1、 1 Scope 1.1 This practice specifies a type U audio frequency test film to be used for adjusting the mechanical and electrical parameters of 35-mm motion-picture magnetic audio reproducers intended for striped release prints perforated CS, operating at 24 frames (96 perforations) per second (approxi
2、mately 90 ft 27 m per minute 18 in or 457 mm per second) for proper playback. 1.2 The International Organization for Standardization recognizes two reference levels for test films: Type U with a reference level of 185 nWb/m and type E with a reference level of 320 nWb/m, in order to account for diff
3、ering meter types in common use in the United States and Europe. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this practice. At the time of publication, the editions indicated were valid. All standards are subject t
4、o revision, and parties to agreements based on this practice are encouraged to investigate the possibility of applying the most recent edition of the standards indicated below. ANSI S4.3-1982 (R1992), Method for Measurement of Weighted Peak Flutter of Sound Recording and Reproducing Equipment ANSI S
5、4.6-1984 (R1992), Method of Measuring Recorded Flux of Magnetic Sound Records at Medium Wavelengths ANSI/IEEE 152-1992, Audio Program Level Measurement Approved November 5, 1999 ANSI/SMPTE 177-1995, Motion-Picture Film (35-mm) Four-Track Magnetic Audio Release Prints Magnetic Striping SMPTE 102-2002
6、, Motion-Picture Film (35-mm) Perforated CS-1870 SMPTE 137-2000, Motion-Picture Film (35-mm) Release Prints Four Magnetic Audio Records 3 Manufacturing 3.1 Film stock Test films made to this practice shall be cut and perforated in accordance with SMPTE 102. Page 1 of 5 pages RP 143-2004 Revision of
7、RP 143-1999 Copyright 2004 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Ave., White Plains, NY 10607 (914) 761-1100 Approved November 8, 2004 SMPTE RECOMMENDED PRACTICE Specifications for Type U Audio Level and Multifrequency Test Film for 35-mm Striped Four-Track Relea
8、se Print Audio Reproducers, Magnetic Type RP 143-2004 Page 2 of 5 pages 3.2 Magnetic coating 3.2.1 Full-coat film For full-coat film, the coating shall extend from edge to edge of the film. The coating shall be on the same side as the striping specified in 3.2.2. 3.2.2 Stripe-coat film For stripe-co
9、at film, the striping shall be in accordance with ANSI/SMPTE 177. 3.2.3 Magnetic particle orientation The film may show a preferred direction for recording due to orientation of the magnetic particles within the coating during manufacture. The preferred direction is the direction which shows the gre
10、atest high-frequency sensitivity. If there is such a preferred direction, it shall be marked by means of an arrow faced in the preferred direction on the head and tail of the film. 3.3 Primary characteristics of test film records 3.3.1 Audio record 3.3.1.1 Full-coat film If the audio record is recor
11、ded on full-coat film, the recording shall extend from one edge of the film to the other. 3.3.1.2 Striped-coat film If the audio record is recorded on striped-coat film, it shall be recorded with individual head elements in accordance with SMPTE 137. The polarity of each head element shall be identi
12、cal with all the other elements, and the gaps shall be in line. 3.3.2 Azimuth The azimuth of the audio records shall be 90 1 to the reference edge of the film. The reference edge is defined in ANSI/SMPTE 177. 3.3.3 Frequency response of the recorded flux With a constant amplitude vs frequency sine-w
13、ave signal applied to the input of the recording system, the relative characteristic of the recorded flux vs frequency decreases with increasing frequency corresponding to a combination of two curves: one falling with increasing frequency in conformity with the impedance of a series combination of a
14、 capacitance and a resistance having a time constant 1; and one falling with increasing frequency in conformity with the impedance of parallel combination of a capacitance and a resistance having a time constant 2(see annex A.4). This characteristic is given by the following equation: L= C0 10 log10
15、 + +221222f)211f21)(RP 143-2004 Page 3 of 5 pages where Lis the flux level in dB, f is the frequency in hertz for which Lis computed, 1is a time constant of 3180 s, 2is a time constant of 35 s, and C0is a constant with a value of 0.19424 calculated to make L= 0 at the reference frequency of 1000 Hz.
16、 The approximate numerical values are given in table 1 (see annex A.6). Table 1 Frequency response Frequency Level in dB 31.5 Hz 40 Hz 63 Hz 125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHz 6.3 kHz 8 kHz 10 kHz 12.5 kHz 14 kHz 16 kHz + 5.66 + 4.29 + 2.32 + 0.84 + 0.35 + 0.19 0 0.57 2.29 4.46 5.93 7.47 9.13 10
17、.01 11.07 3.3.4 Signal identification Each test section and segment shall be preceded by a voice announcement identifying the content at a level whose peak value does not exceed the peak value of the frequency series. 3.4 Test sections 3.4.1 Reference level A 1000 Hz 2% sine-wave tone shall be recor
18、ded at a flux level of 185 nWb/m 11 nWb/m ( 0.5 dB) for a duration of approximately 30 seconds. 3.4.2 Azimuth A 12.5 kHz 2% sine-wave tone shall be recorded at a relative flux level equal to the reference level with the frequency response specified in 3.3.3 applied for a duration of approximately 30
19、 seconds. 3.4.3 Pink noise Pink noise shall be recorded for a duration of approximately 30 seconds. The pink noise test signal shall be recorded at such a level that there is a low statistical probability of peaks exceeding the peak-to-peak amplitude of the reference level. This condition can be ver
20、ified by observing the pink noise signal on an oscilloscope connected to a playback preamplifier when compared with the peak-to-peak signal indicated by the reference level. The pink noise shall be recorded with the frequency response specified in 3.3.3. 3.4.4 Frequency response The 1000-Hz sine-wav
21、e tones for this section shall be recorded at the reference level (185 nWb/m 11 nWb/m absolute). The other sine-wave tones shall be recorded according to the frequency response specified RP 143-2004 Page 4 of 5 pages in 3.3.3 at the flux levels in table 1 with a tolerance on level according to 4.3.
22、The following test-segment tones shall be recorded for a duration of approximately 10 seconds at the given frequencies 2%: 1000, 31.5, 40, 63, 125, 500, 1000, 2000, 4000, 6300, 8000, 10 000, 12 500, 14 000, 16 000, 1000 4 Calibration and quality control 4.1 Flux level The reference level shall be de
23、termined by means of the calibrated short-gap ferromagnetic core reproducer technique described in ANSI S4.6. 4.2 Method The test film shall be calibrated for frequency response using a reproducing head with gap widths made in accordance with SMPTE 137. 4.3 Flux level variation with frequency The fi
24、lm flux level at each frequency from 31.5 Hz through 12.5 kHz shall be within 0.5 dB of the value specified in 3.3.3 when measured with an instrument specified in 4.8. (Flux level variation is defined for the purposes of this clause as the average reading within each tone segment since variation wit
25、h time is specified in 4.4.) 4.4 Flux level variation with time The flux levels shall not vary more than 0.5 dB within the length of each test segment when measured with a standard volume indicator conforming to ANSI/IEEE 152. 4.5 Pink noise The level in each one-third octave band from 31.5 Hz to 12
26、.5 kHz shall be the same within the limits given in 4.3. 4.6 Distortion The total harmonic distortion of the recorded reference level tone (3.4.1) and the frequency response tones (3.4.4) shall not exceed 0.5%. 4.7 Flutter The weighted peak flutter of the audio record shall not exceed 0.1%. Verifica
27、tion of this section shall be made with the film stock to be used for making these test films, and measured in accordance with ANSI S4.3. 4.8 Level measurements Level measurements shall be made with an average-responding, rms-calibrated or a true-rms ac voltmeter having a frequency response of 0.1 d
28、B over a minimum frequency range of 31.5 Hz to 16 kHz. RP 143-2004 Page 5 of 5 pages Annex A (informative) Additional data A.1 Test films specified by this practice could be made in many variations: triacetate or polyester base, full- or stripe-coating, and combinations thereof. Use of test material
29、 with substantial physical differences from other material to be run can lead to high-frequency errors. A.2 The difference in compliance between triacetate and polyester bases will establish different head wear patterns as film is run. A change from one base to the other may cause a temporary loss o
30、f high-frequency response until a new wear pattern is established. Therefore, it is recommended that users employ test films having the same film base as that used for the release prints to be run. A.3 SMPTE RP 45 specifies precautions on this subject. Methods of using this film are found in SMPTE E
31、G 13. A.4 The use of an electrical circuit analogy is provided as a useful means of notation only. Each specified RC circuit should be considered separately, without interaction, and the numerical effect added. A.5 Note that release prints are not supplied wound according to the convention in SMPTE
32、EG 12, so the test film is pulled from the supply reel of a conventional projector clockwise, rather than the more common release-print convention of counter-clockwise winding. A.6 This practice calls for 3180 s low-frequency equalization. Equalization with no low-frequency record boost (a time cons
33、tant of infinity) has been shown to better use the overload characteristic vs. frequency of the magnetic medium when recording typical program material. However, there is some theater equipment in the field which reproduces a flat response only when low-frequency record boost has been applied to rec
34、orded material. The use of the 3180 s time constant is seen as a transitional compromise between the best practice that can be obtained currently and the desired future practice with an infinity time constant. In addition, some older prints may exist which were recorded to a 1590 s time constant whi
35、ch must, on occasion, be accommodated. Annex B (informative) Bibliography SMPTE RP 45-1972 (R1987), Use and Care of Sound Test Films SMPTE EG 12-1994 (R1999), Control of Basic Parameters in the Manufacture of SMPTE Photographic and Magnetic Audio Test Films SMPTE EG 13-1986 (R2002), Use of Audio Magnetic Test Films
