1、 SMPTE EG*24 95 = 357401 0002107 692 EG 24-1995 SM PTE ENG IN EERI NG G U I DELI N E Revision of EG 24-1991 Video and Audio Alignment Tapes and Procedures for 1 -in Type C Helical- Scan Television Analog Recorders 1 Scope This guideline describes the use of a manufacturers alignment tape(s) intended
2、 for aligning type C televi- sion analog recorders to SMPTE specifications. 2 Normative references The following documents contain provisions which, through reference in this text, constitute provisions of this guideline. At the time of publication, the editions indicated were valid. All standards a
3、re subject to revision, and parties to agreements based on this guideline are encouraged to investigate the possibility of applying the most recent edition of the standards indicated below. ANSI S4.6-1982 (R1992), Method of Measuring Recorded Flux of Magnetic Sound Records at Medium Wavelengths ANSV
4、IEEE 152-1 992, Audio Program Level Measure- ment ANSVSMPTE 12M-1995, Television, Audio and Film - Time and Control Code ANSVSMPTE 19M-1991, Television Analog Record- ing - l-in Type C - Records ANSVSMPTE 20M-1991, Television Analog Record- ing - I-in Type C Recorders and Reproducers - Longitudinal
5、Audio Characteristics ANSVSMPTE 26M-1995, Video Recording - 1 -in Helical-Scan Recorders - Raw Stock for Reference Tapes EIA -1 89-A, Encoded Color Bar Signal Page 1 of 6 pages IEEE Std 205-1958 (R1972), Method of Measure- ment of Television Luminance Signal Levels NAB Standard for Magnetic Tape Rec
6、ording and Reproducing (Reel-to-Reel) SMPTE RP 85-1991 (R1995), Tracking-Control Record for 1 -in Type C Helical-Scan Television Tape Recording SMPTE RP 86-1991 (R1995), Video Record Para- meters for I-in Type C Helical-Scan Television Tape Recordi ng IEC Publication 94, Magnetic Tape Sound Recordin
7、g and Reproduction Systems: Dimensions and Char- acteristics ITU-R Report 624-4 (MOD F), Characteristics of Television Systems 3 General specifications 3.1 Recorder The recorder used to record this tape shall comply with ANSVSMPTE 19M. 3.2 Record dimensions The dimensions of pertinent records making
8、 up this tape shall conform to ANSVSMPTE 19M. 3.3 Tape stock The tape stock shall be as specified in ANSVSMPTE 26M. Copyright O 1995 by the SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Ave., White Plains, NY 10607 Approved October 17, 1995 (914) 761-1 100 SMPTE EG*E4 95 835740
9、3 0002308 529 = EO 24-1995 3.4 Tracking control signal 4.3 Audio signal specifications The tracking control signal shall conform to SMPTE RP 85, except that the tolerance specified in clause 3.1 shall be tightened to f 0.4 ms. 3.5 Time and control code The following specifies the various generic sig
10、nals which might be used on a tape. If signals other than these are used on a tape, the nature of the actual signals shall be carefully and fully defined. Time and control code, if provided, shall conform to 4.3.1 Recorded audio flux level ANSI/SMPTE 12M, and shall be recorded on audio 3 The recorde
11、d reference level shall conform to ANSI/SMPTE 20M, except that the short circuit flux recorded on the tape at each frequency shall be within record. The reference flux level for time and control code shall be as defined in ANSVSMPTE 20M. 4 Audio 4.1 General notes f 0.5 dB of the level specified. The
12、 tolerance, f 0.5 dB, may be extended to 12.0 di3 provided the manu- facturer supplies a calibration chart with the tape (see annex A). 4.1.1 Test equipment 4.3.2 Audio test calibration Properly calibrated test equipment including, but not limited to, an rms voltmeter as specified in ANSI/IEEE 152,
13、Or equivalent, is essential for the following tests. 4.1.2 Procedures All adjustments must be made with due attention to the machine manufacturers instructions. The calibration values in decibels furnished with the tape shall represent the levels to be added algebra- cally to the reproducer output l
14、evel when the particular tape is reproduced. With the addition of these values, the output level of the reproducer in decibels will be that which would have resulted if the short circuit flux on the tape at a given frequency had been exactly as specified in ANSVSMPTE 20M. 4.1.3 Audio calibration 4.3
15、.3 Audio flutter McKnight, J.G. Flux and flux-frequency response measurements and standardization in magnetic re- cording. Journal of the SMPTE. 78(6): 457-472; June 1969. Lovick, R. C.; Bartow, R. E.; and Scheg, R. F. Record- 4.3.4 Signals All recorded signals shall conform to ANSVSMPTE 20M unless
16、otherwise specified. ing and calibration of super-8 magnetic reproducer test films. Journal of the SMPTE. 78(6): 473-481 ; June 4.3.5 Reference level tone 1969. 4.2 Confidence heads The reference level tone shall be 1000 Hz f 2% recorded at the reference flux level. All audio adjustments should be m
17、ade to the confi- dence/monitor heads as well as the main recordplay heads to ensure maximum quality in all modes of operation. level. 4.3.6 Pink noise Pink noise, if recorded, shall be 10 dB below reference Page 2 of 6 pages SMPTE EG*(24 95 E 8357401 0002109 465 W 4.3.7 Frequency response The follo
18、wing signals, recorded 10 dB below refer- ence level, shall be contained in this section: 1 kHZ (reference), 63 Hz, 125 Hz, 250 Hz, 1 kHz, 2 kHz, 4 kHz, 8 kHz, 10 kHz, 12.5 kHz, 16 kHz, 1 kHz. The frequency of each recorded signal shall be f 3% of its specified value. The tones shall be recorded in
19、the order given. Each tone shall have a duration of at least 20 seconds except the initial and final 1 kHz reference tones whose duration shall be at least 30 seconds. 4.3.8 Azimuthlstereo phase Azimuth/ctereo phase shall be as specified in ANSVSMPTE 20M, but be tightened to ensure that the relative
20、 phase relationship between the audio 1 and audio 2 signals does not exceed 10“ within the speci- fied range of 1 O0 Hz to 12 kHz. The required frequen- cies shall be as specified in IEC 94. 4.3.9 Crosstalk Tones of 63 Hz, 1 kHz, and 16 kHz shall be recorded on channel 1 only and then channel 2 only
21、. These tones shall be recorded + 8 dB above reference level. 4.4 Definitions 4.4.1 flux level: The absolute short-circuit recorded magnetic flux level in nanowebers per meter (nWb/m). ANSI/SMPTE 20M defines the standard audio reference flux density (see annex A). 4.4.2 frequency response: The ampli
22、tude vs fre- quency characteristic of a circuit or flux given as the frequency-by-frequency deviation, in deci- bels, from either zero deviation or from a speci- fied response. 4.4.3 azimuth: The angle, in a plane parallel to the tape, between the head gaps and a line drawn perpendicular to the refe
23、rence edge of the tape. 4.4.4 height: The distance of a head or record, along the plane of the tape, perpendicular to the reference edge of the tape. 4.4.5 rotation: Rotation of a head around a line which is parallel to the plane of the tape (drawn EG 24-1995 through the centerline of the head as de
24、fined by the manufacturer) and perpendicular to the ref- erence edge of the tape. 4.4.6 zenith: The angle, in a plane perpendicu- lar to the tape, between the head gaps and a line drawn perpendicular to the reference edge of the tape. 4.4.7 peak value: The true peak value of the sig- nal, measured b
25、y observing a true peak-reading measuring device, such as an oscilloscope, and comparing the peak amplitude of the observation to the peak amplitude of the stated reference. 4.4.8 pinknoise: A random noise signal having equal energy in equal logarithmic frequency intervals over the bandwidth of inte
26、rest. 4.4.9 record: The magnetic flux recorded on the tape. 4.5 Use of a reference levei tone 4.5.1 Preliminary adjustments The reference level tone may be used for setting the preliminary head mounting adjustments, such as coarse rotation, azimuth, zenith, and height, by setting the appropriate mec
27、hanical adjustments for highest and most stable output. 4.5.2 Channel polarity The reference level tone may also be used as a relative channel polarity check by using an appropri- ate measuring system such as an X-Y display oscillo- scope or phase meter. 4.5.3 Noise reduction systems The reference l
28、evel tone may also be used for calibra- tion purposes to produce the reference voltage for setting the operating point of level-dependent noise- reduction systems. 4.6 Use of an azimuth tone or tones While observing the output of the two main channels on an appropriate measuring device, such as a ph
29、ase meter or X-Y display oscilloscope, the azimuth, rota- tion, and zenith controls should be adjusted to pro- duce maximum amplitude combined with minimum Page 3 of 6 pages SUPTE EG*24 95 8357403 0002330 387 EG 24-1 995 phase error between the two channels. If more than one azimuth adjustment tone
30、is provided, the initial adjustment is often performed using the lower-fre- quency tone with fine adjustment done using the higher-frequency tone. (Care must be taken to avoid misadjusting azimuth by one full cycle. After final adjustment has been accom- plished using the higher-frequency tone, perf
31、ormance with the lower-frequency tone should be rechecked. Use of the pink noise azimuth alignment procedure below avoids this potential problem.) 5.1.2 Procedures All adjustments must be made in conformance with the machine manufacturers instructions. 5.1.3 Recorded video parameters The recorded vi
32、deo parameters shall conform to those specified in SMPTE RP 86, except that the tolerance specified in clause 5 shall be tightened to I 0.02 MHz and the nominal values specified in other sections shall be held as close as possible. 5.1.4 Video calibration 4.7 Use of pink noise 4.7.1 Azimuth All vide
33、o measurements of luminance levels shall be made in accordance with IEEE Std 205. Pink noise can be used for azimuth adjustment similar to the procedure described above using discrete discrete tones because it produces unambiguous re- sults (one cannot misadjust by one full cycle). 4.7.2 Frequency r
34、esponse Pink noise can also be used for frequency-response adjustment if the machines output is fed to an appro- priate measuring device such as a spectrum analyzer, real-time analyzer, or frequency selective voltmeter. However, because pink noise provides limited fre- quency resolution, and because
35、 it is a stochastic, .e., random, signal, it does not stimulate the mechanism of fringing as greatly as do discrete sine tones. 4.8 Uses of the frequency response tones 5.1.5 Video signals tones. However, pink has an advantage Over Video synchronizing waveforms and video amplitudes shall conform to
36、5.2 Video signal specifications The following specifies the various generic signals which might be used in a tape. If signals other than these are used on a tape, the nature of the actual signals Shall be carefully and 5-2-1 Color bars 100% saturated, 75% amplitude color bars conform- 624-4. defined
37、. ing to EIA-189-A. 5.2.2 Multiburst The frequency response tones may be used for set- ting playback equalization for the flattest possible frequency response. 5 Video 5.1 General notes A white pulse followed by a series of six sine-wave bursts. The white pulse width and the width of each sine-wave
38、burst should be one-seventh the width of the scan line between the end of H blanking and the start of H blanking. The white bar level shall be at 1 O0 IRE units f 1 IRE unit. The axis of the burst shall be at a level of 55 IRE units 1: 1 IRE unit. The peak-to- peak amplitude of the bursts shall be 9
39、0 IRE units I 1 IRE unit. The frequencies of the bursts in time se- quence shall be 500 kHz, l .5 MHz, 2.0 MHz, 3.0 MHz, 3.58 MHz, and 4.2 MHz. 5.1.1 Test equipment 5.2.3 Multipulse A properly calibrated vectorscope and waveform monitor capable of measuring differential gain and differential phase,
40、or equivalent test equipment, are essential for the following tests. A series of pulses whose half-amplitude duration (HAD) is to be 20T for the 1-MHz signal and 10T for the remainder. All amplitudes are to be 1 O0 IRE units Page 4 of 6 pages I 1 IRE unit. The frequencies are to be 1 .O, 2.0, 4.0, 4
41、.8, and 5.8 MHz. 5.2.4 Modulated ramp Acontinuous ramp extending from O to 100 IRE units and repeating at a line rate. Color subcarrier having a peak amplitude of 40 IRE units f 2 IRE units shall be added to the ramp signal. 5.2.5 Window and pulses A window signal, a modulated 12.5T (1.56 microsec-
42、ond) pulse, and a 2T (0.25 microsecond) sine- squared pulse. All signals shall extend from 7.5 IRE units f 2.5 IRE units to 100 IRE units f 1 IRE unit. The window signal shall have a 1 T (0.1 25 microsec- ond) rise time. 5.2.6 Chroma field Aflat, full-field signal corresponding to the cyan bar of EI
43、A-189-A at 75% amplitude. 5.2.7 Gray field A flat, full-field signal at 50 IRE units. 5.4 Use of modulated ramp Modulated ramp may be used to adjust the playback- differential gain and differential-phase performance of the VTR. Adjustment should be made to minimize both differential gain and phase.
44、5.5 Use of muItiburst/muItipuIse Multiburstmultipulse may be used to adjust playback frequency response. General practice is to adjust for maximum flatness of the waveform. 6 Tracking accuracy 6.1 General notes 6.1.1 Test equipment For the following tests, a properly calibrated oscillo- scope, or eq
45、uivalent, is needed. 6.1.2 Procedures Since there is a specific adjustment procedure for each VTR, the manufacturers instructions should be followed. Vertical interval test signals are located on lines 10 through 19. Some or all of the following list of signals may be added to both fields: line 10 l
46、ine 11 line 12 line 13 line 14 line 15 line 17 line 19 2T and 12.5T pulses and 1T bar modulated ramp modulated ramp modulated ramp multiburst multiburst 2T and 12.5T pulses and 1 T bar multiburst EG 24-1995 6.2 Control-track phase and level 5.2.8 Vertical interval test signals Results of measurement
47、s using vertical interval test signals may not be the same as full-field signals due to head-to-tape contact at the ends of the scan. 5.3 Use of color bars Color bars may be used to calibrate luminance, chrominance, and color-burst playback output ampli- tudes, both absolute and relative. Control-tr
48、ack phase and level are best adjusted using a flat-field test signal. It is recommended that a split- field signal not be used for this adjustment. The pro- cedure is to adjust the tracking control for maximum RF output, then verify proper video and sync RF waveforms against the manufacturers specif
49、ications. This adjustment must be performed whenever the control-track head is moved or replaced. This adjust- ment must be made and verified for each video head. Finally, if a control-track level control is provided, the manufacturers specific instructions for this adjust- ment should be followed. 6.3 Track straightness This adjustment is especially critical to interchange- ability because it adjusts the physical relationship of the rotating heads to the tape and, thereby, directly influences conformity with the SMPTE specified track format. It is essential to
