Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1988-01-25
1989-10-10
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358138, 358105, H04N 712
Patent
active
048735736
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods of coding and decoding video signals, to enable the bandwidth of the transmitted (or recorded) signal to be reduced. Although the invention is described in detail with reference to the European 625 line, 50 field/s interlaced standards, the invention is not restricted to any particular standards and may be used with both interlaced and non-interlaced (sequential) systems. Whenever the terms transmitter and receiver are employed (or analagous terms), the terms recorder and playback machine may be understood as unwritten alternatives. The invention is of particular utility in transmitting HDTV (high definition television).
2. Description of the Related Art
1. Chiariglione, L., Corgnier, L. and Guglielmo, M.Pre- and Post-Processing in a Video Terminal using Motion Vectors. 1986. I.B.C. Brighton 1986.
2. Girod, B., Thoma, R. Motion-compensating conversion without loss of vertical resolution line-interlaced television systems. Eurasip Workshop on `Coding of HDTV Signals`, L'Aquila, November 1986.
3. Storey, R. HDTV Motion Adaptive Bandwidth Reduction using DATV. BBC Research Department Report 1986/5. British Patent Application No. 85 31777.
4. Storey, R. Compatible Transmission of HDTV in a 625 line Channel. British Patent Specification No., 86 20110.
5. Thomas, G. A. Bandwidth Reduction by Adaptive Subsampling and Motion Compensation DATV Techniques. October 1986. 128th SMPTE Technical Conference, Oct. 24-29 1986, New York. British Patent Applications 86 06809 and 86 17320.
6. Ninomiya, Y. et al. 1984. A Single Channel HDTV Broadcast System, The MUSE. NHK Laboratory Note No. 304.
SUMMARY OF THE INVENTION
It is possible to effect bandwidth reduction of a still picture by sub-sampling, transmitting different sets of sub-sampling points in a cyclic sequence of fields, e.g. a sequence of four fields, and building up the picture at the receiver by accumulating the points from each cycle of fields. The bandwidth reduction is achieved essentially by temporal filtering. Further reduction may be effected by transmitting only some points in this way and creating the others at the receiver by interpolation.
The temporal filtering procedure cannot be applied to a moving picture area as it would blur the image. It has already been proposed to switch to a low spatial detail filter to provide the compressed bandwidth signal for moving areas (Reference 3). However it is desirable to be able to transmit a moving area which maintains good correlation from field to field with high detail. The loss of resolution when a low spatial detail filter is used is very obvious.
The object of the present invention is to make it possible to effect bandwidth reduction in a manner such that correlated detail of moving areas is not lost.
BRIEF DESCRIPTION OF THE DRAWING
The invention is defined with particularity in the appended claims and will now be described in detail, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 represents a basic sample structure used in a bandwidth reduction system;
FIG. 2 represents reconstructing a detailed image in stationary areas:
FIG. 3a represents an effective sampling lattice used in moving areas to act as a low spatial detail filter;
FIG. 3b represents the required prefilter characteristics;
FIG. 4 represents the interpolation of velocity vectors when vectors are measured across a picture period;
FIG. 5 represents the effect of block size on the number of samples in a block;
FIG. 6 represents a simple two-dimensional linear interpolator;
FIG. 7 represents reconstructing a detailed image using motion vector information;
FIG. 8 represents the reconstruction process shown for a onedimensional case;
FIG. 9 represents the problem of obscured background and how `following back` helps;
FIG. 10 is a block diagram of a complete transmission system embodying the present invention;
FIG. 11 is a block diagram of a second embodiment of the invention;
FIG. 12 and 13 show prefilter character
REFERENCES:
patent: 4692801 (1987-09-01), Ninomiya et al.
patent: 4745474 (1988-05-01), Schiff
patent: 4768092 (1988-08-01), Ishikawa
Borer Timothy J.
Thomas Graham A.
British Broadcasting Corporation
Groody James J.
Kostak Victor R.
O'Connell Robert F.
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