摘要:
Focused error correction and/or focused error detection is used in the information coding system. A speech encoding method, in which the number of speech parameter bits on which error correction coding and/or error detection coding focuses is automatically adjusted in relation to the number of total speech parameter bits as a function of the quality of the information transfer connection. There is no need to reduce the number of bits used for speech encoding. Thus the voice quality of the speech remains high. The error correction and/or error detection is focused on the bits most important for the voice quality e.g., as a function of the C/I (Channel to Interference)13 parameter describing the quality of the information transfer connection. The muting of speech synthesizing occuring in prior systems on poor information transfer connection is reduced by using focused error detection.
摘要:
An improved method for generating comfort noise (CN) in a mobile terminal operating in a discontinuous transmission (DTX) mode. In one embodiment the invention provides an improved method for comfort noise generation, in which a random excitation is modified by a spectral control filter so that the frequency content of comfort noise and background noise become similar. In another embodiment the transmitter identifies speech coding parameters that are not representative of the actual background noise, and replaces the identified parameters with parameters having a median value. In this manner the non-representative parameters do not skew the result of an averaging operation.
摘要:
Encoding audio signals with selecting an encoding mode for encoding the signal categorizing the signal into active segments having voice activity and non-active segments having substantially no voice activity by using categorization parameters depending on the selected encoding mode and encoding at least the active segments using the selected encoding mode.
摘要:
Disclosed herein are methods and apparatus for improving the quality of synthesized speech that is transmitted through a channel that is susceptible to transmission errors. In a presently preferred embodiment of the invention a speech signal is assumed to be first encoded using a Linear Predictive Coding (LPC) technique prior to transmission. The parameters that describe the short-term spectral behavior of the speech signal are received and then applied to and processed by a non-linear median processing block only on an occurrence of a predetermined number of transmission errors in the received LPC speech signal. The median-processed short term speech parameters are subsequently employed, together with a received excitation signal, in a synthesis filter to synthesize a speech signal of improved quality over what would be obtained if the short term speech parameters were not median processed to compensate for the transmission errors.
摘要:
Encoding audio signals with selecting an encoding mode for encoding the signal categorizing the signal into active segments having voice activity and non-active segments having substantially no voice activity by using categorization parameters depending on the selected encoding mode and encoding at least the active segments using the selected encoding mode.
摘要:
An encoder encodes digital signals representative of data by classifying the digital signals into first and second classes indicative of their influence on data quality and subjects them to error detection encoding capable of generating at least two error detection codes which respectively correspond to the first and second classes. A decoder receives the encoded digital signals classified into first and second digital signal classes, decodes the error detection codes, and generates error signals, corresponding to the respective digital signal classes, from which the quality of the received digital signals is estimated and the utility of the received digital signals is determined.
摘要:
When several successive bad frames are received, a speech signal applied to an audio speaker is muted after a certain period of time, whereby the user may switch the phone off even though it is possible for the transmission channel to regain its good quality. Instead of the muting of the phone, the user is, according to the invention, given a specific indication, a weak noise signal, for example, indicating that the call synthesization has been discontinued on purpose. The noise signal may be generated in a noise generator prior to a speech decoder, and the noise signal is summed with the attenuated parameter values of the frames substituted during subsitution process.
摘要:
The invention relates to a method for processing the parameters of a speech coder according to the quality of the transmission connection. The quality of the transmission connection is determined in a quality monitoring member (409) on the basis of erroneous/error-free classifications of single received frames so that for determining the quality of the transmission connection the classifications of single frames performed during several subsequent speech frames are scanned. On the basis of the quality of the transmission connection both the replacement procedure of erroneous speech frames carried out in the replacement member (402) and the processing of the frames detected as error-free carried out in the processing member (406) of error-free frames are controlled so that the effect of the transmission errors on the quality of the decoded speech signal remains insignificant (FIG. 4).
摘要:
A post-processor 317 and method substantially for enhancing synthesised speech is disclosed. The post-processor 317 operates on a signal ex(n) derived from an excitation generator 211 typically comprising a fixed code book 203 and an adaptive code book 204, the signal ex(n) being formed from the addition of scaled outputs from the fixed code book 203 and adaptive code book 204. The post-processor operates on ex(n) by adding to it a scaled signal pv(n) derived from the adaptive code book 204. A gain or scale factor p is determined by the speech coefficients input to the excitation generator 211. The combined signal ex(n)+pv(n) is normalised by unit 316 and input to an LPC or speech synthesis filter 208, prior to being input to an audio processing unit 209.
摘要:
A method for detecting defective speech frames in a receiver of a speech communication system includes a coded speech signal consisting of speech frames conveying speech coding parameters received through a transmission link. The detection method for defective speech frames depends on the quality of the transmission link. If the quality of the transmission link is "poor", unusual parameter values of a speech signal in a speech frame are interpreted as transmission errors, and the speech frame is classified as defective. During a transmission link of "good" quality, all received parameter values possible for speech are accepted and forwarded to a speech decoder. In the latter mode of operation, the detection of defective speech frames is solely based on conventional error detection methods employed in the receiver.