1、 CENELEC EN*bL04L-L 95 = 3404583 03629b9 658 Non-broadcast video tape recorders - Methods of measurement Part 1. General video (NTSCPAL) and audio (longitudinal) characteristics me European Standard EN 61041-1 : 1995 has the status of a British Standard BS EN BS 7434 : Part 1 : 1991 IEC 1041-1 : 199
2、0 61041-1 : 1995 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Electronic Equipment Standards Poiicy Committee (EEL!-) to Technical Conirnit.tee EELi12, upon which the following bodies were represented: Association of Professional Reco
3、rding Services Ltd. Audio Engineering Society British Broadcasting Corporation British Kinematograph, Sound and IPlevision Society British ?ape industry Association Independent Broadcasting Authority Independent Rievision Association National Council for Educational Technology (KCET) Royal Photograp
4、hic Society Royal Television Society Sound and Communication industries Federation Amendments issued since publication I Amd. No. 1 Date Contents Committees responsible National foreword Page L. .Inside front cover . I. III A A Section 1 - General 1.1 Scope 1.2 Normative references 1.3 Environment 1
5、.4 Magnetic tape .“ 1.5 Performance of measurements 1 1 2 2 2 1.6 Interchangeability test 3 Section 2 - Video characteristics, luminance 2.1 Video test signal - General 2.2 AGC operation 3 3 2.3 Luminance amplitude/frequency response 4 2.4 Luminance non-linear distortion 2.5 Luminance waveform disto
6、rtion (linear distortion) 2.6 Luminance transient tearing 2.7 Luminance signal-to-noise rcitio 2.8 Luminance drop-out compensation 8 3.1 Chrominance ampiitude/frequency response 10 Section 3 - Video characteristics, chrominance (PAL/NTSC) 3.2 Chrominance signd-to-noise ratio 3.3 Chrominance-to-lumin
7、ance intermodulation 1 o 1 o 3.4 Luminance-to-chrominance crosstalk 11 3.5 Chrominance-to-luminance displacement 12 3.6 Chrominance-to-luminance crosstalk 1 :3 Section 4 - Time base 4.1 Time base 13 Section 5 - Audio characteristics, longitudinal recording 5.1 Audio test signal - General 1:3 5.2 AGC
8、 operation 14 5.3 Audio characteristics 13 A (normative) - Alternative test signals 29 Annexes ZA (informative) - Other international publications quoted in this standard with the- references of the relevant European publications NA (informative) - Cross-references Inside back cover. - I CENELEC EN+
9、b3043-1 95 3404583 0362972 342 m I BS 7434 : Part i : 1991 Figures 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 A. 1 A. 2 A. 3 A.4 Video test signal: nominal values, horizontal line Video test signal: vertical field Circuit arrangement (see 2.2, 2.3, 2.4, 2.5, 3.1, 3.5) Test signal fo
10、r luminance amplitude/frequency response Rst signal for luminance non-linear distortion (10 steps) Test signal for luminance waveform of linear distortion Luminance waveform distortion (linear distortion) Circuit arrangement: luminance signal-to-noise ratio Rst signal for luminance signal-to-noise r
11、atio Circuit arrangement: luminance drop-out compensation Rst signal for luminance drop-out compensation Test signal for chrominance amplitude/frequency response Circuit arrangement: chrominance-to-luminance intermodulation %st signal for chrominance-to-luminance intermodulation Circuit arrangement:
12、 iuminance-to-chrominance crosstalk Test signal for luminance-to-chrominance crosstalk Rst signal for chrominance-to-luminance displacement Circuit arrangement: chrominance-to-luminance crosstalk Audio test signal level as a function of time Circuit arrangement: determination of 0 dB level Audio amp
13、litude response: determination of O dB level Audio test signal: determination of hold time Audio playback signal: determination of hold time %st signal for luminance ampitude/frequency response Test signai for luminance waveform distortion st signal for luminance signal-to-noise ratio %st simal for
14、chrominance-to-luminance intermodulation 15 15 16 16 17 17 18 19 19 20 20 23 23 23 24 24 25 27 27 28 28 28 28 29 29 30 30 v II CENELEC EN*bLOLiL-L 75 = 3404583 0362773 087 f BS 7434: Part 1 : 1991 National foreword This British Standard has been prepared by Technical Cornnuttee EPYGO and is the Engl
15、ish ianguage version of EN 61041-1 : 1995 Non-broadcasi video .!ape remniem. Meuods of meczsurement Part i: Gaeml video (hRSCP 0,714 V for 525 lines/60 Hz systems. The nominal value of the amplitude of the picture signal shall be regarded as 100 YO when defining signal amplitudes in percent (see fig
16、ure 1). Unless otherwise stated all test signals shall include in each field at least eight lines of 100 % white in order to ensure correct operation of the automatic gain control. These lines shall be located at the end of the vertical blanking area (see figure 2 and note below). r The active field
17、 period shall contain the specific picture test signal for measurement of the video characteristics. Unless otherwise stated the test signal shall be identical in each horizontal line of the ac- tive field period, .e. regarding amplitude, frequency, phase. timing. etc. Unless otherwise stated the ri
18、se time and the fall time of the test signal shall be not less than 2T. NOTE - Alternative test aignals udng white reference in each line are shown in annex A (figures A.l. A.2. A.3 and A.4). See also CCIR Recommendations 471-1 and 569-2. and Report 476-1. 2.2 AGC operation 2.2.1 This measurement de
19、termines the reaction of the automatic gain control to deviations of the amplitude of the input signal from the nominal value. 2.2.2 The circuit arrangement shall be as shown in figure 3. 3 - CENELEC EN*bLO4L-L 95 3404583 0362779 5T7 1041-1 Q IEC Amplitude of output signal from sync rip to white Amp
20、litude of synchronizing signal i 2.2.3 The test signal shall be a monochrome staircase Signal without a chrominance burst as shown in figure 5. +/- +I- +I- +I - +I- +I- I The foliowing test signals shall be used sequentially: a) the amplitude of the test signal from sync tip to white shall be change
21、d by f6 dB while the ratio of the amplitude of the synchronizing signal to the amplitude of the picture signal shall be nominal; b) the amplitude of the synchronizing signal shall be changed by I6 dB while the ampli- tude of he picture signal shall be nominal; c) the amplitude of the picture signal
22、shall be changed by i6 dB while the amplitude of the synchronizing signai shall be nominal. 2.2.4 The output signal shall be measured on an oscilloscope. The measurements shall be made for each condition a), b), c) in 2.2.3. The deviation of the following signal levels from the corresponding nominal
23、 signal levels during playback shall be measured as a percentage of the nominal levels: 1) the amplitude of the output signal from sync tip to white; 2) the amplitude of the synchronizing signal. 2.2.5 The results of measurement shall be reported in a table as shown hereafter: Variation (X) Paramete
24、r 1 8 b C I 2.3 Luminance amplltudeifrequency response 2.3.1 This measurement determines the amplitudeifrequency response of the luminance channel, .e. the amplitude of the output signal relative to a reference level as a function of frequency . 2.3.2 The circuit arrangement shall be as shown in fig
25、ure 3. 2.3.3 The lest signal shall be a sine-wave multiburst signal with or without a chrominance burst according lo figure 4 (see note to clause 2.1). The chrominance burst shall be switched off if the multiburst signal of the playback signal is aff ecled by the activated chrominance channel of the
26、 device under test. 4 - CENELEC EN*b1041-1 95 m 3YOY583 1W1-1 Q IEC The reduced amplitude of the multiburst signal is essential because clipping circuits In use. 03b2980 219 of pre-emphasls m and Signals having ampiitudes greater than those 01 the frequency bursts shall therefore not be used. 2.3.4
27、The output signal shall be measured on an osdlloscope. The reference level V,*, picture signai, Le. from blanking levei to white level. shall be 40 % of the amplitude of the 100 % white output The peak-tepeak amplitude Vpp of each frequency burst of the output signal shall be related to the referenc
28、e level Vref to obtain the amplitudelfrequency response A: 5-P V*ef (a) A (d5) = 20Ig - The method of defining the amplitudeffrequency response by stating the resolution of a certain number of horizontal lines shall not be used. 2.3.5 The results of measurement shall be reported in a table showing t
29、he frequency in MHt and A in dB. 2.4 Luminance non-llnear dlstonlon 2.4.1 This measurement determines the non-linear distortion of the luminance channel, .e. the deviation of grey levels between blanking level and white level of the output picture signal in relation to the grey levels of the input p
30、icture signal. 2.4.2 The circuit arrangement shall be as shown in figure 3. 2.4.3 The test signal shall be a monochrome staircase signal of 5 to 10 steps without a chrominance burst according to figure 5. The nominal amplitude of the steps shall be 100 %/no where no is the maximum number of steps. T
31、he grey level Vt, of the nth step of the test signal shall be: vt, (1 x 100 f 2) % “O 2.4.4 The output signal shall be measured on an oscilloscope. The reference level Vrer (bl shall be the amplitude of the 100 % white output picture signal. .e. from blanking levei to white level. 5 CENELEC EN*b1041
32、-1 95 m 3404583 0162981 155 m 1041-1 Q IEC The amplitude W, of the nth step of the output signal. .e. from blanking level to the nth grey level, shall be measured as a percentage of the reference level V, (b) The non-linear distortion of the luminance channel shall be calculated as the percentage NL
33、 (n) of the deviation of the nth output grey level Von from the nth test signai grey level Vtn: NL (n) = Von - Wtn (percent) 2.4.5 The results of measurement shall be given in a table showing the number n of the step and the percentage NL (n) of the deviation. 2.5 Lumlnance waveform dlstortlon (line
34、ar distortion) 2.5.1 This measurement determines the distortion of a bar and of a 2T pulse caused by the luminance channel. 2.5.2 The circuit arrangement shall be as shown in figure 3. 2.5.3 The test signal shall be in accordance with figure 6 (see note to clause 2.1). The following two conditions o
35、f the test signal shall be used: a) the amplitude of the bar and the 2T pulse shall be 50 %; b) the amplitude of the bar and the 21 pulse shall be 100 %. 2.5.4 The output signal shall be measured on an oscilloscope. The waveform distortions shall be calculated as shown in figures 7.1 to 7.4. 2.5.5 T
36、he results of measurement shall be listed in the order given by figures 7.1 to 7.4 for the two test signal conditions described in 2.5.3. 2.6 Lurnlnance transient tearlng 2.6.1 High-amplitude transients with small rise times may cause malfunctioning of the FM-demodulator causing incorrect levels of
37、the output slgnal, e.g. black or white stripes. 2.6.2 The circuit arrangement is under consideration. 2.6.3 The test signal shall be a square-wave signal having an amplitude of 100 % and a rise/fall time of T. The frequency shall be in the range from 200 kHz to 250 kHr. 2.6.4 The measurement of tran
38、sient tearing is under consideration. 2.6.5 The presentation of the results of measurement is under consideration. 2.7 Lumlnance signal-to-nolse ratlo 2.7.1 This measurement determlnes the ndse behavour of the luminance channel. The influence of the chrominance channel is determined by measuring wit
39、h and without chrominance burst. 2.7.2 The circuit arrangement shall be as shown in figure 8. 2.7.3 The test signal shall be a black and white signal according to figure 9 (see note to clause 2.1). The following two conditions of the test signal shall be used: a) test signal without chrominance burs
40、t; b) test signal wlth chrominance burst. 2.7.4 The noise superimposed on the 50 % grey level of the output signal shall be measured by a noise meter having the following characteristics: The noise meter shall have a gating function in order to guarantee noise measurement in the flat portion of the
41、50 % grey level. The measuring instrument shall be preceded by the following band-limiting filters: a) low-pass filter according to CCIR Recommendation 567, annex II. with: fc - 5 MHr for 625 lines/50 Hr systems; fc = 4.2 MHr for 525 lines/6O Hz systems, recalculated from CCIR Recommen- dation; b) h
42、igh-pass filter according to CCIR Recommendation 567, annex 111, with c) chrominance sub-carrier notch fllter; d) weighting network according to CCIR Recommendation 567, annex II, switchable on/off. fc I: 100 kH; The meter shall read the r.m.s. value, Vrmr, of the noise. The reference level Vrd Le.
43、from blanking level to white level. shall be the amplitude of the 100 Y. white output picture signal, The signal-to-noise ratlo S/N Is defined as: “ref (c) “,In S/N (dB) L: 20 ig - 2.7.5 The results of measurement, Le. the unweighted and weighted values of SIN (dB), shall be stated for the test sign
44、als as defined in items a) and b) of 2.7.3. 7 _ CENELEC EN*bLO4L-L 95 3404583 OLb2983 T28 W 1041-1 Q IEC 2.8 Lumlnance drop-out Compensation 2.8.1 Drop-outs are mainly caused by particles on the surface of the tape increasing the distance between head and tape, which results in a decrease of the out
45、put voltage of the reading head. This measurement determines the ability of the luminance playback channel of the VTR to compensate for drop-out. 2.8.2 The circuit arrangement shall be as shown in figure 10. 2.8.3 The test signal shall be derived from a special prerecorded test tape. The artificial
46、drop-outs shall be achieved by reduction of the recording current during certain time periods. The riseifall time of the envelope of the recording current shall be approximately 2 ps. The recording cumnt shall be the optimum recording current except for the dropout periods. Two kinds of test signal
47、are required for the following measurements: a) Measurement of drop-out compensation level and switching noise The test signal shall be a 50 % white level. In a certain number of non-successive lines a black information shall be inserted according to figure 1 la. Duringa period of 20 ps symmetrical
48、to the black information the recording current shall be reduced to achieve a reduced output voltage from the playback head. The number of special lines shall be at least three. The output voltage of the playback head during the drop-out period compared with the output voltage during periods of optim
49、um current recording shall be: - - - 10 dB in the first special line; 20 dB in the second special line; 30 dB in the third special line. b) Measurement of frequency characteristic and time behaviour The test signal (figure 1 1 b) shall be a 50 % white level superimposed with a sine-wave having a peak-to-peak amplitude of 40 Y. The frequency of the sine wave shall be 0.5 MHz in the first half of the active line period and 2.0 MHz in the second half. In ten successive lines the recording current shall be suppressed by more than 26 dB over a period of 20 ps
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