Rec. ITU-R BT.601-4 1 SECTION 11B: DIGITAL TELEVISION RECOMMENDATION ITU-R BT.601-4 ENCODING PARAMETERS OF DIGITAL TELEVISION FOR STUDIOS (Questions ITU-R 25/11, ITU-R 60/11 and ITU-R 61/11) (1982-1986-1990-1992-1994) Rec. ITU-R BT.601-4 The ITU Radiocommunication Assembly, considering a) that there are clear advantages for television broadcasters and programme producers in digital studio standards which have the greatest number of significant parameter values common to 525-line and 625-line systems; b) that a worldwide compatible digital approach will permit the development of equipment with many common features, permit operating economies and facilitate the international exchange of programmes; c) that an extensible family of compatible digital coding standards is desirable. Members of such a family could correspond to different quality levels, facilitate additional processing required by present production techniques, and cater for future needs; d) that a system based on the coding of components is able to meet some, and perhaps all, of these desirable objectives; e) that the co-siting of samples representing luminance and colour-difference signals (or, if used, the red, green and blue signals) facilitates the processing of digital component signals, required by present production techniques, recommends that the following be used as a basis for digital coding standards for television studios in countries using the 525-line system as well as in those using the 625-line system: 1. Component coding The digital coding should be based on the use of one luminance and two colour-difference signals (or, if used, the red, green and blue signals). The spectral characteristics of the signals must be controlled to avoid aliasing whilst preserving the pass-band response. When using one luminance and two colour-difference signals as defined in Table 1 suitable filters are defined in Figs. 4 and 5. When using ER′ , EG′ , EB′ signals or luminance and colour-difference signals as defined in Table 2 a suitable filter characteristic is shown in Fig. 4. 2. Extensible family of compatible digital coding standards The digital coding should allow the establishment and evolution of an extensible family of compatible digital coding standards. It should be possible to interface simply between any two members of the family. The member of the family to be used for the standard digital interface between main digital studio equipment, and for international programme exchange (i.e. for the interface with video recording equipment and for the interface with the transmission system) should be that defined in § 4. In a higher member of the family the sampling frequencies of the luminance and colour-difference signals (or, if used, the red, green and blue signals) are related by the ratio 4:4:4. The specifications for the 4:4:4 member are defined in § 5.2 Rec. ITU-R BT.601-4 TABLE 1 4:2:2 member of the family 3. Specifications applicable to any member of the family 3.1 Sampling structures should be spatially static. This is the case, for example, for the orthogonal sampling structure specified in § 4 for the 4:2:2 member of the family and in § 5 for the 4:4:4 member. 3.2 If the samples represent luminance and two simultaneous colour-difference signals, each pair of colour-difference samples should be spatially co-sited. If samples representing red, green and blue signals are used they should be co-sited. Parameters 525-line, 60 field/s systems 625-line, 50 field/s systems 1. Coded signals: Y, CR, CB These signals are obtained from gamma pre-corrected signals, namely: EY′ , ER′ – EY′ , EB′ – EY′ (Annex 1, § 2 refers) 2. Number of samples per total line: 2. – luminance signal (Y) 2. – each colour-difference signal 2. – (CR, CB) 858 429 864 432 3. Sampling structure Orthogonal, line, field and frame repetitive. CR and CB samples co-sited with odd (1st, 3rd, 5th, etc.) Y samples in each line 4. Sampling frequency: 2. – luminance signal 2. – each colour-difference signal 13.55 MHz 16.75 MHz The tolerance for the sampling frequencies should coincide with the tolerance for the line frequency of the relevant colour television standard 5. Form of coding Uniformly quantized PCM, 8 (optionally 10) bits per sample, for the luminance signal and each colour-difference signal 6. Number of samples per digital active 6. line: 2. – luminance signal 2. – each colour-difference signal 720 360 7. Analogue-to-digital horizontal timing 7. relationship: 2. – from end of digital active line to OH 16 luminance clock periods 12 luminance clock periods 8. Correspondence between video signal 8. levels and quantization levels: 2. – scale 2. – luminance signal 2. – each colour-difference signal (See § 3.4) (Values are decimal) 0 to 255 220 quantization levels with the black level corresponding to level 16 and the peak white level corresponding to level 235. The signal level may occasionally excurse beyond level 235 225 quantization levels in the centre part of the quantization scale with zero signal corresponding to level 128 9. Code-word usage Code words corresponding to quantization levels 0 and 255 are used exclusively for synchronization. Levels 1 to 254 are available for videoRec. ITU-R BT.601-4 3 TABLE 2 4:4:4 member of the family (1) If used. 3.3 The digital standard adopted for each member of the family should permit worldwide acceptance and application in operation; one condition to achieve this goal is that, for each member of the family, the number of samples per line specified for 525-line and 625-line systems shall be compatible (preferably the same number of samples per line). 3.4 In applications of these specifications, the contents of digital words are expressed in both decimal and hexadecimal forms, denoted by the suffixes “d” and “h” respectively. To avoid confusion between 8-bit and 10-bit representations, the eight most-significant bits are considered to be an integer part while the two additional bits, if present, are considered to be fractional parts. For example, the bit pattern 10010001 would be expressed as 145d or 91h, whereas the pattern 1001000101 would be
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