Abstract:
The invention relates to a method of parametric decoding of a stereo digital audio signal, comprising a step of synthesizing (synth.) the stereo signal, per frequency sub-band, on the basis of a decoded mono signal of formula (I), arising from a downmix of the stereo signal and from spatial information parameters of the stereo signal, in such a way that the signals obtained have the following form: formula (II), wherein formula (III) and formula (IV) represent the channels of the synthesized signal, formula (V) and formula (VI) represent the signals dependent on the decoded mono signal, and c 1[ j ] and c 2[ j ] represent the gains. The gains are characterised in that they are calculated in the following way: formula (VII), wherein formula Î [ j ] is an amplitude ratio between the two channels of the stereo signal, arising from the decoded parameters. The invention also relates to a decoder implementing the method as described.
Abstract:
The invention relates to a method of processing binary errors in a binary frame emanating from a digital audio coder, comprising a step of receiving a current binary frame liable to comprise binary errors. According to the invention, the binary frame comprises sensitive bits to be protected which are catalogued in at least one category according to the type of parameter that they code and the method furthermore comprises the steps of receiving protection bits, of reading the sensitive bits received in the current binary frame, the number of sensitive bits being lower than the number of bits of the binary frame, of detecting binary errors as a function of said protection bits received and of said sensitive bits received and in the event of detecting at least one erroneous bit in said binary frame, of modifying the current binary frame before decoding, as a function of the category in which the erroneous bit is catalogued. The invention also pertains to a device implementing the method according to the invention as well as to a decoder and a coding/decoding system comprising such a device.
Abstract:
The invention concerns a method for switching the decoding rate of an audio signal encoded by a multiple-rate audio coding system, said decoding including at least one step of post-processing dependent on the rate. The invention is characterized in that upon switching from an initial rate to a final rate, said method includes a step of transition by continuously shifting from a signal with initial rate to a signal of final rate, at least one of said signal being subjected to a post-processing. The invention is applicable to transmission of VOIP speech and/or audio signals on data packets.
Abstract:
The invention relates to the processing of a digital signal originating from a decoder and a noise reduction post-processing step, including, in particular, limitation of distortion introduced by the post-processing step in order to deliver a corrected output signal (SOUT), assigning said corrected output signal (SOUT) with: a current amplitude having an intermediary value between a current amplitude value of the post-processed signal (SPOST) and a corresponding current amplitude value of the decoded signal (S'MIC), or the current amplitude of the post-processed signal (SPOST), according to the respective values of the current amplitude of the post-processed signal (SPOST) and by the corresponding current amplitude of the decoded signal (S'MIC).
Abstract:
The invention concerns a module (402) for binary coding of a signal envelope, comprising a coding module (502) of a first variable length mode. According to the invention, the coding module of a first mode incorporates an envelope saturation detector and said coding module (402) also comprises a second coding module (503) of a second mode, arranged parallel to the coding module (502) of the first mode, and a mode selector (504) capable of maintaining one of the two coding modes, based on a code length criterion and on the result derived from the envelope saturation detector. The invention is applicable to coding by audiofrequency signal transform.
Abstract:
The invention relates to a method for generating a dictionary for the vector quantisation of a signal. Said method comprises a step (10) of the statistical analysis of driving vectors representing the signal determining a finished set of code vectors (CITER) representing said driving vectors. The inventive method is characterised in that it also comprises a step (3) of modifying the finished set of code vectors in order to impose a minimum distance between the code vectors modified two-by-two, the set of said modified code vectors forming the dictionary.
Abstract:
The invention concerns a hierarchical encoding system for an audio signal, comprising, at least one core parametric encoding core layer by analysis by synthesis in a first frequency band, a band extending layer designed to enlarge said first frequency band into a second frequency band, called extended band. The invention is characterized in that the system further comprises a layer for enhancing the audio encoding quality in the extended band, based on a transform encoding using a spectral parameter derived from said band extending layer. The invention is applicable to the transmission of speech and/or audio signals on packet networks.
Abstract:
The present invention relates to a technique of coding/decoding by bit planes, in which the whole components of a vector to be coded are decomposed into a binary representation in a succession of bit planes, from the plane of the most significant bits to the plane of the least significant bits. Within the meaning of the invention, the coding of the most significant bit plane is performed, while assigning a first type of coding symbol comprising at least two possible values of symbols ("+", "-") to represent a number of successive zeros in binary in a plane, and two other values (« 0 », « 1 ») for coding the sign of a significant bit, and the coding of the following bit planes up to the least significant bit plane is performed according to the steps of identifying the null bits in the planes already coded and extracting bits with the same positions in a current plane to be coded so as to form a nonsignificant part (Pk nonsig), of identifying the non-null bits in the planes already coded and extracting the bits with the same positions in the current plane to be coded so as to form a significant part (Pk sig), of coding the bits of the nonsignificant part using the first type of symbol, and of coding the bits of the significant part using a second type of symbol to code the value of the bits in the significant part.
Abstract:
The invention relates to a method for post-processing, in an audio decoder, a signal reconstructed by the temporal and frequential shaping (805, 807) of an excitation signal obtained on the basis of at least one parameter in a first frequency band, said temporal and frequential shaping being carried out at least on the basis of a temporal envelope and a frequential envelope received and decoded (801, 802) in a second frequency band. The method is such that, once the shaping (805,807) has been carried out, steps of comparing the amplitude of the reconstructed signal with the received and decoded temporal envelope (s) are followed, and an amplitude compression is applied to the reconstructed signal if at least one threshold of the temporal envelope is exceeded. The invention relates to a post-processing module for implementing the inventive method, and to an audio decoder. It is used for transmitting and storing digital signals such as audiofrequency signals: speech, music, etc.
Abstract:
The invention relates to a hierarchical audio encoder in a frequency band divided into a first sub-band and a second sub-band which are adjacent to each other, said encoder comprising: a core encoder (305) for encoding an original signal in the first sub-band of the frequency band; a calculation stage (306) for calculating a residual signal {e) from the original signal and from the signal supplied by the core encoder; and a device (307) for perceptual weighting of the residual signal {e). According to the invention, the perceptual weighting device comprises a perceptual weighting filter (307) with gain compensation that can perform the spectral continuity between the signal at the output of the perceptual weighting filter with gain compensation and the signal in the second sub-band. The invention can be applied to the transmission and storage of digital signals, such as the audio signals of speech, music, etc.