1、 STD.SMPTE RP 121-ENGL 1777 m 8357Li01 0002751 T57 m SMPTE RECOMMENDED PRACTICE RP 121-1997 Revision of RP 121-1993 Tape Dropout Specifications for 1-in Types B and C Video Tape RecorderslReproducers 1 Scope 1.1 This practice defines the parameters for tape dropouts encountered in the reproduced FM
2、signal of l-in types B and C video magnetic recordersheproducers. 1.2 This practice is intended as an aid in the evaluation of dropout characteristics of magnetic tape, not as a specification for recorderlreproducer setup. 2 Basic parameters Basic parameters of the recorder/reproducer are defined in
3、 the following documents: Type B recorder/reproducer Basic parameters: ANSIISMPTE 15M Carrier frequencies and preemphasis: SMPTE RP 84 Audio frequency response and operating level: ANSIEMPTE 17M Record dimensions: ANSVSMPTE 16M Page 1 of 2 pages Video record parameters: SMPTE RP 86 Tracking-control
4、record: SMPTE RP 85 3 Definition For the purpose of this practice, a dropout is a momentary random reduction of the recovered fre- quency modulated rf playback signal that is-suffi- cient to cause a substantial impairment in the video output signal of a l-in type B or type C tape recorderlreproducer
5、. 4 Specifications The signal level reduction to be classified as a dropout must be at least 5 ps in duration and have an rf level reduction of 16 dB or more. 5 Measurement conditions When dropout measurements are conducted, the pole tip protrusion and tape tension of the video recorderheproducer sh
6、all be as follows: Tracking-control record: SMPTE RP 83 Pole tip Type C recorderheproducer Type C 60 pm k IO pm protrusion: Type B 30 pm f 5 pm ANSIISMPTE 18M Tape tension for the recorde r/rep rod u ce r s ha I I be in accordance with the manufacturers published Basic parameters: Audio frequency re
7、sponse and opera tin g leve I: Tape tension: ANSVSMPTE 20M Record dimensions: ANSIISMPTE 19M specifications. Copyright O 1997 by the SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Ave., White Plains, NY 10607 Approved December 5, 1997 (914) 761-1100 STD=SMPTE RP 123-ENGL 1777 83
8、57903 0002952 993 RP 1 21 -1 997 Annex A (informative) Bibliography ANSIISMPTE 15M-1992, Television Analog Recording - I-in Type B Helical Scan -Basic System Parameters ANSIISMPTE 20M-1996, Television Analog Recording - I-in Type C Recorders and Reproducers - Longitudinal Audio Characteristics ANSII
9、SMPTE 16M-1992, Television Analog Recording - I-in Type B Helical Scan - Records ANSIISMPTE 17M-1992, Television Analog Recording - i-in Type B Helical Scan - Frequency Response and Operating Level ANSIISMPTE 18M-1996, Television Analog Recording - i-in Type C - Basic System and Transport Geometry P
10、arameters SMPTE RP 83-1 996, Specifications of Tracking Control Record for I-in Type B Helical-Scan Television Analog Recording SMPTE RP 84-1 996, Reference Carrier Frequencies and Preemphasis Characteristics for 1 -in Type B Helical-Scan Television Analog Recording SMPTE RP 85-1 991 (R1995). Tracking-Control Record for I-in Type C Helical-Scan Television Tape Recording ANSIISMPTE 19M-1996, Television Analog Recording - I-in Type C - Records SMPTE RP 86-1 991 (RI 995), Video Record Parameters for 1-in Type C Helical-Scan Television Tape Recording Page 2 of 2 pages
