1、A CENELEC EN*b1041-3 95 3404583 OLbb402 983 Non-broadcast video tape recorders - Methods of measurement Part 3. Audio characteristics for FM recording The European Standard EN 61041-3 : i996 has the status of a British Standard BS EN BS 7434 : Part 3 : 1994 1993 61041-3 : 1995 IEC 1041-3 : CENELEC E
2、Nmb1041-3 95 3404583 03661103 81T BS 7434 : Part 3 : 1994 Amd. No. Committees responsible for this British Standard Date The preparation of this British Standard was entrusted by the Electrotechnical Sector Board to Technical Committee EEL122, upon which the following bodies were represented: Associ
3、ation of Professional Kecording Services Ltd. Audio Engineering Society British Broadcasting Corporation British Kinematograph, Sound and Television Society Hritish Ipe Industry Association Federation of the Electronics Industry Independent Television Association National Council for Educational Rch
4、nolo Dynamic range Circuit arrangement: Signal-to-noise ratio AGC on Circuit arrangement: Harmonic distortion Circuit arrangement: Channel crosstalk AGC off; Channel separation AGC off Circuit arrangement: Channel crosstalk AGC on; Channel separation AGC on Crosstalk of channel L from channel R Cros
5、stalk of channel R from channel L Circuit arrangement: AGC operation; Hold time Gain curve (outhn response) Rst signal for attackirecovery time measurement Output signal (attack transient) Cicuit arrangement: Switching noise Low-pass filter characteristics input level and audio FM deviation (modulat
6、ion depth) for various VTR systems 13 13 14 10 15 15 16 16 17 17 18 18 19 19 20 i CENELEC EN*blO43-3 95 3404583 0366405 692 W BS 7434 : Part 3 : 1994 National foreword This Part of BS 7434 has been prepared under the direction of the Electrotechnical Sector Board. It is identical with IEC 1041-3 : 1
7、993 Non- broadcast video tape recordkm - Methods qf ?n,ecmcrmnen.t mrt 3: Audio characteristics for FM recorcIi?y, published by the International Electrotechnical Commission (LEC). In 1995 the European Committee for Electrotechnical Standarmon (CENELEC) accepted IEC 10413 : 1993 as European Standard
8、 EN 61041-3 : 1%5. As a consequence of implementing the Ehropean Standard, this British Standard is renumbered as ES EN 61041-3 and any reference to BS 7434 : Part 3 should be read as a reference to BS EN 61041-3. Vie orignal number BS 7434 : Part 3 has been retained us a secondary identifier. A Cro
9、ss-references International standard IEC 94-3 1979 IEC 268-1 1985 IEC 268-3 1988 IEC 268-8 : 1973 IEC 386 : 1972 IEC 674-4 : 1982 IEC 843 : 1987 IEC 1053-1 1991 IEC 1054 : 1991 Corresponding British Standard BS 6288 Magnetic tupe sound recording and 7vpr0duciu systml.5 Par 3 1 1990 Methods of menrur
10、ing ik cizaracteristics of recording and repromhg equipmmi for sound on rnagnetic tup ES 6840 Sound system equipnmt Part 1 : 1987 Mehds for specifying and rneasring general churacetics used for cquipnwni perjionri (i m Part 3 : 1992 Methods fwspecifyi?q and mcusirritig th, charactdstics of sound sys
11、tem arnplijka Par 8 : 1988 Mehds for spec2;fyin.g and ii-iii/ fh/, clm ractwistics of autamatic gain conii-01 dczicc.s BS 4847 : 1989 Method of rneavurt7nmt ?f .pc?cl fluctuations in sound iecordiug and rqiroditci nq equ ipnenl BS .5817 Spefhtun fw audii.is-iLnl. cidtu CULCI - a sine wave of 1 O00 H
12、z. The input level shall be the reference input level as defined in 1.3.3.2. Two recordings shall be made under the following conditions: 1) The sweep test signal is recorded on channel L. while the sine wave of 1 O00 Hz is recorded on channel R. 2) The sweep test signal is recorded on channel Fi wh
13、ile the sine wave of 1 O00 Hz is recorded on channel L. 2.7.4 The output playback signal of channel L and channel R shall be measured by a spectrum analyser. 2.7.5 The amplitude frequency response curve shall be reported as shown in figure 7 and 8 as follows: - The channel L and channel R recording
14、made according to 2.7.2 1) or 2.7.3 l). - The channet R and channel L recording made according to 2.7.2 2) or.2.7.3 2). 2.7.6 Regarding the amplitude response curves, the channel crosstalk shall be determined by measuring the differences A. B and C in dB between the two curves at the frequency F1, F
15、2 and F3 as shown in figures 7 and 8. 2.7.7 The presentation of results, that is the channel crosstalk, shall be fabulated in dB at the frequencies F1, F2 and F3 for: - crosstalk of channel L from channel A (figure 7); - crosstalk of channel R from channel L (figure 8). The frequencies F1 and F3 are
16、 20 Hz and 15 kHz respectively, F2 is the frequency at which the value of B is greatest. The AGC conditions (off or on) shall also be reported. NOTE - This measurement is in accordance with 12.3.3 of IEC 94-3 and amendment No. 2. 2.8 Channel Separation 2.8.1 This measurement determines the separatio
17、n of one channel from the other chan ne1 . 2.8.2 AGC off The circuit arrangement shall be as shown in figure 5. The test signal shall be a sine wave of 400 Hz. The input levei applied to the VTA shall be as defined in 1.3.3.1. 7 - CENELEC EN*hL041-3 95 m 3404583 OLbb415 531 m t BS 7434 : Part 3 : 19
18、94 Two recordings shall be made under the following conditions: 1) The test signal is recorded on channel L, the input of channel R being terminated by a resistor of 600 R. 2) The test signal is recorded on channel R, the input of channel L being terminated by a resistor of 600 R. 2.8.3 AGCon The ci
19、rcuit arrangement shall be as shown in figure 6. Two test signals shall be used, that is: - a sine wave of 400 Hz; - a sine wave of 1 O00 Hz. The input level shall be the reference input level as defined in 1.3.3.2. Two recordings shall be made under the following conditions: 1) The sine-wave test s
20、ignal of 400 Ht is recorded on channel L while the sine wave of 1 O00 Hz is recorded on channel R. 2) The sine-wave test signal of 400 Hz is recorded on channel R while the sine wave of 1 O00 Hz is recorded on channel L. +. 2.8.4 The audio signal output level of channel L and channel R shall be meas
21、ured by a selective audio level meter (400 Hz) or a spectrum analyser. Playback of recording according to 2.8.2 1) or 2.8.3 1). (VL) L . output level of channel L (VR) L output level of channel R Playback of recording according to 2.8.2 2) or 2.8.3 2) (VR) R . output level of channel R (VL) R outpuf
22、 level of channel L 2.8.5 Separation SCL of channel L from channel R: SCL = 20 lg (dB) PL) R Separation SCR of channel R from channel L: 2.8.6 The presentation of results, that is the value of channel separation SCL and SCR in dB, shall be reported as well as the AGC condition (off or on). 8 - CENEL
23、EC EN*bL04L-3 75 3404583 OLbb4Lb 478 - BS 7434 : Part 3 : 1994 2.9 AGC operation and attackhecovery time 2.9.1 These measurements determine the characteristics of the automatic gain control circuit. They are in accordance with IEC 268-8. 2.9.2 The test circuit arrangement shall be as shown in figure
24、 9. 2.9.3 Gain characteristic measurement The test signal shall be a sine wave of 400 Hz. the amplitude of which shall be increased by equal steps from zero to the value at which the amplitude of the output signal slightly increases (see figure 10). The peak-to-peak amplitude of the output signal sh
25、all be measured by an oscilloscope. The results of this measurement shall be reported as a curve of amplitude (out)/amplitude (in) response as shown in figure 10, where the lower (A) and the upper (8) AGC voltage points indicate the limits of the AGC range. 2.9.4 Attack and recovery time (hold time)
26、 measurement in E to E mode The test signal shall be a sine wave of 1 O00 Hz as shown in figure 11 a, the amplitude of which shall be the reference AGC level point (B) +6 dB for a period of i s and 3 dB below the lower AGC point thereafter. The peak-to-peak amplitude of the output signal shall be me
27、asured by an oscilloscope. The attack and recovery time (hold time) is defined as shown in figure 11 b. 2.9.5 Attack and recovery time measurement in record/playback mode The same method of measurement as in E to E mode (see 2.9.4) shall be used, but with output measurement made during playback. 2.9
28、.6 Presentation of results The characteristics defined in 2.9.3, 2.9.4 and 2.9.5 shall be reported for channel t and R respectively. NOTE - The attack transient characteristic is shown in figure 12 as an example. 2.10 Swltching noise 2.10.1 This measurement determines the disturbance caused by the l
29、inking of signals from successive tracks. This disturbance increases with increasing frequency of the audio signal. 9 CENELEC ENxbL04L-3 75 3404583 OLbb417 304 BS 7434 : Part 3 : 1994 2.1 0.2 The circuit arrangement shall be as shown in figure 13. 2.1 0.3 The test signal shall be a sine wave of 1 O
30、kHz. The input level to the VTR shall be adjusted at 10 dB below the reference input level. 2.10.4 The measuring instrument shall be a quasi peak meter according to IEC 268-1, appendix A, clause A2. The output level V, of the 10 kHz audio signal shall be measured directly. The output level V, of the
31、 disturbance shall be measured via a low-pass filter having a cut-off frequency of 3 kHz and a slope of at least -48 d per octave (figure 14). The signal-to-noise ratio (SIN) S due to signal to switching is defined as: (SIN) S = 20 lg - “ (dB) “* 2.10.5 The presentation of results, that is the signa
32、l-to-noise ratio due to the signal switching, shall be reported in dB for channel L and channel R respectively. 2.1 1 Wow and flutter ? b) Recording mode (e.g. beta II, VHS-SP, 8 mm-SP, etc.); c) Name of the manufacturer; d) Other information (e.g. contents of recording signais etc.). NOTES 1 define
33、d in 3.3.4 and 3.3.5. 2 reproduction quality less critically than as in the a.c. bias recording. 3 It is recommended to use a modulation analyser to assure the accuracy of the frequency deviation as Effects From the electromagnetic properties of tape and the recording current to the heads affect the
34、 Standard for the calibration tapes for non-broadcast video-recorders is in preparation. 12 Video signal generator I t Video input * Audio VTR output Spectrum under test * analyser Figure 1 - Circuit arrangement: Amplitudelfrequency response (2.1) Audio signal generator 1000Hz + 4 Video signal gener
35、ator VTR Audio 1 input Audio signal + undertest I Shielded resistor I of 600R b.u.;t FiIrr 1 weighting characteristics) True r.m.s. IEC 124SI93 Figure 2 - Circuit arrangement: - Signal-to-noise ratio (2.2) - Dynamic range (2.4) AGC off 13 _ CENELEC EN*bL041-3 95 3404.583 OLbb42L 835 BS 7434 : Part 3
36、 : 1994 Video signal generator VTR under test 1 1 I Audio signal generator _+ Gate w ;+4; Input No VI reference signal recording level AGC on Figure 3a - Test signal F=400HZ Filter True r.rn.s. meter VO 1 I I I I I I I I I I 1In I 1 I r2 1 I I IEC 124 Fax: 0181 996 7001. In response to orders for in
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