Differential PCM system for TV line reduction code - uses transform coding and spectral coefficient prediction to reduce TV transmitted line code

摘要

Bit rate reduction coding for the transmission of TV picture information over data transmission facilities at a maximum of 10 kbit/s. The picture , e.g. 100 000 spot images quantised into a 6 bit code representing 64 grey scale steps, is transmitted in ideally 1.5 seconds and at most 3 seconds. A transform code is used to convert the picture signal into a number of spectral coefficient values for transmission in a frame structure. DPCM (Differential PCM) transmission is used with a transmitted prediction for correlating picture samples. Each transmitted frame, w, of a picture, m, is derived by using actual picture spectral coefficient, y(u,v,w,m,), and previous picture (m-1) spectral corresp. coefficient, information so that prediction coefficient information is included. Consequently the difference value for each block, w, results. Further processing derives magnitude classifications, c(w,m), for each sample in the overall picture. The signal from the TV camera (1) is A/D converted (2) and stored (3) in a 16 x 16 format. Transform coding (4) and coefficient classification, DPCM prediction and quantisation (7,8,9,10,11) then precede modem (12) transmission.