Apparatus and method for improved interlace processing

Abstract

An interlaced image processing module and corresponding method facilitate improved processing of interlaced motion images. In one embodiment, the interlaced image processing module receives image data frames having interlaced first and second fields and produces a reference field and error field. The reference field corresponds to the still image content of the interlaced frame, whereas the error field corresponds to the motion content of the interlaced frame, particularly the motion between fields. Motion between fields is thus represented in the error field, without redundant representation of the still image content provided by the first field. Where there is little motion between fields, the error terms will be small so the predictor preserves the coding efficiency provided by any auto-correlation in the image. Further, the interlaced image processing method does not rely upon pixel group classification, and thus avoids classification errors, and the loss of coding efficiency from still image content in motion classified blocks. Finally, problems presented by relative motion between fields are avoided, as are local artifacts. Another embodiment transforms the interlaced fields into frame data having a high frequency field and a low frequency field.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of application Ser. No. 10 / 139,532 filed on May 6, 2002; which in turn is a continuation of application Ser. No. 09 / 943,454, filed Aug. 30, 2001; which in turn is a continuation of application Ser. No. 09 / 696,757, filed Oct. 25, 2000; which in turn is a continuation-in-part of our prior application Ser. No. 09 / 023,636, filed Feb. 13, 1998. The disclosures of these related applications are hereby incorporated herein by reference.TECHNICAL FIELD AND BACKGROUND ART [0002] This application relates generally to digital image signal processing, and more particularly to the compression of interlaced motion images. DESCRIPTION OF THE RELATED ART [0003] Image and motion image signals are increasingly being processed in the digital domain. One set of problems encountered in digital image signal processing result from signal formats used in conventional analog video processing. For example, certain formats, parti...

AI Technical Summary

Benefits of technology

[0009] The present invention provides an apparatus and method for optimized compression of motion images having frames with interlaced first and second fields which avoids the inefficiencies and inadequacies of conventional schemes, including block based approaches.

[0012] The first and second fields are easily recovered from the predicted frame data. One of the fields (e.g., the first) is determined to be the reference field, which is part of the predicted image frames. The remaining field is obtained by summing the prediction and error fields, thus reversing the forward interlaced image processing steps.

[0013] In image processing, still content in a frame can be efficiently encoded, as it is highly correlated. The interlaced motion image compression scheme takes advantage of any and all coding efficiency provided by auto-correlation, because the values in the error field corresponding to still portions of the frame will be small. This is in marked contrast to the block based approach, which can often predict a block having substantial still portions to be a motion block and thus lose the coding benefit of the still portions.

[0014] The apparatus and method for interlaced image processing also solves various other problems present with conventional schemes. For example, the image is processed as a continuous function, and so avoids discontinuous artifacts, and alleviates problems related to motion between fields, since the reference field provides the still content for both fields, and the error field provides the relative motion between the fields.

Problems solved by technology

One set of problems encountered in digital image signal processing result from signal formats used in conventional analog video processing.

There are various problems -introduced by interlaced motion images and the conventional processing methods.

For example, interlaced images may have relative motion between the rasters, which does not correlate well vertically.

However, this would result in very inefficient encoding.

However, if this is done, the encoding advantage of any high correlation in still areas is lost, again resulting in inefficient encoding.

Additionally, if images are processed by field, slight variations in DC errors or quantifier linearity will cause horizontal stripes in a motion free fame viewed as a still.

There are various problems with the block based approach.

Particularly, block based motion analysis can generate boundaries and visual artifacts due to incorrect motion estimation decisions.

Also, block based motion analysis can generate very large local errors, making it unsuitable for applications where local error bounds are desired, as in medical, technical or critical production applications.

Finally, the block based approach can cause an obvious discontinuity or defect where an object in motion spans adjacent blocks, particularly where one block is still processed while an adjacent block is motion processed.

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