Claims

1. An apparatus (130, 130A, 110) for encoding an information signal comprising a plurality of frames, the apparatus comprising:

a modulated lapped transform tool (131) for transforming a time domain, TD, representation of the information signal, or a processed version thereof, into a frequency domain, FD, representation, the modulated lapped transform tool (131) being configured to perform a modulated lapped transform analysis using an analysis windowing function (40, 50, 70, 240) having a meandering portion (44, 64, 244) crossing a linear function (40', 240') in correspondence of at least four points (#1, #2, #3, #4); and

a bitstream writer (137) configured to prepare a bitstream based on the FD representation of the information signal or a processed version thereof,

wherein the analysis windowing function is defined so as to be asymmetric,

wherein the analysis windowing function (40, 240) is defined so as to be, in the meandering portion (44, 94, 244):

greater than the linear function (40', 240') in a first interval (41,241) between a first crossing point (#1) and a second crossing point (#2);

lower than the linear function (40', 240') in a second interval (42, 242) between the second crossing point (#2) and a third crossing point (#3);

greater than the linear function (40', 240') in a third interval (43, 243) between the third crossing point (#3) and a fourth crossing point (#4),

wherein the analysis windowing function is defined so that the absolute maximum value (41', 241') is in one of the first and third interval,

wherein the linear function (40, 240) is a constant function with constant value 1.

2. The apparatus of claim 1,

wherein the analysis windowing function (40, 240) is defined so that the maximum of the analysis windowing function (40, 240) is less than 25% greater than the value of the linear (40, 240) function at the same time instant.

3. An apparatus (130, 130A, 110) for encoding an information signal comprising a plurality of frames, the apparatus comprising:

a modulated lapped transform tool (131) for transforming a time domain, TD, representation of the information signal, or a processed version thereof, into a frequency domain, FD, representation, the modulated lapped transform tool (131) being configured to perform a modulated lapped transform analysis using an analysis windowing function (40, 50, 70, 240) having a meandering portion (44, 64) crossing a linear function (40', 60', 240') in correspondence of at least four points (#1, #2, #3, #4); and

a bitstream writer (137) configured to prepare a bitstream based on the FD representation of the information signal or a processed version thereof,

wherein the analysis windowing function is defined so as to be asymmetric,

wherein the analysis windowing function (40, 240) is defined so that the maximum of the analysis windowing function (40, 240) is less than 25% greater than the value of the linear function at the same time instant,

wherein the linear function is a constant function.

4. An apparatus (130, 130A, 110) for encoding an information signal comprising a plurality of frames, the apparatus comprising:

a modulated lapped transform tool (131) for transforming a time domain, TD, representation of the information signal, or a processed version thereof, into a frequency domain, FD, representation, the modulated lapped transform tool (131) being configured to perform a modulated lapped transform analysis using an analysis windowing function (40, 50, 70, 240) having a meandering portion (44, 64) crossing a linear function (40', 240') in correspondence of at least four points (#1, #2, #3, #4); and

a bitstream writer (137) configured to prepare a bitstream based on the FD representation of the information signal or a processed version thereof.

5. The apparatus of any of the preceding claims, wherein the modulated lapped transform tool is configured to:

scale time input buffers and/or cosine or sine values with values of the analysis windowing function (40, 50, 70, 240).

6. The apparatus of claim 5, wherein the modulated lapped transform tool is configured to use input buffers in the form of

t(n) = x(Z - NF + n) for n = 0..2NF - 1 - Z, and

t(2N - Z + n) = 0 for n = 0..Z - 1

wherein x(n) is a TD sample of the information signal or a processed version of the information signal at the time instant n, NF is the number of samples processed in one frame, and Z is the number of leading zeros in modulated lapped transform window.

7. The apparatus of any of the preceding claims, wherein the modulated lapped transform tool (131) is configured to perform:

where X(k) is the modulated lapped transform frequency value at a frequency index k, n is the time instant, wN(n) is the analysis windowing function, t(n) is a time input buffer, and NF is the number of samples processed in one frame.

8. An apparatus (140, 140A, 120) for decoding an information signal, or a processed version thereof, defined in the frequency domain, FD, the apparatus comprising:

a bitstream reader (141) configured to read a bitstream encoding the information signal; and

an inverse modulated lapped transform tool (147) configured to perform an inverse modulated lapped transform synthesis on the information signal, or a processed version thereof, using a synthesis windowing function (90) having a meandering portion (94) crossing a linear function in correspondence of at least four points (#1, #2, #3, #4),

wherein the synthesis windowing function (90, 290) is defined so as to be asymmetric,

wherein the synthesis windowing function (90, 290) is defined so as to be, in the meandering portion (44, 94, 244):

greater than the linear function in a first interval between a first crossing point and a second crossing point;

lower than the linear function in a second interval between the second crossing point and a third crossing point;

greater than the linear function in a third interval between the third crossing point and a fourth crossing point,

wherein the synthesis windowing function is defined so that the absolute maximum value is in one of the first and third interval,

wherein the linear function is a constant function with constant value 1.

9. The apparatus of claim 8,

wherein the synthesis windowing function (90, 290) is defined so that the maximum of the synthesis windowing function (90, 290) is less than 25% greater than the value of the linear (90, 290) function at the same time instant.

10. An apparatus (140, 140A, 120) for decoding an information signal, or a processed version thereof, defined in the frequency domain, FD, the apparatus comprising:

a bitstream reader (141) configured to read a bitstream encoding the information signal; and

an inverse modulated lapped transform tool (147) configured to perform an inverse modulated lapped transform synthesis of the information signal, or a processed version thereof, using a synthesis windowing function (90, 290) having a meandering portion (94, 294) crossing a linear function in correspondence of at least four points (#1, #2, #3, #4),

wherein the synthesis windowing function is defined so as to be asymmetric,

wherein the synthesis windowing function is defined so that the maximum of the synthesis windowing function is less than 25% greater than the value of the linear function at the same time instant,

wherein the linear function is a constant function.

11. An apparatus (140, 140A, 120) for decoding an information signal, or a processed version thereof, defined in the frequency domain, FD, the apparatus comprising:

a bitstream reader (141) configured to read a bitstream encoding the information signal; and

an inverse modulated lapped transform tool (147) configured to perform an inverse modulated lapped transform synthesis on the information signal, or a processed version thereof, using a synthesis windowing function (90, 290) having a meandering portion (94, 294) crossing a linear function in correspondence of at least four points (#1, #2, #3, #4).

12. The apparatus of any of claims 8 to 11, wherein the inverse modulated lapped transform tool (147) is configured to:

scale values at a time domain aliasing buffer with values of the synthesis windowing function (90).

13. The apparatus of any of claims 8 to 12, wherein the inverse modulated lapped transform tool (147) is configured to generate a time domain, TD, signal representation in the form of

wherein is an aliasing buffer,
is the information signal or a processed version thereof, and NF is the number of samples for a TD frame.

14. The apparatus of any of claims 8 to 13, wherein the inverse modulated lapped transform tool (147) is configured to:

perform a windowing (S162) of the time-aliased buffer.

15. The apparatus of any of claims 8 to 14, wherein the inverse modulated lapped transform tool (147) is configured to perform a windowing operation by performing:

16. The apparatus of any of claims 8 to 15, wherein the inverse modulated lapped transform tool (147) is configured to perform an overlap-and-add operation (S163).

17. The apparatus of any of claims 8 to 16, wherein the inverse modulated lapped transform tool (147) is configured to perform an overlap-and-add operation as:

wherein
is the output value, is a windowed time-aliasing buffer, and NF is

the number of samples in one frame.

18. The apparatus (13, 140, 140A, 110, 120) of any of the preceding claims, wherein:

the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is defined so as to be, in the meandering portion (44, 64, 94): greater than the linear function (40', 240') in a first interval (41, 241,

91) between a first crossing point (#1) and a second crossing point (#2);

lower than the linear function (40', 240') in a second interval (42, 242,

92) between the second crossing point (#2) and a third crossing point (#3);

greater than the linear function (40', 240') in a third interval (43, 243,

93) between the third crossing point (#3) and a fourth crossing point (#4).

19. The apparatus of claim 18, wherein:

the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is defined so that the absolute maximum value (41', 241) is in the first or third interval (41, 43, 241, 243).

20. The apparatus of claim 19, wherein:

the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is defined so that, in the meandering portion (44, 244), a relative maximum value (43', 243') is in the first or third interval (41, 43, 241, 243) and a relative minimum value (42', 242') is in the second interval (42, 242).

21. The apparatus of any of claims 18 to 20, wherein:

the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is defined so that, in the meandering portion (44, 244, 94), the value of the meandering window function in correspondence to at least one of the first and third interval (41, 43, 241, 243, 91, 93) is greater than 0.9.

22. The apparatus of any of the preceding claims, wherein:

the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is defined so as to present, in the meandering portion (44, 244, 94), a value greater than the linear function in an interval comprised of the 30% and 50% of two frames.

23. The apparatus of any of claims 18 to 22, wherein:

the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is defined so that the maximum of the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is less than 25% greater than the value of the linear function at the same time instant.

24. The apparatus of any of claims 18 to 23, wherein:

the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is defined so that the maximum (41', 241') of the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is less than 5% greater than the value of the linear function at the same time instant.

25. The apparatus of any of claims 18 to 24, wherein:

the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is defined so as to present a second numerical differentiation between -3*10-4 and +3*10-4.

26. The apparatus of any of claims 18 to 25, wherein:

the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is defined so as to present a third numerical differentiation between -2*10-5 and +2*10-5.

27. The apparatus of any of the preceding claims, wherein:

the linear function (40', 240') is defined so as to be a non-increasing function.

28. The apparatus of claim 4 or 11, wherein:

the linear function (40', 60') is defined so as to be a strictly decreasing function.

29. The apparatus of any of claims 1-27, wherein:

the linear function (40', 60') is defined so as to be a non-decreasing function.

30. The apparatus of claim 4 or 11, wherein:

the linear function is defined so as to be a strictly increasing function.

31. The apparatus of any of the preceding claims, wherein:

the linear function (40', 240') is defined so as to have a value which is constant or varies of maximum +2% or -2%.

32. The apparatus of any of the preceding claims, wherein:

the linear function (40', 240) is defined so as to have increments between -0.05 and -0.20.

33. The apparatus of any of the preceding claims, wherein:

the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is defined so as to be asymmetric.

34. The apparatus of any of the preceding claims, wherein:

the analysis windowing function (40, 240) and the synthesis windowing function (90) is defined are time reversed versions of each other.

35. The apparatus of any of the preceding claims, further comprising:

a storage space (113) to store the values of the analysis windowing function (40, 60) and/or the synthesis windowing function (90).

36. The apparatus of any of the preceding claims, wherein the modified lapped transform is a modified discrete cosine transform, MDCT, or a modified discrete sine transform, MDST, and the inverse modified lapped transform is an inverse modified discrete cosine transform, IMDCT, or inverse modified discrete sine transform, IMDST.

37. The apparatus of any of the preceding claims, wherein:

the analysis windowing function (40, 240) and/or the synthesis windowing function (90) is a constant function with constant value 1.

38. The apparatus of any of the preceding claims, wherein the analysis windowing function (40) and/or the synthesis windowing function (90) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

39. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (40, 60) and/or the synthesis windowing function (90) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

40. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (40) and/or the synthesis windowing function (90) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

41. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (40) and/or the synthesis windowing function (90) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

42. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (40) and/or the synthesis windowing function (90) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

43. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (40) and/or the synthesis windowing function (90) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1 % of tolerance:

44. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (240) and/or the synthesis windowing function (290) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

45. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (240) and/or the synthesis windowing function (290) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

46. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (240) and/or the synthesis windowing function (290) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

47. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (240) and/or the synthesis windowing function (290) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

48. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (240) and/or the synthesis windowing function (290) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

49. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (240) and/or the synthesis windowing function (290) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

50. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (240) and/or the synthesis windowing function (290) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

51. The apparatus of any of claims 1 to 37, wherein the analysis windowing function (240) and/or the synthesis windowing function (290) comprises at least a succession, in forward or backward order, formed by the following values or at least a sub-succession with 10 of the following values if different from 0, with ±1% of tolerance:

52. An apparatus according to any of the preceding claims, wherein the analysis windowing function and/or synthesis windowing function is defined so as to present a first numerical differentiation between -0.01 and +0.01.

53. An apparatus according to any of the preceding claims, wherein the analysis windowing function and/or synthesis windowing function is defined so as to present a second numerical differentiation between -10-4 and +10-4.

54. An apparatus according to any of the preceding claims third, wherein the analysis windowing function and/or synthesis windowing function is defined so as to present a second numerical differentiation between -10-5 and +10-5.

55. An apparatus according to any of the preceding claims, wherein the information signal is an audio signal.

56. A system comprising:

an encoder 130, 130A, 110) as the apparatus of any of claims 1 to 7 or 18 to 54 in combination with any of claims 1 to 7; and

a decoder (140, 140A, 120) as the apparatus of any of claims 8-17 or 18 to 54 in combination with any of claims 8 to 17.

57. The system of claim 56, wherein the encoder comprises a communication unit (117) configured to transmit a bitstream and/or the decoder comprises a communication unit (126) configured to receive the bitstream.

58. A method comprising performing a modified cosine transformation, MDCT, analysis for transforming a time domain, TD, representation of an information signal, or a processed version thereof, into a frequency domain, FD, representation, using an analysis windowing function (40, 50, 240, 70) having a meandering portion (44, 244) which passes a linear function (40', 240') in correspondence of at least four points (#1, #2, #3, #4).

59. A method comprising performing a modified cosine transformation, MDCT, analysis for transforming a time domain, TD, representation of an information signal, or a processed version thereof, into a frequency domain, FD, representation, using an analysis windowing function (40, 50, 240, 70) having a meandering portion (44, 244) which passes a linear function (40', 240') in correspondence of at least four points (#1, #2, #3, #4),

wherein the analysis windowing function is defined so as to be asymmetric,

wherein the analysis windowing function (40, 240) is defined so as to be, in the meandering portion (44, 94, 244):

greater than the linear function (40', 240') in a first interval (41,241) between a first crossing point (#1) and a second crossing point (#2);

lower than the linear function (40', 240') in a second interval (42, 242) between the second crossing point (#2) and a third crossing point (#3);

greater than the linear function (40', 240') in a third interval (43, 243) between the third crossing point (#3) and a fourth crossing point (#4),

wherein the analysis windowing function is defined so that the absolute maximum value (41', 241') is in one of the first and third interval,

wherein the linear function (40, 240) is a constant function with constant value 1.

60. A method comprising performing a modified cosine transformation, MDCT, analysis for transforming a time domain, TD, representation of an information signal, or a processed version thereof, into a frequency domain, FD,

representation, using an analysis windowing function (40, 50, 240, 70) having a meandering portion (44, 244) which passes a linear function (40', 240') in correspondence of at least four points (#1, #2, #3, #4),

wherein the analysis windowing function is defined so as to be asymmetric, wherein the analysis windowing function (40, 60) is defined so that the maximum of the analysis windowing function (40, 60) is less than 25% greater than the value of the linear function at the same time instant,

wherein the linear function is a constant function.

61. A method comprising performing a modified cosine transformation, MDCT, synthesis for transforming a frequency domain, FD, representation of an information signal, or a processed version thereof, into a time domain, TD, representation, using a synthesis windowing function (90) having a meandering portion (94) which passes a linear function in correspondence of at least four points (#1, #2, #3, #4).

62. A method comprising performing a modified cosine transformation, MDCT, synthesis for transforming a frequency domain, FD, representation of an information signal, or a processed version thereof, into a time domain, TD, representation, using a synthesis windowing function (90) having a meandering portion (94) which passes a linear function in correspondence of at least four points (#1, #2, #3, #4),

wherein the synthesis windowing function (90, 290) is defined so as to be, in the meandering portion:

greater than the linear function in a first interval between a first crossing point and a second crossing point;

lower than the linear function in a second interval between the second crossing point and a third crossing point;

greater than the linear function in a third interval between the third crossing point and a fourth crossing point,

wherein the synthesis windowing function is defined so that the absolute maximum value is in one of the first and third interval,

wherein the linear function is a constant function with constant value 1.

63. A method comprising performing a modified cosine transformation, MDCT, synthesis for transforming a frequency domain, FD, representation of an information signal, or a processed version thereof, into a time domain, TD, representation, using a synthesis windowing function (90) having a meandering portion (94) which passes a linear function in correspondence of at least four points (#1, #2, #3, #4),

wherein the synthesis windowing function is defined so as to be asymmetric,

wherein the synthesis windowing function is defined so that the maximum of the synthesis windowing function is less than 25% greater than the value of the linear function at the same time instant,

wherein the linear function is a constant function.

64. The method of any of claims 58 to 63, wherein the information signal is an audio signal.

65. A non-transitory storage unit storing instructions which, when running on a processor, cause the processor to execute a method according to any of claims 58 to 63.