U.S. Philips Corporation

Philippe A Van Overmeire

Gerard De Haan

Johannes Yzebrand Tichelaar

Franciscus H Bergen

Jilles Ultee

In an extended television signal having signalling bits for conveying control information to control an extended decoder, the signalling bits include a start code and data bits. The start code's main lobe of spectral energy resides in the lower spectral area of a baseband television signal below 2 MHz and preferably below 1.7 MHz. The start code is preferably (almost) DC-free, and the start code has good aperiodic correlation properties and a predetermined minimum bit Hamming distance to the data bits when shifted in the direction of the data bits following the start code.

Start code for signalling bits

A simple and reliable interpolation filter can be provided by a median filter 9 to which signals of the pixels x.sub.1, x.sub.2 and x.sub.3 are applied and which can supply incorrect output values at high spatial frequencies perpendicular to a connection line of pixels x.sub.3 and x.sub.4 located diametrically with respect to a pixel (.) to be interpolated, in conjunction with an averaging circuit 25 to which signals of the pixels x.sub.3 and x.sub.4 are applied and which will not be disturbed at the said frequencies, but will cause disturbances at high spatial frequencies in the direction of this connection line x.sub.3 -x.sub.4, at which last-mentioned frequencies the median filter 9 will function correctly again.

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Brugge, Belgium

Philippe A Van Overmeire