Enabling sampling rate diversity in a voice communication system
First Claim
1. An audio communication endpoint (110, 120, 130) configured to process a received bitstream containing spectral components representing spectral content of an audio signal,wherein the spectral components relate to a first frequency range extending up to a first break frequency, above which any spectral components are unassigned,the audio communication endpoint including:
- a decoder (202, 525) configured to reconstruct the audio signal by means of an inverse transform operating on spectral components relating to a second frequency range extending up to a second break frequency; and
a pre-processor (201, 203, 204;
522, 523, 526), which is operable to adapt the received bitstream in accordance with the second frequency range by removing spectral components or adding neutral-valued spectral components relating to a range between the first and second break frequencies, and is operable to attenuate in the frequency domain, in connection herewith, spectral content in a neighbourhood of a cut-off frequency being the least of the first and the second break frequencies, for thereby achieving a gradual spectral decay,wherein the pre-processor is further configured to characterize the spectral decay of the adapted received bitstream and to base a decision whether to attenuate spectral content at the cut-off frequency on this characterization.
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Abstract
An audio communication endpoint receives a bitstream containing spectral components representing spectral content of an audio signal, wherein the spectral components relate to a first range extending up to a first break frequency, above which any spectral components are unassigned. The endpoint adapts the received bitstream in accordance with a second range extending up to a second break frequency by removing spectral components or adding neutral-valued spectral components relating to a range between the first and second break frequencies. The endpoint then attenuates spectral content in a neighborhood of the least of the first and second break frequencies for thereby achieving a gradual spectral decay. After this, reconstructing the audio signal is reconstructed by an inverse transform operating on spectral components relating to said second range in the adapted and attenuated received bitstream. At small computational expense, the endpoint may to adapt to different sample rates in received bitstreams.
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Citations
18 Claims
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1. An audio communication endpoint (110, 120, 130) configured to process a received bitstream containing spectral components representing spectral content of an audio signal,
wherein the spectral components relate to a first frequency range extending up to a first break frequency, above which any spectral components are unassigned, the audio communication endpoint including: -
a decoder (202, 525) configured to reconstruct the audio signal by means of an inverse transform operating on spectral components relating to a second frequency range extending up to a second break frequency; and a pre-processor (201, 203, 204;
522, 523, 526), which is operable to adapt the received bitstream in accordance with the second frequency range by removing spectral components or adding neutral-valued spectral components relating to a range between the first and second break frequencies, and is operable to attenuate in the frequency domain, in connection herewith, spectral content in a neighbourhood of a cut-off frequency being the least of the first and the second break frequencies, for thereby achieving a gradual spectral decay,wherein the pre-processor is further configured to characterize the spectral decay of the adapted received bitstream and to base a decision whether to attenuate spectral content at the cut-off frequency on this characterization. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method implemented in an audio communication endpoint, comprising:
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receiving a bitstream containing spectral components representing spectral content of an audio signal, wherein the spectral components relate to a first frequency range extending up to a first break frequency, above which any spectral components are unassigned; adapting the received bitstream in accordance with a second frequency range extending up to a second break frequency by removing spectral components or adding neutral-valued spectral components relating to a range between the first and second break frequencies; attenuating, in a frequency domain, spectral content in a neighbourhood of a cut-off frequency being the least of the first and the second break frequencies for thereby achieving a gradual spectral decay whereby the spectral decay characterize the adapted received bitstream such that a decision whether to attenuate spectral content at the cut-off frequency is based upon the characterization; and reconstructing the audio signal by means of an inverse transform operating on spectral components relating to said second frequency range in the adapted and attenuated received bitstream, wherein the method is implemented by one or more processors and one or more memory. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification