MAGNETIC RECORDING AND PLAYBACK APPARATUS

Abstract: A magnetic recording and playback apparatus capable of simultaneously recording a plurality of information sig­ nals on a single magnetic recording medium and, thereby allowing recording a plurality of broadcast programs unat­ tended. A signal to be recorded and associated with one of a plurality of input composite video signals and a signal subjected to signal processing such that a vertical sync signal of another composite video signal is synchronous with that of the one composite video signal are applied to respective rotary heads, the two signals being simulata­ neously recorded on the recording medium.

Description: The invention refers to a recording system in an apparatus for recording and reproducing two discrete composite video signals on and from a single magnetic tape, as set forth in the preamble of claim 1. A recording system of this kind is know from JP-A-56/120279. Now, while a single VTR cannot record but a single TV program, it is sometimes desired to record a plurality of TV programs in the same time zone while in absence. Such a desire has heretofore been fulfilled naturally by preparing a plurality of VTRs commensurate with the number of desired programs. However, preparing a plurality of VTRs is rather awkward because VTRs are still expensive despite the trend toward lower price. Also, since the likelihood of a plurality of desired TV programs existing in a common time zone is not very high, preparation of a plurality of VTRs is inefficient in the aspect of utility. Further, there is an occasion in the program creation in which a single scene may be picked up by two video cameras connected individually to VTRs, i.e., one fixed in place for shooting the whole scene over a wide angle and the other hand-held for shooting telescopic details of the scene. In such a case, at least two VTRs are required. Again, preparing a plurality of VTRs is awkward and inefficient because they are expensive and because the chance of shooting the same scene by use of a plurality of video cameras is rare. From JP-A-56/120279 a recording system of the aforementioned kind is known which is able to record two discrete composite video signals concurrently onto single magnetic tapes. Two record signals derived from the composite video signals are recorded onto tracks of the magnetic tape in a manner that the tracks assigned to the different signal channels alternate with each other. This kind of recording results in some problems concerning cross-talk among the signals of the different channels as every track assigned to one channel is situated between two tracks assigned to the other channel. It is the object of the invention to provide a recording system in an apparatus for recording and reproducing two discrete compostie video signals on and from a single magnetic tape as set forth above which allows a reduction of cross-talk among the video signals of the different channels. This object is attained by the characterizing features of claim 1. Preferred embodiments of the invention are the subject matter of the dependent claims. The above object, the features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a recording system forming part of a recording and playback apparatus and embodying the present invention; Fig. 2 shows rotary heads positioned in a first exemplary relationship in accordance with the present invention; Fig. 3 is a schematic developed view of the head arrangement shown in Fig. 2; Fig. 4 shows a recording pattern provided by the rotary heads in the arrangement of Fig. 2 on a recording medium; Fig. 5 shows rotary heads positioned in a second exemplary relationship in accordance with the present invention; Fig. 6 is a schematic developed view of the head arrangement shown in Fig. 5; Fig. 7 is a schematic developed view of a third example of the head arrangement in accordance with the present invention; Fig. 8 shows a recording pattern attainable with the rotary heads in the arrangement of Fig. 7 on a recoding medium; Fig. 9 is a block diagram showing an example of a playback system forming the other part of the recording and playback apparatus of the present invention; Fig. 10 is a block diagram showing another example of the playback system; Fig. 11 is a block diagram showing a known playback system which can be used for reproducing a program from a tape recorded in accordance with the invention; and Fig. 12 is a block diagram of the memory control shown in Fig. 1. DESCRIPTION OF THE PREFERRED EMBODIMENT Reference will be made to Figs. 1-12 for describing a preferred embodiment of the recording system in accordance with the present invention. First, signal paths along which information signals applied to a recording system of the apparatus pass through to become record signals to be recorded while being subjected to various kinds of signal processing will be explained with reference to Fig. 1. Referring to Fig. 1, the recording system, generally 10, comprises a first input terminal 100, an automatic gain control (AGC) circuit 102, a low-pass filter (LPF) 104, a preemphasis circuit 106, a frequency modulator 108, a mixer 110, a bandpass filter (BPF) 112, an automatic chroma control (ACC) circuit 114, a low frequency range conversion circuit 116, a record amplifier 118, rotary transformers 120 and 122, record heads 124 and 126, a sync detector 128, and a memory control circuit 130. The recording system 10 further comprises a second input terminal 132, an AGC 134, an LPF 136, an analog-to-digital (AD) converter 138, a BPF 140, an ACC 142, a low frequency range conversion circuit 144, an AD converter 146, a sync detector 148, random access memories (RAM) 150 and 152, a digital-to-analog (DA) converter 154, a preemphasis circuit 156, a frequency modulator 158, a mixer 160, a DA converter 162, a record amplifier 164, rotary transformers 166 and 168, and record heads 170 and 172. Routing and signal processing associated with a first video signal (composite video signal) which is a first information signal will be described first. The first video signal is applied to the first input terminal 100 from which three signal paths diverge. In a first signal path, the first video signal is controlled by the AGC 102 to a predetermined signal level and, then, applied to the LPF 104. The LPF 104 separates a luminance signal component from the first video signal and delivers it to the preemphasis circuit 106. The circuit 106 boosts a high frequency component contained in the luminance signal component. The output of the circuit 106 is modulated by the frequency modulator 108 and, then, routed to the mixer 110. In a second signal path, the first video signal is applied to the BPF 112 to have its color signal component separated. The separated color signal component is controlled by the ACC 114 so that a color burst signal thereof gains a predetermined level. The output of the ACC 114 is applied to the low frequency range converter 116. The output of the converter 116 is a low frequency range converted color signal (referred to simply as a converted color signal hereinafter) having a frequency lower than that of the frequency modulated (FM) luminance signal and a phase which is inverted by each 90 degrees at every 1 H (horizontal sync period) (so-called phase-shift (PS) signal processing). The converted color signal is applied to the mixer 110. The mixer 110 mixes the FM luminance signal and converted color signal of the first video signal to produce a record signal to be recorded, which is then delivered to the record amplifier 118. The record amplifier 118 processes the record signal to provide it with an optimum recording current value. The output of the record amplifier 118 is routed through the rotary transformers 120 and 122 to the record heads 124 and 126. In a third signal path, the first video signal is applied to the sync detector 128 whereby a sync signal is separated from the first video signal. The sync signal is applied to the memory control 130. Next, routing and signal processing associated with a second video signal (composite video signal) will be described. The second video signal is applied to the second input terminal 132 from which three signal paths diverge. In a first signal path, the second video signal is controlled by the AGC 134 to a predetermined signal level and, then, applied to the LPF 136. The LPF 136 separates a luminance signal component from the second video signal, the output of LPF 136 being fed to the AD converter 138. In a second signal path, the second video signal is coupled to the BPF 140 to have its color signal component separated. The separated color signal component is routed to the ACC 142 which then controls the input such that the level of a color burst signal becomes constant. The output of the ACC 142 is applied to the low frequency range conversion circuit 144 to be thereby converted to a signal whose frequency lies in a range lower than that of the FM luminance signal of the second video signal, while being subjected to PS signal processing which is opposite in direction to the PS signal processing applied to the color signal of the first video signal. The output of the circuit 144, a converted color signal, is routed to the AD conveter 146. In a third signal path, the second video signal is applied to the sync detector 148 which is adapted to separate a sync signal from the second video signal. The sync signal is delivered to the memory control 130. Now, where a composite video signal is to be recorded in a magnetic tape or like recording medium, a servo circuit for controlling the rotation speed of a head is operated matched to a composite video signal applied thereto and in synchronism with a sync signal contained in the video signal. It follows that where two discrete composite video signals are to be recorded in a single recording medium, or by a single recording and playback apparatus, the servo circuit is operated matched to a main signal (assuming that the first signal is a main signal, the second video signal is a subsignal) and in synchronism with a sync signal contained in the main signal. Although a nominal vertical sync frequency of a composite video signal is 59.94 Hz and the two discrete composite video signals are in approximate synchronization of their vertical sync signals, the two vertical sync signals are often slightly different in phase and sometimes in frequency. If this is a case, recording or playback of them is difficult as such discrepancy accumulates or fluctuate as the recording or playback progresses. To simultaneously record or reproduce such two composite video signals, it is a primary requisite that the phases and frequencies of their vertical sync signals be matched to each other. Such a requisite can be fulfilled if the frequency and phase of the vertical sync signal of the subsignal are matched to those of the vertical sync signal of the main signal with which the recording and playback apparatus is synchronized. The matching may be implemented by a delay circuit of the type using a digital memory as will be described hereinafter. The luminance signal component applied from the LPF 136 to the AD converter 138 is sampled and held by the AD converter 138 in response to sampling clock whose frequency is 2 fsc (fsc representing color a color carrier frequency), the output of the AD converter 138 being a 7-8 bits digital signal. The digital signal is routed to the RAM 150 and, then, written in the RAM 150 in response to write pulses generated by the memory control 130. The converted color signal fed from the low frequency range conversion circuit 144 to the AD converter 146 is converted to a digital signal by, for example, delta modulation in response to sampling clock the frequency of which is similar to that of the above-mentioned sampling clock. The digital signal is applied to the RAM 152 and, like the luminance signal component, written in the RAM 152 in response to write pulses generated by the memory control 130. The memory control 130, comparing the sync signals output from the sync detectors 128 and 148, supplies the RAMs 150 and 152 with read pulses which cause signals read out of the RAMs 150 and 152 to share substantially the same phase with the vertical sync signal of the first video signal. In response to these write pulses, the digital signal already stored in RAM 150 is read out and so is done the digital signal already stored in the RAM 152. Therefore, the digital signals output from the RAMs 150 and 152 (analog-to-digital converted versions of the luminance signal component and converted color signal component of the second video signal produced respectively by the AD converters 138 and 146) are substantially the same in phase as the vertical sync signal of the first video signal. The circuit arrangement of the memory control 130 is shown in Fig. 12. The sync signals from the sync detectors 128 and 148 are fed to an address counters 130₁ and 130₂, respectively. The sync signal from the sync detector 148 is also fed to a clock generator 130₃ which produces clock pulses which are fed to a sampling pulse generator 130₄ and to a read input of the address counter 130₁ and a write input of the address counter 130₂. The pulses are also fed through a gate circuit 130₅ to a data selector 130₆. The data selector 130 which is supplied with output signals from the address counters 130₁ and 130₂ supplies the RAMs 150 and 152 with the read pulses. The digital signal read out of the RAM 150 is converted by the DA converter 154 to an analog signal and supplied as a luminance signal component of the second video signal to the preemphasis circuit 156. The circuit 156 boosts a high frequency component of the luminance signal of the second video signal. The luminance signal component output from the circuit 156 is applied to the frequency modulator 158 and the resulting FM luminance signal component is applied to the mixer 160. Meanwhile, the digital signal read out of the RAM 152 is converted by the DA converter 162 to an analog signal and supplied as a converted color signal of the second video signal to the mixer 160. The mixer 160 mixes the FM luminance signal component and converted color signal component of the second video signal to produce a record signal to be recorded. The record signal is provided with an optimum recording current value by the record amplifier 164 and, then, routed through the rotary transformers 166 and 168 to the associated record heads 170 and 172. Hereinafter will be described, with reference to Figs. 2-8, a recording pattern which is developed on a recording medium by the record signals output from the record system shown in Fig. 1. In Fig. 2, there is shown a first example of a head arrangement in accordance with the illustrative embodiment of the present invention. As shown in Fig. 2, a rotary body 200 such as a rotary drum or a disc plate supports thereon a pair of rotary heads A₁ and A₂ which are disposed at an angular spacing of 180 degrees. The rotary body 100 also supports a rotary head B₁ in a position ahead of the head A₁ by a small angle with respect to a rotating direction of the body 200 (counterclockwise as indicated by an arrow in Fig. 2), i.e., a position adjacent to the head A₁ forming a head group, and a rotary head B₂ in a position behind of the head A₂ by a small angle with respect to the rotating direction of the body 200, i.e., a position adjacent to the head A₂ forming another head group. The heads A₁ and A₂ correspond respectively to the record heads 124 and 126 shown in Fig. 1, and the heads B₁ and B₂ to the record heads 170 and 172. That is, the record signal associated with the first video signal applied to the first input terminal 100 is coupled to the heads A₁ and A₂, and the record signal associated with the second video signal applied to the second input terminal 132 to the heads B₁ and B₂. The head arrangement of Fig. 2 is shown in a developed view in Fig. 3. As shown, the heads A₁ and A₂ have azimuth angles α which are the same in absolute value but opposite in sign. These azimuth angles are so selected to be compatible with currently marketed recording and playback apparatuses (e.g. +6 degrees and -6 degrees). On the other hand, the azimuth angle of the head B₁ is the same in absolute value as that of the head A₁ but opposite in direction, that is, equal to the azimuth angle of the head A₂. The azimuth angle of the head B₂ is the same in absolute value as that of the head A₂ but opposite in direction, that is, equal to the azimuth angle of the head A₁. As also shown in Fig. 3, the heads A₂ and B₁ share the same level, or height, while the heads A₁ and B₂ are higher than the heads A₂ and B₁ by a track pitch TP of tracks produced on a recording medium. In Fig. 3, TP designates the track pitch. Referring to Fig. 4, a recoding pattern developed by the head arrangement of Fig. 2 on a recording medium 202 is shown. In Fig. 4, TP designates the track pitch, and TD a recording width which is covered by one scan of either head group and corresponds to a track pitch designed for VTRs now in the market. In accordance with the illustrative embodiment, one field of information of the first and second video signals are recorded over the recording width TD. Assume that tracks on the recording medium which are provided by the heads A₁ and A₂ and associated with the first video signal constitute a program A as shaded tracks shown in Fig. 4 and those provided by the heads B₁ and B₂ and associated with the second video signal, a program B. The tracks formed by the head A₁ are labeled A₁ in Fig. 4, those formed by the head A₂ labeled A₂, those formed by the head B₁ labeled B₁, and those formed by the head B₂ labeled B₂. A transport direction of the recording medum 202 and a scanning direction of the heads are each indicated by arrows in Fig. 4. In the above condition, the heads at CH₁ in Fig. 3 (heads A₁ and B₁) develop tracks B₁ and A₁ in this order on the recording medium 202, while the heads at CH₂ in Fig. 3 (heads A₂ and B₂) develop tracks A₂ and B₂ in this order on the medium 202. Due to the particular relationship in azimuth angle between the heads A₁, A₂, B₁, and B₂ shown in Fig. 3, the difference in azimuth angle between nearby heads during formation of the recording pattern of Fig. 4 is double the absolute value of each head (e.g. 12 degrees), so that interference between nearby tracks is prevented during recording or playback. Further, the low frequency range conversion circuits 116 and 144 shown in Fig. 1 are constructed such that the phase shift associated with the program A and that associated with the program B are made opposite to each other (e.g. +90 degrees phase shift and -90 degrees phase shift), thereby eliminating crosstalk between the converted color signal components during the recording mode operation. In this construction, if the phase shift is switched by drum F/F pulses (drum switching pulses) in such a manner as to invert the phase shift direction associated with the track A₂ relative to that associated with the track A₁ and invert the phase shift direction associated with the track B₂ relative to that associated with the track B₁, the phase shifts in the nearby tracks in the recording pattern shown in Fig. 4 will be opposite to each other. That is, since the tracks A₁ and B₂ share the same phase shift (e.g. +90 degrees phase shift and labeled "+" in Fig. 4) and so do the tracks A₂ and B₁ (e.g. -90 degrees phase shift and labeled "-" in Fig. 4), crosstalk between the converted color signal components can be eliminated as in the currently available VTRs. In the head arrangement shown in Figs. 2 and 3, the head B₁ is positioned ahead of the head A₁ and the head B₂ behind of the head A₂, the angular spacing between the heads B₁ and B₂ being not 180 degrees. The 180 angular spacing is attainable if the heads are arranged in an alternative relationship shown in Fig. 6. That is, Fig. 5 shows a second example of the head arranement in accordance with the present invention. Fig. 6 is a developed view of the head arranement of Fig. 5. Referring to Fig. 5, a rotary body 200a is shown and rotating in a direction indicated by an arrow. In Figs. 5 and 6, the heads corresponding to the heads A₁, A₂, B₁ and B₂ of Figs. 2 and 3 are labeled C₁, C₂, D₁ and D₂, respectively; CH₁ and CH₂ of Fig. 3 correspond to CH₃ and CH₄, respectively. The azimuth angles of the heads C₁, C₂, D₁ and D₂ are each selected in correspondence with the heads A₁, A₂, B₁ and B₂. Further, the signals applied to the heads C₁, C₂, D₁ and D₂ correspond respectively to those applied to the heads A₁, A₂, B₁ and B₂. The heads C₁ and D₁ at CH₃ in Fig. 6 are arranged in the same manner as the heads A₁ and B₁ of Figs. 2 and 3 and, therefore, produce a similar recording pattern. That is, they form the tracks B₁ and A₁ in this order on the recording medium 202a. The heads C₂ and D₂ at CH₄, on the other hand, are different in arrangement from the heads A₂ and B₂ of Fig. 3 (opposite arrangement) and, therefore, they develop the tracks B₂ and A₂ of Fig. 4 in this order. Hence, should the head C₂ have a substantial width, the track B₂ formed by the head D₂ which is ahead of the head C₂ would partly be erased while the head C₂ is forming the track A₂. It follows that to achieve a desirable recording pattern at least the head C₂ has to be provided with a width which is equal to the track pitch TP. The phase shifts applied to the converted color signal components of the record signals which are applied to the heads of Figs. 5 and 6 are the same as those of the converted color signal components of the record signals which are applied to the heads of Figs. 2 and 3. Therefore, the heads C₁, C₂, D₁ and D₂ in the arrangement of Figs. 5 an 6 will develop a recording pattern which is identical with the recording pattern of Fig. 4. A third example of the head arrangement in accordance with the present invention is shown in Fig. 7 which, like the second example, sets up an angular spacing of 180 degrees between each associated heads. Fig. 8 shows a recording pattern developed on a recording medium by the head arrangement of Fig. 7. In Fig. 7, CH₅ and CH₆ correspond respectively to CH₁ and CH₂ of Fig. 3, and heads E₁, E₂, F₁ and F₂ to the heads A₁, A₂, A₃ and A₄. As shown in Fig. 7, the heads at CH₅ (heads E₁ and F₁) are each spaced 180 degrees from the heads at CH₆ (heads E₂ and F₂). The head F₁ at CH₅ is positioned higher than the head E₁ by a vertical distance equal to the track pitch TP. The centers of the heads E₁ and F₁ are aligned with each other. The head F₂ at CH₆ is higher than the head E₂ by a vertical distance equal to the track pitch TP. The centers of the heads E₂ and F₂ are aligned with each other. The top of the head E₂ and the bottom of the head E₁ are at the same height and so are the top of the head E₁ and the bottom of the head F₂. Further, the top of the head F₂ and the bottom of the head F₁ are at the same height. Referring to Fig. 8, 202a designates a recording medium, TP the track pitch, and TD the recording width covered by one scan of the heads and corresponding to a track pitch designed for current VTRs. In the illustrative embodiment, one field of information of the first and second video signals is recorded over the recording width TD. Assume that tracks on the recording medium 202a developed by the heads E₁ and E₂ and associated with the first video signal constitute a program E as shaded tracks shown in Fig. 8 and those developed by the heads F₁ and F₂ and associated with the second video signal, a program F. In Fig. 8, the tracks formed by the head E₁ are labeled E₁ in the recording pattern, the tracks formed by the head E₂ E₂, the tracks formed by the heads F₁ F₁, and the tracks formed by the heads F₂ F₂. A transport direction of the recording medium 202a and a rotating direction of the heads are each indicated by arrows in Fig. 8. When the head arrangement of Fig. 7 is employed for recording the signals, as shown in Fig. 8, the heads E₁ and F₁ at CH₅ produce the tracks E₁ and F₁ with an space track defined therebetween over a width equal to the track pitch TP. Then, the heads E₂ and F₂ produce the tracks E₂ and F₂. The track E₂ is formed in the above-mentioned empty space which extends over the track pitch TP and stores no information therein. The track F₂ is formed next to the track E₁. The heads E₁ and E₂ are different in azimuth angle from each other (e.g. +6 degrees and -6 degrees) and so are the heads F₁ and F₂ (e.g. +6 degrees and -6 degrees). The heads E₁ and F₁ at CH₅ share the same azimuth angle. In the recording pattern of Fig. 8 provided by such a head arrangement, the adjacent tracks are developed by those heads which have different azimuth angles so that interference therebetween is prevented as in the recording pattern provided by the head arrangement of Figs. 2 and 3. Further, where the head arrangement of Fig. 7 is used to provide tracks in the pattern shown in Fig. 8, the tracks are arranged in the order of E₁, E₂, F₁, F₂, E₁ ... Hence, the phase shift in the record signal applied to the head F₁ nees only be the same as the phase shift in the converted color signal of the record signal applied to the heads E₁ (e.g. +90 degrees phase shift and labeled "+" in Fig. 8) and, likewise, the phase shift in the record signal applied to the head F₂ needs only be the same as the phase shift in the converted color signal of the record signal applied to the head E₂ (e.g. -90 degrees phase shift and labeled "-" in Fig. 8). In the meantime, audio signals are recorded in audio tracks as is the case with current VTRs. Specifically, using audio tracks of a current VTR (stereophonic audio tracks), the program A (or E) may be recorded in the R-channel track of the stereophonic audio tracks and the program B (or F) in the L-channel track. In the illustrative embodiment, the recording system is constructed to simultaneously record in a single recording medium two different programs, i.e., two different video signals which are the first video signal (program A in Fig. 4 or program E in Fig. 8) and the second video signal (program B in Fig. 4 or program F in Fig. 8). Further, the recording system shown and described has recorded low frequency converted color signals to which a phase-shift (PS) signal processing is applied. If desired, the PS signal processing system may be replaced with a so-called phase inversion (PI) signal processing system. In accordance with the PI signal processing system, a low frequency converted color signal the phase of which is inverted by each 180 degrees at every 1 H (horizontal scan period) will be recorded in a certain track, and a low frequency converted color signal aligned in phase in the next track. Reference will be made to Figs. 8-11 for describing a playback system for reproducing the signals recorded in accordance with the illustrative embodiment of the present invention. As shown in a block diagram in Fig. 9, the playback system, generally 20 comprises a playback head 300, a rotary transformer 302, a preamplifier 304, a switch 306, a playback head 308, a rotary transformer 310, a preamplifier 312, a high-pass filter (HPF) 314, a frequency demodulator 316, an LPF 318, a deemphasis circuit 320, a mixer 322, an LPF 324, a high frequency conversion circuit 326, a BPF 328, a comb filter 330, a first output terminal 332, a playback head 334, a rotary transformer 336, a preamplifier 338, a switch 340, a playback head 342, a rotary transformer 344, a preamplifier 346, and a second output terminal 348. A playback arrangement associated with the signal in the program A or E, which is the first video signal applied to the first input terminal 100 of Fig. 1, will be explained first. The signal reproduced by the playback head 300 (first video signal stored in the tracks A₁ of Fig. 4 or the tracks E₁ of Fig. 8) is amplified by the preamplifier 304 to a predetermined signal level and, then, fed to the switch 306. Meanwhile, the signal reproduced by the playback head 308 (first signal stored in the tracks A₂ of Fig. 4 or the tracks E₂ of Fig. 8) is passed through the rotary transformer 310 to the preamplifier 312 to be thereby amplified to a predetermined signal level. The output of the preamplifier 312 is applied to the switch 306 which serves to connect one of the playback heads 300 and 308 which is reproducing an information signal out of the recording medium to the succeeding signal processing circuit. One of the reproduced signals output from the switch 306 is routed to the HPF 314 to separate a frequency modulated component of the reproduced luminance signal. The separated frequency modulated component is demodulated by the frequency demodulator 316 the output of which is applied to the deemphasis circuit 320. The circuit 320 functions to attenuate the high frequency component which has been boosted by the preemphasis circuit 106 of Fig. 1, the output of the circuit 320 being delivered to the mixer 322. The output of the switch 306 is also applied to the LPF 324 to separate the low frequency converted color signal component therefrom. The color signal component has been converted by previously the low frequency conversion circuit 116 of Fig. 1 to lie in a low frequency band. Supplied with the color signal component, the high frequency conversion circuit 326 reconverts the lowered frequency of the input signal back to that of the original color signal component while applying phase shift thereto which is opposite to the previously described phase shift. The output of the circuit 326 is passed through the BPF 328 and comb filter 330 to remove a crosstalk component and, then, fed to the mixer 322. The mixer 322 performs predetermined signal processing on the reproduced luminance signal and the reproduced color signal, then mixes them, and then delivers the composite signal to the first output terminal 332. Next, a playback arrangement associated with the second video signal, or program B, applied to the second input terminal 132 of Fig. 1 will be described. The signal reproduced by the playback head 334 (second video signal stored in the tracks B₁ of Fig. 4 or the tracks F₁ of Fig. 8) is applied to the switch 340 after being amplified by the preamplifier 338 to a predetermined signal level. The signal reproduced by the playback head 342 (second video signal stored in the tracks B₂ of Fig. 4 or the tracks F₂ of Fig. 8) are passed though the rotary transformer 344 to the preamplifier 346 to be thereby amplified to a predetermined signal level, the amplified signal being delivered to the switch 340. The switch 340 connects one of the playback heads 334 and 342 which is reading an information signal output of the recording medium to the succeeding signal processing circuit. The reproduced signal from the switch 340 is fed out from the second output terminal 348 as a reproduced video signal (second video signal) after being processed in the same manner as the reproduced signal associated with the program A (or E). Referring to Fig. 10, there is shown a second example of the playback system of the illustrative recording and playback apparatus. In Fig. 10, the same structural elements as those shown in Fig. 9 are designated by like reference numerals and detailed description thereof will be omitted for simplicity. As shown, the playback system comprises, in addition to the HPF 314, frequency demodulator 316, LPF 318, deemphasis circuit 320, mixer 322, LPF 324, high frequency conversion circuit, BPF 328 and comb filter 330, a playback head 400, a rotary transformer 402, a preamplifier 404, a switch 406, a playback head 408, a rotary transformer 410, a preamplifier 412, a playback head 414, a rotary transformer 416, a preamplifier 418, a switch 420, a playback head 422, a rotary transformer 424, a preamplifier 426, a switch 428, and an output terminal 430. In Fig. 10, the playback heads 400 and 408, rotary transformers 402 and 410, preamplifiers 404 and 412, and switch 406 constitute a network for reproducing the program A or E out of the recording medium (first video signal stored in the tracks A₁ and A₂ of Fig. 4 or the tracks E₁ and E₂ of Fig. 8). Likewise, the playback heads 414 and 422, rotary transformers 416 and 424, preamplifiers 418 and 426, and switch 420 constitute a network for reproducing the program B or F out of the recording medium (second video signal stored in the tracks B₁ and B₂ of Fig. 4 or the tracks F₁ and F₂ of Fig. 8). The switch 428 functions to selectively deliver the signals output from the stitches 406 and 420 to a signal processing circuit which will be decribed, that is, it serves to select either the program A (or E) or the program B (or F). The reproduced signal output from the switch 428 is applied to the output terminal 430 as a reproduced video signal (first or second video signal) after being subjected to signal processing similar to one described in relation with the playback arrangement of Fig. 9. In Fig. 11, the same structural elements as those shown in Fig. 9 are designated by like reference numerals and details thereof will not be described any further. The playback system 40 in Fig. 11 comprises, in addition to the HPF 314, frequency demodulator 316, LPF 318, deemphasis circuit 320, mixer 322, LPF 324, high frequency conversion circuit 326, BPF 328, and comb filter 330, a playback head 500, a rotary transformer 502, a preamplifier 504, a switch 506, a playback head 508, a rotary transformer 510, a preamplifier 512, and an output terminal 514. The playback arrangement shown in Fig. 11 is identical with those installed in VTRs currently in the market. This implies that even an existing VTR is capable of reproducing video signals which were recorded by the recording and playback apparatus of the present invention. Specifically, assuming that the playback system of Fig. 11 is operating to reproduce the signal in the program A (or E), crosstalk from the program B (or F) does not occur during reproduction of the program A (or E) due to the azimuth effect and the difference in phase shift between the nearby tracks. Such insures faithful reproduction of the program A (or E). Concerning the program B (or F), it will be reproduced by adjusting the head tracking of the VTR. Again, the program B (or F) can be faithfully reproduced due to the azimuth effect and the difference in phase shift between the nearby tracks. In accordance with the embodiment described above, a single recording and playback apparatus is enabled to record, unattended, a plurality of desired TV programs which are broadcast in the same time zone. Also, a plurality of video cameras may be connected to a single recording and playback apparatus in order to record video and audio signals as desired. For example, one video camera connected to the apparatus may be fixed in place to pick up a desired scene over a wide angle and another may be held by hand to shoot telescopic details of the same scene.

Claims: A recording system in an apparatus for recording and reproducing two discrete composite video signals in and out of a single magnetic tape, comprising: first record signal processing means (102...118) for providing a first record signal to be recorded from the first one of the composite video signals, second record signal processing means (134...164) for providing a second signal to be recorded from the other one of said composite video signals, a rotary body (200) partially surrounded by said tape (202) and supporting head means (124,126,170,172) for recording said record signals onto the magnetic tape (202) in parallel tracks inclined with respect to the longitudinal direction of said tape (202), wherein said rotary head means comprise a pair of heads (A₁, A2;B₁,B2) for each of said record signals, said heads being switched on and off by a switching arrangement (306,340;406,420,428) and being disposed at the circumference of said rotary body in groups each comprising two heads and recording simultaneously, said groups being circumferentially spaced and each comprising one head of each pair, the heads of one group being offset with respect to each other in axial direction of said rotary body (200), delay means (128,130,148,150,152) for sychronizing the vertical sync signal of one of the composite video signals to the vertical sync signal of the other composite video signal characterized in that a) said switching arrangement switches the heads such that in a pair of adjacent tracks of said tape (202) record signals of one of said composite video signals are recorded whereas in an adjacent pair of adjacent tracks record signals of the other composite video signals are recorded, and b) each of said signal processing means comprises circuit means (116,144) arranged to provide a phase alteration of the colour signals of the composite video signals for every horizontal sync period so that a phase relationship between the respective colour signals recorded respectively on adjacent tracks is opposite to each other to eliminate cross talk therebetween. A recording system as set forth in claim 1 characterized in that the heads of one group have different azimuth angles with respect to each other. A recording system as set forth in claim 1 characterized in that the heads of one group have common azimuth angles. A recording system as claimed in any one of claims 1 to 3, characterized in that the first record signal processing means comprise luminance signal separator means (104) for separating the luminance signal component from the first composite video signal, frequency modulator means (108) for modulating the frequency of the luminance signal component to produce a frequency modulated luminance signal, colour signal separator means (112) for separating the color signal from the first composite video signal, low frequency conversion means (116) for producing a low frequency converted color signal by processing the color signal component such that a phase relationship between the color signal components in nearby tracks varies at every one horizontal scan period and by converting the frequency of the color signal component to one in a low frequency band, and mixer means (103) for mixing the frequency modulated luminance signal and the low frequency converted color signal to produce the first record signal. A recording system as claimed in claim 4, characterized in that the luminance signal component separator means comprises a low-pass filter (104). A recording system as claimed in claim 5, characterized in that the first record signal processing means further comprises automatic gain control means (102) for controlling the signal level of the first composite video signal to predetermined one, and preemphasis means (106) for emphasizing the high frequency component of the luminance signal component which is applied thereto from the low-pass filter (104). A recording system as claimed in claim 4, characterized in that the color signal component separator means comprises a band-pass filter (112). A recording system as claimed in claim 7, characterized in that the first record signal processing means further comprises automatic chroma control means (114) for controlling the level of the color burst signal of the color signal component from the band-pass filter (112) to be constant.

Inventors: UCHIMI, TAKASHI
Applicants: VICTOR COMPANY OF JAPAN, LIMITED
Application year: 1984
Main classification: H04N5
IPC codes: G11B5, H04N9, H04N5