Television – Bandwidth reduction system – Data rate reduction
Patent
1992-02-19
1994-03-22
Britton, Howard W.
Television
Bandwidth reduction system
Data rate reduction
348699, H04N 7137
Patent
active
052969274
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of coding with adjustable parameters of a field of movement in a sequence of animated images.
The analysis of the movement in a sequence of animated images, especially in television, is an operation which is of fundamental importance in the chain of operations carried out in order to process the images.
The known hierarchical methods of estimation such as described, for example, in French Patent Application Number 89 11328 filed in the name of the Applicant appear the most effective up to the present, and the best adapted to the fact that the field of movement of an image can be considered as the assembly of areas of images with constant movement. These methods also exhibit the advantage that they make it possible to obtain a constant movement on homogeneous areas of the image or to find the movement corresponding to the large areas in movement (panoramic . . . ) but also to have good precision especially at the borders of the areas in movement and in the areas with varied movement.
However the problem which is posed is to be able to code the field of vectors obtained in such a way as to obtain as small a data rate as possible. Up until now the present the problem has been resolved by differentiating on the one hand the coding of a field of movement as part of the coding of the image, and on the other hand the specific coding of a field of movement for precise applications especially in television.
Examples of coding of field of movement as part of the image coding have already been the subject of the following publications entitled: IEEE--1987 of recommendation H.261--30 March 1990 and RAE-HONG PARK--Signal processing vol. 18 no. 3--Nov. 89 pages 259-267
Examples of coding of fields of movement for more specific applications like television can be found in the articles entitled: VREESWIJK and Dr. M. R. HAGHIRI --3rd International workshop or HDTV--30th August 1989--Turin HENOT--2nd International workshop on signal processing of HDTV--29 february-2 march 1988 --L'Aquila.
In the first case, coding of the movement vectors represented only approximately 10% of the total digital data rate. In these conditions, there is no necessity, due to this fact, for specific development. The methods utilized are then the same as for the image coding and consist in carrying out coding with variable length adapted to differential methods with respect to the points adjacent to the current point or with respect to the mean of the vicinity, or even adapted to methods by entropy, this latter necessitating the calculation of a histogram. Certain solutions use on the other hand, a decomposition by a coding tree in order to group together the homogeneous areas of the image.
In these different applications the binary cost of the field of movement is not the principal constraint. However the constraints encountered in high-definition television have made it necessary to develop methods of coding which are specific for the movement data. The article by Mr. J. P. Henot quoted above uses coding for using the special correlation which exists in an image, the article by Messrs. VREESWIJK and HAGHIRI describes a use of a relative addressing of the vectors of an image on the preceding one in order to use time correlation.
Nevertheless these methods do not make it possible to regulate the transmission data rate, or sometimes even to obtain a data rate less than 1 Mbit/s with an image quality which remains acceptable.
The aim of the invention is to overcome the above-mentioned drawbacks.
To this end, the subject of the invention is a method of coding with adjustable parameters of a field of movement in a sequence of animated images characterized in that it consists in decomposing each field of movement of the image according to a coding tree and in identifying by a menu each movement vector present in the image by accompanying each vector by its codeword. This decomposition is carried out by macroblock, that is to say in one part of the image or in the entire image (1 single macroblock).
Due to the f
REFERENCES:
patent: 4922341 (1990-05-01), Strobach
patent: 4980764 (1990-12-01), Henot
Frequenz, vol. 43, Nos. 3,4, Mar.-Apr. 1989, M. Gilge et al.: "Codierung von farbigen Bewegtbildszenen mit 64 kbits/s-en neuer Ansatz aur Verwirklichung eines Bildtelefons im ISDN (Teil I+Teil II)", pp. 86-96, 98-108.
2DN International Workshop on Signal Processing of HDTV, L'Aquila, Feb. 29-Mar. 2, 1988, J. P. Henot: "Coding of motion information for high definition television", pp. 355-363.
4th International Colloquium on Advanced Television Systems, Ottawa, Jun. 25-29, 1990, C. M. X. Fernando et al.: "Display processing for HD-MAC", pp. 3B.6.1-3B.6.15.
"Thomson-CSF"
Britton Howard W.
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