Real-time hierarchal pyramid signal processing apparatus

• US 4,674,125 A
• Filed: 04/04/1984
• Issued: 06/16/1987
• Est. Priority Date: 06/27/1983
• Status: Expired due to Term

• Current Assignee: RCA Corporation (General Electric Company)
• Original Assignee: RCA Corporation (General Electric Company)
• Inventors: Carlson, Curtis R., Bessler, Roger F., Arbeiter, James H.
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Couso, Jose L.
• Application Number:
  US06/596,817
• Time in Patent Office: 1,168 Days
• Field of Search: 382/17, 382/41, 382/43, 382/49, 358/133, 358/160, 358/167, 358/166, 358/903, 364/723, 364/724, 364/725, 364/728
• US Class Current: 382/303
• CPC Class Codes: G01R 23/167 with digital filters
• CPC Class Codes: G06F 17/10 Complex mathematical operations function generation by table look-up G06F1/03; evaluation of elementary functions by calculation G06F7/544
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets

Abstract

Pipe-line architecture is employed for analyzing in delayed real time the frequency spectrum of an information component (having one or more dimensions) of a given temporal signal having a highest frequency of interest of no greater than f₀, and/or for synthesizing in delayed real time such a temporal signal from the analyzed frequency spectrum thereof. Such pipe-line architecture is particularly suitable for image-processing the two-dimensional spatial frequencies of television images defined by a temporal video signal.

Claims

1. Signal processing apparatus responsive to a given temporal signal that defines an information component having a frequency spectrum, said apparatus employing pipe-line architecture for analyzing in delayed real time the frequency spectrum of said information component of said given temporal signal, wherein said component corresponds to information having a given number of dimensions, and wherein said frequency spectrum includes a highest frequency of interest which is no greater than a frequency f₀ ;

said apparatus comprising;

a set of N ordinally arranged sampled-signal translation means (where N is a plural integer), each one of said translation means including first and second input terminals and first and second output terminals;

said first input terminal of each one of said second to said Nth translation means of said set being coupled to said first output terminal of its immediately preceding one of said translation means of said set for forwarding a signal from each one of said translation means to its immediately following one of said translation means of said set;

means for applying said given temporal signal to said first input terminal of the first translation means of said set; and

means for applying a separate sampling frequency clock to the second input terminal of each one of said translation means of said set to derive a sample rate for respective signals derived at said first and second output terminals of that translation means equal to the sampling frequency of the clock applied thereto;

wherein;

each one of said translation means of said set exhibits for said information component a low-pass transfer function between its first input terminal and its first output terminal, said low-pass transfer function of each translation means of said set having a nominal cut-off frequency that is a direct function of the sampling frequency of the clock applied to the second input terminal of that one of said translation means of said set;

the clock applied to the second input terminal of said first translation means of said set has a sampling frequency that (1) is twice f₀, and (2) provides for said information component a nominal cut-off frequency for said low-pass transfer function of said first translation means of said set which is less than f₀ ;

the clock applied to the second input terminal of each one of said second to Nth translation means of said set has a sampling frequency that (a) is less than the clock frequency applied to the second input terminal of its immediately preceding one of the translation means of said set, (b) is at least equal to twice any frequency of the information component of the signal applied to its first input terminal, and (c) provides a nominal cut-off frequency for its low-pass transfer function which is less than that of its immediately preceding translation means of said set; and

the information component of said signal derived at said second output terminal of each one of said translation means of said set corresponds to a subtractive difference between the information component of the signal applied to said first input terminal thereof and a direct function of the information component of the signal derived at the first output terminal thereof.

2. The apparatus defined in claim 1, wherein the clock applied to the second input terminal of each one of said second to Nth translation means of said set has a sampling frequency relative to the sampling frequency of the clock applied to the second input terminal of its immediately preceding one of the translation means of said set such that:

each particular dimension of the information component of the signal applied to its first terminal is sampled at a rate which is one-half the rate at which that particular dimension of the information component of the signal applied to the first terminal of said immediately preceding one of the translation means of said set is sampled.

3. The apparatus defined in claim 2, wherein the clock applied to the second input terminal of each one of said second to Nth translation means of said set has a sampling frequency relative to the sampling frequency of the clock applied to the second input terminal of the immediately preceding one of the translation means of said set such that:

there is provided a nominal cut-off frequency for its low-pass transfer function that, for each dimension of the information component of said signal applied to its first terminal, is substantially one-half of the nominal cut-off frequency provided for the corresponding dimension of this information component by the low-pass transfer function of said immediately preceding one of said translation means of said set;

whereby the information component of said signal derived at said second output terminal of each one of said translation means of said set corresponds in each dimension thereof with a different octave of the frequency spectrum of the information component of said given temporal signal in that dimension.

4. The apparatus defined in claim 1, wherein said given temporal signal is an analog signal comprised of an information component corresponding to one-dimensional information.

5. The apparatus defined in claim 1, wherein said given temporal signal is comprised of a video signal defining two-dimensional image information.

6. The apparatus defined in claim 5, wherein said video signal corresponds to successive frames of scanned television images.

7. The apparatus defined in claim 1, wherein each one of said translation means of said set is comprised of:

first means coupled to the first and second input and first output terminals of that one translation means for providing said low-pass transfer function of that one translation means;

said first means including an m-tap convolution filter (where m is a given plural integer of three or more, for convolving the information component of the signal applied to the first terminal of that one translation means with a predetermined kernel function at a sampling frequency corresponding to that of the clock applied to the second input terminal of that one translation means, said predetermined kernel function and said sampling frequency of the convolution filter of that one translation means defining respectively shape and nominal cut-off frequency characteristics of the low-pass transfer function of that one translation means in each dimension of said information component; and

second means coupled to said first means and to the second input and second output terminals of that one translation means for deriving said difference signal at the second output terminal of that one translation means;

said second means including sample-subtractive means and third means comprising delay means for coupling said sample-subtractive means through said delay means to said first means for subtracting in temporal alignment, at the sampling frequency of convolved samples of that one translation means, each of the successively-occurring respective sample levels of convolved samples of that one translation means from each of corresponding successively-occurring respective levels of the information component of the signal applied to the first input terminal of that one translation means prior to its being convolved with said predetermined kernel function of the convolution filter of that one translation means, whereby said sample-subtracting means output comprises each of successively-occurring respective difference sample levels, at the sampling frequency of the convolved samples of that one translation means, said respective difference sample levels constituting the information component of the signal derived at the second output terminal of that one translation means.

8. The apparatus defined in claim 7, wherein said predetermined kernel function of at least one of said translation means of said set defines a low-pass transfer-function shape for that translation means having a gradual roll-off that extends beyond said nominal cut-off frequency thereof.

9. The apparatus defined in claim 7, wherein said respective predetermined kernel functions of at least two of said translation means of said set are substantially similar to one another.

10. The apparatus defined in claim 7, wherein:

said information component is comprised of at least two dimensions, and

the convolution filter of at least one of said translation means is a non-separable filter in at least said two dimensions.

11. The apparatus defined in claim 7, wherein:

said information component is comprised of at least two dimensions, and

the convolution filter of at least one of said translation means is a separable filter in said two-dimensions.

12. The apparatus defined in claim 7, wherein:

said first means of at least one of said translation means of said set is of a given type, said given type of first means being comprised of said convolution filter and a decimator serially coupled between an output of said convolution filter and the first output terminal of that one of said translation means of said set;

said convolution filter of said given type of first means derives at its output a particular sample density in each dimension of said information component that corresponds with the sampling frequency of the clock applied to the second input terminal of that one translation means, and

said decimator of said given type of first means forwards, in each of said dimensions of said information component, only certain ones, but not all, of the convolved samples appearing at the output of the convolution filter of said given type of first means to said first output terminal of that one translation means,

whereby, in each of said dimensions of said information component at said first output terminal of that one translation means, its sample density is reduced with respect to a corresponding sample density in that dimension of said information component at the output of the convolution filter of that one translation means.

13. The apparatus defined in claim 12, wherein said decimator of said given type of first means forwards, in each of said dimensions of said information component, every other one of the samples appearing at the output of the convolution filter of said given type of first means to said first output terminal of that one translation means,

whereby said decimated sample density, in each of said dimensions of said information component, is reduced to one-half said particular sample density of the corresponding dimension of said information component.

14. The apparatus defined in claim 12, wherein:

said third means further includes fourth means coupled between said decimator and said sample-subtracting means for expanding the decimated sample density of said convolved samples in each dimension of said information component, at said first output terminal of that one translation means, back to said particular sample density of said convolved samples in that dimension, at said sample-subtracting means,

said fourth means including a sample expander for inserting additional samples that respectively correspond in occurrence to each convolved sample at the output of said convolution filter that is absent from said decimated sample density, each of said inserted additional samples having a zero-value level, and an interpolation means that is effective in substituting an interpolated-value sample level for said zero-value level of each of said inserted additional samples.

15. The apparatus defined in claim 14, wherein:

said decimator of said given type of first means forwards, in each of said dimensions of said information component, every other one of the samples appearing at the output of the convolution filter of said given type of first means to said first output terminal of that one translation means,

said expander inserts an additional sample in between each pair of successive convolved samples of said decimated sample density in each dimension of said information component, and said interpolation means is comprised of an n-tap interpolation filter (where n is a given plural integer of three or more) having a low-pass transfer function.

16. The apparatus defined in claim 14, wherein:

said convolution filter, said decimator and said fourth means of that one translation means insert a certain total time delay;

the information component of the signal at the first input terminal of that one translation means is applied to said sample-subtracting means thereof through said delay means thereof; and

said delay means of that one translation means inserts a time delay substantially equal to said total time delay inserted by said convolution filter, said decimator and said fourth means of that one translation means.

17. The apparatus defined in claim 12, wherein each of said first to said (N-1)th translation means of said set includes a first means of said given type.

18. The apparatus defined in claim 17, wherein said Nth translation means of said set also includes a first means of said given type.

19. The apparatus defined in claim 17, wherein said Nth translation means of said set includes a first means of an alternative type in which the output of said convolution means is applied directly to said first output terminal of said Nth translation means.

20. The apparatus defined in claim 19, wherein the information component of the signal at the first input of said Nth translation means of said set is applied to said sample-subtracting means thereof through said delay means thereof, said delay means of said Nth translation means of said set inserting a time delay substantially equal to that inserted by said convolution filter thereof.

21. Apparatus for performing real-time spectral analysis comprising:

a cascade connection of low-pass sampling filters operated at successively lower sampling rates, the input signal to said cascade being the signal upon which spectral analysis is to be performed and the output signal being a remnant low-pass spectrum;

means for interleaving the samples of a decimation of a response of each said low-pass sampling filter with nulls and low-pass filtering a resultant interleaved output of said interleaving means to obtain a respective interpolation result;

means for delaying the samples of the input to each low-pass filter in said cascade connection in amount equal to a sum of the delay in response to that filter and the delay in the low-pass filtering of that response interleaved with nulls; and

means for differentially combining the delayed samples of the input to each low-pass filter in said cascade connection with the interpolation result derived from its response, thereby to provide a respective one of the spectrum analyses of the input signal to said cascade connection.

22. Apparatus for performing real time spectral analysis of an electric signal regularly sampled at a rate R comprising a plurality, n in number, of analysis stages consecutively cardinally numbered zero through n for providing as a first output signal and a second output signal thereof separate responses to lower frequency components of its input signal and to higher frequency components of its input signal, the one of said analysis stages numbered zero receiving said electric signal for spectral analysis as its input signal and each other of said analysis stages receiving as its input signal the first output signal of the analysis stage with a next lower cardinal number, said second output signals and the first output signal of the analysis stage numbered n providing the spectral analysis, each of said plurality of analysis stages respectively including:

a first m-stage shift register, m being a positive integer, having the input signal for said analysis stage to its input and being clocked at a clock rate equal to R/2^k, k being a cardinal number of the analysis stage;

means weighting the input signal of the analysis stage and that input signal as delayed in each stage of said first m-stage shift register by a set of coefficients and summing the weighted signals for generating a linear-phase low-pass-filtered response to said analysis stage input signal, which response is said analysis stage first output signal;

a multiplexer operated to alternately select between said analysis stage first output signal and a null value at said R/2.sup.(k-1) rate;

a further m-stage shift register having the signal selected by said multiplexer applied to its input and being clocked at said clock rate equal to R/2.sup.(k-1) ;

means weighting the selected signal of that analysis stage and that signal as delayed in each stage of said of said further m-stage register by said set of weighting coefficients and summing the weighted signals to obtain a re-sampled first output signal for that analysis stage; and

means subtractively combining said re-sampled first output signal for that analysis stage with delayed input signal for that analysis stage, for generating the second output signal for that analysis stage.

23. Apparatus as set forth in claim 22 wherein m is the same for each analysis stage and wherein each analysis stage uses similar value sets of weighting coefficients.

24. Apparatus as set forth in claim 22 wherein said delayed input signal for each analysis stage is obtained from the mth stage of its first m-stage shift register and additionally delayed.

25. A digital filter providing at least one output response and comprising:

a plurality of clocked delay lines having taps consecutively ordinally numbered;

means for clocking said delay lines at successively lower rates as their ordinal numbering increases;

means for applying an input signal to be filtered to the input of the first of said plurality of delay lines;

respective means for weighting samples from said taps of each delay line and combining the weighted samples to obtain a respective filter response;

means for applying the respective filter response derived from the samples taken from each delay line except that with the highest ordinal numbering as input to the delay line with next highest ordinal numbering, at least a portion of the respective filter response derived from the samples taken from the delay line with the highest ordinal numbering being used in the generation of said overall response.

26. A digital filter as set forth in claim 25 wherein the weighted samples from the taps of each delay line are combined to obtain respective filter responses low-pass in nature.

27. A digital filter as set forth in claim 26 wherein the one of the respective filter responses obtained by weighting and combining the samples taken from the delay line with the highest ordinal numbering is used as an output response of said digital filter.

28. A digital filter as set forth in claim 26 including:

a further tapped clocked delay line clocked at the same rate as a selected one of said plurality of tapped delay lines;

means for selectively applying the output of the selected delay line and nulls to the input of said further delay line;

means for weighting samples from the taps of said further delay line and combining the samples to obtain a low-pass filter response; and

means for differentially combining the low-pass filter response thus obtained with the output of the selected one of the delay lines in said plurality for generating an output response of said digital filter.

29. A digital filter as set forth in claim 26 wherein the weighted samples from the taps of a selected one of said plurality of tapped delay lines having an ordinal number one higher than a preceding delay line, are weighted differently on alternate ones of the clock cycles of said preceding delay line and combined on each of those clock cycles to obtain a low-pass filter response;

and wherein the low-pass filter response thus obtained is differentially combined with the output of said preceding delay line to generate an output response of said digital filter.

30. A digital filter as set forth in claim 25 including:

a further tapped clocked delay line clocked at the same rate as a selected one of said plurality of tapped delay lines;

means for selectively applying the output of the selected delay line and nulls to the input of said further delay line;

means for weighting samples from the taps of said further delay line and combining the samples to obtain a response; and

means for combining the response thus obtained with the delayed input to the preceding delay line for generating an output response of said digital filter.

31. A digital filter as set forth in claim 30 where the delayed input to the preceding delay line is obtained by incorporating the delay to one of its taps.

32. A digital filter as set forth in claim 25 wherein the weighted samples from the taps of a selected one of said plurality of tapped delay lines, having an ordinal number one higher than a preceding delay line, are weighted differently on alternate ones of the clock cycles of the preceding delay line and combined on each of those clock cycles the result being combined with the delayed input to the preceding delay line to generate an output response of said digital filter.

33. A digital filter as set forth in claim 32 where the delayed input to the preceding delay line is obtained by incorporating the delay to one of its taps.

34. Signal processing apparatus employing pipe-line architecture for synthesizing in delayed real time a single temporal signal from an ordinally-arranged set of N separate temporal signals;

wherein;

(1) said single temporal signal is comprised of a certain stream of information-component samples that defines the frequency spectrum of information having a given number of dimensions with a particular sample density in each of said dimensions;

(2) the first of said ordinally-arranged set of N separate signals is comprised of a stream of information component samples that defines an uppermost portion of the frequency spectrum of said information with a sample density which is substantially the same as said particular sample density in each of said dimensions;

(3) each of the second to (N-1)th of said ordinally arranged set of N separate signals is comprised of a stream of information component samples that defines an individual portion of the frequency spectrum of said information in each dimension thereof which is below that of a corresponding dimension of said spectrum of that portion defined by its immediately preceding separate one of the signals of said set and is above that of a corresponding dimension of said spectrum of that portion defined by its immediately following separate one of the signals of said set;

(4) said stream of information component samples corresponding to each of the second to (N-1)th of said ordinally arranged set of N separate signals has a sample density for each of its own information dimensions which is smaller than the sample density of the corresponding information dimension of a stream of information component samples corresponding to its immediately preceding separate signal of said set; and

(5) said respective streams of information component samples occur in predetermined time skew relationship with respect to one another;

said apparatus comprising;

a group of (N-1) sampled-signal combining means each of which is individually associated with each of said first to said (N-1)th ordinal ones of said set of separate signals for combining that ordinal one of said set of separate signals with which that combining means is associated with a cumulative total of all those separate signals which follow that ordinal one separate signal in said set;

wherein

each of said combining means associated with said first to said (N-2)th ordinal ones of said set of separate signals includes an adder, first means for forwarding its associated ordinal separate signal as a first input to its adder, and second means for forwarding the output of the adder of the combining means associated with a separate signal immediately following its ordinal separate signal as a second input to its adder with the same sample density as that of its ordinal separate signal;

said combining means associated with said (N-1)th separate signal of said set includes an adder, said first means for applying said (N-1)th separate signal as a first input to its adder, and third means for applying said Nth separate signal as a second input to its adder with the same sample density as said (N-1)th separate signal; and

said respective first means, said respective second means and said third means of said (N-1) combining means of said group inserting respective predetermined amounts of time delay in forwarding said time-skewed separate signals of said set such that, for each of said respective (N-1) combining means, corresponding information samples of the respective streams of information component samples at the first input and at the second input of the adder thereof occur substantially in time coincidence with one another,

whereby said synthesized single temporal signal is obtained at the adder output of said combining means associated with said first separate signal of said set.

35. The apparatus defined in claim 34, wherein:

said second means of the respective combining means individually associated with each one of said first to (N-2)th ordinal ones of said set of separate signals includes a sample expander, responsive to a lower sample density stream of information component samples at said adder output being forwarded, for inserting additional samples in said forwarded stream to raise the sample density at the second input of the adder of that one combining means to the sample density of the ordinal separate signal associated with that one combining means, each of said inserted additional samples having a zero-value level, and an interpolation means that is effective in substituting an interpolated-value sample level for the zero-value level of each of said inserted additional samples.

36. The apparatus defined in claim 35, wherein:

said Nth separate signal of said set has a sample density lower than said (N-1)th separate signal of said set; and

said third means includes a sample expander and interpolation means, like those of said second means, for forwarding said Nth separate signal to the second input of the adder of said third means.

37. The apparatus defined in claim 35, wherein:

said Nth separate signal of said set has substantially the same sample density as said (N-1)th separate signal of said set; and

said third means directly forwards said Nth separate signal to the second input of the adder of said third means.

38. The apparatus defined in claim 35, wherein:

said stream of information component samples corresponding to each of at least the second to (N-1)th of said ordinally arranged set of N separate signals has a sample density for each of its own information dimensions which is one-half the sample density of the corresponding information dimension of the stream of information component samples corresponding to its immediately preceding separate signal of said set;

said expander of a second means inserts an additional sample in between each pair of successive samples of said lower sample density in each dimension of the stream of information component samples at said adder output being forwarded; and

said information means is comprised of an n-tap interpolation filter (where n is a plural given integer) having a low-pass transfer function.

39. The apparatus defined in claim 34, wherein:

said third means and each of said respective second means of said group of N-1 sampled-signal combining means inserts its own predetermined amount of time delay in forwarding its stream of information component samples as a second input to its adder; and

each of said first means of said group of N-1 sampled-signal combining means includes delay means that inserts a particular amount of time delay in forwarding its ordinal separate signal as a first input to its adder which is dependent on both (1) the respective time skew between its ordinal separate signal and each of those separate signals of said set that follow its ordinal separate signal and (2) the total amount of time delay inserted by said third means and all second means of those combining means associated with the separate signals of said set that follow its ordinal separate signal, said particular amount of delay being such that corresponding information samples of the respective streams of information component samples at the first input and at the second input of its adder occur substantially in time coincidence with one another.