The speech encoding apparatus (220) has a first layer encoding section (2201), a first layer decoding section (2202), a delay section (2203), a subtracting section (104), a frequency domain transforming section (101), a second layer encoding section (105) and a multiplexing section (106).

Encoding device, decoding device, and method thereof

The present invention relates to a method and device for improving concealment of frame erasure caused by frames of an encoded sound signal erased during transmission from an encoder (106) to a decoder (110), and for accelerating recovery of the decoder after non erased frames of the encoded sound signal have been received. For that purpose, concealment/recovery parameters are determined in the encoder or decoder. When determined in the encoder (106), the concealment/recovery parameters are transmitted to the decoder (110). In the decoder, erasure frame concealment and decoder recovery is conducted in response to the concealment/recovery parameters. The concealment/recovery parameters may be selected from the group consisting of: a signal classification parameter, an energy information parameter and a phase information parameter. The determination of the concealment/recovery parameters comprises classifying the successive frames of the encoded sound signal as unvoiced, unvoiced transition, voiced transition, voiced, or onset, and this classification is determined on the basis of at least a part of the following parameters: a normalized correlation parameter, a spectral tilt parameter, a signal-to-noise ratio parameter, a pitch stability parameter, a relative frame energy parameter, and a zero crossing parameter.

Method and device for efficient frame erasure concealment in linear predictive based speech codecs

The present invention describes a novel methodology for adjusting a bandwidth extension algorithm by adapting one or more of enhancing perception parameters (e.g., a signal level, a signal energy and/or a gain) of a high-band encoded signal based on the characteristics of the input signal and an encoding performance in a low band with a codec utilizing audio-band-split coding by separate encoders and decoders for each audio band. The adaptation is based on the low-band coding algorithm. It can be at least two types of such an algorithm: e.g., an algebraic code excitation linear prediction (ACELP) algorithm for a speech-like input signal and a transform algorithm of a non-speech-like input signal, such that when the ACELP coding is selected, the corresponding enhancing perception parameter is gradually tuned down and when the encoding algorithm is changed to the transform coding, the corresponding enhancing perception parameter is gradually tuned up.

Signal adaptation for higher band coding in a codec utilizing band split coding

An audio signal is conveyed more efficiently by transmitting or recording a baseband of the signal with an estimated spectral envelope and a noise-blending parameter derived from a measure of the signal's noise-like quality. The signal is reconstructed by translating spectral components of the baseband signal to frequencies outside the baseband, adjusting phase of the regenerated components to maintain phase coherency, adjusting spectral shape according to the estimated spectral envelope, and adding noise according to the noise-blending parameter. Preferably, the transmitted or recorded signal also includes an estimated temporal envelope that is used to adjust the temporal shape of the reconstructed signal.

Broadband frequency translation for high frequency regeneration

Described is a transmission system (10) comprising a transmitter (12) for transmitting an input signal to a receiver (14) via a transmission channel (16). The transmitter (12) comprises a splitter (20) for splitting up the input signal into at least first and second frequency band signals. The transmitter (12) further comprises a first encoder (22) for encoding the first frequency band signal into a first encoded frequency band signal and a second encoder (24) for encoding the second frequency band signal into a second encoded frequency band signal. The transmitter (12) is arranged for transmitting the first and second encoded frequency band signals via the transmission channel (16) to the receiver (14). The receiver (14) comprises a first decoder (26) for decoding the first encoded frequency band signal into a first decoded frequency band signal and a second decoder (28) for decoding the second encoded frequency band signal into a second decoded frequency band signal. The receiver (14) further comprises a combiner (30) for combining the first and second decoded frequency band signals into an output signal and reconstruction means (48) for reconstructing the second decoded frequency band signal when the second decoded frequency band signal is not available. The transmission system (10) is characterized in that the reconstruction means (48) are arranged for reconstructing the second decoded frequency band signal from the first decoded frequency band signal. In this way, errors occurring in the receipt or decoding of the second frequency band signal can be concealed by reconstructing the missing part(s) on the basis of the first frequency band signal which was received and decoded correctly. Preferably, this reconstruction is done by means of bandwidth extension.

Wideband signal transmission system

A common narrow-band speech signal is expanded into a wide-band speech signal. The expanded signal gives the impression of a wide-band speech signal regardless of what type of vocoder is used in a receiver. The robust techniques suggested herein are based on speech acoustics and fundamentals of human hearing. That is the techniques extend the harmonic structure of the speech signal during voiced speech segments and introduce a linearly estimated amount of speech energy in the wide frequency-band. During unvoiced speech segments, a fricated noise may be introduced in the upper frequency-band.

U. Lindgren

Papers

Speech bandwidth extension