SMPTE RP 6-1994 Recorded Carrier Frequencies and Preemphasis Characteristics for 2-in Quadruplex Video Magnetic Tape Recording for 525-Line 60-Field Television Systems.pdf

1、SMPTE RP*b 94 I 8357403 0003517 278 I SMPTE RECOMMENDED PRACTICE RP 6-1994 Revision of RP 6-1985 Recorded Carrier Frequencies and Preemphasis Characteristics for 2-in for 525- Li ne/60- Fi el d Television Systems Quadruplex Video Magnetic Tape Recording 1 Scope 1.1 This practice specifies parameters

2、 of the recorded information essential to the inter- change of 2-in quadruplex video magnetic tape recording of monochrome and NTSC color signals for 525-line/60-field television systems. The parameters include video preemphasis characteristics and recorded carrier frequencies for all recording prac

3、tices and video pilot speci- fications for practice SHBP. 2.1.1 Video processing and signal generating circuits used only for practice SHBP; 2.1.2 A video preemphasis network; 2.1.3 A linear frequency modulator having con- stant deviation with respect to the modulating video frequencies; 2.1.4 An am

4、plifier of the frequency-modulated carrier to provide alternating-current drive to the pole tips. 1.2 Practices defined are: 3 Preemphasis 1.2.1 practice SHBP: This practice is suitable for color and monochrome signals. A video pilot signal is added to the recorded information to be used as a playba

5、ck reference. 1.2.2 practice HB: t lis practice is suitable for color and monochrome sigiials. 1.2.3 practice LBM: This practice is suitable only for monochrome signals. (It is considered to be obsolescent and is included for reference purposes only.) 1.2.4 practice LBC: This practice is suitable fo

6、r color and monochrome signals. (it is considered to be obsolescent and is included for reference purposes only.) 2 Recording chain 2.1 A recording chain consisting of elements specified by this practice will contain, in order of signal flow, the following elements: Page 1 of 3 pages 3.1 Preemphasis

7、 is defined by the frequency and phase characteristics of a network as shown in figure 1. Accuracy of preemphasis time constants shall be maintained by including source and load impedances (not shown) in the calculation of circuit values. 3.2 Time constant values specifying the pre- emphasis network

8、 for each practice are listed in the table below: LBC LBM SHBP HB Time constant ti (ns) 333.3 240 26.4 31.7 Time constant 2 (ns) 2500 600 132 240 Tolerance I 0.25% Not Not Not specified specified specified Copyright O 1994 by the SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Av

9、e., White Plains, NY 10607 (914) 761-1100 Approved February 28, 1994 SUPTE RP*b 74 8357403 0001518 304 = RP 6-1994 I 4 - i v out w72 + 1 Vin w71 + 1 = 2*f Figure 1 - Video preemphasis characteristic circuit 4 Recorded carrier frequencies Carrier frequencies corresponding to reference video levels sh

10、all be as indicated in the table below: Blanking 9.9 7.9 (MHz) Sync tip 9.58 7.06 (MW 5 Head current 5.2 The reference recording is made with a flat amplitude-vs-frequency current drive to a head with metal pole tips. 6 Practice SHBP 6.8 6.5 5.0 5.79 4.28 5.5 6.1 All recordings made using this pract

11、ice shall have a video pilot signal added to the video information prior to the frequency-modulation process. 6.2 Monochrome television signals shall have a pseudo-burst added to sync tip and horizontal blanking interval for the purpose of identification and pilot generation (see 6.6). t 0.05 f 0.05

12、 6.3 Unless otherwise indicated, all parameter specifications show relationships among pilot, burst, and video information prior to preemphasis. The point of insertion of generated signals into the video information path is not specified. 5.1 The amplitude vs frequency characteristic of the recordin

13、g current applied to the head shall produce a recording such that repro- duced video, with no reproduce equalization changes, is the same as the following refer- ence recording. 6.4 In order to ensure that no spurious com- ponents from the input video signal are recorded in the pilot frequency band,

14、 a band-reject filter shall be placed in the video signal path prior to addition of the pilot signal. Attenuation of all Page 2 of 3 pages SMPTE RP*b 94 = 835740L 0001519 040 RP 6-1994 components within t 100 kHz of the pilot frequency shall be 16 dB or greater. B 6.5 Pilot specifications: 6.5.1 The

15、 pilot frequency shall be exactly 1.5 times the color subcarrier or pseudo-burst fre- quency of the video information to be recorded. 6.5.2 The pilot phase shall be such that positive- or negative-going zero crossings of pilot coin- cide with the negative-going zero crossings of the R-Y color compon

16、ent signal. Tolerance of zero crossing coincidence shall be t 2.3 ns for color signals. Phase and tolerances are unspecified for monochrome signals. 6.5.3 Amplitude of the pilot is defined by a measure- ment in the FM spectrum at the output of the modulator to reduce tolerance errors associated with

17、 the input video signal. With no chroma signal present (except burst), the amplitude of the first order pilot sidebands shall be 24 di3 t 0.2 di3 below the amplitude of the unmodulated carrier. (This pilot amplitude corresponds to a peak- to-peak video pilot level equal to 1/6 of the sync tip to pea

18、k white level of a full amplitude video signal.) 6.5.4 The amplitude of any spurious components shall be at least 30 dB below the pilot level. 6.6 Pseudo-burst specifications for mono- chrome signal only. 6.6.1 The pseudo burst shall start 0.4 ps t 0.2 ps after the 50% amplitude point of the leading

19、 edge of sync. The start of pseudo burst is defined by the zero crossing that precedes the first half cycle of subcarrier that is 50% or greater of the pseudo-burst amplitude. 6.6.2 The pseudo burst shall end 7.8 ps I 0.4 ps after the 50% amplitude point of the leading edge of sync. The end of the p

20、seudo burst is defined by the zero crossing that follows the last half cycle of subcarrier that is 50% or greater of pseudo-burst amplitude. 6.6.3 The 10% to 90% rise and fall times of pseudo-burst envelope shall be less than 0.5 ps. The leading edge of sync, 10% to 90% points, shall contain no burs

21、t. 6.6.4 The amplitude of the pseudo burst shall be 40 IRE units t 4 IRE units. 6.6.5 The amplitude of any spurious components shall be at least 33 dB below the pseudo-burst level. DC components produced by insertion of the pseudo burst into the video signal shall be less than t 1 IRE unit. 6.6.6 The frequency of the pseudo burst shall be 3.58 MHz I 0.02 MHz. Rate of change of the frequency of the pseudo burst shall be less than 1 kHz per second. Page 3 of 3 pages