Enabling sampling rate diversity in a voice communication system
First Claim
1. A audio communication server for exchanging bitstreams with a plurality of audio communication endpoints,each of said bitstreams containing spectral components representing spectral content of an audio signal and conformal to a predefined bitstream format allowing transmission of spectral components up to a maximum frequency,wherein the spectral components in each incoming bitstream relate to a frequency range extending up to an input break frequency which is selectable by each corresponding audio communication endpoint,said server comprising:
- a mixer configured to receive a plurality of incoming bitstreams and to output, based thereon, a bitstream representing an audio signal being an additive mix of at least one of the incoming bitstreams; and
a selector configured to output, from the audio communication server, an outgoing bitstream being either a bitstream output by the mixer or a bitstream reproducing an active one of the incoming bitstreams,wherein the selector is configured to monitor the incoming bitstreams for audio activity and to output, in response to having exactly one active incoming bitstream, an outgoing bitstream reproducing the active incoming bitstream.
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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 moving 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 neighbourhood 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. A audio communication server for exchanging bitstreams with a plurality of audio communication endpoints,
each of said bitstreams containing spectral components representing spectral content of an audio signal and conformal to a predefined bitstream format allowing transmission of spectral components up to a maximum frequency, wherein the spectral components in each incoming bitstream relate to a frequency range extending up to an input break frequency which is selectable by each corresponding audio communication endpoint, said server comprising: -
a mixer configured to receive a plurality of incoming bitstreams and to output, based thereon, a bitstream representing an audio signal being an additive mix of at least one of the incoming bitstreams; and a selector configured to output, from the audio communication server, an outgoing bitstream being either a bitstream output by the mixer or a bitstream reproducing an active one of the incoming bitstreams, wherein the selector is configured to monitor the incoming bitstreams for audio activity and to output, in response to having exactly one active incoming bitstream, an outgoing bitstream reproducing the active incoming bitstream. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of operating an audio communication server for exchanging bitstreams with a plurality of audio communication endpoints,
each of said bitstreams containing spectral components representing spectral content of an audio signal and conformal to a predefined bitstream format allowing transmission of spectral components up to a maximum frequency, wherein the spectral components in each incoming bitstream relate to a frequency range extending up to an input break frequency which is selectable by each corresponding audio communication endpoint, wherein the audio communication server comprises a mixer and a selector, said method comprising: -
receiving, by the mixer, a plurality of incoming bitstreams and outputting based thereon, by the mixer, a bitstream representing an audio signal being an additive mix of at least one of the incoming bitstreams; and outputting from the audio communication server, by the selector, an outgoing bitstream being either a bitstream output by the mixer or a bitstream reproducing an active one of the incoming bitstreams, the method further comprising; monitoring, by the selector, the incoming bitstreams for audio activity and to outputting by the selector, in response to having exactly one active incoming bitstream, an outgoing bitstream reproducing the active incoming bitstream. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification