Image analysis – Image compression or coding – Predictive coding
Reexamination Certificate
1999-11-05
2003-08-12
Johns, Andrew W. (Department: 2621)
Image analysis
Image compression or coding
Predictive coding
C382S236000, C382S242000
Reexamination Certificate
active
06606414
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to the encoding of a video data stream, particularly of a digitalized image.
2. Description of the Related Art
Greater and greater significance is being accorded to an efficient encoding of digitalized image data (video data stream) in the field of telecommunications technology, specifically in the area of image processing. The encoding of the data should be implemented such that an optimally great compression of the information is achieved given optimally little information loss.
Various methods for encoding a video data stream are known, for example MPEG (Moving Picture coding Experts Group), see the publication by D. Le. Gall, The Video Compression Standard for Multimedia Applications, Communications of the ACM; the publication by H. Sun, Architectures for MPEG Compressed Bitstream Scaling, IEEE Transactions on Circuits and Systems for Video Technology and the publication by A. Jain, Image Data Compression: A Review, Proceedings of the IEEE; JPEG (Joint Photographic Experts Group), see the publication by G. Wallace, The JPEG Still Picture Compression Standard, Communications of the ACM, the standard H. 261, see ITU-T H.261, International Telecommunication Union, standard H.263, see the publication by Ming Liou, Overview of the p×64 kbit/s Video Coding Standard, Communication of the ACM.
These methods, which are referred to as block-based image encoding methods, employed principles of prediction encoding and of transformation encoding and entropy encoding.
In the prediction, encoding method difference images are generated by subtraction of predicted image data from the original image data to be encoded.
What is referred to as a motion-compensated prediction is employed for the prediction. The fundamentals of the motion estimation required for this purpose and their application for motion-compensated prediction are familiar to a person skilled in the art, see the publication by A. N. Netravali und J. D. Robbins, Motion Compensated Television Coding: Part I, Bell System Technical Journal. The motion estimation ensues for an image block to be encoded such that the luminance information (brightness information) that is respectfully allocated to a picture element of the image of the image block to be encoded is compared to luminance information of an area having the same shape in a stored, chronologically preceding image. The comparison usually ensues by forming the absolute differences of the individual luminance values. The comparison ensues for the image block to be encoded to a plurality of areas of the preceding image, these being referred to below as preceding image blocks. The difference images now only contain the difference of the luminance values of the image block and the luminance values of the preceding image block that coincides “best” in the motion estimation.
The topical correlations present in the difference images between neighboring picture elements are utilized with the assistance of a suitable transformation, for example with the assistance of discrete cosign transformation (DCT). The transformation encoding employed supplies transformation encoding coefficients that are subjected to a quantization and to an entropy encoding. Subsequently, the transformation encoding coefficients are transmitted to a receiver, whereby the entire encoding method is implemented in an inverse way. After implementing the decoding, step direct information about the picture elements are again available at the receiver.
Methods for what is referred to as object-based image encoding are known from the publication ISO/IEC JTC1/SC29/WG11, MPEG-4 Video Verification Model Verson 5.0 Doc. In these object-based methods. In these methods, methods for motion estimation and transformation encoding are likewise utilized.
All difference images are always subjected to a transformation encoding in the known methods for image encoding described above. When individual blocks are very similar as a result of the motion estimation, the difference of the image block to be encoded at the corresponding image block of the preceding image yields extremely small values that can be quantized into zero in the quantization of the transformation encoding coefficients under certain circumstances. Previously, however, the differences of the luminance values of the individual image blocks were subjected to a transformation encoding in the known, block-based encoding methods.
SUMMARY OF THE INVENTION
The present invention based on the problem of reducing the outlay for encoding and decoding a video data stream.
The problem is solved with the method for encoding a digitalized image with image segments that include picture elements to which a respective encoding information is allocated, upon employment of a stored, chronologically proceeding image having preceding image segments that have preceding picture elements to which a respectively preceding encoding information is allocated, whereby a preceding image segment is selected depending on a predetermined start vector that indicates a topical shift of the image segment relative to the preceding image segment; whereby an error criterion is formed between encoding information of the image segment and preceding encoding information of the preceding image segment; whereby the error criterion is formed such that the differences of the encoding information of different picture elements are differently weighted; whereby a check is carried out to see whether the error criterion is smaller than a first threshold; whereby, when the error criterion is smaller than the first threshold, the image segment is not subjected to any residual error encoding; whereby, otherwise, the image segment is subjected to the residual error encoding and to an entropy encoding.
The invention also provides an apparatus for encoding a digitized image with image segments that include picture elements to which an encoding information is respectively allocated, upon employment of a stored, chronologically preceding image with preceding image segments that have preceding picture elements to which respectively preceding encoding information is allocated, comprising a, processor unit that is configured such that a preceding image segment is selected proceeding from a predetermined start vector with which a topical shift of the image segment relative to the preceding image segment is indicated; an error criterion between encoding information of the image segment and preceding encoding information of the preceding image segment is formed; a check is carried out to see whether the error criterion is smaller than a first threshold; when the error criterion is smaller then the first threshold, the image segment is not subjected to any residual error encoding; otherwise, the image segment is subjected to the residual error encoding and an entropy encoding.
The method as described above for encoding a digitalized image with image segments that comprise picture elements to which respective encoding information is allocated ensues upon employment of a stored, chronologically preceding image with preceding image segments that comprise preceding picture elements to which a respective preceding encoding information is allocated. A preceding image segment is selected dependent on a start vector that indicates a topical shift of the image segment relative to the preceding image segment. An error criterion between the encoding information of the image segment and the preceding encoding information of the preceding image information is formed and a check is carried out to see whether the error criterion is lower than a first threshold. When the error criterion is lower than the first threshold (S
1
), the image segment is not subjected to any residual error encoding. Otherwise, the image segment is subjected to a residual error encoding and to an entropy encoding.
What is to be understood by a chronologically preceding image is the preceding, reconstructed image. What is to be understood by a preceding image segment and a pre
Pandel Jürgen
Salai Albert
Dang Duy M.
Johns Andrew W.
Schiff & Hardin & Waite
Siemens Aktiegesellschaft
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