Television – Format conversion – Changing number of fields for standard conversion
Patent
1992-09-09
1994-06-28
Kostak, Victor R.
Television
Format conversion
Changing number of fields for standard conversion
348384, 348447, H04N 701, H04N 712
Patent
active
053251997
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for upconverting the field rate of a television signal. In particular it is concerned with upconversion of time division multiplex signals such as HD-MAC although it is also applicable to frequency division signals such as PAL, NTSC or SECAM.
DESCRIPTION OF THE RELATED ART
One major disadvantage of a 50 Hz field rate for High Definition Television (HDTV) signals is that display on large screens is severely prejudiced by the presence of brightness flicker. The generally accepted remedy for this is to unconvert the field-rate of the received signal to a higher value, such as 75 or 100 Hz, before display. There is a wide range of techniques available for such upconversion, some of which use a fixed algorithm and some of which are motion-adaptive or motion compensated; of the latter techniques some take advantage of Digitally Assisted Television (DATV) information, sent as part of the transmission coding bandwidths, and some do not. Examples of known techniques are given in BBC Research Report 1985/5 entitled `The Improved Display of 625-line television pictures: adaptive interpolation`, and in a paper entitled `Motion compensated Field Rate Conversion for HD-MAC Display` by G M X Fernando and D W Parker. Proc. 1988 International Broadcasting Convention pp 216-219.
It is important that the final format chosen for the transmitted HDTV signal (which will include the information transmitted via DATV) should allow for the greatest number of possible receiver options. The performance achieved from the best of the algorithms developed for bandwidth compressing HDTV into available MAC satellite broadcasting channel is sufficient to suggest that display upconversion is the weakest link in the signal processing chain. This is because the fundamental processes involved in display upconversion are very different from those in bandwidth compression. Display upconversion attempts to generate new information (additional television fields corresponding to instants in time at which no incoming field existed), whereas bandwidth compression merely attempts to minimise the loss of already existing information in the signal transmission system.
Most of the higher-quality bandwidth compression systems are motion-compensated, motion-adaptive algorithms, whereby the incoming television picture is split into a number of small blocks. Each block is encoded separately, via one or two or more coding branches. The coding branch that is considered to be producing the closest approximation to each block of the incoming signal is selected for transmission of that particular block; such a strategy is known as `fidelity checking` or `a posteriori` motion detection. Motion compensation is used in at least one of the coding branches to allow fine detail to be transmitted, spread out over several fields, on picture areas tracked by an appropriate motion vector. In areas where no reliable motion vector exists--or, in some algorithms, where the magnitude of the detected motion vector exceeds a certain threshold--a `fallback`, non-motion-compensated, branch is used; this branch transmits each television field separately, but at a lower spatial resolution. Branches are usually identified according to the time period over which a complete picture is built up; thus a 40 msec branch transmits each HDTV picture spread out over a period of 40 msec. Examples of these bandwidth compression systems are described in a paper entitled `Motion Compensated DATV Bandwidth Compression for HDTV`]by R Storey, Proc. 1988 International Broadcasting Convention pp 78-81; and a paper entitled `HD-MAC coding of high definition television signals` by F.W.P. Vreeswijk Proc. 1988 International Broadcasting Convention pp 62-65.
Field-rate upconversion of the reconstructed HDMAC signal can take advantage of the information transmitted via the DATV channel. For example, one prior art technique demonstrated in the Eureka 95 pavilion at the 1988 International Broadcasting Co
REFERENCES:
patent: 4963965 (1990-10-01), Haghiri et al.
patent: 4985767 (1991-01-01), Haghiri et al.
patent: 5081531 (1992-01-01), Parker
IEE Colloquium, "Image Processing for HDTV", London, Oct. 26, 1989, G. M. X. Fernando: Motion compensated display conversion, pp. 4/1-4/3.
SMPTE Journal, vol. 98, No. 11, Nov. 1989, (White Plains, New York, US) Y. C. Faroudja et al.: "A progress report on improved NTSC", pp. 817-822.
A. Roberts, B. Eng., "The improved display of 625-line television pictures: Adaptive interpolation", BBC Research Report, 1985/5; pp. 1-5.
G. M. X. Fernando, "Motion Compensated Display Conversion", Proc. 1988 International Broadcasting Convention; pp. 216-219.
F. W. P. Vreeswijk et al., "HD-MAC Coding of High Definition Television Signals", Proc. 1988 International Broadcasting Convention, pp. 62-65.
T. I. P. Trew et al., "Spatially Adaptive Sub-Branches for HD-MAC", Proc. 1988 International Broadcasting Convention, pp. 66-69.
G. M. X. Fernando, "Motion Compensated Field Rate Conversion for HD-MAC Display", Proc. 1988 International Broadcasting Convention, pp. 216-219.
British Broadcasting Corporation
Kostak Victor R.
O'Connell Robert F.
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