Reverse coding system for interlaced scanned moving pictures

Abstract

The invention provides a reversible coding system for an interlaced scanned moving picture based on reversible discrete cosine transform which controls selection of frame/field discrete cosine transform so as to assure a high degree of compatibility with an ordinary discrete cosine transform coding system. A motion compensated predictive error is detected from an input signal, and a frame-scan block and a field-scan block are produced for each block of the input signal by a frame/field scan production circuit. One of the blocks is selected by a switch, and reversible discrete cosine transform is performed for the selected block. Upon the selection, first and second estimated error calculation circuits estimate error amounts when reversible discrete cosine transform is performed for the frame- and field-scan blocks and then inverse discrete cosine transform is performed for the resultant blocks. The error amounts are compared with each other, and the lower one of them is selected by a comparator.

What is claimed is:  
     
         1 . A reversible moving picture coding system, comprising: 
 means for determining a motion vector from an interlaced scanned input video signal;    means for producing a motion compensated predictive picture from a picture for reference using the motion vector;    means for subtracting the motion compensated predictive picture from the input video signal to produce a predictive error picture;    means for producing a frame-scanned block and a field-scanned block from the predictive error signal;    means for estimating an error amount when reversible discrete cosine transform is performed for the frame-scanned block and then ordinary inverse discrete cosine transform is performed for the resultant block on the decoding side and outputting the estimated error amount as an estimated error amount for a frame-scanned block;    means for estimating an error amount when reversible discrete cosine transform is performed for the field-scanned block and then ordinary inverse discrete cosine transform is performed for the resultant block on the decoding side and outputting the estimated error amount as an estimated error amount for a field-scanned block;    means for comparing the estimated error amount for the frame-scanned block and the estimated error amount for the field-scanned block with each other to produce a scan selection signal and outputting the scan selection signal;    means for selecting one of the frame-scanned block and the field-scanned block in accordance with the scan selection signal and outputting the selected scanned block as an adaptive-scanned block; and    means for performing reversible discrete cosine transform for the adaptive-scanned block to produce an adaptive-scan transform coefficient block.    
     
     
         2 . A reversible moving picture coding system, comprising: 
 means for determining a motion vector from an interlaced scanned input video signal;    means for producing a motion compensated predictive picture from a picture for reference using the motion vector;    means for subtracting the motion compensated predictive picture from the input video signal to produce a predictive error picture;    means for producing a first frame-scanned block and a first field-scanned block from the predictive error picture;    means for performing reversible discrete cosine transform for the first frame-scanned block to produce a frame-scan transform coefficient block and outputting the frame-scan transform coefficient block;    means for performing reversible discrete cosine transform for the first field-scanned block to produce a field-scan transform coefficient block and outputting the field-scan transform coefficient block;    means for selecting one of the frame-scan transform coefficient block and the field-scan transform coefficient block in accordance with a scan selection signal and outputting the selected transform coefficient block as an adaptive-scan transform coefficient block;    means for performing ordinary inverse discrete cosine transform for the frame-scan transform coefficient block, locally decoding a result of the ordinary inverse discrete cosine transform using the motion vector to produce a frame-scan decoded block and outputting the frame-scan decoded block;    means for performing ordinary inverse discrete cosine transform for the field-scan transform coefficient block, locally decoding a result of the ordinary inverse discrete cosine transform using the motion vector to produce a field-scan decoded block and outputting the field-scan decoded block;    means for producing a second frame-scanned block and a second field-scanned block from the input video signal;    means for determining an error between the frame-scan decoded block and the second frame-scanned block to calculate an error amount for a frame-scanned block and outputting the error amount for the frame-scanned block;    means for determining an error between the field-scan decoded block and the second field-scanned block to calculate an error amount for a field-scanned block and outputting the error amount for the field-scanned block; and    means for comparing the error amount for the frame-scanned block and the error amount for the field-scanned block to produce the scan selection signal and the outputting the scan selection signal.    
     
     
         3 . A reversible moving picture coding system, comprising: 
 means for determining a motion vector from an interlaced scanned input video signal;    means for producing a first motion compensated predictive picture from a picture for reference using the motion vector;    means for subtracting the first motion compensated predictive picture from the input video signal to produce a predictive error picture;    means for producing a first frame-scanned block and a first field-scanned block from the predictive error picture;    means for selecting one of the first frame-scan transform coefficient block and the first field-scan transform coefficient block in accordance with a scan selection signal and outputting the selected transform coefficient block as an adaptive-scan transform coefficient block;    means for performing reversible discrete cosine transform for the adaptive-scanned block to produce an adaptive-scan transform coefficient block;    means for performing linear operation for the first frame-scanned block to estimate a predictive error when reversible transform cosine transform is performed for the first frame-scanned block and then ordinary inverse discrete cosine transform is performed for the resultant block on the decoding side and outputting the predictive error as a frame-scan estimated predictive error block;    means for performing linear operation for the first field-scanned block to estimate a predictive error when reversible transform cosine transform is performed for the first field-scanned block and then ordinary inverse discrete cosine transform is performed for the resultant block on the decoding side and outputting the predictive error as a field-scan estimated predictive error block;    means for transforming the adaptive-scan transform coefficient block by ordinary inverse discrete cosine transform and producing and outputting a second motion compensated predictive picture using the motion vector;    means for producing a frame-scan predictive block and a field-scan predictive block from the second motion compensated predictive picture;    means for adding the frame-scan predictive block to the frame-scan estimated predictive error block to produce a frame-scan estimated block;    means for adding the field-scan predictive block to the field-scan estimated predictive error block to produce a field-scan estimated block;    means for producing a second frame-scanned block and a second field-scanned block from the input video signal;    means for determining an error between the second frame-scanned block and the frame-scan estimated block and calculating and outputting an estimated error amount for a frame-scanned block;    means for determining an error between the second field-scanned block and the field-scan estimated block and calculating and outputting an estimated error amount for a field-scanned block; and    means for comparing the estimated error amount for the frame-scanned block and the estimated error amount for the field-scanned block to produce the scan selection signal and the outputting the scan selection signal.    
     
     
         4 . A reversible moving picture coding system, comprising: 
 means for determining a motion compensated predictive error from an input picture signal and producing a frame-scanned block and a field-scanned block from the motion compensated predictive error for each block;    means for estimating error amounts when reversible discrete cosine transform is performed for the frame-scanned block and the field-scanned block and then ordinary inverse discrete cosine transform is performed for the resultant blocks on the decoding side and selecting that one of the blocks whose estimated error amount is the smaller than the other estimated error amount; and    means for performing reversible discrete cosine transform for the selected scanned block.