1、SMPTE RP*2 95 I 8357401 0003836 972 RP 92-1995 SMPTE RECOMMENDED PRACTICE Revision of RP 92-1950 SDecifications for Audio Level and Multifrequency Test Films for 8-mm Type S Audio Reproducers, Magnetic Type 1 Scope This practice specifies two audio frequency test films to be used for adjusting the s
2、ensitivity and frequency response of 8-mm type S motion-picture magnetic audio reproducers; one operating at 24 and the other at 18 frames per second. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this practice. At t
3、he time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent edition of the standards indicated below. ANSI 54.3-1982 (R1992), Method for Me
4、asurement of Weighted Peak Flutter of Sound Recording and Reproducing Equipment. ANSVIEEE 152-1 992, Audio Program Level Measure m en ts ANSVSMPTE 149-1 994, Motion-Picture Film (8-mm Type S) - Perforated 1 R ANSI/SMPTE 164-1 993, Motion-Picture Film (8-mm Type S) - Magnetic Audio Record - Position,
5、 Dimensions and Reproducing Speed ANSWMPTE 223M-1991, Motion-Picture Film - Safety Film Page 1 of 4 pages 3 Test film signal 3.1 Frequencies 3.1.1 Type 24 film The audio record on the type 24 film shall be an original recording which will reproduce at the frequen- cies specified in clause 4 when the
6、 linear velocity of the film is 24 frames per second or approximately 20 ft (6.1 m) per minute (4 in or 10.2 cm per second). 3.1.2 Type 18 film The audio record on the type 18 film shall be an original recording which will reproduce at the frequen- cies specified in clause 4 when the linear velocity
7、 of the film is 18 frames per second or approximately 15 ft (4.6 m) per minute (3 in or 7.6 cm per second). 3.2 Distortion The total harmonic distortion of the recorder signals shall not exceed 1%. 3.3 Audio record The location and dimensions of the recorded audio record shall be in accordance with
8、ANSI/SMPTE 164. 3.4 Signal fluctuation The signal levels shall not fluctuate more than -c 0.5 dB within the test section lengths. 3.5 Flutter The weighted peak flutter of the audio record shall not exceed 2 0.1 0% when measured in accordance with ANSI S4.3. Copyright O 1995 by the SOCIETY OF MOTION
9、PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Ave., White Plains, NY 10607 (914) 761-1100 _ Approved January 31, 1995 SUPTE RP*92 95 M 8357403 O001837 809 RP 92-1995 3.6 Azimuth Tle azimuth of the audio record shall be 90“ 2 5 to the reference edge of the film. 3.7 Signal identification East tes
10、t section and segment shall be preceded by voice announcements identifying the content. Voice announcements shall be recorded at a level approxi- mately 1 O dB below program level (see 4.4). 4 Test sections 4.1 Azimuth section 4.1.1 Frequency Afrequency of 5000 Hz for type 18 film or 6300 Hz fol typ
11、e 24 film 2 2% shall be recorded ahead of all other tones on the film. 4.1.2 Recorded level The azimuth frequency shall be a recording having an rms short circuit flux per unit track width of 19.85 nWb/m for type 18 or 16.08 nWb/m for type 24. 4.1.3 Duration The minimum duration of this section shal
12、l be 30 s. 4.1.4 Purpose The purpose of this section is to confirm reproduce head azimuth before response check. 4.2.4 Purpose The purpose of this section is to establish a compara- tive reference level for the following frequency re- sponse section. 4.3 Frequency response section 4.3.1 Frequencies
13、The following test segment frequencies in hertz 2 2% shall be recorded in the order given: 5000 for type 18 or 6300 for type 24 azimuth / 400 reference level / 7500 for type 18 or 1 O O00 and 8000 for type 24 / 6300 / 5000 / 31 50 / 2000 / 1 O00 / 500 / 31 5 / 200 / 1 O0 / 50 / 400 program level 4.3
14、2 Recorded levels The values in table 1 may be expressed as a curve that is the composite of a) the inverse of the voltage attenuation of a single resistance-capacitance high- pass filter having a time constant, TI, and b) the voltage attenuation of a single resistance-capacitance low-pass filter h
15、aving a time constant, z2. The ordi- nates of this curve, expressed in decibels, are where o = 2,f, f = frequency in hertz, TI = 3180 ps, and t2 = 90 ps. 4.2 Reference frequency section 4.3.3 Flux level variation 4.2.1 Frequency A frequency of 400 Hz 2 2% shall be recorded ahead of the frequency res
16、ponse section. 4.2.2 Recorded level The reference frequency shall be a recording having an rms short circuit flux per tinit track width of 58.50 nWb/m I 1 O nWb/m (1 O dB below program level). 4.2.3 Duration The minimum duration of this section shall be 30 s. The film flux level at each frequency in
17、 respect to the value specified in 4.3.2 shall be as follows: Type 24 film 50 to 100 Hz t1 -2dB 200 to 5000 Hz 2 1 dB 6300 to 10 O00 HZ i 1 -2 dB Tbpe 18 film 50 to 100 HZ + 1 -2 dB 200 to 3150 Hz 11 dB 5000 to 7500 Hz +1 -2dB Page 2 of 4 pages SMPTE RP*2 95 8357403 0001838 745 Ip 4.3.4 Duration The
18、 duration of frequency response test segments shall be approximately 1 O s. Table 1 - Flur level versus frequency Frequency (Hz) - 6300 azimuth (type 24 only) 5000 azimuth (type 18 only) 400 reference levei IO O00 (type 24 only) 8000 (type 24 only) 7500 (type 18 only) 6300 5000 31 50 2000 1 O00 500
19、31 5 200 1 O0 50 I i 400 program level i Short circuit flux (nWb/m) 16.08 19.85 58.50 10.37 12.85 13.65 16.08 19.85 29.14 39.44 51.87 57.56 59.33 60.96 66.45 84.18 185.00 -1 1.22 9.39 O 5.03 3.17 2.64 -1 1.22 - 9.39 - 6.05 - 3.43 - 1.04 - 0.14 + 0.12 + 0.36 + 1.11 + 3.16 +10.00 4.4 Program level sec
20、tion 4.4.1 Frequency A frequency of 400 Hz t 2% shall be recorded after the frequency response section. 4.4.2 Recorded level The program level frequency shall be a recording having an rms short circuit flux per unit track width of 185 nWb/m $. 1 O nWb/m. RP 92-1995 4.4.3 Duration The minimum duratio
21、n of this section shall be 30 s. 4.4.4 Purpose The purpose of this section is to verify and reestablish the program level after the possible preceding adjust- ments. 5 Film stock 5.1 The film stock shall be full-coat, splice-free, of the low-shrinkage, safety type in compliance with ANSVSMPTE 223, a
22、nd cut and perforated in accordance with ANSI/SMPTE 149. 5.2 The film stock shall be conditioned for 10 days at 20C 2 3C (68F 2 5.4“F) at a relative humidity of 50% 2 10% prior to recording. 5.3 The film shall be recorded and packaged within the temperature and humidity limits speci- fied in 5.2. Th
23、e recorded film shall be packaged in a metal can and sealed either with a low-mois- ture permeability plastic tape or a fabric tape having a moisture barrier. 6 Identification Each test film shall be suitably identified. 7 Calibration 7.1 Flux The short circuit flux on the test film shall be deter-
24、mined by means of the calibrated short-gap ferromag- netic core reproducer technique. The technique is described in ANSI 54.6. 7.2 Level fluctuation The signal level measurements specified in 3.4 shall be measured with a standard volume indicator con- forming to ANSMEEE 152. NOTE - Test films made i
25、n accordance with this practice are available from the Society of Motion Picture and Televi- sion Engineers. Page 3 of 4 pages SMPTE RP*72 75 U 8357403 0003839 bBL RP 92-1 995 Annex A (informative) Bib1 iography ANSI S4.6-1982 (R1992), Method of Measuring Recorded Flux of Magnetic Sound Records at Medium Wavelengths Page 4 of 4 pages
