1. A method for low-frequency emphasizing the spectrum of a sound signal transformed in a frequency domain and comprising transform coefficients grouped in a number of blocks, comprising:
calculating a maximum energy for one block having a position index;
calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and

for each block, determining from the factor a gain applied to the transform coefficients of the block;
wherein the method for low-frequency emphasizing the spectrum of a sound signal further comprises applying an adaptive low-frequency emphasis to the spectrum of the sound signal to minimize a perceived distortion in lower frequencies of the spectrum.', 'calculating a maximum energy for one block having a position index;', 'calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and', 'computing an energy of the block; and', 'computing the factor from the calculated maximum energy and the computed energy of the block; and', 'for each block, determining from the factor a gain applied to the transform coefficients of the block;', 'wherein the method for low-frequency emphasizing the spectrum of a sound signal further comprises applying an adaptive low-frequency emphasis to the spectrum of the sound signal to minimize a perceived distortion in lower frequencies of the spectrum.

2. A method for low-frequency emphasizing the spectrum of a sound signal as defined in claim 1, wherein the transform coefficients are Fast Fourier Transform coefficients.

3. A method for low-frequency emphasizing the spectrum of a sound signal transformed in a frequency domain and comprising transform coefficients grouped in a number of blocks, comprising:
calculating a maximum energy for one block having a position index;
calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and

for each block determining from the factor a gain applied to the transform coefficients of the block;
wherein the method for low-frequency emphasizing the spectrum of a sound signal further comprises grouping the transform coefficients in blocks of a predetermined number of consecutive transform coefficients.', 'calculating a maximum energy for one block having a position index;', 'calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and', 'computing an energy of the block; and', 'computing the factor from the calculated maximum energy and the computed energy of the block; and', 'for each block determining from the factor a gain applied to the transform coefficients of the block;', 'wherein the method for low-frequency emphasizing the spectrum of a sound signal further comprises grouping the transform coefficients in blocks of a predetermined number of consecutive transform coefficients.

4. A method for low-frequency emphasizing the spectrum of a sound signal transformed in a frequency main and comprising transform coefficients grouped in a number of blocks, comprising:
calculating a maximum energy for one block having a position index;
calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and

for each block determining from the factor a gain applied to the transform coefficients of the block;
wherein:
calculating a maximum energy for one block comprises: computing the energy of each block up to a given position in the spectrum; and storing the energy of the block with maximum energy; and
determining a position index comprises: storing the position index of the block with maximum energy.', 'calculating a maximum energy for one block having a position index;', 'calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and', 'computing an energy of the block; and', 'computing the factor from the calculated maximum energy and the computed energy of the block; and', 'for each block determining from the factor a gain applied to the transform coefficients of the block;', 'wherein:
calculating a maximum energy for one block comprises: computing the energy of each block up to a given position in the spectrum; and storing the energy of the block with maximum energy; and
determining a position index comprises: storing the position index of the block with maximum energy.', 'calculating a maximum energy for one block comprises: computing the energy of each block up to a given position in the spectrum; and storing the energy of the block with maximum energy; and', 'determining a position index comprises: storing the position index of the block with maximum energy.

5. A method for low-frequency emphasizing the spectrum of a sound signal as defined in claim 4, wherein computing the energy of each block up to a given position in the spectrum comprises:
computing the energy of each block up to the first quarter of the spectrum.', 'computing the energy of each block up to the first quarter of the spectrum.

6. A method for low-frequency emphasizing the spectrum of a sound signal transformed in a frequency domain and comprising transform coefficients grouped in a number of blocks, comprising:
calculating a maximum energy for one block having a position index;
calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and

for each block, determining from the factor a gain applied to the transform coefficients of the block;
wherein computing the factor for each block comprises:
computing a ratio Rm for each block with a position index m smaller than the position index of the block with maximum energy, using the relation Rm=Emax/Em where Emax is the calculated maximum energy and Em the computed energy for block corresponding to position index m.', 'calculating a maximum energy for one block having a position index;', 'calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and', 'computing an energy of the block; and', 'computing the factor from the calculated maximum energy and the computed energy of the block; and', 'for each block, determining from the factor a gain applied to the transform coefficients of the block;', 'wherein computing the factor for each block comprises:
computing a ratio Rm for each block with a position index m smaller than the position index of the block with maximum energy, using the relation Rm=Emax/Em where Emax is the calculated maximum energy and Em the computed energy for block corresponding to position index m.', 'computing a ratio Rm for each block with a position index m smaller than the position index of the block with maximum energy, using the relation Rm=Emax/Em where Emax is the calculated maximum energy and Em the computed energy for block corresponding to position index m.', '7. A method for low-frequency emphasizing the spectrum of a sound signal as defined in claim 6, comprising setting the ratio Rm to a predetermined value when Rm is larger than said predetermined value.', '8. A method for low-frequency emphasizing the spectrum of a sound signal as defined in claim 6, comprising setting the ratio Rm=R(m-1) when Rm>R(m-1).', '9. A method for low-frequency emphasizing the spectrum of a sound signal as defined in claim 6, wherein computing the factor further comprises calculating a value (Rm)1/4, and applying the value (Rm)1/4 as a gain for the transform coefficient of the corresponding block.', '10. A method for low-frequency emphasizing the spectrum of a sound signal transformed in a frequency domain and comprising transform coefficients grouped in a number of blocks, comprising:
calculating a maximum energy for one block having a position index;
calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and

for each block, determining from the factor a gain applied to the transform coefficients of the block;
wherein computing the factor comprises setting the factor to a predetermined value when the factor is larger than said predetermined value.', 'calculating a maximum energy for one block having a position index;', 'calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and', 'computing an energy of the block; and', 'computing the factor from the calculated maximum energy and the computed energy of the block; and', 'for each block, determining from the factor a gain applied to the transform coefficients of the block;', 'wherein computing the factor comprises setting the factor to a predetermined value when the factor is larger than said predetermined value.', '11. A method for low-frequency emphasizing the spectrum of a sound signal transformed in a frequency domain and comprising transform coefficients grouped in a number of blocks, comprising:
calculating a maximum energy for one block having a position index;
calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and

for each block, determining from the factor a gain applied to the transform coefficients of the block;
wherein computing the factor comprises setting the factor for one block to the factor of the preceding block when the factor of said one block is larger than the factor of the preceding block.', 'calculating a maximum energy for one block having a position index;', 'calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and', 'computing an energy of the block; and', 'computing the factor from the calculated maximum energy and the computed energy of the block; and', 'for each block, determining from the factor a gain applied to the transform coefficients of the block;', 'wherein computing the factor comprises setting the factor for one block to the factor of the preceding block when the factor of said one block is larger than the factor of the preceding block.', '12. A device for low-frequency emphasizing the spectrum of a sound signal transformed in a frequency domain and comprising transform coefficients grouped in a number of blocks, comprising:
a calculator of a maximum energy for one block having a position index;
a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
computes an energy of the block; and
computes the factor from the calculated maximum energy and the computed energy of the block; and

a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block;
wherein the transform coefficients are grouped in blocks of a predetermined number of consecutive transform coefficients.', 'a calculator of a maximum energy for one block having a position index;', 'a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
computes an energy of the block; and
computes the factor from the calculated maximum energy and the computed energy of the block; and', 'computes an energy of the block; and', 'computes the factor from the calculated maximum energy and the computed energy of the block; and', 'a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block;', 'wherein the transform coefficients are grouped in blocks of a predetermined number of consecutive transform coefficients.', '13. A device for low-frequency emphasizing the spectrum of a sound signal as defined in claim 12, wherein the transform coefficients are Fast Fourier Transform coefficients.', '14. A device for low-frequency emphasizing the spectrum of a sound signal transformed in a frequency domain and comprising transform coefficients grouped in a number of blocks, comprising:
a calculator of a maximum energy for one block having a position index;
a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
computes an energy of the block; and
computes the factor from the calculated maximum energy and the computed energy of the block; and

a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block;
wherein the maximum energy calculator:
computes the energy of each block up to a predetermined position in the spectrum; and
comprises a store for the maximum energy; and
comprises a store for the position index of the block with maximum energy.', 'a calculator of a maximum energy for one block having a position index;', 'a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
computes an energy of the block; and
computes the factor from the calculated maximum energy and the computed energy of the block; and', 'computes an energy of the block; and', 'computes the factor from the calculated maximum energy and the computed energy of the block; and', 'a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block;', 'wherein the maximum energy calculator:
computes the energy of each block up to a predetermined position in the spectrum; and
comprises a store for the maximum energy; and
comprises a store for the position index of the block with maximum energy.', 'computes the energy of each block up to a predetermined position in the spectrum; and', 'comprises a store for the maximum energy; and', 'comprises a store for the position index of the block with maximum energy.', '15. A device for low-frequency emphasizing the spectrum of a sound signal as defined in claim 14, wherein the maximum energy calculator computes the energy of each block up to the first quarter of the spectrum.', '16. A device for low-frequency emphasizing the spectrum of a sound signal transformed in a frequency domain and comprising transform coefficients grouped in a number of blocks, comprising:
a calculator of a maximum energy for one block having a position index;
a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
computes an energy of the block; and
computes the factor from the calculated maximum energy and the computed energy of the block; and

a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block;
wherein the factor calculator:
computes a ratio Rm for each block with a position index m smaller than the position index of the block with maximum energy, using the relation Rm=Emax/Em where Emax is the calculated maximum energy and Em the computed energy for the block corresponding to the position index m.', 'a calculator of a maximum energy for one block having a position index;', 'a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
computes an energy of the block; and
computes the factor from the calculated maximum energy and the computed energy of the block; and', 'computes an energy of the block; and', 'computes the factor from the calculated maximum energy and the computed energy of the block; and', 'a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block;', 'wherein the factor calculator:
computes a ratio Rm for each block with a position index m smaller than the position index of the block with maximum energy, using the relation Rm=Emax/Em where Emax is the calculated maximum energy and Em the computed energy for the block corresponding to the position index m.', 'computes a ratio Rm for each block with a position index m smaller than the position index of the block with maximum energy, using the relation Rm=Emax/Em where Emax is the calculated maximum energy and Em the computed energy for the block corresponding to the position index m.', '17. A device for low-frequency emphasizing the spectrum of a sound signal as defined in claim 16, wherein the factor calculator sets the ratio Rm to a predetermined value when Rm is larger than said predetermined value.', '18. A device for low-frequency emphasizing the spectrum of a sound signal as defined in claim 16, wherein the factor calculator sets the ratio Rm=R(m-1) when Rm>R(m-1).', '19. A device for low-frequency emphasizing the spectrum of a sound signal as defined in claim 16, wherein:
the factor calculator computes a value (Rm)1/4; and
the gain calculator applies the value {Rm)1/4 as a gain for the transform coefficient of the corresponding block.', 'the factor calculator computes a value (Rm)1/4; and', 'the gain calculator applies the value {Rm)1/4 as a gain for the transform coefficient of the corresponding block.

20. A device for low-frequency emphasizing the spectrum of a sound signal transformed in a frequency domain and comprising transform coefficients grouped in a number of blocks, comprising:
a calculator of a maximum energy for one block having a position index;
a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
computes an energy of the block; and
computes the factor from the calculated maximum energy and the computed energy of the block; and

a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block;
wherein the factor calculator sets the factor to a predetermined value when the factor is larger than said predetermined value.', 'a calculator of a maximum energy for one block having a position index;', 'a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
computes an energy of the block; and
computes the factor from the calculated maximum energy and the computed energy of the block; and', 'computes an energy of the block; and', 'computes the factor from the calculated maximum energy and the computed energy of the block; and', 'a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block;', 'wherein the factor calculator sets the factor to a predetermined value when the factor is larger than said predetermined value.

21. A device for low-frequency emphasizing the spectrum of a sound signal transformed in a frequency domain and comprising transform coefficients grouped in a number of blocks, comprising:
a calculator of a maximum energy for one block having a position index;
a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
computes an energy of the block; and
computes the factor from the calculated maximum energy and the computed energy of the block; and

a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block;
wherein the factor calculator sets the factor for one block to the factor of the preceding block when the factor of said one block is larger than the factor of the preceding block.', 'a calculator of a maximum energy for one block having a position index;', 'a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
computes an energy of the block; and
computes the factor from the calculated maximum energy and the computed energy of the block; and', 'computes an energy of the block; and', 'computes the factor from the calculated maximum energy and the computed energy of the block; and', 'a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block;', 'wherein the factor calculator sets the factor for one block to the factor of the preceding block when the factor of said one block is larger than the factor of the preceding block.

22. A method for processing a received, coded sound signal comprising:
extracting coding parameters from the received, coded sound signal, the extracted coding parameters including transform coefficients of a frequency transform of said sound signal, wherein the transform coefficients are grouped in a number of blocks and are low-frequency emphasized using following steps:
(i) calculating a maximum energy for one block having a position index;
(ii) calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and

(iii) for each block, determining from the factor a gain applied to the transform coefficients of the block; and
processing the extracted coding parameters to synthesize the sound signal; and
processing the extracted coding parameters comprising low-frequency de-emphasizing the low-frequency emphasized transform coefficients.', 'extracting coding parameters from the received, coded sound signal, the extracted coding parameters including transform coefficients of a frequency transform of said sound signal, wherein the transform coefficients are grouped in a number of blocks and are low-frequency emphasized using following steps:', '(i) calculating a maximum energy for one block having a position index;', '(ii) calculating a factor for each block having a position index smaller than the position index of the block with maximum energy, the calculation of a factor comprising, for each block:
computing an energy of the block; and
computing the factor from the calculated maximum energy and the computed energy of the block; and', 'computing an energy of the block; and', 'computing the factor from the calculated maximum energy and the computed energy of the block; and', '(iii) for each block, determining from the factor a gain applied to the transform coefficients of the block; and', 'processing the extracted coding parameters to synthesize the sound signal; and', 'processing the extracted coding parameters comprising low-frequency de-emphasizing the low-frequency emphasized transform coefficients.

23. A method for processing a received, coded sound signal as defined in claim 22, wherein:
extracting coding parameters comprises dividing the low-frequency emphasized transform coefficients into a number K of blocks of transform coefficients; and
low-frequency de-emphasizing the low-frequency emphasized transform coefficients comprises scaling the transform coefficients of at least a portion of the K blocks to cancel the low-frequency emphasis of the transform coefficients.', 'extracting coding parameters comprises dividing the low-frequency emphasized transform coefficients into a number K of blocks of transform coefficients; and', 'low-frequency de-emphasizing the low-frequency emphasized transform coefficients comprises scaling the transform coefficients of at least a portion of the K blocks to cancel the low-frequency emphasis of the transform coefficients.

24. A method for processing a received, coded sound signal as defined in claim 23, wherein:
low-frequency de-emphasizing the low-frequency emphasized transform coefficients comprises scaling the transform coefficients of the first K/s blocks of said K blocks of transform coefficients, s being an integer.', 'low-frequency de-emphasizing the low-frequency emphasized transform coefficients comprises scaling the transform coefficients of the first K/s blocks of said K blocks of transform coefficients, s being an integer.

25. A method for processing a received, coded sound signal as defined in claim 24, wherein scaling the transform coefficients comprises:
computing the energy εk of each of the K blocks of transform coefficients;
computing the maximum energy εmax of one block amongst the first K/s blocks; and
computing for each of the first K/s blocks a factor fack; and
scaling the transform coefficients of each of the first K/s blocks using the factor fack of the corresponding block.', 'computing the energy εk of each of the K blocks of transform coefficients;', 'computing the maximum energy εmax of one block amongst the first K/s blocks; and', 'computing for each of the first K/s blocks a factor fack; and', 'scaling the transform coefficients of each of the first K/s blocks using the factor fack of the corresponding block.

26. A method for processing a received, coded sound signal as defined in claim 25, wherein computing for each of the first K/s blocks, up to a position index of the block with maximum energy, a factor fack comprises using the following expressions:
fac0=max((ε0/εmax)0.5,0.1)

fack=max((εk/εmax)0.5,fack-1) for k=1, . . . ,K/sâx88x921,

where εk is the energy of the block with index k.', 'fac0=max((ε0/εmax)0.5,0.1)', 'fack=max((εk/εmax)0.5,fack-1) for k=1, . . . ,K/sâx88x921,', 'where εk is the energy of the block with index k.

27. A decoder for processing a received, coded sound signal comprising:
an input decoder portion supplied with the received, coded sound signal and implementing an extractor of coding parameters from the received, coded sound signal, the extracted coding parameters including transform coefficients of a frequency transform of said sound signal, wherein the transform coefficients are low-frequency emphasized using a device for low-frequency emphasizing the spectrum of the sound signal transformed in a frequency domain and comprising transform coefficients grouped in a number of blocks, the device including
(i) a calculator of a maximum energy for one block having a position index;
(ii) a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
(a) computes an energy of the block; and
(b) computes the factor from the calculated maximum energy and the computed energy of the block; and

(iii) a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block; and

a processor of the extracted coding parameters to synthesize the sound signal, said processor comprising a low-frequency de-emphasis module supplied with the low-frequency emphasized transform coefficients.', 'an input decoder portion supplied with the received, coded sound signal and implementing an extractor of coding parameters from the received, coded sound signal, the extracted coding parameters including transform coefficients of a frequency transform of said sound signal, wherein the transform coefficients are low-frequency emphasized using a device for low-frequency emphasizing the spectrum of the sound signal transformed in a frequency domain and comprising transform coefficients grouped in a number of blocks, the device including
(i) a calculator of a maximum energy for one block having a position index;
(ii) a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
(a) computes an energy of the block; and
(b) computes the factor from the calculated maximum energy and the computed energy of the block; and

(iii) a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block; and', '(i) a calculator of a maximum energy for one block having a position index;', '(ii) a calculator of a factor for each block having a position index smaller than the position index of the block with maximum energy, wherein the factor calculator, for each block:
(a) computes an energy of the block; and
(b) computes the factor from the calculated maximum energy and the computed energy of the block; and', '(a) computes an energy of the block; and', '(b) computes the factor from the calculated maximum energy and the computed energy of the block; and', '(iii) a calculator of a gain, for each block and in response to the factor, the gain being applied to the transform coefficients of the block; and', 'a processor of the extracted coding parameters to synthesize the sound signal, said processor comprising a low-frequency de-emphasis module supplied with the low-frequency emphasized transform coefficients.

28. A decoder as defined in claim 27, wherein:
the extractor divides the low-frequency emphasized transform coefficients into a number K of blocks of transform coefficients; and
the low-frequency de-emphasis module scales the transform coefficients of at least a portion of the K blocks to cancel the low-frequency emphasis of the transform coefficients.', 'the extractor divides the low-frequency emphasized transform coefficients into a number K of blocks of transform coefficients; and', 'the low-frequency de-emphasis module scales the transform coefficients of at least a portion of the K blocks to cancel the low-frequency emphasis of the transform coefficients.