Digital television at 45 Mbit/s.

We describe an algorithm and a real-time hardware implementation for coding composite NTSC signals sampled at four times color subcarrier into 45 Mb/s while preserving 'Network Quality'. Adaptive differential pulse code modulation and variable word- length coding are used to minimize the data rate for the channel. This requires a buffer to smooth the data rate. Buffer overflow is prevented by quantizer selection and by subsampling.