Data compression using a feedforward quantization estimator
First Claim
1. A method of preparing a digital video signal, having a data rate, Din, for transmission as an encoded output signal, said encoded output signal to be transmitted over a channel having a preselected constant data rate capacity, Dout, which is less than the data rate Din, said method comprising the steps of:
- (a) transforming said video signal to a spatial-frequency domain digital signal formatted in groups of transform coefficients of generally varying information content;
(a1) estimating trial quantizing parameters from one of the groups;
(b) selecting in response to said trial quantizing parameters values of final quantizing parameters Qf for the groups of transform coefficients in accordance with their respective generally varying information content, which parameters Qf when applied to quantize the coefficients would generate respective encoded output signals with a predetermined number of encoded bits corresponding to said constant data rate Dout ;
(c) quantizing said groups of transform coefficients of generally varying information content to integral values in response to respective said quantizing parameters, Qf, to generate therewith groups of quantized coefficients of essentially constant information content; and
(d) encoding said groups of quantized coefficients of essentially constant information content to produce said encoded output signal of said predetermined number of encoded bits corresponding to said constant data rate Dout.
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Abstract
An image data compression technique is described which utilizes calculating means and a selected series of bit calculating stages having delays, to estimate one or more quantization parameters for such data. The estimation process preferably is iterated a number of times, with the values found through each estimation being used as the trial values for subsequent estimations. In addition, an initial trial value is selected by a data look ahead technique, which assures that its value is within range of the final quantization parameter used to quantize the data. The final quantization parameter insures that the compressed data fits within a predetermined number of encoded data bits to be transmitted or recorded, for example, in a recording medium.
200 Citations
16 Claims
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1. A method of preparing a digital video signal, having a data rate, Din, for transmission as an encoded output signal, said encoded output signal to be transmitted over a channel having a preselected constant data rate capacity, Dout, which is less than the data rate Din, said method comprising the steps of:
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(a) transforming said video signal to a spatial-frequency domain digital signal formatted in groups of transform coefficients of generally varying information content; (a1) estimating trial quantizing parameters from one of the groups; (b) selecting in response to said trial quantizing parameters values of final quantizing parameters Qf for the groups of transform coefficients in accordance with their respective generally varying information content, which parameters Qf when applied to quantize the coefficients would generate respective encoded output signals with a predetermined number of encoded bits corresponding to said constant data rate Dout ; (c) quantizing said groups of transform coefficients of generally varying information content to integral values in response to respective said quantizing parameters, Qf, to generate therewith groups of quantized coefficients of essentially constant information content; and (d) encoding said groups of quantized coefficients of essentially constant information content to produce said encoded output signal of said predetermined number of encoded bits corresponding to said constant data rate Dout. - View Dependent Claims (2, 3, 4, 5, 6)
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7. Apparatus for compressing a data signal defining a video image into a data space of a predetermined number of bits, comprising:
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means for transforming said data signal to a digital signal formatted in groups of transform coefficients of generally varying information content; means responsive to said groups of transform coefficients of generally varying information content for first estimating trial numerical processing parameters from a first of the groups, and then in response to the trial numerical processing parameters estimating the values of final numerical processing parameters which will quantize said transform coefficients into said data space of a predetermined number of bits; and means for applying said estimated parameters subsequently to the same said groups of transform coefficients which were used to estimate the parameters, to compress said groups of transform coefficients into respective data spaces of said predetermined number of bits.
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8. Apparatus for compressing a data signal defining a video image, comprising:
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means for transforming said data signal to a digital signal formatted in predetermined groups of transform coefficients; means responsive to said predetermined groups of transform coefficients for estimating the value of a numerical processing parameter for quantizing said transform coefficients; means for applying said estimate subsequently to said predetermined groups of transform coefficients which were used to estimate said numerical processing parameter; and wherein said means for estimating includes parameter estimator means having a plurality of bit calculating stages for estimating said numerical processing parameter which is to be applied to the same predetermined groups of transform coefficients. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A method of preparing a digital signal for transmission as an encoded output signal formed of data blocks having a predetermined number of bits, comprising the steps of:
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transforming said digital signal to a spatial-frequency domain digital signal formatted in groups of transform coefficients of generally varying information content; selecting via a plurality of previous trial bit calculating steps, final quantizing parameters to be applied to the same said groups of transform coefficients, which final quantizing parameters, when applied to said groups of transform coefficients of generally varying information content, will provide substantially said predetermined number of bits in each of said data blocks; quantizing said groups of transform coefficients in response to said final quantizing parameters to generate integral values of groups of quantized coefficients having substantially the same information content; and encoding said quantized coefficients to produce said encoded output signal of data blocks, with said substantially predetermined number of bits in each data block. - View Dependent Claims (15, 16)
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Specification