1、 STD-SMPTE 2LM-ENGL 3777 13357903 0002907 99T SMPTE STANDARD ANSIEMPTE 21 M-1997 Revision of ANCIISMPTE 21M-1986 for Video Recording - 3/4-in Type E Helical Scan - Records 1 Scope This standard specifies the location of the edges of the video, audio, and trackingcontrol records and the mechanical se
2、paration of the simultaneously recorded information of the video and audio records, as recorded on a 31441-1 type E helical-scan video tape recording cassette system, operating at a tape speed of 95.3 mm/s (3.752 n/s.). Page 1 of 6 pages to the reference edge and passing through the trailing edge of
3、 the video track at its highest point (trailing edge at the end of the video track). 2.7 upstream: Pertaining to locations on the tape longitudinally displaced from a given ref- erence point in the direction opposite tape travel. 2 Definitions 2.1 downstream: Pertaining to locations on the tape long
4、itudinally displaced from a given refer- ence point in the direction of tape travel. 2.2 longitudinal: Pertaining to dimensions parallel to the direction of tape travel. 3 General specifications 3.1 Dimensions Metric dimensions are primary. 3.2 Measurement conditions 2.3 reference edge: The lower ed
5、ge of the magnetic tape nearest the reference plane of the cassette. 2.4 trailing edge of video track: The u p s t re a m edge of the video track. 2.5 transverse: Pertaining to dimensions perpendicular to the direction of tape travel. Thedimensionsshall bemeasuredwith notransverse Or longitudinal te
6、nsion applied to the tape. 3.3 Measurement environment The temperature shall be 23C I1“C (73F f 2F) with a relative humidity of (50 k 2)%. 3.4 Magnetic coating 2.6 transverse reference line: An imaginary line on the magnetically recorded tape perpendicular With the direction of tape travel as shown
7、in figure 1, the magnetic coating is on the surface facing the observer. The users attention is called to the possibility that compliance with this standard may require use of an invention covered by patent rights. willingness to grant a license under these rights on reasonable and nondiscriminatory
8、 terms and conditions to applicants desiring to obtain such a license. Details may be obtained from the publisher. By publication of this standard, no position is taken with respect to the validity of this claim or of any patent rights in connection therewith. The patent holder has, however, filed a
9、 statement of No representation or warranty is made or implied that this is the only license that may be required to avoid infringement in the use of this standard. CAUTION NOTICE This Standard may be revised or withdrawn at any time The procedures of the Standard Developer require that action be ta
10、ken io 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 the Standard Developer Printed in USA Copyright O 1997 by THE SOCIETY OF L American National Standar
11、d MOTION PICTURE ANDTELEVISION ENGINEERS 595 W Harisdale Ave Wlite Plains, NY 10607 (914) 761-1100 Approved October 2, 1997 STD-SMPTE 21M-ENGL 1977 W 8357401 0002908 88b ANCIISMPTE 21 M-I997 I Y AY- -$: fl -7-1 L e as n a I aa u) z aa u) E Q, .- .- ci o U aa S m E E 2 ic u) .- 8 E u) E z W S m c O .
12、- ci E S UJ G C O o x o 2 r Page 2 of 6 pages - STD-SMPTE ZLM-ENGL 1797 D 8357403 0002909 712 ANSIISMPTE 21 M-I 997 3.5 Tape speed 3.7 Video head drum diameter The tape speed shall be 95.3 mm/sI 0.2 mm/s (3.752 ink 1: 0.008 ink). The video head drum diameter shall be 110.00 mm $r 0.01 mm (4.3307 in
13、1: 0.0004 in). 3.6 Video writing speed 4 Dimensions The video writing speed shall be 10.26 m/s (404 ink). The transverse and longitudinal dimensions shall be as specified in figure 1 and table I. Table 1 - Recorded magnetic tape records Dimensions Millimeters Inches A AI B BI B2 C CI D E EI F G H Hi
14、 J K L M Pl PI S V W o Audio No. I width Audio No. 1 reference Audio No. 2 width Audio No. 2 reference Audio track total width Video area lower limit Video effective area lower limit Video area upper limit Control track width Control track reference Tape width Video track center from reference edge
15、Audio guard band to tape edge Audio-to-audio guard band Audio-to-video guard band Video track pitch (calculated) Audio and control head position from Video track width Address track width Address track lower limit Video guard band width Video width Video effective width Video track angle, moving tap
16、e stationary tape end of 180“ scan 0.80 f 0.05 0.0315 f 0.0020 1 .o0 nom 0.0394 nom 0.80 f 0.05 0.0315 f 0.0020 2.50 nom 0.0984 nom 2.30 f 0.08 0.0906 f 0.0031 2.70 min 0.1063 min 3.05 min 0.1201 min 8 20 max 0.7165 max 0.60 nom 0.0236 nom + 0.28 840 - 0.18 19.00 f 0.03 10.45 i 0.05 0.2 tr 0.1 0.7 n
17、om 0.2 nom 0.137 nom 74.0 f 0.5 0.085 f 0.007 0.50 f 0.05 2.90 f 0.15 0.052 nom 15.5 nom 14.80 f 0.01 4“ 57 33.2“ 4“ 54 49.1“ 0.7480 f 0.0012 0.4114 I 0.0020 0.008 0.004 0.028 nom 0.008 nom 0.00539 nom 2.913 0.020 0.00335 f 0.00028 0.0197 f 0.0020 0.1142 I 0.0059 0.00205 nom 0.610 nom 0.5827 5 0.000
18、4 See clause 7.2 Page 3 of 6 pages ANSIISMPTE 21 M-1997 5 Audio- and control-head position The distance (L) on the tape pattern from the end of the 180“ scan of a video head (So) to the audio and control head position is 74.0 mm k 0.5 mrn (2.913 in I 0.020 in), as shown in figure I. 6 Audio record d
19、isplacement Program audio or other information which is time coincident with video information recorded at a point, So, of any vide track shall be recorded on audio No. 2 at a distance, L, downstream from that point (So). (See figure 2.) 7 Video head switching 7.1 The switching position between the
20、two heads during playback shall lie between the 5th and 8th horizontal lines before the leading edge of the vertical sync signal, as shown in figure 2. 7.2 When the address track (dimension P) is used, the video head switching position ahead of the vertical sync signal shall be between 0.5 and 3 hor
21、izontal lines (see figure 2). 7.3 The rf output of both video heads shall extend past the switching point by approximately 3 horizontal lines to provide approximately 6 horizontal lines of overlap. I_ 5-BH -1 (See Sec. 7.2) Playback r-f rnvokp. Vertical 8ynC Miniinum ovkp (See 7.3) Figure 2 -Switchi
22、ng position of two video heads Page 4 of 6 pages STD-SMPTE 2LM-ENGL 1777 8357401, 0002711 370 = ANSIISMPTE 21 M-I 997 8 Tape back-tension The tape back-tension in the record mode shall be 0.60 N to 0.80 N (61 gf to 82 gf) when measured at the entrance of the drum, as shown in figure 3. A full-supply
23、 cassette (60 minutes) shall be inserted in the recorder and the tape threaded past the entrance guide post. Tension shall be measured with a suitable spring balance as the tape is pulled off the reel at r-ormal tape speed. The t-ominal ratio of tension between the maximum tape pack diameter of 118
24、mm (4.64 in) and the minimum tape Pack dkneter of 38 rnm (1 .SO in) on a 60-minute cassette shall be 3:1. Figure 3 -Tape path and guidance Page 5 of 6 pages STD-SMPTE 23M-ENGL 1997 D 8357LiOL 0002732 207 ANSIISMPTE 21M-1997 Annex A (informative) Bibliography ANSIISMPTE 22M-1997, Video Recording - 3/4-in Type E Helical Scan - Cassette for 3/4-in Type E Helical-Scan Television Tape Cassette Record in g SMPTE RP 87-1 995, Reference Carrier Frequencies, Preemphasis Characteristic and Audio and Control Signals Page 6 of 6 pages
