1. A method of indexing pulse positions and amplitudes in an algebraic codebook for efficient encoding and decoding of a sound signal, - wherein:', '- the codebook comprises a set of pulse amplitude/position combinations;', '- each pulse amplitude/position combination defines a number of different positions and comprises both zero-amplitude pulses and non-zero-amplitude pulses assigned to respective positions of the combination; and', '- each non-zero-amplitude pulse assumes one of a plurality of possible amplitudes; and - wherein said indexing method comprises: forming a set of at least one track of said pulse positions; restraining the positions of the non-zero-amplitude pulses of the combinations of the codebook in accordance with the set of at least one track of pulse positions; establishing a procedure 7 for indexing the position and amplitude of one non-zero-amplitude pulse when only the position of said one nonzero-amplitude pulse is located in one track of said set; establishing a procedure 2 for indexing the positions and amplitudes of two non-zero-amplitude pulses when only the positions of said two non-zero-amplitude pulses are located in one track of said set; and when the positions of a number X of non-zero-amplitude pulses are located in one track of said set, wherein X> 3: dividing the positions of said one track into two sections; using a procedure X for indexing the positions and amplitudes of said X non-zero-amplitude pulses, said procedure X comprising: identifying in which one of the two track sections each non-zero-amplitude pulse is located; calculating subindices of said X non-zero-amplitude pulses using the established procedures 7 and 2 in at least one of said track sections and entire track; and calculating a position-and-amplitude index of said X non-zero-amplitude pulses by combining said subindices.

2. A method of indexing pulse positions and amplitudes as defined in claim 1 , comprising interleaving the pulse positions of each track with the pulse positions of the other tracks.

3. A method of indexing pulse positions and amplitudes as defined in claim 1 , wherein calculating a position-and-amplitude index of said X non-zero-amplitude pulses comprises: calculating at least one intermediate index by combining at least two of said subindices; and calculating the position-and-amplitude index of said X nonzero-amplitude pulses by combining the remaining subindices and said at least one intermediate index.

4. A method of indexing pulse positions and amplitudes as defined in claim 1 , wherein said procedure 7 comprises producing a position-and-amplitude index including a position index indicative of the position of said one non-zero-amplitude pulse in said one track, and an amplitude index indicative of the amplitude of said one non-zero- amplitude pulse.

5. A method of indexing pulse positions and amplitudes as defined in claim 4, wherein the position index comprises a first group of bits, and the amplitude index comprises at least one bit.

6. A method of indexing pulse positions and amplitudes as defined in claim 5, in which said at least one bit of the amplitude index is a bit of higher rank.

7. A method of indexing pulse positions and amplitudes as defined in claim 5, wherein said plurality of possible amplitudes of each non-zero-amplitude pulse comprises +1 and -1 , and wherein said at least one bit of the amplitude index is a sign bit.

8. A method of indexing pulse positions and amplitudes as defined in claim 1 , wherein: said plurality of possible amplitudes of each non-zero- amplitude pulse comprises +1 and -1; and the procedure 7 comprises producing a position-and- amplitude index of said one non-zero-amplitude pulse having the form:', '', 'wherein p is a position index of said one non-zero-amplitude pulse in said one track, s is a sign index of said one non-zero- amplitude pulse, and 2M is the number of positions in said one track.

9. A method of indexing pulse positions and amplitudes as defined in claim 8, wherein the number of positions in said one track is 16, and wherein the position-and-amplitude index is a 5-bit index represented in the following table:10. A method of indexing pulse positions and amplitudes as defined in claim 1 , wherein said procedure 2 comprises producing a position-and-amplitude index including: first and second position indices respectively indicative of the positions of the two non-zero-amplitude pulses in said one track; and an amplitude index indicative of the amplitudes of said two non-zero-amplitude pulses

11. A method of indexing pulse positions and amplitudes as defined in claim 10, wherein, in the position-and-amplitude index: the amplitude index comprises at least one bit; the first position index comprises a first group of bits; and the second position index comprises a second group of bits

12. A method of indexing pulse positions and amplitudes as defined in claim 11 , wherein, in the position-and-amplitude index: said at least one bit of the amplitude index is a bit of higher rank; the bits of the first group are bits of intermediate rank; and the bits of the second group are bits of lower rank

13. A method of indexing pulse positions and amplitudes as defined in claim 11 , wherein said plurality of possible amplitudes of each non-zero-amplitude pulse comprises +1 and -1 , and wherein said at least one bit of the amplitude index is a sign bit

14. A method of indexing pulse positions and amplitudes as defined in claim 10, wherein the procedure 2 comprises: when said two pulses have a same amplitude, producing an amplitude index indicative of the amplitude of the non-zero-amplitude pulse whose position is indicated by the first position index, producing a first position index indicative of the smaller position of the two non-zero- amplitude pulses in said one track, and producing a second position index indicative of the larger position of the two non-zero-amplitude pulses in said one track; and when said two pulses have different amplitudes, producing an amplitude index indicative of the amplitude of the non-zero-amplitude pulse whose position is indicated by the first position index, producing a first position index indicative of the larger position of the two non-zero- amplitude pulses in said one track, and producing a second position index indicative of the smaller position of the two non-zero-amplitude pulses in said one track

15. A method of indexing pulse positions and amplitudes as defined in claim 1 , wherein the procedure 2 comprises, when the position of a first non-zero-amplitude pulse of position index p0 and sign index Ïx83o, and the position of a second non-zero-amplitude pulse of position index pi and sign index Ïx83i are located in one track of said set, producing a position-and-amplitude index of said first and second non- zero-amplitude pulses of the form:', 'If Ïx83o = Ïx83i ti Po âx89¤ Pi', '', ', ,2M = Po + Pιx2 + Ïx830 2', 'If Ïx83o âx89xa0 Ïx83i', '', 'Îx9b? ->2', 'I2 = Po + Pf 2 + Ïx83v', '', 'where 2 -> is the number of positions in said one track

16. A method of indexing pulse positions and amplitudes as defined in claim 15, wherein the number of positions in said one track is 16, and wherein the position-and-amplitude index is a 9-bit index represented in the following table:17. A method of indexing pulse positions and amplitudes as defined in claim 1 , wherein, when X= 3 ; dividing the positions of said one track into two sections comprises dividing the positions of said one track into lower and upper track sections; and the procedure 3 comprises: identifying one of the upper and lower track sections which contains the positions of at least two non-zero- amplitude pulses; calculating a first subindex of said at least two nonzero-amplitude pulses located in said one track section using the procedure 2 applied to the positions of said one track section; calculating a second subindex of the remaining non- zero-amplitude pulse using the procedure 7 applied to the positions of the entire said one track; and producing a position-and-amplitude index of the three non-zero-amplitude pulses by combining said first and second subindices.18. A method of indexing pulse positions and amplitudes as defined in claim 17, wherein: calculating a first subindex of said at least two non-zero-amplitude pulses located in said one track section using the procedure 2 comprises, when the positions of said at least two non-zero-amplitude pulses are located in the upper section, shifting the positions of said at least two non-zero-amplitude pulses from the upper section to the lower section.', "19. A method of indexing pulse positions and amplitudes as defined in claim 18, wherein shifting the positions of said at least two non-zero-amplitude pulses from the upper section to the lower section comprises masking a number of least significant bits of the position indices of said at least two non-zero-amplitude pulses with a mask consisting of said number of 1's.", '20. A method of indexing pulse positions and amplitudes as defined in claim 17, wherein calculating a first subindex of said at least two non-zero-amplitude pulses located in said one track section using the procedure 2 comprises inserting a section index indicating the one of said lower and upper track sections in which said at least two non-zero- amplitude pulses are located.

21. A method of indexing pulse positions and amplitudes as defined in claim 17, wherein the number of positions in said one track is 16, and wherein the position-and-amplitude index is a 13-bit index represented in the following table:', '

22. A method of indexing pulse positions and amplitudes as defined in claim 1 , wherein: said procedure 7 comprises producing a position-and-amplitude index including a position index indicative of the position of said one non-zero-amplitude pulse in said one track, and an amplitude index indicative of the amplitude of said one non-zero-amplitude pulse, wherein the position index comprises a first group of bits, and the position index comprises at least one bit; said procedure 2 comprises producing a position-and-amplitude index including first and second position indices respectively indicative of the positions of the two non-zero-amplitude pulses in said one track, and an amplitude index indicative of the amplitudes of said two non-zero- amplitude pulses, wherein the amplitude index comprises at least one bit, the first position index comprises a first group of bits, and the second position index comprises a second group of bits; when X= 3 : dividing the positions of said one track into two sections comprises dividing the positions of said one track into lower and upper track sections; and the procedure 3 comprises: identifying one of the upper and lower track sections which contains the positions of at least two non-zero-amplitude pulses; calculating a first subindex of said at least two non-zero-amplitude pulses located in said one track section using the procedure 2 applied to the positions of said one track section; calculating a second subindex of the remaining non-zero-amplitude pulse using the procedure 7 applied to the positions of the entire said one track; and producing a position-and-amplitude index of the three non-zero-amplitude pulses by combining said first and second subindices.

23. A method of indexing pulse positions and amplitudes as defined in claim 22, wherein when X= 4 : dividing the positions of said one track into two sections comprises dividing the positions of said one track into lower and upper track sections; and the procedure 4 comprises:', '- when the upper track section contains the positions of the four nonzero amplitude pulses: further dividing the upper track section into lower and upper track subsections; identifying one of the upper and lower track subsections which contains the positions of at least two non-zero-amplitude pulses; calculating a first subindex of said at least two non-zero- amplitude pulses located in said one track subsection using the procedure 2 applied to the positions of said one track subsection; calculating a second subindex of the remaining two nonzero-amplitude pulse using the procedure 2 applied to the positions of the entire upper track section; and producing a position-and-amplitude index of the four nonzero-amplitude pulses by combining said first and second subindices;', '- when the lower track section contains the position of one non-zero- amplitude pulse and the upper track section contains the positions of the three other non-zero amplitude pulses: calculating a first subindex of said one non-zero-amplitude pulses located in the lower track section using the procedure 7 applied to the positions of said lower track section; calculating a second subindex of the remaining three non- zero-amplitude pulses located in the upper track section using the procedure 3 applied to the positions of the upper track section; and producing a position-and-amplitude index of the four nonzero-amplitude pulses by combining said first and second subindices;', '- when the lower track section contains the positions of two non-zero- amplitude pulses and the upper track section contains the positions of the two other non-zero amplitude pulses: calculating a first subindex of said two non-zero-amplitude pulses located in the lower track section using the procedure 2 applied to the positions of said lower track section; calculating a second subindex of the remaining two nonzero-amplitude pulses located in the upper track section using the procedure 2 applied to the positions of the upper track section; and producing a position-and-amplitude index of the four nonzero-amplitude pulses by combining said first and second subindices;', '- when the lower track section contains the positions of three non-zero- amplitude pulses and the upper track section contains the position of the other non-zero amplitude pulse: calculating a first subindex of said three non-zero- amplitude pulses located in the lower track section using the procedure 3 applied to the positions of said lower track section; calculating a second subindex of the remaining non-zero- amplitude pulse located in the upper track section using the procedure 7 applied to the positions of the upper track section; and producing a position-and-amplitude index of the four nonzero-amplitude pulses by combining said i first and second subindices;', '- when the lower track section contains the positions of the four non-zero amplitude pulses: further dividing the lower track section into lower and upper track subsections; identifying one of the upper and lower track subsections which contains the positions of at least two non-zero-amplitude pulses; calculating a first subindex of said at least two non-zero- amplitude pulses located in said one track subsection using the procedure 2 applied to the positions of said one track subsection; calculating a second subindex of the remaining two non- zero-amplitude pulse using the procedure 2 applied to the positions of the entire lower track section; and producing a position-and-amplitude index of the three nonzero-amplitude pulses by combining said first and second subindices.

24. A method of indexing pulse positions and amplitudes as defined in claim 23, wherein the procedure 4 comprises:', '- when said one track subsection is the upper subsection, calculating a first subindex of said at least two non-zero-amplitude pulses located in said one track subsection using the procedure 2 comprises shifting the positions of said at least two non-zero-amplitude pulses from the upper track subsection to the lower track subsection.', "25. A method of indexing pulse positions and amplitudes as defined in claim 24, wherein shifting the positions of said at least two non-zero-amplitude pulses from the upper subsection to the lower subsection comprises masking a number of least significant bits of the position indices of said at least two non-zero-amplitude pulses with a mask consisting of said number of 1's.", '26. A method of indexing pulse positions and amplitudes as defined in claim 23, wherein when X=5 : dividing the positions of said one track into two track sections comprises dividing the positions of said one track into lower and upper sections; and the procedure 5 comprises: detecting one of the lower and upper track sections in which the positions of at least three non-zero amplitude pulses are located; calculating a first subindex of three non-zero- amplitude pulses located in said one track section using the procedure 3 applied to the positions of said one track section; calculating a second subindex of the remaining two non-zero-amplitude pulses using the procedure 2 applied to the positions of the entire said one track; and producing a position-and-amplitude index of the five non-zero-amplitude pulses by combining said first and second subindices.

27. A method of indexing pulse positions and amplitudes as defined in claim 23, wherein when X=5 : dividing the positions of said one track into two sections comprises dividing the positions of said one track into lower and upper track sections; and the procedure 5 comprises:', '- when the upper track section contains the positions of the five non-zero amplitude pulses: calculating a first subindex of three non-zero-amplitude pulses located in said upper track section using the procedure 3 applied to the positions of said upper track section; calculating a second subindex of the remaining two nonzero-amplitude pulses using the procedure 2 applied to the positions of the entire said one track; and producing a position-and-amplitude index of the five nonzero-amplitude pulses by combining said first and second subindices;', '- when the lower track section contains the position of one non-zero- amplitude pulse and the upper track section contains the positions of the four other non-zero amplitude pulses: calculating a first subindex of three non-zero-amplitude pulses located in the upper track section using the procedure 3 applied to the positions of said upper track section; calculating a second subindex of the remaining two non- zero-amplitude pulses using the procedure 2 applied to the positions of the entire said one track; and producing a position-and-amplitude index of the five nonzero-amplitude pulses by combining said first and second subindices; - when the lower track section contains the positions of two non-zero- amplitude pulses and the upper track section contains the positions of the three other non-zero amplitude pulses: calculating a first subindex of said three non-zero- amplitude pulses located in the upper track section using the procedure 3 applied to the positions of said upper track section; calculating a second subindex of the remaining two nonzero-amplitude pulses located in the lower track section using the procedure 2 applied to the positions of the entire said one track; and producing a position-and-amplitude index of the five nonzero-amplitude pulses by combining said first and second subindices; - when the lower track section contains the position of three non-zero- amplitude pulses and the upper track section contains the positions of the other two non-zero amplitude pulses: calculating a first subindex of said three non-zero- amplitude pulses located in the lower track section using the procedure 3 applied to the positions of said lower track section; calculating a second subindex of the remaining two non- zero-amplitude pulses located in the upper track section using the procedure 2 applied to the positions of the entire said one track; and producing a position-and-amplitude index of the five nonzero-amplitude pulses by combining said first and second subindices;', '- when the lower track section contains the positions of four nonzero amplitude pulses and the upper track section contains the position of the other non-zero amplitude pulse: calculating a first subindex of three non-zero-amplitude pulses located in the lower track section using the procedure 3 applied to the positions of said lower track section; calculating a second subindex of the remaining two nonzero-amplitude pulses using the procedure 2 applied to the positions of the entire said one track; and producing a position-and-amplitude index of the five nonzero-amplitude pulses by combining said first and second subindices;', '- when the lower track section contains the positions of the five non- zero-amplitude pulses: calculating a first subindex of three non-zero-amplitude pulses located in the lower track section using the procedure 3 applied to the positions of said lower track section; calculating a second subindex of the remaining two non- zero-amplitude pulses using the procedure 2 applied to the positions of the entire said one track; and producing a position-and-amplitude index of the five nonzero-amplitude pulses by combining said first and second subindices.

28. A method of indexing pulse positions and amplitudes as defined in claim 27, wherein when X=6 : dividing the positions of said one track into two sections comprises dividing the positions of said one track into lower and upper track sections; and the procedure 6 comprises:', '- when the upper track section contains the positions of the six non-zero amplitude pulses: calculating a first subindex of five non-zero-amplitude pulses located in said upper track section using the procedure 5 applied to the positions of said upper track section; calculating a second subindex of the remaining non-zero- amplitude pulse using the procedure 7 applied to the positions of the upper track section; and producing a position-and-amplitude index of the six nonzero-amplitude pulses by combining said first and second subindices;', '- when the lower track section contains the position of one non-zero- amplitude pulse and the upper track section contains the positions of the five other non-zero amplitude pulses: calculating a first subindex of the five non-zero-amplitude pulses located in the upper track section using the procedure 5 applied to the positions of said upper track section; calculating a second subindex of the non-zero-amplitude pulse located in the lower track section using the procedure 7 applied to the positions of said lower track section; and producing a position-and-amplitude index of the six nonzero-amplitude pulses by combining said first and second subindices;', '- when the lower track section contains the positions of two non-zero- amplitude pulses and the upper track section contains the positions of the four other non-zero amplitude pulses: calculating a first subindex of the four non-zero-amplitude pulses located in the upper track section using the procedure 4 applied to the positions of said upper track section; calculating a second subindex of the remaining two nonzero-amplitude pulses located in the lower track section using the procedure 2 applied to the positions of said lower track section; and producing a position-and-amplitude index of the six nonzero-amplitude pulses by combining said first and second subindices; - when the lower track section contains the positions of three non-zero- amplitude pulses and the upper track section contains the positions of the other three non-zero amplitude pulses: calculating a first subindex of said three non-zero- amplitude pulses located in the lower track section using the procedure 3 applied to the positions of said lower track section; calculating a second subindex of the remaining three nonzero-amplitude pulses located in the upper track section using the procedure 3 applied to the positions of the upper track section; and producing a position-and-amplitude index of the six nonzero-amplitude pulses by combining said first and second subindices;', '- when the lower track section contains the positions of four non-zero amplitude pulses and the upper track section contains the positions of the other two non-zero amplitude pulses: calculating a first subindex of the four non-zero-amplitude pulses located in the lower track section using the procedure 4 applied to the positions of said lower track section; calculating a second subindex of the remaining two nonzero-amplitude pulses located in the upper track section using the procedure 2 applied to the positions of said upper track section ; and producing a position-and-amplitude index of the six non- zero-amplitude pulses by combining said first and second subindices;', '- when the lower track section contains the positions of five non-zero- amplitude pulses and the upper track section contains the position of the remaining non-zero amplitude pulse: calculating a first subindex of the five non-zero-amplitude pulses located in the lower track section using the procedure 5 applied to the positions of said lower track section; calculating a second subindex of the remaining non-zero- amplitude pulse located in the upper track section using the procedure 7 applied to the positions of said upper track section; and producing a position-and-amplitude index of the six nonzero-amplitude pulses by combining said first and second subindices; and', '- when the lower track section contains the positions of the six non-zero- amplitude pulses: calculating a first subindex of five non-zero-amplitude pulses located in the lower track section using the procedure 5 applied to the positions of said lower track section; calculating a second subindex of the remaining non-zero- amplitude pulse located in the lower track section using the procedure 7 applied to the positions of the lower track section; and producing a position-and-amplitude index of the six nonzero-amplitude pulses by combining said first and second subindices.

29. A device for indexing pulse positions and amplitudes in an algebraic codebook for efficient encoding and decoding of a sound signal, - wherein:', '- the codebook comprises a set of pulse amplitude/position combinations; - each pulse amplitude/position combination defines a number of different positions and comprises both zero-amplitude pulses and non-zero-amplitude pulses assigned to respective positions of the combination; and - each non-zero-amplitude pulse assumes one of a plurality of possible amplitudes; and - wherein said indexing device comprises: means for forming a set of at least one track of said pulse positions; means for restraining the positions of the non-zero-amplitude pulses of the combinations of the codebook in accordance with the set of at least one track of pulse positions; means for establishing a procedure 7 for indexing the position and amplitude of one non-zero-amplitude pulse when only the position of said one non-zero-amplitude pulse is located in one track of said set; means for establishing a procedure 2 for indexing the positions and amplitudes of two non-zero-amplitude pulses when only the positions of said two non-zero-amplitude pulses are located in one track of said set; and when the positions of a number X of non-zero-amplitude pulses are located in one track of said set, wherein X> 3: means for dividing the positions of said one track into two sections; means for conducting a procedure X for indexing the positions and amplitudes of said X non-zero-amplitude pulses, said procedure X conducting means comprising: means for identifying in which one of the two track sections each non-zero-amplitude pulses is located; and means for calculating subindices of said X non-zero- amplitude pulses using the established procedures 7 and 2 in at least one of said track sections and entire track; and means for calculating a position and amplitude index of said X non-zero-amplitude pulses, said index calculating means comprising means for combining said subindices.

30. A device for indexing pulse positions and amplitudes as defined in claim 29, comprising means for interleaving the pulse positions of each track with the pulse positions of the other tracks.

31. A device for indexing pulse positions and amplitudes as defined in claim 29, wherein the means for calculating a position-and- amplitude index of said X non-zero-amplitude pulses comprises: means for calculating at least one intermediate index by combining at least two of said subindices; and calculating the position-and-amplitude index of said X nonzero-amplitude pulses by combining the remaining subindices and said at least one intermediate index.

32. A device for indexing pulse positions and amplitudes as defined in claim 29, wherein said procedure 7 comprises means for producing a position-and-amplitude index including a position index indicative of the position of said one non-zero-amplitude pulse in said one track, and an amplitude index indicative of the amplitude of said one non-zero-amplitude pulse.

33. A device for indexing pulse positions and amplitudes as defined in claim 32, wherein the position index comprises a first group of bits, and the amplitude index comprises at least one bit.

34. A device for indexing pulse positions and amplitudes as defined in claim 33, in which said at least one bit of the amplitude index is a bit of higher rank.

35. A device for indexing pulse positions and amplitudes as defined in claim 33, wherein said plurality of possible amplitudes of each non-zero-amplitude pulse comprises +1 and -1 , and wherein said at least one bit of the amplitude index is a sign bit.

36. A device for indexing pulse positions and amplitudes as defined in claim 29, wherein: said plurality of possible amplitudes of each non-zero- amplitude pulse comprises +1 and -1 ; and the procedure 7 comprises means for producing a position- and-amplitude index of said one non-zero-amplitude pulse having the form:', 'UP= P +sÏx872M', 'wherein p is a position index of said one non-zero-amplitude pulse in said one track, s is a sign index of said one non-zero- amplitude pulse, and 2M is the number of positions in said one track.

37. A device for indexing pulse positions and amplitudes as defined in claim 36, wherein the number of positions in said one track is 16, and wherein the position-and-amplitude index is a 5-bit index represented in the following table:', '

38. A device for indexing pulse positions and amplitudes as defined in claim 29, wherein said procedure 2 comprises means for producing a position-and-amplitude index including: first and second position indices respectively indicative of the positions of the two non-zero-amplitude pulses in said one track; and an amplitude index indicative of the amplitudes of said two non-zero-amplitude pulses.

39. A device for indexing pulse positions and amplitudes as defined in claim 38, wherein, in the position-and-amplitude index: the amplitude index comprises at least one bit; the first position index comprises a first group of bits; and the second position index comprises a second group of bits.

40. A device for indexing pulse positions and amplitudes as defined in claim 39, wherein, in the position-and-amplitude index: said at least one bit of the amplitude index is a bit of higher rank; the bits of the first group are bits of intermediate rank; and the bits of the second group are bits of lower rank.

41. A device for indexing pulse positions and amplitudes as defined in claim 39, wherein said plurality of possible amplitudes of each non-zero-amplitude pulse comprises +1 and -1 , and wherein said at least one bit of the amplitude index is a sign bit.

42. A device for indexing pulse positions and amplitudes as defined in claim 39, wherein the procedure 2 comprises:', '- when said two pulses have a same amplitude: means for producing an amplitude index indicative of the amplitude of the non-zero-amplitude pulse whose position is indicated by the first position index; means for producing a first position index indicative of the smaller position of the two non-zero-amplitude pulses in said one track; means for producing a second position index indicative of the larger position of the two non-zero-amplitude pulses in said one track; and', '- when said two pulses have different amplitudes: means for producing an amplitude index indicative of the amplitude of the non-zero-amplitude pulse whose position is indicated by the first position index; means for producing a first position index indicative of the larger position of the two non-zero-amplitude pulses in said one track; and means for producing a second position index indicative of the smaller position of the two non-zero-amplitude pulses in said one track.

43. A device for indexing pulse positions and amplitudes as defined in c