For details of the analog interface, see Component analog HD interface, on page 485.

OECF, described on page 320; this process is loosely called gamma correction.

The colorimetric properties of the primary estimates are supposed to conform to BT.709 primaries described on page 290: DTV transmission standards call for BT.709, and modern consumer displays use BT.709. However, as I write in 2011, nearly all 50 Hz program material is created and mastered using EBU primaries (see EBU Tech. 3213 primaries, Table 26.4 on

page 293), and nearly all 60 Hz program material is created and mastered using SMPTE primaries (see SMPTE RP 145 primaries, Table 26.5 on page 293).

I expect the situation in mastering to change upon the introduction of new studio display technologies such as OLEDs – but among content creators and broadcasters, old habits die hard.

Luma (Y’)

Luma is a weighted sum of nonlinear R’, G’, and B’ components according to the BT.709 luma coefficients:

The luma component Y’, being a weighted sum of nonlinear R’G’B’ components, has no simple relationship with the CIE relative luminance (Y) used in colour science. The formulation of luma in HD differs from that of SD; see SD and HD luma chaos, on page 350. Video encoding specifications typically place no upper bound on luma bandwidth. Video encoding specifications typically place no upper bound on luma bandwidth.

Component digital 4:2:2 interface

Y’CBCR components are formed by scaling Y’, B’-Y’, and R’-Y’ components, as described in CBCR components for BT.709 HD on page 371. TRS is inserted as described in

SDI and HD-SDI sync, TRS, and ancillary data on

page 433. The HD-SDI interface is described in HD-SDI coding, on page 440. It is standard to subsample according to the 4:2:2 scheme (sketched in the third column of Figure 12.1, on page 124). Image quality wouldn’t suffer if subsampling were 4:2:0 – that is, if colour differences were subsampled vertically as well as horizontally – but this would be inconvenient for hardware design and interface.

SMPTE ST 274, 1920× 1080 Scanning and Analog and Parallel Digital Interfaces for Multiple Picture Rates.

HD equipment based on 1125/60 scanning and 1920×1035 image format, with nonsquare sampling, according to SMPTE 240M, was deployed for several years. That system is obsolete. (It can now be considered as a 1035i variant of 1080i30 or 1080i29.94 having 1035 picture lines instead of 1080, nonsquare sampling, and slightly different colorimetry.)

24 ≈23.976

1.001

30 ≈29.97

1.001

60 ≈59.94

1.001

This chapter details a family of high-definition television systems standardized in SMPTE ST 274. The systems have an image format of 1920× 1080, an aspect ratio of 16:9, and square sampling.

SMPTE ST 274 represents agreement on colorimetry according to the international standard BT.709. Previous revisions of SMPTE ST 274 allowed use of 240M colour and luma parameters on an “interim” basis. It will take some time for manufacturers and users to complete the transition to the new standard.

Scanning

1920× 1080 video represents stationary or moving twodimensional images sampled temporally at a constant rate of 24⁄1.001, 24, 25, 30⁄1.001, 30, 50, 60⁄1.001, or 60 frames per second. The base sampling rate is

74.25 MHz; this rate is modified by the ratio 1000⁄1001 for systems having noninteger frame rate, and doubled to 148.5 MHz (possibly times 1000⁄1001 ) for progressive systems at frame rates higher than 30 Hz. All of these systems have 1125 total lines (LT); the number of samples per total line (STL) is adapted to achieve the desired frame rate. Table 42.1 above summarizes the scanning parameters.

For studio video, the tolerance on frame rate is normally ±10 ppm. In practice the tolerance applies to a master clock at a high frequency, but for purposes of computation and standards writing it is convenient to reference the tolerance to the frame rate.

A frame comprises a total of 1125 horizontal raster lines of equal duration, uniformly scanned top to