Television receiver including a teletext decorder

DETAILED DESCRIPTION A particular object of the invention is to provide a teletext decoder circuit which does not include a separate 6 MHz oscillator but in which for other reasons clock pulses, which are already present in the television receiver, can be used as reference clock pulses, which reference clock pulses generally do not occur at a rate which is a rational multiple of the rate at which the display clock pulses must occur.
According to the invention, the generator circuit is adapted to partition the series of reference clock pulses applied thereto into groups of N reference clock pulses each, in which N clock pulse periods correspond to the desired width of a character to be displayed, and to select of each such group m.
sub.
1 clockpulses to function as display clock pulses; the converter circuit is adapted to supply each character picture element code during a period which is dependent on the ordinal number of the character picture element code in the series of m.
sub.
1 character picture element codes.
The invention has resulted from research into teletext decoder circuits for use in the field of digital video signal processing in which a 13.
5 MHz clock generator is provided for sampling the video signal.
The 13.
5 MHz clock pulses supplied by this clock generator are now used as reference clock pulses.
The generator circuit partitions these reference clock pulses into groups of N clock pulses periods each.
The width of such a group is equal to the desired character width.
Since a character comprises rows of m.
sub.
1 picture elements, m.
sub.
1 reference clock pulses are selected from such a group which clock pulses are distributed over this group as regularly as possible.
Since the mutual distance between the display clock pulses thus obtained is not constantly the same, further measures will have to be taken to prevent undesired gaps from occurring between successive picture elements when a character is displayed.
Since the length of a picture element is determined by the period during which the converter circuit supplies a given character picture element code, this period has been rendered dependent on the ordinal number of the character picture element code in the series of m