1、SMPTE RECOMMENDED PRACTICE RP 128-2002 Revision of RP 128-1997 Specifications for Audio Level and Multifrequency Test Film for 70-mm Striped Six-Track Release Print Audio Reproducers, Magnetic Type Page 1 of 4 pages This practice specifies an audio frequency test film to be used for adjusting the se
2、nsitivity and frequency response of 70-mm striped six-track motion-picture magnetic audio reproducers intended for release prints operating at 120 perforations per second or approximately 11 2 ft (34 m) per minute. 2 Normative references The following standards contain provisions which, through refe
3、rence in this text, constitute provisions of this practice. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this practice are encouraged to investigate the possibility of applying the most recent edition of the
4、standards indicated below. AES 6-1982, Method for Measurement of Weighted Peak Flutter of Sound Recording and Reproducing Equipment AES 7-1982 (R1992), Method of Measuring Recorded Flux of Magnetic Sound Records at Medium Wavelengths ANSVSMPTE 185-1993, Motion-Picture Film (70-mm) - Six Magnetic Rec
5、ords on Release Prints - Position, Dimensions, Reproducing Speed and Identity SMPTE 11 9-1 999, Motion-Picture Film (70-mm) - Perforated 65-mn-1, KS-1870 SMPTE 223M-2001, Motion-Picture Film - Safety Film 3 Test film signal 3.1 Frequencies The audio record on the film shall be a recording which will
6、 reproduce at the frequencies specified in 6.4 when the linear speed of the film is 120 perforations per second or approximately 11 2 t (34 m) per minute (22.4 in 56.9 crn per second). 3.2 Distortion The total harmonic distortion of the recorded reference signal shall not exceed 0.2% (see 6.1). 3.3
7、Audio record The audio record shall be recorded in accordance with ANWSMPTE 185. Copyright O 2002 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdaie Ave., White Plains, NY 10607 (914) 761-1100 Approved July 26,2002 RP 128-2002 3.4 Signal fluctuations The signal levels shall n
8、ot fluctuate more than f 0.5 dB within each test section length. 3.5 Flutter The weighted peak flutter of the audio record shall not exceed f 0.04% when measured in accordance with AES 6. 3.6 Azimuth The azimuth of the audio records shall be 90“ f 3 to the reference edge of the film. 3.7 Signal iden
9、tification Each test section and segment shall be preceded by voice announcements identifying the content at a level whose peak value does not exceed the peak level of the frequency series. 4 Filmstock 4.1 The film stock shall be splice-free and of the low-shrinkage, safety type in compliance with S
10、MPTE 223M, and striped in accordance with ANSVSMPTE 185, unless full-coat stock is used. 4.1.1 Test films shall be made on a base cut and perforated in accordance with dimensions specified in SMPTE 11 9. Test materials made on acetate shall be clearly marked with a usage date. 4.2 The film stock sha
11、ll be conditioned for 10 days at 20C f 3C (68F f 5.4“F) at a relative humidity of (50 f lo)% prior to recording. 4.3 The film shall be recorded and packaged within the temperature and humidity limits specified in 4.2. The recorded film shall be packaged in a metal can and sealed either with a low-mo
12、isture permeability plastic tape or a fabric tape having a moisture barrier. 5 Identification Each test film shall be suitably identified to include the date of manufacture. 6 Test section 6.1 Reference level Asine wave with a frequency of 1000 Hzf2% shall be recorded ahead of the azimuth section, h
13、aving an absolute short circuit recorded level of 185 nWb/m f 10 nWb/m for a duration of approximately 30 seconds. 6.2 Azimuth A frequency of 16 kHz +- 2% shall be recorded ahead of the pink noise section having an absolute short circuit recorded level of 25.86 nWb/m f 10 nWb/m for a duration of app
14、roximately 30 seconds. 6.3 Pink noise The pink noise test signal used for this section shall have equal energy in equal logarithmic frequency intervals within the audio bandwidth. The lower limit shall correspond to the lower bandwidth of a 31.5 Hz-octave band filter of the ANSI class II type, and t
15、he upper limit to the upper bandwidth of a 16 kHz-octave band filter of the Page 2 of 4 pages RP 128-2002 ANSI class II type. (Test bandwidths must be within these limits). The level in each one-third octave band from 40 Hz to 12.5 kHz shall be the same within +- 1 dB. The pink noise signal shall be
16、 recorded so that there shall be a low statistical probability of the extreme peaks within the signal saturating the magnetic film. The peak level of the wide band pink noise spectrum shall be essentially equal to that of the corresponding frequency response test segments. The recorded pink noise sh
17、all have the characteristic specified in 6.5 and a duration of approximately 30 seconds. (The pink noise test may also be used for multitrack azimuth adjustment using an oscilloscope lissajous figure from the two outside prime tracks of multitrack equipment.) 6.4 Frequency response The 1000-Hz frequ
18、encies of this multifrequency section shall be recorded 6 dB below (92.50 nWb/m) the 185 nWb/m reference. The following test segment frequencies in hertz f 2% shall be sine waves recorded in the order given: 1000,31.5,40,63,125,250,500,1000,2000,4000,6300,8000,10 000,12 500,14 000,16 000,1000. 6.5 R
19、ecorded levels With a constant-amplitude sine-wave signal applied to the input of the recording system, 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 combinat
20、ion of a capacitance and a resistance having a time constant of z = 35 ps and 31 80 p. (A time constant is a shorthand notation, such as illustrated by a frequency response curve, having a shape which results from a time constant of one or more microseconds. This is a convenient way of defining a re
21、sponse curve and is never intended as a recommended electrical circuit.) The characteristic defined above is obtained by the following calculation: where La is the recorded relative short circuit magnetic flux level in decibels, f is-the frequency in hertz for which Lo is computed, TI is a time cons
22、tant of 31 80 ps, zh is a time constant of 35 ps, and Co is a constant with a value of 0.1 94 calculated to make Lo = O at the reference frequency of 1000 Hz. The approximate numerical values are given in table 1. 6.6 Flux level variation The film flux level at each frequency from 31.5 Hz through 16
23、 kHz shall be within k 0.5 dB of the value specified in 6.5. (See table 1 .) 6.7 Duration The duration of frequency response test segments shall be approximately 10 seconds, except for the 16-kHz tone which shall be approximately 30 seconds for azimuth and highifrequency equalization adjustments. Pa
24、ge 3 of 4 pages RP 12-2002 Table 1 - Flux levels versus frequency in nanowebers per meter and decibels Frequency, Hz f 1 O00 31.5 40 63 125 250 500 1 O00 2000 4000 6300 8000 10 O00 12 500 14 O00 16 O00 1 O00 Short circuit flux) nWb/m 92.50 177.68 133.86 120.82 1 01.89 96.30 94.55 92.50 86.62 71 .O6
25、55.35 46.73 39.1 4 32.33 29.22 25.86 92.50 Relative leve I*) LQ 0 + 5.67 + 4.29 + 2.32 + 0.84 + 0.35 + 0.19 0 - 0.57 - 2.29 - 4.46 - 5.93 - 7.47 - 9.13 -1 0.01 -1 1 .O7 0 )Calculated using the equation P = 92.50 x aniioglo (LQ/20). kalculated using the equation given in 6.5. 7 Calibration 7.1 Flux T
26、he short circuit flux on the test film shall be determined by means of the calibrated short-gap ferromagnetic core reproducer technique. This technique is described in AES 7. 7.2 Level The signal level specified in 3.4 shall be measured with an rms voltmeter calibrated in decibels with an accuracy o
27、f k 0.1 dB over the bandwidth 31.5 Hz to 16 kHz. 7.3 Method The test film shall be calibrated on a reproducing head made in accordance with ANSI/SMPTE 185. NOTE - It has been shown that a straight 35 ps curve should be used for maximum use of the magnetic medium. It is recognized, however, that it is necessary forthe immediate future to continueto add 31 80 ps because some theater equipment is unable to compensate for the low end. Page 4 of 4 pages
