Video tape recorder system having means for suppressing video track crossover noise during slow and fast motion operation

Abstract

A helical scan video tape recorder suitable for slow and fast motion modes of operation is disclosed. A plurality of video fields are recorded in each video track extending across the video tape such that the burst of noise produced when the magnetic head crosses over the guard band between separate video tracks during the slow or fast mode of operation of the video recorder is encountered in only one of the field regions in the video track. This burst of noise is utilized to control the television monitor circuit so that the video field region which is free of noise is reproduced on the monitor while the video field region which contains the noise is blanked out from the monitor. As the noise progresses from one field region to the succeeding field region in the video track, means is provided for automatically switching to display of the noise-free field region. Means is provided for at times controlling the brightness of the monitor to compensate for those instances at switchover where two fields are reproduced in succession without the intervening blank period. A ramp generator circuit is provided for compensating for the change in timing of the vertical sync pulses during the slow and fast motion periods. In another embodiment, an additional magnetic head is utilized for reproducing the noise-free video field during the time period that the monitor would ordinarily be blanked out to thereby provide a 100 percent duty cycle in the video monitor.

I claim: 
     
       1. The method of recording video signals on a magnetic tape of a video tape recorder at a normal longitudinal tape speed and reproducing said video signals from said magnetic tape at normal longitudinal tape speeds and at speeds different from normal longitudinal tape speeds comprisng the steps of recording a plurality of separate non-redundant video fields in series in each one of a sequence of video tracks recording along the tape,   scanning the video tracks with a magnetic reproduce head to reproduce .[.the recorded fields in order.]. .Iadd.at least one recorded field per track .Iaddend.for display on a video display means,   said reproduce head crossing over the space on the magnetic tape between adjacent video tracks and producing a noise on the video signal when the longitudinal tape speed is changed from the normal speed, and .Iadd.detecting the occurrence of said noise and .Iaddend.blanking out that particular .Iadd.noisy .Iaddend.field in each track at which the head crossover between adjacent tracks occurs.Iadd., whereby at least one noise-free field in each track is reproduced for display.Iaddend..   
     
     
       2. The method as claimed in claim 1 including the step of reproducing for display on the video display means another field on said track during the period of time said particular field is being blanked out. 
     
     
       3. The method of recording video signals on a magnetic tape of a video recorder at a normal longitudinal tape speed and reproducing said video signals from said magnetic tape at normal longitudinal tape speeds and at speeds different from normal longitudinal tape speeds comprising the steps of recording a plurality of separate non-redundant video fields in series in each one of a sequence of video tracks recorded along the tape,   scanning the video tracks with a magnetic reproduce head to reproduce .[.the recorded fields in order.]. .Iadd.at least one recorded field per track .Iaddend.for display on a video display means,   said reproduce head crossing over the space on the magnetic tape between adjacent video tracks and producing a noise on the video signal when the longitudinal tape speed is changed from the normal speed, detecting the occurrence of said noise at crossover, and blanking out from display in response to the detection of said noise that particular field in each track at which the head crossover between adjacent tracks occurs.Iadd., whereby at least one noise-free field in each track is reproduced for display.Iaddend..   
     
     
       4. The method as claimed in claim 3 including the step of reproducing for display on the video display means another field on said track during the period of time said particular field is being blanked out. 
     
     
       5. The method as claimed in claim 3 including the step of producing a corrected vertical sync signal for each of the vertical sync periods between the fields recorded on the magnetic tape for use by the signal display means. 
     
     
       6. The method as claimed in claim 5 including the step of producing tachometer pulses from the rotating head assembly of the video recorder, said tachometer pulses serving to produce said corrected vertical sync pulses, and producing a linearly sloping analog signal for adjusting the time spacing between said corrected vertical sync pulses. 
     
     
       7. A video recorder system for reproducing a plurality of separate non-redundant video fields recorded in series in a track across a magnetic tape, the tracks being recorded sequentially along the tape, comprising reproducing means including a reproduce head for scanning along each series of fields in each track in sequence to reproduce .[.the separate fields in order.]. .Iadd.at least one recorded field per track .Iaddend.for display on a signal display means, means for changing the .[.relative speed of the magnetic tape and the reproduce head.]. .Iadd.longitudinal tape speed from the longitudinal tape speed during recording .Iaddend.to change the speed at which the video tracks are reproduced, whereby the reproduce head crosses over the space on the magnetic tape between adjacent tracks, .[.and.]. .Iadd.means for detecting the occurrence of noise generated at the head crossover and .Iaddend.means for blanking out that particular .Iadd.noisy .Iaddend.one of the plurality of fields in each track at which said crossover occurs.Iadd., whereby at least one noise-free field in each track is reproduced for display.Iaddend..   
     
     
       8. A video recorder as claimed in claim 7 including means for reproducing another field from said track for display on said signal display means during the period of time said particular field is being blanked out. 
     
     
       9. A video recorder as claimed in 8 wherein said means for reproducing said other field comprises a second reproduce head spaced from the first reproduce head, and means for switching the display means from said first reproduce head to said second reproduce head during the period of time said first head is scanning the field at which said crossover occurs. 
     
     
       10. A video recorder as claimed in claim 7 including means for producing a corrected vertical sync signal for each of the vertical sync periods between the fields recorded on the magnetic tape for use by the signal display means. 
     
     
       11. A recorder as claimed in claim 10 including means for dimming the brightness of said signal display means during the reproduction times of the field displayed immediately before and the field displayed immediately after the switchover from blanking said particular one field to blanking said different field. 
     
     
       12. A video recorder system for reproducing a plurality of separate non-redundant video fields recorded in series in a track across a magnetic tape, the tracks being recorded sequentially along the tape, comprising reproducing means including a reproduce head for scanning along each series of fields in each track in sequence to reproduce .[.the separate fields in order.]. .Iadd.at least one recorded field per track .Iaddend.for display on a signal display means, means for changing the .[.relative speeds of the magnetic tape and the reproduce head.]. .Iadd.longitudinal tape speed from the longitudinal tape speed during recording .Iaddend.to change the speed at which the video fields are reproduced, whereby the reproduce head crosses over the space on the magnetic tape between adjacent tracks and produces a burst of noise at the crossover, and means for detecting said noise and operating in response thereto for blanking out that particular one of the plurality of fields in each track during which said crossover occurs.Iadd., whereby at least one noise-free field in each track is reproduced for display.Iaddend..   
     
     
       13. A video recorder as claimed in claim 12 including means for reproducing another field from said track for display on said signal display means during the period of time said particular field is being blanked out. 
     
     
       14. A video recorder as claimed in 13 wherein said means for reproducing said other field comprises a second reproduce head spaced from the first reproduce head, and means for switching the display means from said first reproduce head to said second reproduce head during the period of time said first head is scanning the field at which said crossover occurs. 
     
     
       15. A video recorder as claimed in claim 12 including means for producing a corrected vertical sync signal for each of the vertical sync periods between the fields recorded on the magnetic tape for use by the signal display means. 
     
     
       16. A recorder as claimed in claim 15 including means for dimming the brightness of said signal display means during the reproduction times of the field displayed immediately before and the field displayed immediately after the switchover from blanking said particular one field to blanking said different field. 
     
     
       17. In a system for reproducing video signals from a magnetic tape recorded at a predetermined longitudinal tape speed and having a plurality of video tracks angularly disposed across said magnetic tape and spaced by guard bands, each of said video tracks including a plurality of complete, successive, non-redundant fields, said fields positioned in said tracks so that the portions of said video tracks at each tape edge contain at least a segment of a vertical blanking interval, the combination comprising means for scanning said video tracks to reproduce .[.said fields.]. .Iadd.at least one field per track.Iaddend.,   means for longitudinally transporting said magnetic tape at said recorded tape speed or at another speed, and   means for .[.blanking out reproduced fields containing.]. .Iadd.detecting .Iaddend.noise picked up by said scanning means from said guard bands when said magnetic tape is transported at speeds different from said recorded tape speed.Iadd., and   means for blanking out reproduced fields containing said noise, whereby at least one noise-free field in each track is reproduced.Iaddend..   
     
     
       18. The combination of claim 17 wherein said other speed is zero whereby a still frame is reproduced. 
     
     
       19. The combination of claim 17 wherein said other speed has a direction of tape travel reversed from the direction of tape travel during recording whereby reverse action motion is reproduced. 
     
     
       20. The combination of claim 17 further comprising means for producing corrected vertical sync signals.   
     
     
       21. The combination of claim 20 further comprising means for displaying said reproduced fields, and   means for dimming the brightness of said signal display means during the reproduction times of consecutively displayed adjacent fields.   
     
     
       22. In a system for recording and reproducing a video signal on magnetic tape, the combination comprising input means for providing a video signal having a field rate of n times 60, where n is a whole positive integer,   tape transport means for longitudinally transporting said tape a first predetermined speed during recording and for longitudinally transporting said tape during reproducing at said first predetermined speed or at another speed,   recording means receiving said video signal for recording said video signal on said magnetic tape in a plurality of video tracks angularly disposed across said magnetic tape and spaced by guard bands, each of said video tracks including a plurality of complete, successive, non-redundant fields, said fields positioned in said tracks so that the portions of said video tracks at each tape edge contain at least a portion of a vertical blanking interval,   means for scanning said video tracks to reproduce .[.said fields.]. .Iadd.at least one field per track.Iaddend.,   means for .[.blanking out reproduced field containing.]. .Iadd.detecting .Iaddend. noise picked up by said scanning means when said magnetic tape is longitudinally transported at speeds different from said first predetermined speed.Iadd., and   means for blanking out reproduced fields containing said noise, whereby at least one noise-free field per track is reproduced.Iaddend..   
     
     
       23. The combination of claim 22 wherein said other speed is zero whereby a still frame is reproduced. 
     
     
       24. The combination of claim 22 wherein said other speed has a direction of tape travel reversed from the direction of tape travel during recording whereby reverse action motion is reproduced. 
     
     
       25. The combination of claim 22 wherein said recording means provides that the horizontal blanking intervals in each video track are substantially aligned with the horizontal blanking intervals in adjacent video tracks. 
     
     
       26. The combination of claim 25 wherein n is a whole positive integer greater than one. 
     
     
       27. The combination of claim 26 further comprising means for producing corrected vertical sync signals. 
     
     
       28. The combination of claim 27 further comprising means for displaying said reproduced fields, and means for dimming the brightness of said signal display means during the reproduction times of consecutively displayed adjacent fields.