-equivalent signal block comes from, the bit need b_m for a time-equivalent signal block corresponding to the number of bits by which the q samples in that time-equivalent signal block should be represented; and

allocating, from an available number of bits B, where B is a positive integer, n_m bits to each of the q samples of each of the time-equivalent signal blocks in accordance with the bit need b_m for each of the time-equivalent signal blocks by at least twice;

(a) allocating to the time-equivalent signal block having the bit need b_m which is highest (i) a first number of bits if bits have not already been allocated to that time-equivalent signal block or (ii) an additional second number of bits if bits already been allocated to that time-equivalent signal block, where the first number is greater than the second number, and

(b) reducing (i) the bit need b_m for the time-equivalent signal block having the bit need b_m which is highest and (ii) the available number of bits B.

51. The method as in claim 50, further comprising preallocating a predetermined number of bits to at least one of the time-equivalent signal blocks prior to (a) allocating bits to the time-equivalent signal block having the bit need b_m which is highest and (b) reducing (i) the bit need b_m for the time-equivalent signal block having the b_m which is highest and (ii) the available number of bits B.

52. The method as claimed in claim 50, further comprising allocating a flag value to at least one of the time-equivalent signal blocks, which flag value indicates that no bits are to be allocated to that time-equivalent signal block.

53. The method as claimed in claim 50, wherein allocating the n_m bits to each of the q samples of each of the time-equivalent signal blocks includes performing the following operations of in a routine S₁ :

(a) determining which time-equivalent signal block has a highest bit need b_j, where b_j is a variable which denotes the bit need b_m for that time-equivalent signal block and j is an integer which denotes the same subband signal which m denotes for that time-equivalent signal block; and

(b1) if bits have not already been allocated to the time-equivalent signal block having the highest bit need b_j, then

(i) allocating a₁ bits to n_j, where n_j is a variable which denotes the n_m bits allocated to each of the q samples of the time-equivalent signal block having the highest bit need b_j, to arrive at a value for n_j,

(ii) subtracting a₂ from the highest bit need b_j to arrive at a reduced value for b_j, and

(iii) subtracting a₁ ·

q+x from B to arrive at a reduced value for B;

or

(b2) if bits have already been allocated to the time-equivalent signal block having the highest bit need b_j, then

(i) allocating c₁ additional bits to n_j to arrive at an increased value for n_j,

(ii) subtracting c₂ from the highest bit need b_j to arrive at a reduced value for b_j, and

(iii) subtracting c₁ ·

q from B to arrive at a reduced value for B;

where x is an integer greater than unity corresponding to a number of bits necessary to represent a scale factor for the time-equivalent signal block having the highest bit need b_j ; and

a₁, a₂, c₁ and c₂ are numbers greater than zero, where a₁ is greater than c₁ and a₂ is greater than or equal to c₂.

54. The method as claimed in claim 53, wherein a₁ is equal to a₂ and c₁ is equal to c₂.

55. The method as claimed in claim 53, wherein the operations of the routine S₁ are continuously repeated until B has been reduced below c₁ ·

q.

56. The method as claimed in claim 53, wherein the operations of the routine S₁ are continuously repeated until either B has been reduced below c₁ ·

q or the bit need b_m for each of the time-equivalent signal blocks becomes less than or equal to a flag value.

57. The method as claimed in claim 56, wherein A_k0 is equal to a₁ and A_k1 is equal to a₂.

58. The method as claimed in claim 53, wherein the following operations are performed for at least one of the time-equivalent signal blocks prior to performing the operations of the routine S₁ :

subtracting A_k1 from b_k, where b_k is a variable which denotes the bit need b_m for that at least one time-equivalent signal block and k is an integer which denotes the same subband signal which m denotes for that at least one time-equivalent signal block, to arrive at a reduced value for b_k ;

allocating A_k0 bits to n_k, were n_k is a variable which denotes the n_m bits allocated to each of the q samples of that at least one time-equivalent signal block, to arrive at a value for n_k ; and

subtracting A_k0 ·

q+x from B to arrive at a reduced value for B;

where A_k0 and A_k1 are numbers greater than zero.