Selective post filter
First Claim
1. An interharmonic noise attenuation post filter adapted to receive an input signal, which comprises a preliminary audio signal decoded according to one of a plurality of decoding modes and to supply an output audio signal, the interharmonic noise attenuation post filter comprising:
- a control section for selectively operating the post filter in one of the following modes;
i) a filtering mode, wherein the post filter filters the preliminary audio signal to obtain a filtered signal and supplies the filtered signal as an output audio signal;
orii) a pass-through mode, wherein the post filter supplies the unfiltered preliminary audio signal as an output audio signal,said control section being adapted to receive a post-filtering signal that is generated in response to a value of a data field associated with a time frame of the preliminary audio signal, and to disable the post filter while the post filter is operating in the pass-through mode in response to the post-filtering signal.
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Accused Products
Abstract
In one aspect, the invention provides an audio encoding method characterized by a decision being made as to whether the device which will decode the resulting bit stream should apply post filtering including attenuation of interharmonic noise. Hence, the decision whether to use the post filter, which is encoded in the bit stream, is taken separately from the decision as to the most suitable coding mode.
In another aspect, there is provided an audio decoding method with a decoding step followed by a post-filtering step, including interharmonic noise attenuation, and being characterized in a step of disabling the post filter in accordance with post filtering information encoded in the bit stream signal. Such a method is well suited for mixed-origin audio signals by virtue of its capability to deactivate the post filter in dependence of the post filtering information only, hence independently of factors such as the current coding mode.
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Citations
15 Claims
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1. An interharmonic noise attenuation post filter adapted to receive an input signal, which comprises a preliminary audio signal decoded according to one of a plurality of decoding modes and to supply an output audio signal, the interharmonic noise attenuation post filter comprising:
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a control section for selectively operating the post filter in one of the following modes; i) a filtering mode, wherein the post filter filters the preliminary audio signal to obtain a filtered signal and supplies the filtered signal as an output audio signal;
orii) a pass-through mode, wherein the post filter supplies the unfiltered preliminary audio signal as an output audio signal, said control section being adapted to receive a post-filtering signal that is generated in response to a value of a data field associated with a time frame of the preliminary audio signal, and to disable the post filter while the post filter is operating in the pass-through mode in response to the post-filtering signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of decoding a bit stream signal as an audio time signal, comprising:
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decoding a bit stream signal as a preliminary audio time signal in one of a plurality of decoding modes, the bit stream signal being segmented into time frames; and post-filtering, by a post filter, the preliminary audio time signal by attenuating interharmonic noise, thereby obtaining an audio time signal, characterized in that the post-filtering step is selectively omitted responsive to post-filtering information encoded in the bit stream signal, and wherein the post filter is adapted to receive, for each time frame, a data field associated with the time frame, and responsive to a value of the data field, enable or disable the post filter for post-filtering the preliminary audio time signal. - View Dependent Claims (11)
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12. An encoder system for encoding an audio time signal as a bit stream signal, including an encoding section operable in several coding modes, for encoding an audio time signal as a bit stream signal, the encoder system comprising:
a decision section adapted to decide whether post filtering, which includes attenuation of interharmonic noise, is to be disabled at a decoder operable for decoding of the bit stream signal separately from deciding on the coding mode and to encode this decision in the bit stream signal as post filtering information, wherein the bit stream signal is segmented into time frames and the encoding includes adding a value to a data field of each time frame to enable or disable a post filter in the decoder that is operable for post filtering the decoded bit stream signal. - View Dependent Claims (13, 14)
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15. A method of encoding an audio time signal as a bit stream signal, the method comprising:
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encoding an audio time signal as a bit stream signal in one of several coding modes, wherein the bit stream signal is segmented into time frames and the encoding includes adding a value to a data field of each time frame to enable or disable a post filter in a decoder that is operable for post filtering the decoded bit stream signal; and deciding whether post filtering, which includes attenuation of interharmonic noise, is to be disabled at the decoder operable for decoding of the bit stream signal separately from deciding on the coding mode and encoding this decision in the bit stream signal as post filtering information.
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Specification