Patent ID: 7280959

Claim:
A method for transforming a first signal into a second signal comprising supplying the first signal to a signal transforming device to produce the second signal, wherein the signal transforming device has a codebook and is selected from the group consisting of a) an encoder, wherein the first signal is coded into the second signal and b) a decoder, wherein the first signal is decoded into the second 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 the codebook pulse amplitudes and positions are indexed by: 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; indexing according to a first procedure, hereinafter named procedure 1, 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; indexing according to a second procedure, hereinafter named procedure 2, 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 further procedure associated wit said number X, hereinafter named 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 procedures 1 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.