1、 - STD-SMPTE 23UM-ENGL 377b 8357403 0002578 57b SMPTE STANDARD ANSVSMPTE 230M-1996 Revision of ANSIICMPTE 230M-1991 for Television Analog Recording - U2-h Type L- Electrical Parameters, Control Code and Tracking Control 1 Scope 1.1 This standard specifies the electrical pa- rameters of video, audio,
2、 time and control code, and tracking-control signais for 1/2-n type L helical-scan video tape recorders operating with video signals having a typical scanning structure of 525 lines, 59.94 fields per second, and 2:l interlace. This standard specifies two recording modes: Mode 1 uses oxide-particte t
3、ape, and mode 2 uses metal-particle tape and permits audio frequency modulation (AFM) signals to be recorded. 1.2 Where nominal values are given without tol- erances, interchange performance will be limited by implementation accuracy. 2 Normative references The following standards contain provisions
4、 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 re
5、cent edition of the standards indicated below. ANSIIEEE 152-1 992, Audio Program Level Measure- ment ANWSMPTE 12M-1995, Television, Audio and Film -Time and Control Code ANSI/SMPTE 238M-1992, Television Analog Record- ing - 1/2-in Type L - Tapes and Cassettes Page 1 of 13 pages IEC 268-12 (1987), Pa
6、rt 12: Application of Connec- tors for Broadcast and Similar Use ITU-R BT.470-4, Television Systems 3 Video recording This component video recording system is intended to operate compatibly in an NTSC environment. To achieve this, the levels and ratios used in the format are derived from the monochr
7、ome or composite input signal as defined in 3.4. The video recording system shall provide separate signal paths for the luminance and color-difference signals. These component signals shall be recorded on two separate tracks designated respectively as the Y track for the luminance signal and the C t
8、rack for the color-difference signals. The R-Y and B-Y color- difference signals shall be recorded in the form of a compressed time-division multiplexed signal on the C track. When operating in mode 2, two AFM signals may be recorded in addition to the compressed color- difference signals. 3.1 Mode
9、selection 3.1.1 Two modes of operation are defined for the following tape types: - Oxide-particle tape: Mode 1 - Metal-particle tape: Mode 2 3.1.2 Sensing of tape type shall be automatic by means of a sensing hole in the cassette as described in ANSVSMPTE 238M. CAUTION NOTICE: This Standard may be r
10、evised or withdrawn at any time. The procedures of the Standard Developer require that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of publication. Purchasers of standards may receive current information on all standards by calling or writing
11、the Standard Developer. Printed in USA. L American National Standard Copyright O 1996 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Harisdale Ave., White Plains, NY 10607 (914) 761-1100 Approved October 10,1996 _ STD-SMPTE 230fl-ENGL L77b 8357LiOL 0002577 Li02 ANSVCMPTE 2301111-19
12、96 3.2 Luminance channel 3.2.1 Signal Processing Asigna1 processing system, as specified in this stand- ard, shall contain the following elements in the order of the signal flow. 3.2.1.1 A means for modifying the sync portion of the luminance signal. 3.2.1.2 A means for insertion of a vertical inter
13、- val subcarrier is required in mode 2 when the signal to be recorded has been decoded from a composite source as defined in ITU-R BT.470-4. The vertical interval subcarrier (VISC) is optional in mode 1. INPUT LUMINANCE SIGNAL MODIFIED LUMINANCE SKiNAL 3.2.1.3 A video nonlinear preemphasis process.
14、3.2.1.4 A video preemphasis network. 3.2.1.5 A means for clipping the video signal after preemphasis. 3.2.1.6 A linear frequency modulator having constant deviation with respect to the amplitude of the modulating frequencies. 3.2.1.7 An amplifier to provide current drive to the Y channel record head
15、s. 3.2.2 Modification of sync portion Means shall be used to modify the pulse width and amplitude of the sync portion as shown in figure 1. Uduu 525 12 3 4 5 6 ? 9 I u- i -ORIGINAL WAVEFORM- I (NOT MOOIFIED) I INPUT LUMINANCE SIGNAL I I MODIFIED LWINANCE SIGNAL L NOTES 2 Rise time a-b should be 180
16、ns with an approximate gaussian shape at the 10% and 90% points. 3 Dimension c is the midpoint of the a-b transition. 4 See annex A.1, of this signal may or may not be present. It is not part of the format. Figure 1 - Waveform of the modified luminance sync (vertical sync and equalizing pulse portio
17、n remains unmodified) Page 2 of 13 pages STD-SMPTE 230M-ENGL L97b , H.P.F. L.P.F. - 3.2.3 Luminance nonlinear preemphasis - The luminance signal shall receive nonlinear preem- phasis (see figure 2). The characteristics shall be as shown in table 1. LIMITER - M Table 1 - Video nonlinear preemphasis c
18、haracteristics MHz 0.2 0.5 1 .o 1.5 2.0 3.0 4.0 5.0 dalue: Input (d6) -30 -20 -15 -10 -5 O 0.4 0.4 0.4 0.4 0.3 0.2 1.9 1.7 1.7 1.4 0.8 0.4 4.6 4.0 3.5 2.4 1.3 0.7 6.7 5.6 4.6 3.0 1.6 0.9 8.0 6.6 4.9 3.3 1.8 1.1 9.5 7.5 5.3 3.6 2.2 1.3 9.9 7.6 5.3 3.6 2.2 1.4 9.9 7.3 5.1 3.3 2.0 1.2 are in decibels.
19、NOTE - The phase of the side chain (Q2) shall be equal to the phase of the input signal (l) at 3.58 MHz pnorto the mixing. Figure 2 - Block diagram of video nonlinear preernphasis 3.2.4 Luminance preemphasis Preemphasis is defined by the frequency and phase characteristics of the network shown in fi
20、gure 3 when fed from a zero impedance source and feeding an infinite impedance load. 3.2.5 Amplitude clipping For an input signal where blanking is at 0% and peak white at loo%, any positive or negative amplitude excursion exceeding the levels shown in table 2 shall be clipped. rn 8357401 0002580 32
21、4 rn ANCVSMPTE 230M-1996 O 1 - O Figure 3 - Preemphasis network Table 2 - Luminance amplitude clipping characteristics I Mode 1 Mode 2 Positive excursion limit +310% nom +324% nom +315% max +329% max Negative excursion limit -125% nom -214% nom -1 30% max -21 9% max I 3.2.6 Recorded carrier frequenc
22、y Carrier frequencies corresponding to reference video levels shall be as shown in table 3 when recording a flat-field signal. Table 3 - Carrier frequencies corresponding to reference video levels Mode 1 Mode 2 100% white 6.4 MHz nom 7.7 MHz nom 7.0 MHz nom 50% level 5.7 MHz nom Blanking 4.97 f 0.05
23、 MHz 6.27 f 0.05 MHz Sync tip 4.4 MHz nom 5.7 MHz nom Deviation 1.43 f 0.05 MHz 1.43 f 0.05 MHz (blanking to peak white) 3.2.7 Y track record head current 3.2.7.1 The amplitude of the record current for the Y track shall be such that the maximum level of remanent flux on the tape is produced when re
24、cording a Y signal with 50% amplitude flat field. 3.2.7.2 The amplitude of the Y track record cur- rent shall decrease with increasing frequency in the range 2 MHz to 10 MHz, according to a straight line contained within limit lines as shown in figure 4. Page 3 of 13 pages ANSVSMPTE 2301111-1996 O R
25、ECORD HEAD - ldB CURRENT TOLERANCE I I O a I O I I O I I O I O I I I I I I O I . B I 1 F, F, 10MHz 2MHr Frequency Y C F, = Blanking Frequency F2 = 100% White frequency F, = Minimum Chrm Frequency F2 = Maximum Chroma Frequency Figure 4 - Record equalization 3.3 C channel 3.3.1 Signal processing A sig
26、nal processing system, as specified by this standard, shall contain the following elements in the order of the signal flow: 3.3.1.1 A means of compressing the time scale of the R-Y and B-Y signals over a period of one horizontal line such that they may be time multi- plexed into one horizontal line.
27、 3.3.1.2 A means of adding a horizontal timing pulse. 3.3.1.3 A video nonlinear preemphasis process. 3.3.1.4 A video preemphasis network. 3.3.1.5 A means for clipping the video signal after preem p has is. 3.3.1.6 A linear frequency modulator having con- stant deviation with respect to the amplitude
28、 of the modulating frequencies. 3.3.1.7 A high-pass filter to reduce the low fre- quency component amplitude of the FM chromi- nance signal. 3.3.1.8 A means of combining the frequency modulated audio signal and the frequency modu- lated chrominance signal in mode 2 when the AFM signals are present.
29、3.3.1.9 An amplifier to provide amplitude current drive to the C channel record heads 3.3.2 Time compression and multiplexing 3.3.2.1 The R-Y and B-Y signals shall each be compressed into a half-time scale as shown in figure 5. 3.3.2.2 The compressed R-Y and B-Y signals shall be multiplexed alternat
30、ely and delayed by one horizontal line with respect to the luminance signal as shown in figure 6. Page 4 of 13 pages MODIFIED LUMINANCE SIGNAL COMPRESSED TIME DIVISION MULTIPLEXED CHROMINANCE SIGNALS STD*SMPTE 230M-ENGL Lb W 8357403 0002582 TT7 ANSVSMPTE 230M-1996 t HORIZONTAL SYNC EDGE 1 HORIZONTAL
31、 LINE REFERENCE EDGE OF Y TIMING PULSE a I- - It I I h JL ARBITRARY TIME REFERENCE COINCIDENT IN Y. R-Y. BY DOMAIN H-Y c O -1 05 5 2% HALF HORIZONTAL LINE 2.45 f 0.2 REFERENCE EDGE CoMPRECsoN START POINT OF C TIMING PULSE c r: B-Y I I _-_ I -_ c HALF HORIZONTAL UNE I * - lWff.5/77/7.5 Color Bars - -
32、 - 10017.5/100/7.5 Color Ban Where T2 is = 112 Ti - 0.01 pi I T2 +At I i12 Ti + 0.01 ps At = + 0.006 ps; refer to annex A.2. Figure 5 - Waveform of compressed R-Y, &Y signals (525/60) 1 HORIZONTAL LINE I I I Yn + 2 Yn t 1 Il INPUT SIGNAL Yn INPUT R-Y SIGNAL COMPRESSED AND MULTIPLEXED R-YIB-Y SIGNAL
33、INPUT 8-Y SIGNAL I I (R-Y)n t 2 I (R-Y)n t 1 I (R- I Figure 6 - Time compression and multiplexing system Page 5 of 13 pages ANSVSMPTE 230M-1996 3.3.3 Addition of horizontal timing pulses The horizontal timing pulses which are continuous through the vertical interval shall be added to the compressed
34、and multiplexed R-Y and B-Y signals as shown in figure 6. The sync shall have an approximate gaussian shape with a fall time of 220 ns between the 10% and 90% points. 3.3.4 R-Y and B-Y nonlinear preemphasis The video signal shall receive nonlinear preemphasis which has the characteristics shown in t
35、able 1 and figure 2. 3.3.5 R-Y and B-Y preemphasis Preemphasis is defined by the frequency and phase characteristics of the network as shown in figure 3, when fed from a zero impedance source and feeding an infinite impedance load. 3.3.6 Amplitude clipping For an input signal of (100, 7.5, 77, 7.5)
36、color bars which produces a color-difference signal defined as 100% for clipping reference, any positive or negative amplitude excursions shall be clipped according to limits defined in table 4. 3.3.7 Recorded carrier frequency The carrier frequencies obtained using a flat field input test signal wi
37、th appropriate levels corresponding to reference video (100, 7.5, 77, 7.5) color bar levels shall be as shown in table 5. 3.3.8 C track record head current 3.3.8.1 The amplitude of the record current for the C track shall be such that the maximum level of remanent flux on the tape is produced when r
38、ecording the chrominance blanking level. 3.3.8.2 The amplitude of the C track record cur- rent shall decrease with increasing frequency in the range 2 MHz to 10 MHz according to a straight line contained within limit lines as shown in figure 4. 3.3.9 Low-frequency amplitude of chrominance FM signal
39、If the AFM signals are recorded in mode 2, the chromi- nance signal shall be subject to high-pass filtering prior to combining with the AFM signals. The filter response is shown in figure 7. Table 4 - Chrominance amplitude clipping characteristics Mode 1 Mode 2 Positive excursion limit +175% nom +23
40、0% nom +l8OYO max +235% max Negative excursion limit -305% nom -305% nom -31 0% max -31 0% max Table 5 - Recorded carrier frequency Mode 1 Mode 2 Positive video excursion 4 MHt nom 4.8 MHz nom Negative video excursion 5 MHz nom 5.8 MHz nom Blanking Sync tip 5.55 MHz nom 6.35 MHz nom Deviation peak t
41、o peak 4.5 MHz f 0.05 MHz 5.3 MHz f 0.05 MHz 1 .O MHz f 0.05 MHz 1 .O MHz f 0.05 MHz Page 6 of 13 pages STDeSMPTE 230M-ENGL 379b 8357903 0002589 87T 9 O w D 5 a z m U 27 I- !- ml i 310k 540k 1 Frequency (Hr) Figure 7 - Low-frequency amplitude of chrominance FM signal (in mode 2 when AFM signal is pr
42、esent) 3.4 Reference Y, R-Y, B-Y amplitudes The reference Y, R-Y, and B-Y component signal amplitudes shall be as shown in table 6. Table 6 - NTSC 75% color bar amplitude (1 00/1.5/77/7.5) Luminance % Color difference With 7.5% YO setup R-Y B-Y Gray Yellow Cyan Green Magen ta Red Blue White Sync 76.
43、9 69.0 56.1 48.2 36.2 28.2 15.4 100.0 -40. O O + 8.1 -50.0 -41.9 +41.9 +50.0 - 8.1 O - O -50. O +16.9 -33.1 +33.1 -1 6.9 +50.0 O - NOTE - The ratio of 100% amplitude of luminana and chrominance shall be 714:700. ANSVSMPTE 23OM-1996 4 Decoding and color field identification 4.1 Vertical interval subc
44、arrier o/lSC) reference 4.1.1 When operating in mode 2, a VISC signal shall be inserted on lines 11 and 274 of the Y signal prior to any signal preemphasis. This sig- nal shall only be present when the signal to be recorded is the result of decoding a composite NTSC signal with a coherent subcarrier
45、. The VISC signal is optional in mode 1. 4.1.2 The format of the VISC signal is shown in figure 8. 4.1.3 The frequency of the VISC signal shall be equal to the frequency of the subcarrier of the NTSC video signal. 4.1.4 The phase of the VISC signal shall be within k 5“ of the burst phase of the NTSC
46、 signal prior to decoding. 4.2 Field identification 4.2.1 When operating in mode 1 and mode 2, a color field identification signal shall be inserted into the chrominance as shown in figure 9, when the signal to be recorded is the result of decod- ing a composite NTSC signal meeting ITU-R BT.470-4. 4
47、.2.2 When operating in mode 2 and recording signals that originated directly from color com- ponents, the identification signal shall identify a four-field sequence as shown in figure 9. When there is an associated time code signal, it is preferred that the flag indicating field one corre- spond to
48、an even-numbered time code frame. 4.2.3 When there is no way to detect the begin- ning of a four-field color sequence, the sequence may start arbitrarily. 4.2.4 When operating in mode 1, the color field identification signal referred to in 4.2.2 and 4.2.3 is optional. Page 7 of 13 pages STD*SMPTE 23
49、0M-ENGL 177b W 8357401 0002585 70b D ANSVSMPTE 23OM-1996 HORIZONTAL SYNC EDGE 1 HORIZONTAL LINE L b VISC FREQUENCY = fsc / d 13+ 1 Fs -. - 100% = White Peak Level of 100/7.5/77/7.5 Color Bars COLOR FRAME A (FIELD 1 AND 2) 15TH LINE COLOR FRAME 6 (FIELO 3 AND 4) 15TH UNE Figure 8 - Vertical interval subcarrier signal R-Y B-Y I- I i I HALF HORIZONTAL LINE I HALF HORIZONTAL UNE I -1- I COMPRESSION START POINT -1 r- Figure 9 - Color field identification signal (525/60) Page 8 of 13 pages STD*SMPTE 230M-ENGL 399b m 8357403 000258b b42 m 5 Longitudinal audio signal recordi
