Work towards defining standards for digital television transmission codecs has been proceeding for many years. A draft specification for 140 Mbit/s coding using blanking removal and differential pulse code modulation is given in CCIR Recommendation 721. A draft specification for a codec operating at 30–45 Mbit/s and using the discrete cosine transform has been defined by the European Telecommunications Standards Institute. The paper briefly reviews bit-rate-reduction techniques and describes the 140 and 34 Mbit/s codecs.