An efficient, widely compatible system required that distribution be free of detailed requirements specific to display, and that necessary additional display processing unique to that display class be conducted only at the display. The variety of display systems, already numerous, continues to increase. Each system or variant has its own set of specifications, performance characteristics, and requirements, including electro-optic transfer function, color gamut, scanning sequence, etc. Display signal processing might include transformation at the display to the appropriate luminance range and chrominance, to display primaries and reference white, matrixing to achieve metameric color match, adaptation to surround, plus conversion to scanning progressive or scanning interlaced, etc. Display processing may not be required for transmission if there is unique point-to-point routing clearly identified and appropriate processing has been provided in distribution. But it is frequently required for emission to a diffuse population of display systems.