EP0509576A2
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EP
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Method and apparatus for determining a quantizing factor for processes involving multiple compression/decompression of data
Assignee: Ampex Systems Corp
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Filing: 1992-04-01
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Granted: —
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Expires: 2012-04-01
Abstract
Abstract The invention provides techniques for changing the quantization used in multiple generations of data quantization such that the errors incurred in subsequent generations are substantially the same as the error incurred in the first generations even though the complexity of the data has been changed. In a preferred embodiment, quantizing factors are selected from a preselected finite non-degenerative set of quantizing factors provided in the form of arrays of a periodic series of individual quantizer values, wherein a special numerical relationship is maintained between corresponding quantizer values in successive arrays. A different quantizing factor may be selected for each generation of compression/decompression as required by changing data complexity as when performing a layering process during the generations. In another embodiment, an over-quantizing factor is chosen large enough to compress the data to a greater extent than that required in the first generation, such that sufficient compression still is provided in subsequent generations even though the same quantizing factor is used while the complexity of the data is being changed. If for some reason the complexity of the data changes faster than expected, it is necessary to change the quantizing factor to fit the data into the allotted space. To moderate the associated increase in noise, the invention technique incudes a dither rounding process wherein a psuedo random number sequence in the range of 0...1.0 is selectively added as determined by a threshold. The invention also includes estimating a quantizing factor applied in a previous generation of image recording if this information is not available explicitly, by distinguishing the peaks and/or valleys of histogram. The amplitudes of the peaks and/or valleys represent the number of counts of the respective values of frequency coefficients to be quantized.
Inventors
- 👤 John P. Watney
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 06:25
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/76; H04N5/91; H04N5/92; H04N5/926; H04N5/9261; H04N5/9264; H04N19/00; H04N19/10; H04N19/102; H04N19/124; H04N19/126; H04N19/134; H04N19/136; H04N19/14; H04N19/146; H04N19/149; H04N19/154; H04N19/169; H04N19/17; H04N19/176; H04N19/189; H04N19/192; H04N19/40; H04N19/46; H04N19/60; H04N19/90
Claims Analysis
Total Claims: 31
Claim 1
Independent Claim
77 words
A method of selecting quantizing factors which limits the quantizing noise introduced during a corresponding data quantizing and dequantizing process when performing multi-generations of data quantizing and dequantizing, comprising the step of determining quantizing factors for first and subsequent generations which limit the degradation in the quality of the data typically caused by variations in the data being introduced in subsequent generations to substantially the degradation incurred in the quantizing and dequantizing process in the first generation.
Claim 2
Dependent Claim
83 words
A method according to claim 1, wherein the step of determining includes the steps of estimating an optimum quantizing factor which compresses the data sufficiently to fit the data into an allotted data space; selecting an over-quantizing factor which is larger than said optimum quantizing factor to substantially over-compress the data such that the data does not fill the allotted data space; and using the same larger over-quantizing factor in subsequent compression processes during the corresponding successive multi-generations of data quantizing and dequantizing.
Claim 3
Dependent Claim
54 words
A method according to claim 2, wherein the data represent an image and the complexity of the image data is changed in selected generations, wherein the step of selecting includes providing excess compression by selecting an over-quantizing factor as a function of the expected cumulative change in image data complexity performed in subsequent generations.
Claim 4
Dependent Claim
99 words
A method according to claim 3, including supplying a trial array of quantizer values; determining whether the trial array of quantizer values fits the image data into the allotted data space; performing any necessary iterations on the quantizer values until the image data fits into the allotted data space; identifying said over-quantizing factor which substantially over-compresses the image data in response to said iterations; selecting an array of quantizer values corresponding to the over-quantizing factors which over-compresses the image data; and quantizing the image data in response to the selected array of quantizer values which over-compress the image data.
Claim 5
Dependent Claim
58 words
A method according to claim 2, including the steps of transforming the data into selected transform coefficients prior to over-compressing the data; changing the larger over-quantizing factor in one of the successive multi-generations of data processing; and applying a pseudo random number sequence to selected transform coefficients which exceed a selected threshold, to randomly round off the coefficients.
Claim 6
Dependent Claim
36 words
A method according to claim 5, including the step of generating the pseudo random number sequence within a range of 0 to 1.0 and with a pre-selected energy spectrum, for use in the step of applying.
Claim 7
Dependent Claim
68 words
A method according to claim 2, wherein a generation subsequent to a first generation is to be compressed and said over-quantizing factor is not known, including the steps of transforming the data into respective transform coefficients prior to compressing the data; generating a histogram of selected coefficients of the respective transform coefficients; and detecting the peaks or valleys of the histogram to determine the quantizing factor used previously.
Claim 8
Dependent Claim
78 words
A method according to claim 1, wherein the step of determining includes the steps of selecting a first quantizing factor which would just fit the compressed data into the allotted data space; selecting a second quantizing factor which is larger than the first quantizing factor; compressing the data in response to the second quantizing factor; and using the same larger second quantizing factor in subsequent compression processes performed during the corresponding successive multi-generations of data quantizing and dequantizing.
Claim 9
Dependent Claim
58 words
A method according to claim 1, wherein the step of determining includes the steps of providing a finite non-degenerative set of quantizing factors; selecting a quantizing factor from said non-degenerative set which provides sufficient compression to fit the compressed data into the allotted data space; and repeating the step of selecting for each subsequent multi-generation of data processing.
Claim 10
Dependent Claim
43 words
A method according to claim 9, wherein the data represents an cage and the step of providing includes providing a set of quantizing factors corresponding to multiple arrays of quantizer values, wherein corresponding quantizer values in successive arrays have a predetermined numerical relationship.
Claim 11
Dependent Claim
25 words
A method according to claim 10, wherein the numerical relationship is of the order of three and the non-degenerative set of quantizing factors are linear.
Claim 12
Dependent Claim
61 words
A method according to claim 11, wherein the image data are in the form of transform coefficients, including the step of deriving the linear non-degenerative set of quantizing factors from the relationship q value = K* (3**n), where K is a constant for any one transform coefficient across the set of quantizing factors, and n is any positive integer including zero.
Claim 13
Dependent Claim
20 words
A method according to claim 10, wherein the quantizing factors are an approximation of the non-degenerative set of quantizing factors.
Claim 14
Dependent Claim
27 words
A method according to claim 10, wherein the non-degenerative set of quantizing factors are non-linear and the numerical relationship is less than on the order of three.
Claim 15
Dependent Claim
43 words
A method according to claim 10, including storing a plurality of lookup tables corresponding to the non-degenerative multiple arrays of quantizer values; and selecting the lookup table which properly compresses the image data to readily fit the data into the allotted data space.
Claim 16
Dependent Claim
98 words
A method according to claim 10, further including supplying a trial array of quantizer values; determining whether the trial array of quantizer values fits the image data into the allotted data space; performing any necessary iterations on the quantizer values until the image data fits into the allotted data space; identifying a quantizing factor from said non-degenerative set which provides sufficient compression to provide said image data fit; selecting an array of quantizer values from said non-degenerative set which corresponds to said quantizing factor; and quantizing the image data in response to the selected array of quantizer values.
Claim 17
Dependent Claim
94 words
A method according to claim 1, including the steps of transforming the data into selected arrays of transform values; providing a plurality of arrays of quantizer values wherein each array has a quantizing factor commensurate with an average of the quantizer values; selecting a quantizing factor from a plurality of lookup tables which provides sufficient compression to fit the data, after compression, into the allotted data space; quantizing the arrays of transform values in response to the selected quantizing factor; and repeating the above steps for subsequent data compressed during each of said multi-generations.
Claim 18
Dependent Claim
69 words
A method according to claim 17, wherein the compressed data is decompressed in a decompression process, including the steps of recovering the compressed data along with a signal identifying the quantizing factors used in the compression process; storing a plurality of lookup tables corresponding to the lookup tables used in the compression process; and decompressing the compressed data in response to a lookup table selected by the identifying signal.
Claim 19
Independent Claim
85 words
A system for quantizing and dequantizing image data, including apparatus for selecting quantizing factors which limit the amount of distortion incurred by the image data in subsequent generations due to variations of the image data being introduced during at least some of subsequent multi-generations of quantizing and dequantizing, said apparatus being characterised by means for selecting quantizing factors which limit the degradation in image quality by variations in the image data being introduced in subsequent generations to substantially the degradation incurred in the first generation.
Claim 20
Dependent Claim
94 words
Apparatus according to claim 29, for compressing the image data into an allotted data space, means for transforming the image into selected arrays of transform values; means receiving the transform values for selecting an over-quantizing factor which over-compresses the image data such that the data does not fill the allotted data spaces; and means receiving the selected arrays of transform values for quantizing the transform values in response to the over-quantizing factor, to provide the over-compressed image data; wherein said quantizing means applies the same over-quantizing factor to transform values in said successive multi-generations.
Claim 21
Dependent Claim
111 words
Apparatus according to claim 19, for compressing the image data into an allotted data space, further comprising means for transforming the image data into selected arrays of transform values; means receiving the transform values for estimating a quantizing factor for properly fitting the data when compressed into the allotted data space; means for providing a predetermined finite non-degenerative set of quantizing factors in the form of arrays of quantizer values; means storing the arrays of quantizer values for supplying an array commensurate with the estimated quantizing factor in response to the estimating means; and means for compressing an array of transform values in response to a respective array of quantizer values.
Claim 22
Dependent Claim
144 words
Apparatus for selecting quantizing factors for compressing image data into allotted data spaces through successive multi-generations of image data processing during which the complexity of the image data is changed, comprising means for varying the complexity of the image data in at least one of the multi-generations; means for transforming the image data into selected arrays of transform coefficients in each of the multi-generations; means receiving the transform coefficients for selecting quantizing factors which limit the degradation incurred by the image data in the successive multi-generations to the degradation inherent in the compression process during the first generation, while providing sufficient compression to fit the compressed data into the allotted data spaces in each of the multi-generations; and means receiving the selected arrays of transform coefficients for quantizing the transform coefficients of each of the multi-generations in response to the respective selected quantizing factor.
Claim 23
Dependent Claim
49 words
Apparatus according to claim 22, wherein the selecting means provides an over-quantizing factor which substantially over-compresses the image data such that the data does not fill an allotted data space, and wherein the selecting means further provides the same over-quantizing factor through the successive multi-generations of image data processing.
Claim 24
Dependent Claim
70 words
Apparatus according to claim 23, wherein the selecting means includes means for providing a trial array of quantizer values which correspond to a mid-range quantizing factor for an image of average image complexity; means for storing a preselected number of arrays of selectively increasing quantizer values; and means responsive to the trial array for deriving said over-quantizing factor in the form of one of said stored arrays of quantizer values.
Claim 25
Dependent Claim
39 words
Apparatus according to claim 23, including means for producing a histogram of selected arrays of the transform coefficients; and means for detecting the peaks or valleys of the histogram to determine a quantizing factor used in a previous generation.
Claim 26
Dependent Claim
41 words
Apparatus according to claim 23, wherein the over-quantizing factor is changed to another quantizing factor, including means for applying a psuedo random number sequence to the arrays of transform coefficients which exceed a selected threshold, to randomly round off the coefficients.
Claim 27
Dependent Claim
80 words
Apparatus according to claim 22, wherein the selecting means includes means for providing a finite non-degenerative set of quantizing factors; and means for selecting a quantizing factor from the non-degenerative set which provides sufficient compression to fit the compressed image data into an allotted data space of a respective generation; wherein said selecting means thereafter selects a quantizing factor from the non-degenerative set in response to the change in complexity of the image data in each of the successive multi-generations.
Claim 28
Dependent Claim
52 words
Apparatus for rounding a transform coefficient in a compression process, comprising means for generating a pseudo random number sequence; means for adding the pseudo random number sequence to the transform coefficient; and means for truncating any fractional part of the summation to leave only an integer part as the rounded transform coefficient.
Claim 29
Dependent Claim
32 words
Apparatus according to claim 28, including means for providing a preselected threshold; wherein the adding means adds the pseudo random number sequence to transform coefficients which are greater than the preselected threshold.
Claim 30
Dependent Claim
70 words
Apparatus for determining a quantizing factor used in a previous generation of image data compression, comprising means for transforming the image data into corresponding transform values; means receiving the transform values for determining the number of occurrences of amplitudes of selected transform values; and means responsive to the determining means for distinguishing the amplitude which as the largest or the smallest number of occurrences indicative of the previous quantizing factors.
Claim 31
Dependent Claim
35 words
Apparatus according to claim 30, wherein the determining means includes counter means for counting the number of occurrences of the amplitudes of selected transform values; and means for generating a histogram of the amplitude occurrences.
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