Communication terminal with a parameterised bandwidth expansion, and method for the bandwidth expansion thereof
View Patent ↗The disclosure relates to a communication terminal having a bandwidth expansion device for expanding the bandwidth of a narrowband voice signal, on a low-frequency and/or high-frequency side, by synthesizing at least one frequency band on the basis of the narrowband voice signal. A qualitatively satisfactory bandwidth expansion is thus performed using a plurality of net bit rates. The bandwidth expansion device is further connected to a memory containing a lookup table comprising at least one parameter value for the bandwidth expansion, for at least two net bit rates of the narrowband voice signal. A method for expanding a bandwidth of a narrowband voice signal having at least two net bit rates in a communication terminal is also disclosed herein.
1. A communication device, comprising:
a bandwidth expansion device for expanding a bandwidth of a narrowband speech signal at its low-frequency and/or high-frequency end by synthesis of at least one frequency band contained within said narrowband speech signal, the narrowband speech signal having at least two net bit rates; and
a memory unit, communicatively coupled to said bandwidth expansion device, wherein said memory unit stores a reference table that includes at least one parameter value used for the bandwidth expansion for the at least two net bit rates of the narrowband speech signal, wherein the reference table takes account, as parameters, of an amount of energy in a synthesized frequency band and of a spectral structure of the synthesized frequency band, and wherein the spectral structure of the synthesized frequency band takes account of a probability of occurrences of artifacts at specific frequencies in the narrowband speech signal.
2. A method for expanding a bandwidth of a narrowband speech signal for a communication terminal, the method comprising:
a) detecting a net bit rate of the narrowband speech signal for the communication terminal;
accessing a memory that includes a reference table, the reference table including associations between at least two net bit rates and parameter values used for bandwidth expansion, in order to determine the at least one parameter value which is suitable for the detected net bit rate, wherein the reference table takes account, as parameters, of an amount of energy of a synthesized frequency band, and a spectral structure of the synthesized frequency band, and wherein the spectral structure of the synthesized frequency band takes account of a probability of occurrences of artifacts at specific frequencies in the narrowband speech signal; and
c) expanding the bandwidth by means of a bandwidth expansion device on the basis of the parameters determined for the detected net bit rate in step b).
3. The method according to claim 2 , wherein the amount of energy of the synthesized frequency band decreases as the net bit rate decreases.