1、 Copyright 2015 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 3 Barker Avenue, White Plains, NY 10601 (914) 761-1100 Approved February 24, 2015 Table of Contents Page Foreword . 2 Intellectual Property 2 1 Scope . 3 2 Conformance Notation . 3 3 Normative Reference . 3 4 Recorded Characte
2、ristic. 4 5 Tolerances . 4 Page 1 of 5 pages SMPTE ST 217:2015 Revision of SMPTE 217-1998 SMPTE STANDARD Motion-Picture Film (70-mm) Striped Release Prints Recorded Characteristics of Magnetic Audio Records SMPTE ST 217:2015 Page 2 of 5 pages Foreword SMPTE (the Society of Motion Picture and Televis
3、ion Engineers) is an internationally-recognized standards developing organization. Headquartered and incorporated in the United States of America, SMPTE has members in over 80 countries on six continents. SMPTEs Engineering Documents, including Standards, Recommended Practices, and Engineering Guide
4、lines, are prepared by SMPTEs Technology Committees. Participation in these Committees is open to all with a bona fide interest in their work. SMPTE cooperates closely with other standards-developing organizations, including ISO, IEC and ITU. SMPTE Engineering Documents are drafted in accordance wit
5、h the rules given in its Standards Operations Manual. SMPTE ST 217 was prepared by Technology Committee 20F. Intellectual Property At the time of publication no notice had been received by SMPTE claiming patent rights essential to the implementation of this Engineering Document. However, attention i
6、s drawn to the possibility that some of the elements of this document may be the subject of patent rights. SMPTE shall not be held responsible for identifying any or all such patent rights. SMPTE ST 217:2015 Page 3 of 5 pages 1 Scope This standard specifies the recorded characteristic of magnetic au
7、dio records on 70-mm striped motion-picture release prints, when reproduced at 120 perforations per second (approximately 112 ft 34 m per minute or 22.4 in 569 mm per second) which is 24 frames (5 perforations) per second. 2 Conformance Notation Normative text is text that describes elements of the
8、design that are indispensable or contains the conformance language keywords: “shall“, “should“, or “may“. Informative text is text that is potentially helpful to the user, but not indispensable, and can be removed, changed, or added editorially without affecting interoperability. Informative text do
9、es not contain any conformance keywords. All text in this document is, by default, normative, except: the Introduction, any section explicitly labeled as “Informative“ or individual paragraphs that start with “Note:” The keywords “shall“ and “shall not“ indicate requirements strictly to be followed
10、in order to conform to the document and from which no deviation is permitted. The keywords, “should“ and “should not“ indicate that, among several possibilities, one is recommended as particularly suitable, without mentioning or excluding others; or that a certain course of action is preferred but n
11、ot necessarily required; or that (in the negative form) a certain possibility or course of action is deprecated but not prohibited. The keywords “may“ and “need not“ indicate courses of action permissible within the limits of the document. The keyword “reserved” indicates a provision that is not def
12、ined at this time, shall not be used, and may be defined in the future. The keyword “forbidden” indicates “reserved” and in addition indicates that the provision will never be defined in the future. A conformant implementation according to this document is one that includes all mandatory provisions
13、(“shall“) and, if implemented, all recommended provisions (“should“) as described. A conformant implementation need not implement optional provisions (“may“) and need not implement them as described. Unless otherwise specified, the order of precedence of the types of normative information in this do
14、cument shall be as follows: Normative prose shall be the authoritative definition; Tables shall be next; followed by formal languages; then figures; and then any other language forms. 3 Normative Reference Note: All references in this document to other SMPTE documents use the current numbering style
15、 (e.g. SMPTE ST 221:2003) although, during a transitional phase, the document as published (printed or PDF) may bear an older designation (such as SMPTE 221-2003). Documents with the same root number (e.g. 221) and publication year (e.g. 2003) are functionally identical. The following standard conta
16、ins provisions that, through reference in this text, constitute provisions of this standard. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying
17、the most recent edition of the standard indicated below. SMPTE ST 221:2003, Motion-Picture Film (70-mm) Six-Track Audio Release Prints Magnetic Striping SMPTE ST 217:2015 Page 4 of 5 pages 4 Recorded Characteristic With a constant-amplitude sine-wave signal applied to the input of the recording syst
18、em, the relative characteristic in effective values of the short circuit magnetic flux versus frequency shall decrease with increasing frequency proportionately to the impedance of a parallel combination of a capacitance and a resistance having time constants of 35 and 3180 s (see note 1). The chara
19、cteristic defined above is obtained by the following equation: where L is the recorded relative short circuit magnetic flux level in decibels, f is the frequency in hertz for which L is computed, | is the low-frequency time constant of 3180 s, h is the high-frequency time constant of 35 s, and C0 is
20、 a constant with a value of 0.19424 calculated to make L = 0 at the reference frequency of 1000 Hz. The approximate numerical values are given in the table (see Note 2). Frequency, Hz f Relative Level L 31.5 40 50 80 100 160 400 1000 2500 4000 6300 8000 10 000 12 500 16 000 + 5.66 + 4.29 + 3.21 + 1.
21、63 + 1.16 + 0.59 + 0.23 0.00 0.95 2.29 4.46 5.93 7.47 9.13 11.07 5 Tolerances Magnetic audio records on the film shall be recorded to the characteristic specified in clause 2 within the tolerances given in Figure 1. Notes: 1 A time constant is a shorthand notation, such as illustrated by a frequency
22、 response curve, having a shape which results from a time constant of one or more microseconds. This is a convenient way of defining a response curve and is not intended as a recommended electrical circuit. 2 The corresponding reproducing characteristic is that which gives a flat response. SMPTE ST
23、217:2015 Page 5 of 5 pages 3 It can be shown that a low-frequency time constant of infinity would ideally be used for best headroom versus frequency of the medium. However, some theatre equipment in the field is incapable of meeting the tolerances when using a time constant of infinity. As a result, a low-frequency pre-emphasis of 3180 s was adopted as an essential compromise. In addition, some older prints exist which were recorded with a 1590 s time constant. Figure 1 Tolerances on recorded levels
