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US5487087A
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Signal quantizer with reduced output fluctuation
Assignee: Texas Instruments Inc
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Filing: 1994-05-17
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Granted: 1996-01-23
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Expires: 2014-05-17
Abstract
Abstract A new signal quantization scheme is proposed which reduces fluctuation of the output signal by a signal quantizer (10) providing a quantized output signal and multiplying(18) said input signal X by a factor (1-w 1 )and finding a difference signal Δ n (11) between both the input signal and the previous input signal and multiplying (16) that by a weighting factor w 2 from a control (13). The previous quantizer output signal Q prev is summed (17) with the weighted difference signal Δ in w 2 and the sum is weighted by a weighting factor w 1 at a multiplier (19) to yield w 1 (Q prev +w 2 Δ in ). This signal is then summed at an adder (21) and applied to the quantizer (10) so that the quantizer is forced to match the fluctuation in the input signal as well as the signal itself. When applied to speech encoding algorithms such as the North American digital cellular telephone standard VSELP, the new quantizer results in more natural sounding background noise.
Inventors
- 👤 Alan V. McCree
- 👤 Vishu R. Viswanathan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 11:11
CPC Classifications
G; G10; G10L; G10L19/00; G10L19/012; G10L19/04; G10L19/06; H; H04; H04B; H04B14/00; H04B14/02; H04B14/04; H04B14/046
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
165 words
A signal quantizer with reduced output fluctuation comprising: a signal quantizer for providing a quantized output signal Q; means responsive to an input signal X for multiplying said input signal by 1-w 1 where w 1 is a first weight factor having a value between 0 and 1; means responsive to said input signal X to be quantized for providing a difference signal Δ in w 2 equal to the difference between said input signal X and a previous input signal X prev multiplied by a second weight factor w 2 where w 2 has a value between 0 and 1; means for adding to a previous quantizer output signal Q prev said difference signal Δ in w 2 and multiplying by said weight factor w 1 to yield w 1 (Q prev +w 2 Δ in ): means for summing (1-w 1 ) X and w 1 (Q prev +w 2 Δ in ) to yield X'; means for applying X' to said quantizer.
Claim 2
Dependent Claim
165 words
A signal quantizer with reduced output fluctuation comprising: a signal quantizer for providing a quantized output signal Q; means responsive to an input signal X for multiplying said input signal by 1-w 1 where w 1 is a first weight factor having a value between 0 and 1; means responsive to said input signal X to be quantized for providing a difference signal Δ in w 2 equal to the difference between said input signal X and a previous input signal X prev multiplied by a second weight factor w 2 where w 2 has a value between 0 and 1; means for adding to a previous quantizer output signal Q prev said difference signal Δ in w 2 and multiplying by said weight factor w 1 to yield w 1 (Q prev +w 2 Δ in ): means for summing (1-w 1 ) X and w 1 (Q prev +w 2 Δ in ) to yield X'; means for applying X' to said quantizer.
Claim 3
Dependent Claim
27 words
The quantizer of claim 1 wherein w 1 and w 2 weight factors are based on the power level and/or rate of spectral change of input signal.
Claim 4
Dependent Claim
84 words
The quantizer of claim 2 wherein w 2 is based on transition strength T which is estimated from a change in power level and spectral tilt from a previous frame and w 1 is based on transition strength and signal strength S which is determined by comparing the power P for a speech frame with a long-term estimate of the background noise level P noise wherein: w.sub.1 =0.075(1-T)(1-S) and w.sub.2 =T and ##EQU9## , wherein T is transition strength and S is signal strength.
Claim 5
Independent Claim
188 words
A method of quantizing an input signal X comprising the steps of: providing a quantizer responsive to an input signal providing a quantized output signal Q; multiplying said input signal X by 1-w 1 to yield (1-w 1 ) X where w 1 is a first weight factor having a weight value between 0 and 1; subtracting said input signal X from a previous input signal to provide a difference signal Δ in ; multiplying said difference signal Δ in by a second weight factor w 2 to yield Δ in w 2 where w 2 has a value between 0 and 1; adding a previous quantizer output Q prev to said multiplied difference signal Δ in w 2 to yield summed signal Q prev +w 2 Δ in ; multiplying said summed signal Q prev +W 2 Δ in by weight factor w 1 to yield double weighted signal w 1 (Q prev +w 2 Δ in ); summing said signal equal to w 1 (Q prev +w 2 Δ in ) and X (1-w 1 ) to yield X'; and applying signal X' to said quantizer.
Claim 6
Independent Claim
188 words
A method of quantizing an input signal X comprising the steps of: providing a quantizer responsive to an input signal providing a quantized output signal Q; multiplying said input signal X by 1-w 1 to yield (1-w 1 ) X where w 1 is a first weight factor having a weight value between 0 and 1; subtracting said input signal X from a previous input signal to provide a difference signal Δ in ; multiplying said difference signal Δ in by a second weight factor w 2 to yield Δ in w 2 where w 2 has a value between 0 and 1; adding a previous quantizer output Q prev to said multiplied difference signal Δ in w 2 to yield summed signal Q prev +w 2 Δ in ; multiplying said summed signal Q prev +W 2 Δ in by weight factor w 1 to yield double weighted signal w 1 (Q prev +w 2 Δ in ); summing said signal equal to w 1 (Q prev +w 2 Δ in ) and X (1-w 1 ) to yield X'; and applying signal X' to said quantizer.
Claim 7
Dependent Claim
27 words
The method of claim 4 wherein said weight factors w 1 and w 2 are based on the power level and/or spectral change of said input signal.
Claim 8
Dependent Claim
62 words
The method of claim 4 wherein w 2 is based on transition strength T which is estimated from the change in power level and spectral tilt from the previous frame and w 1 is based on transition strength and signal strength S which is estimated by comparing the power for the speech frame with a long-term estimate of the background noise level.
Claim 9
Dependent Claim
186 words
In a speech encoding system comprising sampling of speech signal and A/D converting to digital signal; a coefficient analyzer responsive to said digital signal, said coefficient analyzer comprising: a signal quantizer for providing a quantized output signal Q; means responsive to an input signal X for multiplying said input signal by 1-w 1 where w 1 is a first weight factor having a value between 0 and 1; means responsive to said input signal X to be quantized for providing a difference signal Δ in w 2 equal to the difference between said input signal X and a previous input signal X prev multiplied by a second weight factor w 2 where w 2 has a value between 0 and 1; means for adding to a previous quantizer output signal Q prev said difference signal Δ in w 2 and multiplying by said weight factor w 1 to yield w 1 (Q prev +w 2 Δ in ); means for summing (1-w 1 ) X and w 1 (Q prev +w 2 Δ in ) to yield X'; and means for applying X' to said quantizer.
Claim 10
Dependent Claim
186 words
In a speech encoding system comprising sampling of speech signal and A/D converting to digital signal; a coefficient analyzer responsive to said digital signal, said coefficient analyzer comprising: a signal quantizer for providing a quantized output signal Q; means responsive to an input signal X for multiplying said input signal by 1-w 1 where w 1 is a first weight factor having a value between 0 and 1; means responsive to said input signal X to be quantized for providing a difference signal Δ in w 2 equal to the difference between said input signal X and a previous input signal X prev multiplied by a second weight factor w 2 where w 2 has a value between 0 and 1; means for adding to a previous quantizer output signal Q prev said difference signal Δ in w 2 and multiplying by said weight factor w 1 to yield w 1 (Q prev +w 2 Δ in ); means for summing (1-w 1 ) X and w 1 (Q prev +w 2 Δ in ) to yield X'; and means for applying X' to said quantizer.
Claim 11
Dependent Claim
224 words
An encoder system comprising: a simple encoder with reduced bit rate; a full encoder operating at normal bit rate with a quantizer with reduced output fluctuations; a speech/noise detector responsive to input speech for detecting the presence of speech and if noise coupling the input to said simple encoder and if speech to said full encoder; said full encoder comprising a quantizer comprising: a signal quantizer for providing-a quantized output signal Q; means responsive to an input signal X for multiplying said input signal by 1-w 1 , where w 1 is a first weight factor having a value between 0 and 1; means responsive to said input signal X to be quantized for providing a difference signal Δ in w 2 equal to the difference between said input signal X and a previous input signal X prev multiplied by a second weight factor w 2 where w 2 has a value between 0 and 1; means for adding to a previous quanitzer output signal Q prev said difference signal Δ in w 2 and multiplying by said weight factor w 1 to yield w 1 (Q prev +w 2 Δ in ); means for summing (1-w 1 ) X and w 1 (Q prev +w 2 Δ in ) to yield X 40 ; and means for applying X 40 to said equalizer.
Claim 12
Dependent Claim
224 words
An encoder system comprising: a simple encoder with reduced bit rate; a full encoder operating at normal bit rate with a quantizer with reduced output fluctuations; a speech/noise detector responsive to input speech for detecting the presence of speech and if noise coupling the input to said simple encoder and if speech to said full encoder; said full encoder comprising a quantizer comprising: a signal quantizer for providing-a quantized output signal Q; means responsive to an input signal X for multiplying said input signal by 1-w 1 , where w 1 is a first weight factor having a value between 0 and 1; means responsive to said input signal X to be quantized for providing a difference signal Δ in w 2 equal to the difference between said input signal X and a previous input signal X prev multiplied by a second weight factor w 2 where w 2 has a value between 0 and 1; means for adding to a previous quanitzer output signal Q prev said difference signal Δ in w 2 and multiplying by said weight factor w 1 to yield w 1 (Q prev +w 2 Δ in ); means for summing (1-w 1 ) X and w 1 (Q prev +w 2 Δ in ) to yield X 40 ; and means for applying X 40 to said equalizer.
References Cited (Backward Citations)
US4974235A
Cited
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