1、-STD*SMPTE RP 144-ENGL 1777 8357403 000374L TT5 = SMPTE RECOMMENDED PRACTICE Basic System and Transport Geometry Parameters for U2-h Type L Format RP 144-1 999 Revision of RP 144-1995 1 Scope This practice specifies the tape speed, scanner parameters, tape tension, and test conditions for achieving
2、the record dimensions specified in ANSVSMPTE 229M. The parameters are for refer- ence purposes only and should not be interpreted as the only method available to attain the specifications in ANSIKMPTE 230M. 2 Definitions 2.1 basic dimension: A fundamental dimension to which no tolerance is applicabl
3、e. 2.2 center span tension: A calculated value of the tape tension at a point midway between the tape entrance and exit guides of the scanner in a video tape recording system. 2.3 drum: A cylindrical column around which the tape is at least partially wrapped in order to form the head-to-tape interfa
4、ce of a video tape recording system. 2.4 effectivedrumdiameter: A value of drum diameter which, when used in theoretical calcu- lations, will correspond to the actual video recording produced. The effective value is equal to or greater than the actual drum diameter. 2.5 helix angle: The angle formed
5、 between the path of the rotating pole tips and the tape refer- ence edge-guiding system. 2.6 lead signal overlap: That p o rt i o n of the helical record which is required to provide a duplicate (overlap) recording. Page 1 of 3 pages 2.7 lowerdrum: The part of the drum which contacts the reference
6、edge of the tape and provides tape guiding. 2.8 scanner: A mechanical assembly containing a drum, rotating pole tips, and tape-guiding elements used to record and reproduce video tape recordings (see figure 1A). 2.9 trackangle: The angle of the video record with respect to the reference edge of the
7、tape. 2.10 upperdrum: That part of the drum which does not contact the reference edge of the tape (see figure 1B). 2.11 wrap angle: The angle at the center of the drum rotation subtended by the lines of contact between the drum and the reference edge of the tape. 3 General specifications 3.1 Dimensi
8、ons in this practice are given in the metric system. 3.2 Tests and measurements conducted on the recorder to measure the parameters specified in this practice should be conducted under the fol- lowing conditions: Temperature for drum diameter 20C k 0.5“C Temperature for all other tests 20C f 1 .O“C
9、Relative humidity (50 f 2)% Barometric pressure 86 kPa to 106 kPa Conditioning time before testing 24 hours 4 Tapespeed The tape speed shall be 11 8.582 mds, basic. Copyright O 1999 by he SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartcdale Ave., White Plains, NY 10607 (914) 761-1100
10、Approved November 5,1999 ,6,.(REFERENCE) CH 1 LUMINANCE p/ CH 1 CHROMINANCE FiGURE 1A TOP VIEW TAPE EXIT TAPE ENTRANCE DIRECTKN OF TAPE MOTION AND UPPER DRUM ROTATION I 74.4SrnA P-p74.4(n FiGURE 16 DRUM SHOWING TAPE WRAP SIM VIMI 0.0775 -. .- (C“W USTANCE) Figure 1 - Chrominance and luminance pole t
11、ips 5 Representative scanner parameters 5.1 2 Actual lower drum diameter 5.1 Drum diameter and structure The actual lower drum diameter shall be 74.487 mm + 0.000 mm - 0.008 mm. The effective drum diameter, tape tension, helix angle, and tape speed taken together completely determine the track angle
12、. Different methods of design andlor minor variations in drum diameter and tape tension ,ill produce recordings for interchange purposes. video head tips. 5-1.3 “Wer drum section The upper drum section shall rotate together with the 5.1.1 Actual upper drum diameter The actual upper drum diameter sha
13、ll be 74.487 mm + 0.008 rnm - O.Oo0 rnm. 5.1.4 Center span tension The center span tension shall be 0.46 N f 0.05 N. Page 2 of 3 pages STD-SMPTE RP LiV-ENGL 1999 H 8357403 0003943 878 RP144-1999 5.1.5 Helix angle The helix angle formed by the scanner and all asso- ciated tape guides shall be 4.6 I0.
14、003“. 5.2 Scanner pole tips Four circumferential pole tips shall be located as shown in figure 1. 5.2.1 Pole tip projection Each pole tip shall project radially 0.040 mm + 0.010 mm - 0.025 mm above the outer surface of the upper drum. 5.2.2 Luminance pole tips Two pole tips circumferentially spaced
15、at 180“ k 0.003“ shall be produced for recording the luminance signal. 5.2.3 Chrominance pole tips Each luminance pole tip shall have an associated pole tip for recording the time-associated chrominance signal, and when applicable, the AFM audio signals. Chrominance pole tips shall be located at a c
16、hordal distance of 4.396 mm k 0.010 mm in a counter- rotational direction from the associated luminance pole tips, and are axially displaced from the associ- ated luminance pole tips by 0.0745 lr 0.0030 mm in a direction away from the reference edge of the tape. (See figure 1 B.) 5.2.4 Channel ident
17、ification Suitable means, such as a pulse generator producing one pulse per drum revolution, shall be provided to permit identification of the luminancekhrominance- recording pole-tip pair which records field 1. This pair is identified as channel 1 and the remaining pair as channel 2. Annex A (infor
18、mative) Bibliography ANSIISMPTE 229M-1996, Television Analog Recording - 1/2-in Type L - Records ANSIISMPTE 230M-1996, Television Analog Recording - 1/2-in Type L - Electrical Parameters, Control Code and Tracking Control SMPTE 238M-1998, Television Analog Recording - 112411 Type L - Tapes and Cassettes Page 3 of 3 pages
