Sampling rate converting method and apparatus
AssigneeSony Corporation
InventorsMakoto Akune, Tadao Suzuki
Life of this patent
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Abstract
A sampling rate converting method and apparatus for converting the sampling frequency of a 1-bit digital data obtained a .SIGMA..DELTA. modulator to 32 kHz, 48 kHz, 96 kHz or 192 kHz without producing jitter. A decimation filter 3 decimates the sampling frequency of 1-bit digital data of 2.8224 MHz supplied from an input terminal 2 by 1/2-tuple decimation. An interpolation filter 4 oversamples the frequency of the output of the decimation filter 3 by quintuple oversampling with an integer ratio of 1:5. A decimation filter 5 decimates the frequency of the output of the interpolation filter 4 by 1/21-tuple decimation with an integer ratio of 21:1.
Claims9
A method for converting 1-bit digital audio data that is quantized by a first sampling frequency Fi.times..alpha. (Hz) to multi-bit digital audio data that is quantized by a second sampling frequency lower than the first sampling frequency Fi.times..alpha. (Hz), where Fi and .alpha. are integers, the method comprising the steps of:
- performing a first variable decimation step of multiplying the 1-bit digital audio data by 1/.beta. and producing multi-bit digital data, where .beta. is an integer;
- performing an oversampling step of multiplying the multi-bit digital data produced by said first variable decimation step by 5.times.m, where m is an integer;
- and
- performing a second variable decimation step of multiplying the multi-bit digital data that is sampled by (Fi.times..alpha..times.5.times.m)/.beta. (Hz) by 1/(7.times.n), where n is an integer,
- whereby the input 1-bit digital audio data that is quantized by the first sampling frequency Fi.times..alpha. (Hz) is converted to the multi-bit digital audio data that is quantized by the second sampling frequency (Fi.times..alpha..times.5.times.m)/(.beta..times.7.times.n)(Hz) less than the first sampling frequency Fi.times..alpha. (Hz).
A sampling rate converting apparatus for converting 1-bit digital audio data that is quantized by a first sampling frequency Fi.times..alpha. (Hz) to multi-bit digital audio data that is quantized by a second sampling frequency lower than the first sampling frequency Fi.times..alpha. (Hz), where Fi is an integer and a is an integer, the apparatus comprising:
- first variable decimation means for multiplying the 1-bit digital audio data received as an input signal by 1/.beta. and producing multi-bit digital data, where .beta. is an integer,
- over sampling means for multiplying the multi-bit digital data produced by said first variable decimation means by 5.times.m, where m is an integer, and
- second variable decimation means for multiplying the multi-bit digital data that is sampled by (Fi.times..alpha..times.5.times.m) /.beta. (Hz) by 1/(7.times.n), where n is an integer,
- whereby the input 1-bit audio data that is quantized by the first sampling frequency Fi.times..alpha. (Hz) is converted to the multi-bit digital audio data that is quantized by the second sampling frequency (Fi.times..alpha..times.5.times.m)/(.beta..times.7.times.n)(Hz) that is lower than the first sampling frequency Fi.times..alpha. (Hz).
A method for converting 1-bit digital audio data that is quantized by a first sampling frequency Fi.times..alpha. (Hz) to multi-bit audio data that is quantized by a second sampling frequency lower than the first sampling frequency Fi.times..alpha. (Hz), where Fi is an integer and .alpha. is an integer, the method comprising the steps of:
- performing a first variable decimation step of multiplying the 1-bit digital audio data by 1/.beta., and producing multi-bit digital data, where .beta. is an integer;
- performing an oversampling step of multiplying the multi-bit digital data produced by said first variable decimation step by .delta., where .delta. is an integer;
- and
- performing a second variable decimation step of multiplying the multi-bit digital data that is sampled by (Fi.times..alpha..times..delta.)/B.times.J (Hz) by 1/.sigma., where .sigma. is an integer,
- whereby the input 1-bit digital audio data that is quantized by the first sampling frequency Fi.times..alpha. (Hz) is converted to the multi-bit digital audio data that is quantized by the second sampling frequency (Fi.times..alpha..times..delta.)/B.times..sigma. (Hz) that is lower than the first sampling frequency Fi.times..alpha. (Hz).
An apparatus for converting 1-bit digital audio data that is quantized by a first sampling frequency Fi.times..alpha. (Hz) to multi-bit digital audio data that is quantized by a second sampling frequency lower than the first sampling frequency Fi.times..alpha. (Hz), where Fi and .alpha. are integers, the apparatus comprising:
- first variable decimation means for multiplying the 1-bit digital audio data of an input signal by 1/.beta. and producing multi-bit digital data, where .beta. is an integer,
- over sampling means for multiplying the multi-bit digital data produced by said first variable decimation means by .delta., wherein .delta. is an integer, and
- second variable decimation means for multiplying the multi-bit digital data that is sampled by (Fi.times..alpha..times..sigma.)/.beta. (Hz) by 1/.sigma., where .sigma. is an integer,
- whereby the input 1-bit audio data that is quantized by the first sampling frequency Fi.times..alpha. (hz) is converted to the multi-bit digital audio data that is quantized by the second sampling frequency (Fi.times..alpha..times..delta.)/(.beta..times..sigma.)(Hz) that is lower than the first sampling frequency Fi.times..alpha. (Hz).
Dependencies are inferred from the claim text.