1、-STD.SMPTE RP 85-ENGL 1999 9 8357401 OU113721 Ln.7 SMPTE RECOMMENDED PRACTICE RP 85-1999 Revision of RP 85-1991 Tracking-Control Record for i-in Type C Helical-Scan Television Tape Recording 1 Scope This practice specifies the characteristics of the track- ingcontrol record and the relationship betw
2、een the recorded video and trackingcontrol signal for 1 -in type C helical-scan television tape recorders operat- ing on 525/60 monochrome or NTSC color systems. 2 Tracking-control record 2.1 The tracking-control record consists of a series of constant flux levels alternating in polar- ity at a fiel
3、d rate as shown in figure 1. An extra pair of transitions is added to alternate frames. 2.2 The polarity of the tracking-control record flux shall be such that the south poles of mag- netic domains point in the direction of tape travel during the vertical interval identifying fields I and III, and t
4、he north poles of the magnetic domains point in the direction of tape travel during the FRAME A (EVEN) Page 1 of 2 pages vertical interval identifying fields II and IV. Therefore, the north-to-south transition which occurs during fields II and IV will be adjacent south magnetic poles, that is, the t
5、ransition area will attract the south-seeking pole of a bar mag- netic. 2.3 The amplitude of the tracking control re- corded flux shall be at least 30 dB above the residual flux of any previous recording. 2.4 The 10%-to-90% rise time of record current required to produce the specified flux level cha
6、nges shall be 0.015 ms f 0.010 ms. 2.5 The width of the record-current pulses for the extra pair of transitions on alternate frames shall be 0.20 ms f 0.03 ms or 0.40 ms k 0.06 ms for the N-S-N transitions. Signal timing shall be measured at the zero-crossing points of record head current. FRAME B (
7、ODD) I FIELD 11 I FIELD III VIDEO SIGNAL I N 8.34+0.8 MS 262.5 fO.OlH 8.34fOBMS CONTROL SIGNAL S N S II Figure 1 - Tracking control waveform and timing Copyright O 1999 by the SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartcdale Ave., White Plains, NY 10607 (914)761-1100 Approved Nove
8、mber 5,1999 RP 85-1999 STD-SMPTE RP 135-ENGL 3 Tracking control and video timing 3.1 Recording current transitions representing video fields shall occur 8.34 ms f 0.80 ms after the negative-going transition of the third broad pulse, as shown in figure 1. The south-to-north transition shall occur in
9、fields I and II, identified as the fields which end with a half line of video information. 3.2 Alternate frames shall be identified by an extra pair of transitions of recorded flux occur- ring at the south-to-north transition of every other frame, as shown in figure 1. 3.3 It -is possible to use the
10、 alternate-frame identification to specify odd and even frames, as designated by EIA Industrial Electronics Tenta- tive Standard No. 1. When not limited by other system requirements, the alternate-f rame identi- fication shall represent frame A (even). Since not all video signals meet the EIA standa
11、rd and certain types of edits may prohibit compliance with the specified frame identification, the repro- duce system must be able to use or ignore the alternate-frame information as directed by the operator. Annex A (informative) Bibliograph y ANCIISMPTE 18M-1996, Television Analog Recording - 1 -in Typa C - Basic System and Transport Geometry Pa- rarneters EIA Industrial Electronics Tentative Standard No. 1, Color Television Studio Picture Line Amplifier Output Drawing Page 2 of 2 pages
