SMPTE ST 3-1998 Television Analog Recording - Frequency Response and Operating Level of Recorders and Reproducers - Audio 1 Record on 2-in Tape Operating at 15 and 7 5 in s.pdf

1、SMPTE STANDARD SMPTE 3-1 998 Revision of ANSVSMPTE 3-1992 for Television Analog Recording - Frequency Response and Operating Level of Recorders and Reproducers - Audio 1 Record on 2-in Tape Operating at 15 and 7.5 ink 1 Scope This standard specifies the frequency response and operating level for rec

2、orders and reproducers for audio 1 record for 2-in quadruplex video magnetic tape recording at 15 ids and 7.5 in/s (381 mm/s and 190.5 mm/s), as defined in ANSVSMPTE 6. It also specifies the field method of calibration of recorders and reproducers, utilizing the test tapes as defined in ANSVSMPTE 8

3、and ANSVSMPTE 11. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on

4、this standard are encouraged to investigate the possibility of applying the most recent edition of the standards indicate below. ANSMEEE 152-1 992, Audio Program Level Measure- ment ANSVSMPTE 6-1 993, Video Recording - 2-in Quad- ruplex Tape - Video, Audio and Tracking-Control Records ANSVSMPTE 8-1

5、995, Video Recording - Quadru- plex Recorders Operating at 15 in/s - Audio Level and Multifrequency Test Tape ANWSMPTE 11 -1 995, Video Recording - Quadru- plex Recorders Operating at 7.5 in/s - Audio Level and Multifrequency Test Tape Page 1 of 3 pages 3 Operating level 3.1 Recording and reproducin

6、g level indicator The audio recording and reproducing levels of avideo magnetic tape recorder shall be monitored and ad- justed with a standard volume indicator (vu meter), as specified in ANSMEEE 152. 3.2 Recorder operating level When a tape record is recorded from a sinusoidal voltage having a fre

7、quency of 1 O00 Hz, such that the rms short circuit tape flux per unit track width on the record is 110 nanowebers per meter f 3 nWb/m of track width, the recording volume indicator shall be adjusted to deflect to its reference level (O dB) scale mark. 3.3 Reproducer operating level When a tape reco

8、rd having an rms sinusoidal flux per width of 110 nWb/m and a frequency of 1000 Hz is reproduced, the reproducing volume indicator shall deflect to its reference level (O dB) scale mark. 4 Frequency response 4.1 Recorder fluxifrequency response When a tape record is recorded from a constant voltage

9、level applied to the input terminals of the recording system, the short circuit tape flux level on the record versus frequency, L+ (f), shall be as given by the following equation: L+ (f) re 11 O nWb/m = 0.2 + 1 O logio l + (FI /f)*/l + (f/Ft$*I dBl Copyright O 1998 by THE SOCIETV OF MOTION PICTURE

10、AND TELEVISION ENGINEERS 595 W. Hartsdale Ave., White Plains, NY 10607 (914) 761-1100 Approved June 3,1998 where f is the frequency at which the response is being computed; FI is the low-frequency transition frequency, 80 Hz; and Fh is the high-frequency tran- sition frequency, 4500 Hz. A graph of t

11、his equation is shown in figure 1. 4.2 Reproducer fluflrequency response When a tape record having a short circuit tape flux level versus frequency given in 4.1 is reproduced, the output voltage level of the reproducer versus fre- quency shall be constant. 5 Field method of calibrating recorders and

12、 reproducers 5.1 The practical calibration of a reproducer shall be performed by reproducing the audio level and multifrequency test tape defined in ANSVSMPTE 8 or ANSVSMPTE 11. The practical calibration of a recorder shall then be performed by recording on a medium representative of that to be used

13、, and comparing the recording so made with the recording on the test tape. 5.2 The flux/frequency response of a reproducer shall be calibrated by reproducing the frequency response test section of the specified test tape. The reproducing equalizer is adjusted so that RELATIVE LEVEL OF SHORT CIRCUIT

14、FLUX (dB 1 output voltage level versus frequency of the re- producer is constant. 5.3 The operating level of a reproducer shall be calibrated by reproducing the audio operating level test section of the specified test tape. The reproducing gain control is adjusted so that the reproducing volume indi

15、cator deflects to its ref- erence level (O dB) scale mark. 5.4 The flux/frequency response of a recorder shall be calibrated by comparing the tape flux recorded by the recorder (with constant input voltage level), to the flux recorded on the fre- quency response test section of the specified test ta

16、pe. The recording equalizer is adjusted so that the tape flux level versus frequency of a recorder (including the tape) is the same as that on the test tape. 5.5 The operating level of a recorder shall be calibrated by comparing the tape flux recorded by the recorder when the recording volume indi-

17、cator deflects to its reference level (O dB) scale mark, to the recording of the audio operating level test section of the specified test tape. The recording gain control is adjusted so that, when the recording volume indicator deflects to its reference level (O dB) scale mark, the recorded tape flu

18、x is the same as that on the test tape. SHORT CIRCUIT FLUX PER UNIT TRACK WIDTH (nWb/m ) +IO O -10 40 50 Ml 100 160 200 315400 630800l 1.25 b6 2.5 3J5 5 6.3 IO 123 -20 31.5 63 125 250 500 Ik 2k 4k 8k 16k I10 FREQUENCY IN HERTZ Figure 1 - Flux and flux level vs frequency Page 2 of 3 pages STD-SMPTE 3

19、-ENGL 1796 6357403 0003309 352 SMPTE 3-1998 Annex A (informative) Additional data Previous frequency response standards for recorders and reproducers have been given in terms of a “standard repro- ducing system,” having an “ideal” reproducing head followed by a standardized RC equalizing network who

20、se time con- stant was given. Because an adequate description of the “ideal” head and its interconnection to the following network is quite lengthy, it is simpler to specify the system responses in terms of the basic physical quantity for the recorded signal, the “short circuit tape flux.” The conce

21、pts are explained in detail by J. G. McKnight in the paper Flux and flux-frequency meas- urements and standardization in magnetic recording, J. SMPTE, 78: 457-472; June 1969. Rather than specifying flux/frequency response in terms of admittances of electrical networks, the equation and graph of the response function have been specifically given. The equation does in fact describe the response of the previously specified RC equalizing network with “time constants” of 2000 microseconds and 35 pm. Page 3 of 3 pages