 In 1967, University of London researchers A.H. Robinson and C. Cherry proposed run-length encoding (RLE), a lossless compression scheme, to reduce the transmission bandwidth of analog television signals.The earliest digital video coding algorithms were either for uncompressed video or used lossless compression, both methods inefficient and impractical for digital video coding.Digital video was introduced in the 1970s, initially using uncompressed pulse-code modulation (PCM) requiring high bitrates around 45200 Mbit/s for standard-definition (SD) video, which was up to 2,000 times greater than the telecommunication bandwidth (up to 100kbit/s) available until the 1990s.