The ratio of the amount of data in the non-compressed digital video signal to the compressed version. Modern compression techniques start with component television signals but a variety of sampling systems are used, 4:2:2 (‘Studio’ MPEG-2), 4:2:0 (MPEG-2), 4:1:1 (NTSC, DVCPRO), etc. The compression ratio should not be used as the only means to assess the quality of a compressed signal. For a given technique, greater compression can be expected to result in lower picture quality, but different techniques give widely differing quality of results for the same compression ratio. The more modern technologies, MPEG-4, (H 264), VC-1, JPEG 2000 and the latest HEVC (H.265), are more efficient than MPEG-2. The only sure method of judgment is to make a very close inspection of the resulting pictures – where appropriate, re-assessing their quality after onward video processing.