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Method for image compression coding in an image transmission system
| Details |
Inventors: Virtamo, Jorma; Valli, Seppo;
Assignee: Valtion Teknillinen Tutkimuskeskus (Espoo, FI)
Primary Examiner: Chin; Stephen
Assistant Examiner: Vo; Don
Attorney, Agent or Firm: Merchant, Gould, Smith, Edell, Welter & Schmidt, P.A.
An image compression coding method of a digital image transmission system utilizes a known vector quantization process. In the method, at the transmitting end the block (13) to be coded is divided into quadrants (14); each quadrant is subjected to vector quantization in a sub-coder (19), utilizing a classified codebook (20), the class thereof being defined on the basis of the vector index (1) of the original block and the quadrant label (A', B', C', D') of the sub-block; the vector index (j) of the sub-block with respect to this classified codebook (20) is transmitted to the receiving end; at the receiving end, there is utilized a classified codebook which is chosen on the basis of the transmitted vector index (i) of the original block and the quadrant label (A', B', C', D') of the sub-block; at the receiving end, the chosen classified codebook, which is identical with the classified codebook at the transmitting end, the code vector index of the transmitted sub-block, so that a reconstruction is obtained for the sub-block. When designing each classified codebook, the utilized image set which receives a class index corresponding to the particular class of the codebook, when the above-described method is applied to the training image set itself. |
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DETAILED DESCRIPTION The object of the present invention is to introduce a new method for image compression coding in an image transmission system, whereby the block size problem can be avoided at least to some extent.
Another object of the invention is to achieve a new compression coding method, whereby problems connected to modified vector quantization processes can be overcome.
The method of the invention is characterized by the novel features enlisted in patent claim 1.
In the method of the invention for image compression coding in an image transmission system, particularly for carrying out image compression in a digital image transmission system, there is utilized a VQ process where the image is divided into blocks at the transmitting end, and for each block there is searched in the codebook a best corresponding codevector, and the vector index of this codevector, i.
e.
its location in the codebook, is transmitted to the receiving end, where the respective codevector is looked up in an identical codebook on the basis of the index, and the image is reconstructed block by block with the aid of the codevectors; the said codebook is designed beforehand by means of training images, which images are in similar fashion divided into blocks according to the employed block size.
In the method of the invention at the receiving end, the block to be coded is divided into quadrants or sub-blocks; each sub-block is subjected to vector quantization by a classified codebook, and the class thereof is defined on the basis of the vector index of the original block and the quadrant label of the sub-block; the vector index of the sub-block, with respect to this classified codebook, is transmitted to the receiving end; at the receiving end, there is utilized a classified codebook which is chosen on the basis of the vector index of the transmitted original block and the quadrant label of the sub-block; at the receiving end, the codevector in question is looked up in the chosen classified codebook which is identical with the classified codebook at the transmitting end, on the basis of the vector index of the transmitted sub-block, so that a reconstruction is obtained for the sub-block; and in the method of the invention, while creating each classified codebook, the employed training image material is that part of the original training image set which belongs to the respective class, i
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Image Analysis 
