Audio signal conversion using frequency band division
First Claim
1. A system for encoding an analog audio input signal comprisinganalog band splitter means, coupled to said analog audio input signal, for generating a first band audio signal and a second band audio signal,first gain controlled amplifier means, coupled to said first band audio signal, for generating an amplitude controlled first band signal,second gain controlled amplifier means, coupled to said second band audio signal for generating an amplitude controlled second band signal,analog multiplexer means, coupled to said amplitude controlled first band signal and said amplitude controlled second band signal, for generating an analog time division multiplexed signal, andanalog to digital converter means, coupled to said analog time division multiplexed signal, for generating a digitized time division multiplexed signal,wherein said first and said second gain controlled amplifier means are transconductance cells with a linear transfer characteristic.
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Accused Products
Abstract
The present invention includes a system and method for audio signal conversion using frequency band division. By making use of the statistical properties of an audio signal, the system and method achieves significant coding efficiency, on the order of twice that achieved by linear PCM. Quantization is performed on multiple frequency bands of audio data which have different power density characteristics and sample rate requirements.
4 Citations
25 Claims
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1. A system for encoding an analog audio input signal comprising
analog band splitter means, coupled to said analog audio input signal, for generating a first band audio signal and a second band audio signal, first gain controlled amplifier means, coupled to said first band audio signal, for generating an amplitude controlled first band signal, second gain controlled amplifier means, coupled to said second band audio signal for generating an amplitude controlled second band signal, analog multiplexer means, coupled to said amplitude controlled first band signal and said amplitude controlled second band signal, for generating an analog time division multiplexed signal, and analog to digital converter means, coupled to said analog time division multiplexed signal, for generating a digitized time division multiplexed signal, wherein said first and said second gain controlled amplifier means are transconductance cells with a linear transfer characteristic.
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2. A system for encoding an analog audio input signal comprising
analog band splitter means, coupled to said analog audio input signal, for generating a first band audio signal and a second band audio signal, first gain controlled amplifier means, coupled to said first band audio signal, for generating an amplitude controlled first band signal, second gain controlled amplifier means, coupled to said second band audio signal, for generating an amplitude controlled second band signal, analog multiplexer means, coupled to said amplitude controlled first band signal and said amplitude controlled second band signal, for generating an analog time division multiplexed signal, and analog to digital converter means, coupled to said analog time division multiplexed signal, for generating a digitized time division multiplexed signal, wherein said analog multiplexer means samples said amplitude controlled first band signal at a first rate, and samples said amplitude controlled second band signal at a second rate.
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5. An audio signal conversion system comprising an analog band splitter having an input, a first output, and a second output,
said input of said analog band splitter coupled to an analog audio input signal, said first output of said analog band splitter generating a first band audio signal, said second output of said analog band splitter generating a second band audio signal, a first gain controlled amplifier having an input and an output, said input of said first gain controlled amplifier coupled to said first band audio signal, said output of said first gain controlled amplifier generating an amplitude controlled first band signal, a second gain controlled amplifier having an input and an output, said input of said second gain controlled amplifier coupled to said second band audio signal, said output of said second gain controlled amplifier generating an amplitude controlled second band signal, an analog multiplexer having a first input, a second input, and an output, said first input of said analog multiplexer coupled to said amplitude controlled first band signal, said second input of said analog multiplexer coupled to said amplitude controlled second band signal, said output of said analog multiplexer generating an analog time division multiplexed signal, and an analog to digital converter having an input and an output, said input of said analog to digital converter coupled to said analog time division multiplexed signal, said output of said analog to digital converter generating a digitized time division multiplexed signal, wherein said first and said second gain controlled amplifiers are transconductance cells with a linear transfer characteristic.
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6. An audio signal conversion system comprising an analog band splitter having an input, a first output, and a second output,
said input of said analog band splitter coupled to an analog audio input signal, said first output of said analog band splitter generating a first band audio signal, said second output of said analog band splitter generating a second band audio signal, a first gain controlled amplifier having an input and an output, said input of said first gain controlled amplifier coupled to said first band audio signal, said output of said first gain controlled amplifier generating an amplitude controlled first band signal, a second gain controlled amplifier having an input and an output, said input of said second gain controlled amplifier coupled to said second band audio signal, said output of said second gain controlled amplifier generating an amplitude controlled second band signal, an analog multiplexer having a first input, a second input, and an output, said first input of said analog multiplexer coupled to said amplitude controlled first band signal, said second input of said analog multiplexer coupled to said amplitude controlled second band signal, said output of said analog multiplexer generating an analog time division multiplexed signal, and an analog to digital converter having an input and an output, said input of said analog to digital converter coupled to said analog time division multiplexed signal, said output of said analog to digital converter generating a digitized time division multiplexed signal, wherein said first and said second gain controlled amplifiers include a control input, and further including an automatic gain control (AGC) circuit, said AGC circuit including a first input, a second input, a first digital output, a second digital output, a first analog output, and a second analog output, said first input and said second input of said AGC circuit coupled to said digitized time division multiplexed signal, said first digital output of said AGC circuit generating a first digital gain control signal, said second digital output of said AGC circuit generating a second digital gain control signal, said first analog output of said AGC circuit generating a first analog gain control signal, and said second analog output of said AGC circuit generating a second analog gain control signal.
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9. An audio signal conversion system comprising an analog band splitter having an input, a first output, and a second output,
said input of said analog band splitter coupled to an analog audio input signal, said first output of said analog band splitter generating a first band audio signal, said second output of said analog band splitter generating a second band audio signal, a first gain controlled amplifier having an input and an output, said input of said first gain controlled amplifier coupled to said first band audio signal, said output of said first gain controlled amplifier generating an amplitude controlled first band signal, a second gain controlled amplifier having an input and an output, said input of said second gain controlled amplifier coupled to said second band audio signal, said output of said second gain controlled amplifier generating an amplitude controlled second band signal, an analog multiplexer having a first input, a second input, and an output, said first input of said analog multiplexer coupled to said amplitude controlled first band signal, said second input of said analog multiplexer coupled to said amplitude controlled second band signal, said output of said analog multiplexer generating an analog time division multiplexed signal, and an analog to digital converter having an input and an output, said input of said analog to digital converter coupled to said analog time division multiplexed signal, said output of said analog to digital converter generating a digitized time division multiplexed signal, wherein said analog multiplexer samples said amplitude controlled first band signal at a first rate, and samples said amplitude controlled second band signal at a second rate.
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12. A system for encoding an analog audio input signal comprising
analog band splitter means, coupled to said analog audio input signal, for generating a first band audio signal and a second band audio signal, first gain controlled amplifier means, coupled to said first band audio signal, for generating an amplitude controlled first band signal, second gain controlled amplifier means, coupled to said second band audio signal, for generating an amplitude controlled second band signal, first analog to digital converter means, coupled to said amplitude controlled first band signal, for generating a digitized amplitude controlled first band signal, second analog to digital converter means, coupled to said amplitude controlled second band signal for generating a digitized amplitude controlled second band signal, and digital multiplexer means, coupled to said digitized amplitude controlled first band signal and said digitized amplitude controlled second band signal, for generating a digital time division multiplexed output signal, wherein said first and said second gain controlled amplifier means are transconductance cells with a linear transfer characteristic.
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13. A system for encoding an analog audio input signal comprising
analog band splitter means, coupled to said analog audio input signal, for generating a first band audio signal and a second band audio signal, first gain controlled amplifier means, coupled to said first band audio signal, for generating an amplitude controlled first band signal, second gain controlled amplifier means, coupled to said second band audio signal, for generating an amplitude controlled second band signal, first analog to digital converter means, coupled to said amplitude controlled first band signal, for generating a digitized amplitude controlled first band signal, second analog to digital converter means, coupled to said amplitude controlled second band signal for generating a digitized amplitude controlled second band signal, and digital multiplexer means, coupled to said digitized amplitude controlled first band signal and said digitized amplitude controlled second band signal, for generating a digital time division multiplexed output signal, wherein said first analog to digital converter means samples said amplitude controlled first band signal at a first rate, and said second analog to digital converter means samples said amplitude controlled second band signal at a second rate.
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16. A system for encoding an analog audio input signal comprising
analog band splitter means, coupled to said analog audio input signal, for generating a first band audio signal and a second band audio signal, first gain controlled amplifier means, coupled to said first band audio signal, for generating an amplitude controlled first band signal, second gain controlled amplifier means, coupled to said second band audio signal, for generating an amplitude controlled second band signal, first analog to digital converter means, coupled to said amplitude controlled first band signal, for generating a digitized amplitude controlled first band signal, second analog to digital converter means, coupled to said amplitude controlled second band signal for generating a digitized amplitude controlled second band signal, digital multiplexer means, coupled to said digitized amplitude controlled first band signal and said digitized amplitude controlled second band signal, for generating a digital time division multiplexed output signal, wherein said first and said second gain controlled amplifiers include a control input, and further including an automatic gain control (AGC) circuit, said AGC circuit including a first input, a second input, a first digital output, a second digital output, a first analog output, and a second analog output, said first input of said AGC circuit coupled to said amplitude controlled first band signal, said second input of said AGC circuit coupled to said amplitude controlled second band signal, said first digital output of said AGC circuit generating a first digital gain control signal, said second digital output of said AGC circuit generating a second digital gain control signal, said first analog output of said AGC circuit generating a first analog gain control signal, and said second analog output of said AGC circuit generating a second analog gain control signal.
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19. A system for encoding an analog audio input signal comprising
analog band splitter means, coupled to said analog audio input signal, for generating a first band audio signal and a second band audio signal, first gain controlled amplifier means, coupled to said first band audio signal, for generating an amplitude controlled first band signal, second gain controlled amplifier means, coupled to said second band audio signal, for generating an amplitude controlled second band signal, first analog to digital converter means, coupled to said amplitude controlled first band signal, for generating a digitized amplitude controlled first band signal, Second analog to digital converter means, coupled to said amplitude controlled second band signal for generating a digitized amplitude controlled second band signal, digital multiplexer means, coupled to said digitized amplitude controlled first band signal and said digitized amplitude controlled second band signal, for generating a digital time division multiplexed output signal, and wherein said first analog to digital converter samples said amplitude controlled first band signal at a first rate, and said second analog to digital converter samples said amplitude controlled second band signal at a second rate.
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22. A method for digitally encoding an analog audio input signal, comprising the steps of:
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splitting said analog audio input signal into a first frequency band signal and a second frequency band signal; amplifying said first frequency band signal by a first continuously variable signal, said first continuously variable signal inversely proportional to the instantaneous amplitude of said first frequency band signal; amplifying said second frequency band signal by a second continuously variable signal, said second continuously variable signal inversely proportional to the instantaneous amplitude of said second frequency band signal; generating a digitized representation of said amplified first frequency band signal and said amplified second frequency band signal; and multiplexing said digitized amplified first frequency band signal, said digitized amplified second frequency band signal, a digitized representation of said first continuously variable signal, and a digitized representation of said second continuously variable signal to generate a digital time division multiplexed signal capable of being reconstructed as said analog audio input signal. - View Dependent Claims (23)
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24. A method for encoding an analog audio input signal, comprising the steps of:
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splitting said analog audio input signal into a first frequency band signal and a second frequency band signal; amplifying said first frequency band signal by a first continuously variable signal, said first continuously variable signal inversely proportional to the instantaneous amplitude of said first frequency band signal; amplifying said second frequency band signal by a second continuously variable signal, said second continuously variable signal inversely proportional to the instantaneous amplitude of said second frequency band signal; time division multiplexing said amplified first frequency band signal and said amplified second frequency band signal to generate an analog time division multiplexed signal; converting said analog time division multiplexed into a first digital time division multiplexed signal; and time division multiplexing said first digital time division multiplexed signal, a digitized representation of said first continuously variable signal, and a digitized representation of said second continuously variable signal to generate a second digital time division multiplexed signal capable of being reconstructed as said analog audio input signal. - View Dependent Claims (25)
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Specification