[3] The standard specifies a scheme for digital encoding of colors as triplets of small integers, a widescreen format with 1080 active lines per picture and 1920 square pixels per line (a 16:9 aspect ratio), as well as several details of signal capture, transmission, and display.

Recommendation ITU-R BT.709-6 defines a common image format (CIF) where picture characteristics are independent of the frame rate.

For BT.709, their coordinates in the CIE 1931 chromaticity diagram are In the BT.709 standard, a color value is conceptually represented by three numbers

If these numbers are interpreted as Cartesian coordinates in a three-dimensional space, the representable colors correspond to points in an axis-aligned cube of side 1, with corner

are supposed to be proportional to the physical intensity of each primary, namely emitted or received light power per unit of area.

For efficiency reasons, the standard specifies a non-linear transformation of each component signal, resulting in

[7] In practice, display gamma depends on various factors such as the capabilities of the monitor, the viewing conditions, and desired visual effects (such as contrast or saturation stretching).

[8][9][7][10] A suggested corresponding reference electro-optical transfer characteristic function for flat panel displays used in HDTV studio production has been specified in ITU-R BT.1886[11] and EBU Tech 3320.

is called "luminance" in the standard, and is roughly an approximation of the CIE Y coordinate (which is presumed to measure the perceptual brightness of the color) modified by the non-linear function above.

is computed from the non-linear RGB components, this equivalence is correct only for shades of gray.

For digital storage, transmission, and processing, the BT.709 standard specifies that the non-linear color coordinates

This quantization shall be performed by simple scaling and rounding, so as to yield integers that span a proper subset of the

Quantized color coordinates outside the nominal ranges above are allowed, but typically they would be clamped for broadcast or for display (except for Superwhite and xvYCC).

[3]: p4 [14] The creation of a worldwide HDTV standard was approved in 1989 by the Comité consultatif international pour la radio (CCIR) as "Recommendation XA/11 MOD F".

[2] These early versions still left many unanswered questions, and the lack of consensus toward a worldwide HDTV standard was evident.

[3] The standard strictly determined the picture size but offered several options for the pixel scanning order and frame rate.

This allows manufacturers to create a single television set or display for all markets world-wide.

It had long been known that a non-linear encoding of colors was more efficient than a linear one because human vision is more sensitive to brightness changes at low light levels.

[16] The BT.709 encoding function is not a simple power law because the latter has infinite slope at the origin, which emphasizes camera noise and is problematic for analog-to-digital converters.

While BT.709 has eased the compatibility issue in terms of the consumer and television set manufacturer, broadcast facilities still use a particular frame rate based on region, such as 29.97 in North America, or 25 in Europe meaning that broadcast content still requires at least frame rate conversion.

NTSC, PAL, and SECAM are all interlaced formats in a 4:3 aspect ratio, and at a relatively low resolution.

Scaling them up to HD resolution with a 16:9 aspect ratio presents a number of challenges.

First is the potential for distracting motion artifacts due to interlaced video content.

Cropping the top and/or bottom of the standard-definition frame may or may not work, depending on if the composition allows it and if there are graphics or titles that would be cut off.

Alternately, pillar-boxing can show the entire 4:3 image by leaving black borders on the left and right.

When encoding Y’CBCR video, BT.709 creates gamma-encoded luma (Y’) using matrix coefficients 0.2126, 0.7152, and 0.0722 (together they add to 1).

[25] These problems can be handled with video processing software which can be slow, or hardware solutions[26] which allow for realtime conversion, and often with quality improvements.

On the other hand, for projects that originated on film, but completed their online master using video online methods would need to re-telecine the individual needed film takes and then re-assemble, a significantly greater amount of labor and machine time is required in this case, versus a telecine for a conformed negative.

The creators of sRGB chose to use the same primaries and white point as Rec.709, but changed the tone response curve (sometimes referred to as gamma) to better suit the intended use in offices and brighter conditions than television viewing in a dark living room.

709 and sRGB share the same primary chromaticities and white point chromaticity; however, sRGB is explicitly output (display) referred with an equivalent gamma of 2.2 (the actual function is also piecewise to avoid near black issues).