Koninklijke Ptt Nederland N.v.

Koninklijke P.t.t.

Johannes Franciscus Koppelmans

Arian Koster

Dolf A Schinkel

Arthur Meijboom

By providing a digital video memory arrangement with first and second address generating circuits, digital video signals can be written at a first location of a non-mechanical memory and (almost) immediately read out from a second location of the non-mechanical memory, with the reading out both being capable of featuring backward and forward jumps. As a consequence of a coupling between the first and the second address generating circuits it becomes impossible to, on the one hand, unjustly pass with jumping in the read signal the running or stopped write signal and, on the other hand, unjustly pass with the running read signal the stopped write signal. To this end the second address generating circuits dispose over determining circuits for determining, in response to at least the write signal and the read signal, a permitted address jump.

Video memory arrangement

Known transcoders for compressed video signals comprise a decoder and a coder coupled thereto, between which a data signal is transmitted. Because compressed video signals comprise so-called difference pictures and normal pictures, both the decoder and the coder should have a feedback loop which is utilized in decoding and coding a difference picture and is not utilized in decoding and coding a normal picture. For example, for the purpose of prediction means (motion compensation and motion estimation) present in the feedback loop of the coder, much computation has to be carried out in the coder. The computation required is considerably reduced by concomitantly transmitting one or more information signals in addition to the data signal in a transcoder according to the invention, and complete decoding and complete coding no longer takes place.

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The Hague, Netherlands

Johannes Franciscus Koppelmans