Multi-band spectral audio encoding

Details Multi-band spectral audio encoding Multi-band spectral audio encoding

H - Electricity

04

H

H04H 60/31 (2008.01) H04H 60/41 (2008.01) G10L 19/00 (2006.01)

Patent

CA 2405179

An encoder includes a sampler that samples an audio signal and that generates from the samples a plurality of short blocks of sampled audio. Each of the short blocks has a duration less than a minimum audibly perceivable signal delay. A processor combines the plurality of short blocks into a long block. The long block is transformed into a frequency domain signal having a plurality of independently modulatable frequency indices. The frequency difference between adjacent indices is determined by the minimum duration and the sampling rate of the sampler. A neighborhood of frequency indices is selected so that the frequency difference between a lowest index and a highest index within the neighborhood is less than a predetermined value. Two or more of the indices are modulated in the neighborhood so as to make a selected one of the indices an extremum while keeping the total energy of the neighborhood constant. A plurality of frequency bands are so coded. A decoder decides that a bit or bits have been received if, in a majority of the frequency bands, the decoder detects a modulated index.

L'invention concerne un codeur comprenant un ~chantillonneur con×u pour ~chantillonner un signal audio et pour produire plusieurs s~quences courtes de signal audio ~chantillonn~ ~ partir des ~chantillons. Chacune des s~quences courtes pr~sente une dur~e inf~rieure ~ un retard de signal minimum pouvant Útre per×u de par l'oreille. Un processeur regroupe la multitude de s~quences courtes en une s~quence longue. La s~quence longue est transform~e en un signal de domaine fr~quentiel pourvu de plusieurs indices de fr~quences modulables ind~pendamment. La diff~rence de fr~quence entre les indices adjacents est d~termin~e par la dur~e minimum et la vitesse d'~chantillonnage de l'~chantillonneur. Une zone avoisinante aux indices de fr~quence est s~lectionn~e de sorte que la diff~rence de fr~quence entre l'indice le plus bas et l'indice le plus haut, ~ l'int~rieur mÚme de la zone avoisinante, soit inf~rieure ~ une valeur pr~d~termin~e. Au moins deux des indices sont modul~s dans la zone avoisinante de mani­re ~ faire d'un de ces indices un extr~mum, alors mÚme que l'~nergie totale de la zone avoisinante reste constante. Plusieurs bandes de fr~quence sont cod~es de cette mani­re. Un d~codeur d~termine qu'un ou que plusieurs bits ont ~t~ re×us si, dans la plupart des bandes de fr~quence, il d~tecte un indice modul~.

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