Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1988-04-04
1989-11-28
Britton, Howard W.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358138, 358140, H04N 701, H04N 712
Patent
active
048841382
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a method of transmitting a video signal at a higher line standard over a transmission channel for signals at a lower standard, and to transmitting and receiving apparatus for use in the method.
Various methods have been proposed for transmitting high definition images, at a reduced bandwidth, but at the same basic line rate as is used for source and display. One example of this type of system is NHK's "MUSE", which operates entirely at 1125 lines. Other techniques have been proposed for packing extra spatial detail, but usually less than is claimed for HDTV ("high-definition television"), into a standard channel such as C-MAC or D2-MAC. These two approaches are described respectively the following papers, (1) Ninomaya, Y. et al. 1984. A single Channel HDTV Broadcast System - The Muse. NHK Laboratory Note No 304, and (2) Arragon, J-P. et al. 1986. Transmission d'images de Television a Haut Definition Compatible avec le Standard D2-MAC Paquet. Acta Electronica 27,1-2.
SUMMARY OF THE INVENTION
In one aspect the invention provides a method of transmitting a video signal originating at a relatively higher line standard (lines per picture) over a transmission channel for signals at a lower line standard by transmitting samples of more than one line of the higher standard on a single line at the lower standard. A receiver capable of receiving signals at the higher standard can separate out the samples to reconstruct the higher standard, while a receiver capable of receiving only signals at the lower standard will still receive a workable signal. A degree of compatibility is thus retained.
The invention in its various aspects is defined in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail by way of example with reference to the accompanying drawings, in which:
FIG. 1 is a diagram illustrating the bandlimiting provided in a bandwidth compression prefilter in three dimensional space for stationary picture areas (or well-correlated moving areas);
FIG. 2 is a diagram similar to FIG. 1 for areas in which uncorrelated movement occurs;
FIG. 3 is a diagram illustrating the sampling structure for a 4:1 bandwidth reduction;
FIG. 4 is a diagram illustrating the subsequent re-ordering of the samples to produce a signal for transmission at standard e.g. 625 line rate;
FIG. 5 is a block circuit diagram of a circuit which can be used at the transmitter to re-order or "shuffle" the samples, using two RAM stores;
FIG. 6 is a diagram illustrating the sample shuffling with the circuit of FIG. 5 on an illustrative line having only eight samples;
FIG. 7 is a block circuit diagram of a sample shuffler using one RAM circuit; and
FIG. 8 is a diagram similar to FIG. 6 for the circuit of FIG. 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
This specification describes a method of allowing transmission of 1249-line HDTV resolution signals via a 625 line based trnasmission channel.
In implementing the method the first operation is to bandwidth reduce the signal. This operation can be done by applying pre-filters as shown in FIGS. 1 and 2 to stationary and moving areas respectively. FIGS. 1 and 2 illustrate the band limiting applied in a three-dimensional space having a horizontal frequency axis n in cycles per picture width (c/pw), a vertical frequency axis n in cycles per picture height (c/ph) and a time axis f related to the field frequency. The stationary area filtering is defined by the octohedral shape shown in FIG. 1 which has apices half-way along the m and n axes to the next repeat and only a quarter of the way along the f axis. In the moving-area filter characteristic defined by the cuboid shape in FIG. 2, the filter surface intersects the m and n axes one quarter of the way along while the f axis is intersected half-way along. A movement detector is used to apply the characteristic of FIG. 2 in areas of movement and the characteristics of FIG. 1 in stationary areas.
An added level of sophistication is to add
REFERENCES:
patent: 2810780 (1957-10-01), Loughlin
patent: 2921124 (1960-01-01), Graham
patent: 4389668 (1983-06-01), Faureau
patent: 4605950 (1986-08-01), Goldberg
Wendlen, Broder, "Extended Definition Television with High Picture Quality", S.M.P.T.E. Journal, vol. 92, No. 10, Oct., 1983.
Arragon, Jean-Pierre, et al., "Transmission d'images de television a haute definition compatible avec le standard D2-MAC/paquet", ACTA Electronica 27,1-2, 1986.
Thomas, Graham A., "HDTV Bandwidth Reduction by Adaptive Subsampling and Motion Compensation Datv Techniques", S.M.P.T.E. Paper at Technical Conference, Oct. 1986.
Ninomiya, Yuichi, "A Single Channel Broadcast System--The Muse", NHK Laboratories Note, Sep., No. 304, Japan, 1984.
British Broadcasting Corporation
Britton Howard W.
O'Connell Robert F.
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