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SMPTE STANDARD SMPTE 296M-2001 Revision of ANSI/SMPTE 296M-1997 for Television — 1280 × 720 Progressive Image Sample Structure — Analog and Digital Representation and Analog Interface Page 1 of 14 pages Contents 1 Scope 1 Scope 2 Normative references 3 General 4 Timing 5 System colorimetry 6 Raster structure 7 Digital representation 8 Digital timing reference sequences (SAV, EAV) 9 Ancillary data 10 Bit-parallel interface 11 Analog sync 12 Analog interface Annex A Production aperture Annex B Pre- and post-filtering characteristics Annex C Bibliography 1.1 This standard defines a family of progressive image sample systems for the representation of stationary or moving two-dimensional images sampled temporally at a constant frame rate and having an image format of 1280 pixels by 720 lines and an aspect ratio of 16:9 as given in table 1. All systems in the table have the common characteristic that all the samples gathered within a single temporal unit, a frame, shall be spatially contiguous and provide a complete description of that frame (4.2) This standard specifies: – R′G′B′ color encoding; – R′G′B′ analog and digital representation; – Y′P′BP′R color encoding, analog representation, and analog interface; and – Y′C′BC′R color encoding and digital representation. Table 1 – Image sampling systems System nomenclature Luma or R′G′B′ samples per active line (S/AL) Active lines per frame (AL/F) Frame rate, Hz Luma or R′G′B′ sampling frequency (fs), MHz Luma sample periods per total line (S/TL) 1 1280 × 720/60 1280 720 60 74.25 1650 2 1280 × 720/59.94 1280 720 60/1.001 74.25/1.001 1650 3 1280 × 720/50 1280 720 50 74.25 1980 4 1280 × 720/30 1280 720 30 74.25 3300 5 1280 × 720/29.97 1280 720 30/1.001 74.25/1.001 3300 6 1280 × 720/25 1280 720 25 74.25 3960 7 1280 × 720/24 1280 720 24 74.25 4125 8 1280 × 720/23.98 1280 720 24/1.001 74.25/1.001 4125 NOTE – For systems 4 through 8, analog video interface is not preferred. See clause 12. Total lines per frame 750 750 750 750 750 750 750 750 Copyright © 2001 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Ave., White Plains, NY 10607 (914) 761-1100 Approved January 4, 2001 SMPTE 296M-2001 Designers should be aware that serial digital interfaces for formats other than Y′C′BC′R have not been defined. A bit-parallel digital interface is incorporated by reference in clause 10. NOTE – Throughout this standard, references to signals represented by a single primed letter (e.g., R′, G′, and B′) are equivalent to the nomenclature in earlier documents of the form ER′, EG′, and EB′, which in turn refer to signals to which the transfer characteristics in 5.4 have been applied. Such signals are commonly described as being gamma corrected. 1.2 This standard specifies multiple system formats (table 1). It is not necessary for an implementation to support all formats to be compliant with this standard. However, an implementation must state which of the system formats are supported. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent edition of the standards listed below. SMPTE 274M-1998, Television — 1920 × 1080 Scanning and Analog and Parallel Digital Interfaces for Multiple Picture Rates SMPTE 291M-1998, Television — Ancillary Data Packet and Space Formatting SMPTE RP 160-1997, Three-Channel Parallel Analog Component High-Definition Video lnterface SMPTE RP 177-1993 (R1997), Derivation of Basic Television Color Equations CIE Publication 15.2 (1986), Colorimetry, Second Edition IEC 60169-8 (1978-01), Radio Frequency Connectors, Part 8: R.F. Coaxial Connectors with Inner Diameter of Outer Conductor 6.5 mm (0.256 in) with Bayonet Lock — Characteristic Impedance 50 Ohms (Type BNC) plus amendments IEC 60169-8-am1 (1996-03) and IEC 60169-8-am2 (1997-11) ITU-R BT.709-4 (09/00), Parameter Values for the HDTV Standards for Production and International Programme Exchange 3 General 3.1 The speci ficat ion of a system cl aiming compliance with this standard shall state: – which of the systems of table 1 are implemented; – which of the analog R′G′B′ or Y′P′BP′R and/or which of the digital R′G′B′ or Y′C′BC′R interfaces are implemented; and – whether the digital representation employs eight bits or 10 bits per sample in its uniformly quantized (linear) PCM coding. 3.2 Digital codeword values in this standard are expressed as decimal values in the 10-bit representation. An eight-bit system shall either round or truncate to the most significant eight bits as specified in 7.10. 4 Timing 4.1 Timing shall be based on a reference clock of the sampling frequency indicated in table 1, which shall be maintained to a tolerance of ± 10 ppm. 4.2 A frame shall comprise the indicated total lines per frame, each line of equal duration as determined by the sampling frequency (fs) and the samples per total line (S/TL). Samples may be obtained in an optoelectronic conversion process sequentially, simultaneously, or via a combination of both, provided all samples in the frame are contiguous in the image and obtained within the same temporal frame period. The samples within each line shall be uniformly delivered to and collected from the interface in a spatially left-to-right sequence; lines in a frame shall be uniformly delivered to and collected from the interface in a spatially top-to-bottom sequence. Lines are numbered in time sequence according to the raster structure described in clause 6. 4.3 Timing instants in each line shall be defined with respect to a horizontal datum denoted by 0H which is established by horizontal synchronizing (sync) information in clauses 8 and 11. Each line shall be Page 2 of 14 pages SMPTE 296M-2001 divided into a number of reference clock intervals, of equal duration, as specified by the column S/TL in table 1. The time between any two adjacent sample instants is called the reference clock interval T. T = 1/fs. 5 System colorimetry 5.1 Equipment shall be designed in accordance with the colorimetric analysis and optoelectronic transfer function defined in this clause. This corresponds to ITU-R BT.709. 5.2 Picture information shall be linearly represented by red, green, and blue tristimulus values (RGB), lying in the range 0 (reference black) to 1 (reference white), whose colorimetric attributes are based upon reference primaries with the following chromaticity coordinates, in conformance with ITU-R BT.709, and whose white reference conforms to CIE D65 as defined by CIE 15.2: Red primary Green primary Blue primary Reference white CIE x 0.640 0.300 0.150 0.3127 CIE y 0.330 0.600 0.060 0.3290 5.3 From the red, green, and blue tristimulus values, three nonlinear primary components, R′, G′, and B′, shall be computed according to the optoelectronic transfer function of ITU-R BT.709, where L denotes a tristimulus value and V′ denotes a nonlinear primary signal: V′ =  4.5L, 1.099L0.45 – 0.099, 0 ≤ L< 0.018 0.018 ≤ L ≤ 1.0 5.4 To ensure the proper interchange of picture information between analog and digital representations, signal levels shall be completely contained in the range specified between reference black and reference white specified in 7.6 and 12.4, except for overshoots and undershoots due to processing. 5.5 The Y′ component shall be computed as a weighted sum of nonlinear R′G′B′ primary components, using coefficients calculated from the reference primaries according to the method of SMPTE RP 177: Y′ = 0.2126R′ + 0.7152G′ + 0.0722B′ NOTE – Because the Y′ component is computed from nonlinear R′G′B′ primary components rather than from the linear tristimulus RGB values, it does not represent the true luminance value of the signal, but only an approximation. To distinguish it from luminance, the term luma is used for the Y′ signal. For more information, see e.g. Poynton, A Technical Introduction to Digital Video. 5.6 Color-difference component signals P′B and P′R, having the same excursion as the Y′ component, shall be computed as follows: P ′B = 1 – 0.5 0.0722 ( B ′ – Y ′ ) P ′R = 1 – 0.5 0.2126 ( R ′ – Y ′ ) P′B and P′R are filtered and may be coded as C′B and C′R components for digital transmission. Example filter templates are given in figure B.2. 6 Raster structure 6.1 For details of vertical timing, see figures 1 and 2. 6.2 In a system according to this standard, each frame shall comprise 750 lines including: – Vertical blanking: lines 1 through 25 inclusive (including vertical sync, lines 1 through 5 inclusive) and lines 746 through 750 inclusive; and – Picture: 720 lines, lines 26 through 745 inclusive. 6.3 Ancillary signals, as distinct from ancillary data, may be conveyed during vertical blanking, lines 7 through 25 inclusive. The portion within each of these lines that may be used for ancillary data is defined in 9.3. Ancillary signals shall not convey picture information although they may be employed to convey other related or unrelated signals, coded similarly to picture information. Further specification of ancillary signals is outside the scope of this standard. 6.4 During time intervals not otherwise used, the R′, G′, B′ or Y′, P′B, C′B, P′R, and C′R components shall have a blanking level corresponding to zero. 6.5 The production aperture defines a region 1280 samples by 720 lines. The horizontal extent of the production aperture shall have the Page 3 of 14 pages SMPTE 296M-2001 0 FRAME Pi ctur e 27 Pi ctur e Pi ctur e Figure 1 – Vertical timing (analog representation) FRAME Picture Picture Figure 2 – Vertical timing (digital representation) Picture 50% point of its leading transition at reference luma sample 0 and the 50% point of its trailing transition at luma sample 1279. The production aperture defines the maximum extent of picture information. For further information, consult annex A. 6.6 The aspect ratio of the image represented by the production aperture shall be 16:9. The sample aspect ratio is 1:1 (square pixels). 6.7 The center of the picture shall be located at the center of the production aperture, midway between samples 639 and 640, and midway between lines 385 and 386. 6.8 Each edge of the picture width, measured at the 50% amplitude point, shall lie within six reference clock intervals of the production aperture. 7 Digital representation 7.1 Digital representation shall employ either R′G′B′ or Y′C′BC′R components, as defined in clause 5 or clause 6, uniformly sampled. NOTE – Each component is prepared as an individual channel. Combinations of channels may be presented to an appropriate interface for signal interchange. For example, the Y′ channel and the multiplexed C′B/C′R channel data together comprise a source format for the serial interface specified in SMPTE 292M. 7.2 The digital signals described here are assumed to have been filtered to reduce or prevent aliasing upon sampling. For information regarding filtering, consult annex B. 7.3 The characteristics of the digital signals are based on the assumption that the location of any required sin (x)/x correction is at the point where the signal is converted to an analog format. Page 4 of 14 pages SMPTE 296M-2001 7.4 R′G′B′ signals and the Y′ signal of the Y′C′BC′R interface shall be sampled orthogonally, line- and picture-repetitive, at the sampling frequency, fs. The period of the sampling clock shall be denoted T. R′G′B′ samples shall be cosited with each other. 7.5 A luma sampling number in a line is denoted in this standard by a number from 0 through one less than the total number of samples in a line. Luma sample number zero shall correspond to the first active video sample. The luma sample numbering is shown in figure 3. Note that the distance between 0H and the start of SAV is 256 samples. NOTE – The active video digital representation is 1280 clock periods (0-1279) in length. 7.6 Digital R′, G′, B′, and Y′ components shall be computed as follows: L′D = Floor (219DL′+ 16D + 0.5); D = 2n-8 where L′ is the component value in abstract terms from zero to unity, n takes the value 8 or 10 corresponding to the number of bits to be represented, and L′D is the resulting digital code. The unary function Floor yields the largest integer not greater than its argument. NOTE – This scaling places the extrema of R′, G′, B′, and Y′ components at codewords 64 and 940 in a 10-bit representation or codewords 16 and 235 in an eight-bit representation. 0H Analog Waveform (Y’R’G’B’) Durations in References Clock Periods (T) 256T A.T B.T 4T 40T 40T 4T C.T 1280T Luma Sample Numbering Digital Data Stream pabcde f ghi 4T BT j k l mno 4T EAV ANCILLARY DATA or BLANKING CODEWORDS SAV 1280T VIDEO DATA pa bcd Duration in ref. Clock periods (EAV) NOTES 1 Horizontal axis not to scale. 2 0H is the analog horizontal timing reference point, and in the analog domain, is regarded as the start of the line. 3 A line of digital video extends from the first word of EAV to the last word of video data. Figure 3 – Analog and digital timing relationships Page 5 of 14 pages SMPTE 296M-2001 7.7 Digital C′B and C′R components of the Y′C′BC′R set shall be computed as follows: C′D = Floor (224DC′ + 128D + 0.5); D = 2n-8 where C′ is the component value in abstract terms from – 0.5 to + 0.5, and C′D is the resulting digital code. The unary function Floor yields the largest integer not greater than its argument. NOTE – This scaling places the extrema of C′B and C′R at codewords 64 and 960 in a 10-bit representation or codewords 16 and 240 in an eight-bit representation. 7.8 C′B and C′R signals shall be horizontally subsampled by a factor of two with respect to the Y′ component. C′B and C′R samples shall be cosited with even-numbered Y′ samples. The sample number zero of C′B and C′R corresponds to the first active video 0 sample. For information regarding filtering, consult annex B. The subsampled C′B and C′R signals shall be timemultiplexed on a sample basis, in the order C′BC′R. The first data word of an active line shall be a C′B sample. The multiplexed signal is referred to as C′B/C′R. NOTE – Systems 7 and 8 have 2063 C′B sample periods and 2062 C′R sample periods per line. The C′B/C′R multiplexer must be reset every line at sample number zero. 7.9 Code values having the eight most significant bits all zero or all one — that is, 10-bit codes 0, 1, 2, 3, 1020, 1021, 1022, and 1023 — are employed for synchronizing purposes and shall be prohibited from video, ancillary signals, and ancillary data. 7.10 A system having an eight-bit interface shall address the conversion of 10-bit video data to eight bits with an appropriate process that minimizes video artifacts such as quantization noise. Ancillary data in 10-bit format shall be converted to eight-bit format by truncating the two least significant bits. In both cases, when converting eight-bit data to 10-bit data, the two least significant bits of the 10-bit word shall be set to 0. NOTE – SMPTE is addressing rounding for all eight-bit/10bit digital video standards. SMPTE 291M describes the handling of ancillary data between eight-bit and 10-bit interfaces in annex D. 7.11 For Y′, R′, G′, and B′ signals, undershoot and overshoot in video processing may be accommodated by the use of codewords 4 through 63 and codewords 941 through 1019 in a 10-bit system, or codewords 1 through 15 and codewords 236 through 254 in an eight-bit system. For C′B and C′R signals, undershoot and overshoot in video processing may be accommodated by the use of codewords 4 through 63 and codewords 961 through 1019 in a 10-bit system, or codewords 1 through 15 and codewords 241 through 254 in an eight-bit system. 8 Digital timing reference sequences (SAV, EAV) 8.1 SAV (start of active video) and EAV (end of active video) digital synchronizing sequences shall define synchronization across the digital interface. Figures 2, 3, and 4 show the relationship of the SAV and EAV sequences to digital and analog video. 8.2 An SAV or EAV sequence shall comprise four consecutive codewords: a codeword of all ones, a codeword of all zeros, another codeword of all zeros, and a codeword including F (frame), V (vertical), H (horizontal), P3, P2, P1, and P0 (parity) bits. An SAV sequence shall be identified by having H = 0; EAV shall have H = 1 (tables 3 and 4 show details of the coding). 8.3 When digitized, every line shall include a four-sample EAV sequence commencing 110 clocks prior to 0H (for systems 1 and 2); 440 clocks prior to 0H (for system 3); 1760 clocks prior to 0H (for systems 4 and 5); 2420 clocks prior to 0H (for system 6);and 2585 clocks prior to 0H (for systems 7 and 8). When digitized, every line shall include a four-sample SAV sequence commencing 256 clocks after 0H (for all systems [1, 2, 3, 4, 5, 6, 7, and 8]). The EAV sequence immediately preceding the 0H datum of line 1 shall be considered to be the start of the digital frame as shown in figure 2. Page 6 of 14 pages 10-bit 8-bit 960 240 C’B/C’R 512 128 SMPTE 296M-2001 EA V EAV SAV 64 16 940 235 EAV EAV SAV Y’,R’,G’,B’ 64 16 a-d e h k -n o luma sample numbers a-d e 0H NOTES Notes 1 Figure 3/table 21 Fsihguorew3/ntaublme 2bsehroiwngnumobfelurinmg aof lsuamma spalmepnleumnumbeberrss ffoorreaecahcohf thoefsytshteemssycsotveemreds covered in this standard. in this standard. 2 0H is the analo2 gOHhios rthizeoannatalolgthimorizinongtarletimfeinrgenrecfeerepncoeinpoti.nt. Figure 4 – Digital representation — Horizontal timing details Table 2 – Values for figures 3 and 4 and table 5 for different systems Luma sample numbering Systems a b c d e f g h i j k l mn o p 1,2 1280 1281 1282 1283 1284 1350 1389 1390 1391 1430 1646 1647 1648 1649 0 1279 3 1280 1281 1282 1283 1284 1680 1719 1720 1721 1760 1976 1977 1978 1979 0 1279 4,5 1280 1281 1282 1283 1284 3000 3039 3040 3041 3080 3296 3297 3298 3299 0 1279 6 1280 1281 1282 1283 1284 3660 3699 3700 3701 3740 3956 3957 3958 3959 0 1279 7,8 1280 1281 1282 1283 1284 3825 3864 3865 3866 3905 4121 4122 4123 4124 0 1279 System Duration in reference clock periods (T) A B C 1,2 70 362 1650 3 400 692 1980 4,5 1720 2012 3300 6 2380 2672 3960 7,8 2545 2837 4125 NOTE – Figure 3 and table 2 representations show nominal relationship values between the analog and digital representations. See figure 5 and table 5 for tolerance values for the analog sync including rise and fall tolerances. Page 7 of 14 pages SMPTE 296M-2001 Table 3 – Video timing reference codes Bit 9 8 7 6 5 4 3 2 number (MSB) Word Value 0 1023 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 3 1 F V H P3 P2 P1 P0 1 0 (LSB) 1 1 0 0 0 0 0 0 Bit number Function 0 Value of 1 (F/V/H) 2 3 9 1 Fixed 1 1 1 1 Table 4 – Protection bits for SAV and EAV 8 7 6 5 4 3 F V H P3 P2 P1 0 0 0 0 0 0 0 0 1 1 1 0 0 1 0 1 0 1 0 1 1 0 1 1 2 1 0 P0 0 0 Fixed Fixed 0 0 0 1 0 0 1 0 0 0 0 0 8.4 F/V/H flags – The EAV and SAV of all lines shall have F = 0. – The EAV and SAV of lines 1 through 25 inclusive and lines 746 through 750 inclusive shall have V = 1. – The EAV and SAV of lines 26 through 745 inclusive shall have V = 0. – The EAV of line 1 shall be considered the start of the digital frame. 8.5 A line which in the analog representation is permitted to convey ancillary signals may convey digitized ancillary signals. 9 Ancillary data 9.1 Ancillary data may optionally be included in the blanking intervals of a digital interface according to this standard. 9.2 The interval between the end of EAV and the start of SAV may be employed to convey ancillary data packets. Designers should be aware that when SMPTE 292M serial interface is employed, the first four samples after EAV are reserved for other usage. 9.3 The interval between the end of SAV and the start of EAV of any line that is outside the vertical extent of the picture (as defined in clause 6.2), and that is not employed to convey digitized ancillary signals, may be employed to convey ancillary data packets. NOTE – Currently SMPTE is defining the switching point(s) for all serial digital video interfaces. The reader is cautioned to be aware that ancillary data should be placed taking into account the switching point. 9.4 Ancillary data packets may be conveyed across each of the three R′, G′, and B′ channels, or across each of the three Y′, C′B/C′R channels. 9.5 In the case of 10-bit representation, intervals not used to convey SAV, video data, EAV, ancillary signals, or ancillary data shall convey the codeword 64 (black) in the R′, G′, B′, Y′ channels, or 512 in the C′B/C′R channels. They shall be 16 and 128, respectively, in the case of 8-bit representation. Page 8 of 14 pages SMPTE 296M-2001 9.6 For specifications of the details of ancillary data, see SMPTE 291M. 10 Bit-parallel interface The electrical and mechanical parameters of the bit-parallel interface are specified in clauses 10, 11, 12, and 13 of SMPTE 274M, which are incorporated by reference. It is anticipated that in future revisions of SMPTE 274M that auxiliary component A will be eliminated. 11 Analog sync 11.1 Details of analog sync timing are shown in figures 1, 3, and 5 and are summarized in table 5. 11.2 A positive zero-crossing of a trilevel sync pulse shall define the 0H datum for each line. A negative-going transition precedes this instant by 40 reference clock intervals, and another negative-going transition follows this instant by 40 reference clock intervals. + 300 mV Vertical 0 Sync - 300 mV d 0H + 350 mV + 300 mV P’B,P’R 0 BLANKING BROAD PULSE b g - 300 mV - 350 mV 0H + 700 mV + 300 mV Y’,R’,G’,B’ 0 - 300 mV c a e f 0H Figure 5 – Analog levels and timing Page 9 of 14 pages SMPTE 296M-2001 Table 5 – Analog sync timing (Systems 1 - 8) a See figure 5 b See figure 5 c See figure 5 d See figure 5 e See figure 5 f See figure 5 Sync rise and fall time g Total line Active line Duration (T) 40 1540 40 260 260 1540 Tolerance (T) ±3 –6 +0 ±3 –0 +6 –0 +6 –6 +0 4 Table 2 ’C’ 1280 ± 1.5 – 12 +0 11.3 Positive transition of a trilevel sync pulse shall be skew-symmetric with a rise time from 10% to 90% of 4 ± 1.5 reference clock periods. The 50% (midpoint) point of each negative transition shall be coincident with its ideal time within a tolerance of ± 3 reference clock periods. 11.4 The trilevel sync pulse shall have structure and timing according to figures 3 and 5. The positive peak of the trilevel sync pulse shall have a level of +300 mV ± 6 mV; its negative peak shall have a level of –300 mV ± 6 mV. The amplitude difference between positive and negative sync peaks shall be less than 6 mV. 11.5 Each line that includes a vertical sync pulse shall maintain blanking level, here denoted zero, except for the interval(s) occupied by sync pulses. During the horizontal blanking interval, areas not occupied by sync shall be maintained at blanking level, here denoted zero. 11.6 Each frame shall commence with five vertical sync lines, each having a broad pulse. The leading 50% point of a broad pulse shall be 260T after the preceding trilevel zero crossing. The trailing 50% point of a broad pulse shall be 1540T after the preceding trilevel zero crossing. 12 Analog interface NOTE – This clause applies to all frame rates in table 1. However, direct analog interconnection of slow-rate systems (30 Hz and below) is not preferred, except for synchronizing signals. 12.1 An analog interface according to this standard may employ either the R′G′B′ component set or the Y′P′BP′R component set. 12.2 R′G′B′ and Y′ channels shall have a nominal bandwidth of 30 MHz. 12.3 Each component signal shall be conveyed electrically as a voltage on an unbalanced coaxial cable into a pure resistive impedance of 75 Ω. 12.4 For the Y′, R′, G′, and B′ components, reference black (zero) in the expressions of 5.5 shall correspond to a level of 0 Vdc, and reference white (unity) shall correspond to 700 mV. 12.5 P′ B and P′R co mpo ne nt s are an al o g versions of the C′B and C′R components of 5.6, in which zero shall correspond to a level of 0 Vdc and reference peak level (value 0.5 of equations in 5.6) shall correspond to a level of +350 mV. 12.6 Trilevel sync according to clause 11 shall be added to each analog component. 12.7 Each of the electrical signals in an analog interface employs a connector that shall conform to IEC 60169-8, with the exception that the impedance of the connector may be 75 Ω, or to SMPTE RP 160. Page 10 of 14 pages SMPTE 296M-2001 Annex A (informative) Production aperture A.1 Production aperture A production aperture for the studio digital signal defines an active picture area of 1280 pixels × 720 lines as produced by signal sources such as cameras, telecines, digital video tape recorders, and computer-generated pictures conforming to this standard. A.2 Analog blanking tolerance A.2.1 The duration of the maximum active analog video signal measured at the 50% points is standardized as 1280 clock periods. However, the analog blanking period may differ from equipment to equipment and the digital blanking may not coincide with the analog blanking in actual implementation. A.2.2 To maximize the active video duration in picture origination sources, it is desirable to have analog blanking match digital blanking. However, recognizing the need for reasonable tolerance in implementation, analog blanking may be wider than digital blanking (see figures 3 and 5). A.2.3 To accommodate a practical implementation of analog blanking within various studio equipment, a tolerance of six clock periods is provided at the start and end of active video. Accordingly, the analog tolerance to parameters b and e of table 5 are as follows: Parameter b e Definition 0H to end of active video 0H to start of active video Nominal value (T) 1540 260 Tolerance (T) –6 +0 –0 +6 Preferred practice is to provide a full production aperture signal at the output of an analog source prior to first digitization, reserving the tolerance for possible subsequent analog processes. A.2.4 The re lationsh ip of the as socia ted analog representation (inclusive of this tolerance) with the production aperture is shown in figure 5. A.3 Transient regions A.3.1 Th is s tan da rd de fine s a pi ctu re a sp ec t ra tio of 16:9 with 1280 pixels per active line and 720 active lines per frame. However, digital processing and associated spatial filtering can produce various forms of transient effects at picture blanking edges and within adjacent active video that should be taken into account to allow practical implementation of the studio standard. A.3.2 Analog transients. The following factors contribute to these effects: – Bandwidth limitation of component analog signals (most noticeably, the ringing on color-difference signals); – Analog filter implementation; – Amplitude clipping of analog signals due to the finite dynamic range imposed by the quantization process; – Use of digital blanking in repeated analog-digital-analog conversions; and – Tolerance in analog blanking. A.4 Clean aperture A.4.1 The bandwidth limitation of an analog signal (pre- and postfiltering) can introduce transient ringing effects which intrude into the active picture area. Also, multiple digital blanking operations in an analog-digital-analog environment can increase transient ringing effects. Furthermore, cascaded spatial filtering and/or techniques for handling the horizontal and vertical edges of the picture (associated with complex digital processing in post-production) can introduce transient disturbances at the picture boundaries, both horizontally and vertically. It is not possible to impose any bounds on the number of cascaded processes which might be encountered in the practical post-production system. Hence, recognizing the reality of those picture edge transient effects, the definition of a system design guideline is introduced in the form of a subjectively artifact-free area, called clean aperture. A.4.2 The clean aperture defines an area within which picture information is subjectively uncontaminated by all edge transient distortions. In order to minimize the effects on subsequent compression or transmission processes, the contaminated area should be confined within 16 pixels and 9 lines of the production aperture edges. A.4.3 The clean aperture of the picture defines a region 1248 samples in width by 702 lines high, symmetrically located in the production aperture. The clean aperture shall be substantially free from transient effects due to blanking and picture processing. An encroachment of 6 samples maximum on each of the left and right edges of the production aperture is allowed for horizonal blanking errors generated by analog processing. Vertical blanking shall be as specified with zero tolerance. A.4.4 This yields a minimum clean aperture of 1248 horizontal active pixels by 702 active lines whose quality is guaranteed for final release. The clean aperture lies within the production aperture as shown in figure A.1. A.4.5 It is good practice to minimize variations in analog blanking and to use techniques in digital processing that minimize or prevent transients in the allowed contaminated area as well as inside the clean aperture. Figure A.1 – Clean aperture Page 11 of 14 pages SMPTE 296M-2001 Annex B (informative) Pre- and post-filtering characteristics B.1 Figure B.1 depicts example filter characteristics for preand post-filtering of Y′, R′, G′, and B′ component signals. Figure B.2 depicts example filter characteristics for preand post-filtering of P′B and P′R component signals. B.2 The passband frequency of the component Y′, R′, G′, and B′ signals is nominally 30 MHz. B.3 The value of the amplitude ripple tolerance in the passband is ± 0.05 dB relative to the insertion loss at 100 kHz. Figure B.1 – Example filter template for Y′ and R′G′B′ components Page 12 of 14 pages Insertion loss (dB) Relative to the value at 100 kHz 60 50 40 30 20 10 0 0 50 dB 40 dB 6 dB 0.20 fs 0.25 fs 0.30 fs 0.37 fs Frequency Template for insertion loss SMPTE 296M-2001 Insertion loss (dB) Relative to the value at 100 kHz +0.05 0 -0.05 0 0.20 fs Template for passband ripple NOTE - The value of fs is given in table 1 Group Delay (T) Relative to the value at 100 kHz +0.110 +0.075 0 -0.075 -0.110 0 0.14 fs 0.20 fs Template for passband group-delay Figure B.2 – Example filter template for P′B and P′R components B.4 The i ns ertio n lo ss c ha rac teris tic s o f th e fi lters a re frequency-scaled from the characteristics of ITU-R BT.601. Insertion loss is 12 dB or more at half the sampling frequency of the Y′, R′, G′, and B′ components, and 6 dB or more at half the sampling frequency of the P′B and P′R components relative to the insertion loss at 100 kHz. B.5 The specifications for group-delay in the filters are sufficiently tight to produce good performance while allowing the practical implementation of the filters. Page 13 of 14 pages SMPTE 296M-2001 Annex C (informative) Bibliography SMPTE 292M-1998, Television — Bit-Serial Digital Interface for High-Definition Television Systems ITU-R BT.601-5 (10/95), Studio Encoding Parameters of Digital Television for Standard 4:3 and Wide-Screen 16:9 Aspect Ratios ITU-R BT.1361 (1998), Worldwide Unified Colorimetry and Related Characteristics of Future Television and Imaging Systems Poynton, Charles. A Technical Introduction to Digital Video. John Wiley & Sons Page 14 of 14 pages




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