Arrangement for two-dimensional DPCM coding

Claim 1

In an arrangement for two-dimensional differential pulse code modulation of digital picture element signal values, and of the type in which a controlled quantizer receives and quantizes differential pulse code modulation values, which are the difference between the digital picture signal values and assessed values (x), and in which the most recently calculated digital picture signal value (A) prior to the signal value (x) being processed and adjoining calculated picture element signal values (B,C,D) above and on each side of the recently calculated picture element signal value (x) being processed are delayed in delay means and used for calculating the assessed values (x), the improvement therein comprising: a quantizer controller connected to the delay means to receive the calculated picture signal values (A,B,C,D) and connected to and operable to control the quantizer, said quantizer controller comprising a plurality of serially-connected registers for receiving and storing the adjoining calculated signal values (B,C,D); comparison means connected to said plurality of registers and operable to compare the amplitudes represented by the adjoining calculated picture element signal values (B,C,D) with one another and to produce respective first control signals (C11, C12, C13), representing the differences between the amplitudes; extrema selection control means connected to said comparison means and operable in response to said first control signals to select and produce second control signals (S1,S2) selecting the extrema values (E), (F) of the amplitudes of the calculated picture element signal values (B, C, D); first multiplex means connected to said plurality of registers and to said extrema selection control means and operable in response to said second control signals to through-connect the extrema values (E), (F); substraction means connected to said first multiplex means for receiving the extrema values (E), (F) and connected to the delay means for receiving the most recently calculated picture element signal value (A), and operable to produce the difference values (A-F), (A-E) and (F-E) along with operational sign bits; a difference selection control connected to said subtraction means for receiving said operational sign bits and responsive thereto to produce third control signals for defining the maximum difference value (MD); second multiplex means connected to said subtraction means and to said difference selection control and responsive to said third control signals to through-connect the maximum difference value (MD) of the difference values (A-F), (A-E) or (F-E); and threshold logic means connected between said multiplex means and the quantizer to control the quantizer.