Coding and modulation for bandwidth compression of television and facsimile signals
P. Bylanski · Spiral (Imperial College London) · 1966
Two aspects relevant to the coding of picture signals with a view to compression of signal bandwidth are considered.Firstly: the problem of combining the information associated with the run length representation of the picture signal, for transmission over a practical channel, is studied.A solution is proposed in terms of combined amplitude and phase modulation and an analysis is presented which demonstrates the feasibility of the technique.Secondly, several aspects of the digram representation of the picture signal are studied.The second order redundancy is experimentally determined using a digital technique.The results obtained lead to the design of several simple and efficient digram -based codes for black and white facsimile pictures, resulting in useful reduction of signal bandwidth.These codes are implemented and assessed experimentally.An adaptive encoding technique is proposed whereby errors produced by a non-uniquely decodable code may be minimised in a controlled way by the use of predictive feedback at the encoder.3.