1、SMPTE RP*b 91 m 835Lt1 0000583 059 m SMPTE RECOMMENDED PRACTICE Video Record Parameters for i-in Type C Helical-Scan Television Tape Recording RP 86-1 991 Revision of RP 86-1985 1 scope This practice specifies parameters of the recorded information essential to the interchange of 1 -in type C helica
2、l-scan television tape recordings of the 525/60 monochrome or NTSC color systems. The parame- ters include video preemphasis characteristics, re- corded carrier frequencies, and record-current frequency response. 2 Signal processing 2.1 A signal processing system consisting of el- ements specified b
3、y this practice will contain, in order of signal flow, the following elements: 2.1.1 A means to modify the burst amplitude 2.1.2 A video preemphasis network 2.1.3 A linear frequency-modulator having con- stant deviation with respect to modulating fre- quencies 2.1.4 An amplifier of the frequency-mod
4、ulated carrier to provide alternating current drive to the video and sync record heads 3 Burst amplitude A means shall be used to increase the burst amplitude of the signal to be recorded by 6.0 dB f 0.1 dB with respect to the video and sync portion of the composite video waveform. Phase of the burs
5、t shall be main- tained to within f 1“. 4 Preemphasis 4.1 Preemphasis is defined by the frequency and phase characteristics of a network such as Page 1 of 2 pages are shown in figure 1. Accuracy of the preempha- sis time constants shall be maintained by includ- ing source and load impedances (not sh
6、own) in calculation of circuit values. 4.2 Time-constant values specifying the preem- phasic networks are: Time constant tl = 240 ns Time constant t2 = 600 ns L tl = - Ri+ R L VIDEO IN t= R Vout jwti+ 1 ti - - Vin - joti+ 1 tz Figure 1 - Frequency and phase characteristics 5 Recorded carrier frequen
7、cies Carrier frequencies corresponding to reference video levels shall be: Peak-white Blanking 10.00 MHz f 0.05 MHz 7.90 MHz f 0.05 MHz Sync-tip 7.06 MHz nom 6 Record head current 6.1 Amplitude of the record current s,all ,e such that a maximum tape-flux level is produced when Copyright C 1991 by th
8、e SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartxiale Ave., White Plains, NY 10607 (914) 761-1100 Approved June 5,1990 SUPTE RP*8b 91 O 8357403 0000584 T5 lW RP 86-1 991 recording a signal with 50% average picture level. 6.2 The amplitude versus frequency characteris- tic of the curr
9、ent applied to the record head windings shall decrease with increasing fre- Annex A (informative) Bibliography ANSVSMPTE 18M-1991, Television Analog Recording - 1-in Type C - Basic System and Transport Geometry Parameters quency. The recorded tape-flux frequency char- acteristic shall be equivalent to recording a con- stant current versus frequency sine wave modified by one time-constant low-pass filter with a 6-MHz, 3-dB bandwidth driving a head with pole tips made of ferrite material. Q Page 2 of 2 pages
