Spatial bandwidth testing for digital data-compressed video systems

DETAILED DESCRIPTION What is claimed is: 1.
A method of spatial bandwidth testing for a digital data-compressed video system comprising the steps of: generating a complex test signal having a range of frequencies in each of the horizontal, vertical and temporal dimensions; applying the complex test signal to the input of the video system; acquiring a portion of the complex test signal as a control frame and a corresponding portion of the output from the video system as a test frame; dividing the control and test frames into corresponding blocks of pixel data; obtaining an array of spectral coefficients for each block to produce a reference array of coefficients for blocks from the control frame and a test array of coefficients for blocks from the test frame; comparing the reference array and the test array to obtain a ratio between the corresponding coefficients; and plotting the ratios to provide a visual display of characteristics of the video system.
2.
A method as recited in claim 1 wherein the complex test signal comprises a modified zoneplate signal having a range of frequencies from a minimum to a maximum value in both horizontal and vertical directions.
3.
A method as recited in claim 2 wherein the minimum frequency value in both horizontal and vertical directions occurs at the upper left-hand corner of a video display of the modified zoneplate signal.
4.
A method as recited in claim 2 wherein the minimum frequency value in both horizontal and vertical directions occurs at the middle of the left-hand side of a video display of the modified zoneplate signal.
5.
A method as recited in claim 1 wherein the portion of the complex test signal and the corresponding portion of the video system output comprise one frame of video data.
6.
A method as recited in claim 1 wherein the obtaining step comprises the step of determining the maximum coefficient for each block of the control array.
7.
A method as recited in claim 6 wherein the comparing step comprises the step of determining a gain characteristic for the video system as a function of the ratio of the corresponding test coefficients to the coefficients of the control array that exceed a given percentage of the value of the maximum coefficients for each block