Method and terminal for encoding or decoding an analog signal
View Patent ↗An analog signal divided into time frames is encoded and a synthetic signal is formed on the model thereof in a time frame manner via a synthesis filter which is excited by an excitation signal. The excitation signal is formed by at least one adaptive code list containing a plurality of scanning values provided with a defined scanning space. For the actual excitation signal, a segment corresponding to the time frame length is selected from the plurality of scanning values via a speech-based frequency parameter which can take non-integer values and, in such a case, the values intermediate to the scanning values defined by the speech-based frequency parameter are formed in such a way that the time space between the intermediate values and the scanning values is reduced and the totality of the intermediate and the scanning values is used for forming the excitation signal.
1. A method for encoding an analog signal subdivided into time frames and to which a synthetic signal is matched, comprising:
using a communication terminal device to encode an analog signal by breaking down the analog signal into time frames and synthetically producing a synthetic signal to match the analog signal time frame by time frame via a synthesis filter, the communication terminal device having at least one adaptive codebook that contains a plurality of sample values, the sample values being comprised of at least one excitation signal from earlier time frames;
exciting the synthesis filter via an excitation signal, the excitation signal formed by the communication terminal device performing an excitation signal generation method comprising:
selecting a segment corresponding to a length of a current time frame from a plurality of the sampled values contained in the at least one adaptive codebook using a reference parameter dependent on a basic voice frequency that assumes non-integer values that identify locations for intermediate values positioned between the sampled values,
choosing intermediate values corresponding to the sampled values, and
using all the sampled values and all the intermediate values for forming the excitation signal.
2. The method as claimed in claim 1 , wherein a fixed codebook is additionally used for forming the excitation signal.
3. The method as claimed in claim 1 , wherein the reference parameter is represented as a fraction of a whole number and wherein a time interval between sampled values and intermediate values is also reduced by the number.
4. The method as claimed in claim 3 , wherein a fixed codebook is additionally used for forming the excitation signal.
5. The method as claimed in claim 4 , wherein intermediate values for an entry in the fixed codebook are generated by a time shifting of the fixed codebook entry.
6. The method as claimed in claim 4 , wherein intermediate values are generated via an interpolation of signal components of an entry in the fixed codebook.
7. The method as claimed in claim 1 , wherein a white noise signal is additionally used for forming the excitation signal.
8. The method as claimed in claim 7 , wherein the white noise signal is recorded from the environment or generated by a noise generator.
9. The method as claimed in claim 1 , wherein the intermediate values are formed via an interpolation of the already existing sampled values.
10. The method as claimed in claim 1 , wherein the excitation signal is filtered by a Wiener FIR filter.
11. A communication terminal having at least one adaptive codebook that contains a plurality of sample values, the sample values being comprised of at least one excitation signal from earlier time frames, the communication terminal comprising:
a synthesis filter excited via an excitation signal, the excitation signal formed via an excitation signal generation method comprising:
selecting a segment corresponding to a length of a current time frame from a plurality of the sampled values contained in the at least one adaptive codebook using a reference parameter dependent on a basic voice frequency that assumes non-integer values that identify locations for intermediate values positioned between the sampled values,
choosing intermediate values corresponding to the sampled values, and
using all the sampled values and all the intermediate values for forming the excitation signal; and
wherein the communication terminal uses the synthesis filter to encode the analog signal.
12. A receiver having a receiving unit for receiving encoding parameters, comprising:
a receiver for receiving an encoded signal;
a computing unit configured for decoding the encoded signal, wherein the signal encoded via the method comprising:
using a communication terminal device to encode an analog signal by breaking down the analog signal into time frames and synthetically producing a synthetic signal to match the analog signal time frame by time frame via a synthesis filter, the communication terminal device having at least one adaptive codebook that contains a plurality of sample values, the sample values being comprised of at least one excitation signal from earlier time frames;
exciting the synthesis filter via an excitation signal, the excitation signal formed by the communication terminal device performing an excitation signal generation method comprising:
selecting a segment corresponding to a length of a current time frame from a plurality of the sampled values contained in the at least one adaptive codebook using a reference parameter dependent on a basic voice frequency that assumes non-integer values that identify locations for intermediate values positioned between the sampled values,
choosing intermediate values corresponding to the sampled values, and
using all the sampled values and all the intermediate values for forming the excitation signal.