Data compression method and apparatus for video signal

Claim 2

A data compression apparatus as claimed in claim 1 wherein said control means comprises: (a) horizontal bandpass limitation means responsive to said total and said difference for limiting bandpass of said video data before said orthogonal converting with bandpass width thereof controlled in accordance with said total; and (b) vertical bandpass limitation means for limiting bandpass of said video data before said orthogonal converting with bandpass width thereof controlled in accordance with said total, center frequencies of said first and second bandpass limitation means being different from each other, bandpass widths of said horizontal and vertical bandpass limitation means being controlled differently in accordance with said difference.

Claim 3

A data compression apparatus as claimed in claim 1, further comprising step size control means for determining a step size of quantizing performed by said quantizing means in accordance with said difference and said total power and for causing said quantizing means to quantize said video data using said determined step size.

Claim 4

A data compression apparatus for video data having: dividing means for dividing said video data into unit blocks, converting means for orthogonally converting said video data at each of unit blocks, quantizing means for quantizing said orthogonally converted video data, and coding means for run-length-coding said quantized video data, comprising: (a) filter processing means for filtering said video data in the horizontal and vertical directions separately; (b) power detection means for detecting powers of said video data in the horizontal and vertical directions; (c) difference detection means for detecting a difference between said powers of said video data filtered in the horizontal and the vertical directions; (d) amount-of-code converting means for, in accordance with said difference, converting a total of said powers to an amount of data which is a predictive value indicative of an amount of data run-length-coded; (e) target setting means for setting a first target; (f) bandpass limiting value converting means for producing bandpass limiting values of the horizontal and vertical direction in accordance with difference between said first target value and said amount of coded data; (g) bandpass limitation value conversion means for producing a bandpass limitation values of horizontal and vertical directions in accordance with a difference between said amount of coded data and said first target; (h) target setting means for setting a second target of the amount of coded data of said video data; (i) step size converting means for producing a step size signal in accordance with said second target, said amount of coded data, and said bandpass limitation values; (j) bandpass limitation control means for controlling bandpass limitation of said video data before processed by said orthogonally converting means in horizontal and vertical directions in accordance with said bandpass limitation values; and (k) quantizing means for quantizing said video data orthogonally converted with quantizing step size thereof controlled in accordance with said step size signal.

Claim 6

A method as claimed in Claim 5, wherein said step (c) comprising steps of (a) in response to said total and said difference, bandpass-limiting said video data before said orthogonally converting with a first bandpass width for said bandpass-liming controlled in accordance with said total of said powers; and (b) in response to said total and said difference, bandpass-limiting said video data before said orthogonally converting with a second bandpass width for said bandpass-limiting controlled in accordance with said total of said powers, center frequencies of said first and second bandpass widths being different from each other, said first and second bandpass widths being controlled differently in accordance with said difference.

Claim 7

A method as claimed in Claim 6, wherein said step (c) further comprising a step of producing a quantizing step size control signal in accordance with said total and said difference, wherein said orthogonally converted video data is quantized with quantizing step size controlled in accordance with said quantizing step size control signal.