Abstract:
A recording apparatus operates in any one of a standard mode and a high-quality mode. The apparatus records a video signal of a standard format during the standard mode of operation. The apparatus records a video signal of a high-quality format during the high-quality mode of operation. A signal processing circuit for use in the apparatus includes a first device for subjecting a first signal to a nonlinear emphasis process to convert the first signal into a second signal. A second device operates for selecting one of the first signal and the second signal in response to whether the apparatus operates in the standard mode or the high-quality mode, and for outputting the selected signal as a third signal. A third device operates for subjecting the third signal to a nonlinear de-emphasis process to convert the third signal into a fourth signal. A fourth device operates for selecting one of the third signal and the fourth signal in response to whether the apparatus operates in the standard mode or the high-quality mode, and for outputting the selected signal as a fifth signal. A fifth device operates for separating a sync signal from the fifth signal. During the standard mode of operation of the apparatus, the first device selects the first signal, and the fourth device selects the third signal. During the high-quality mode of operation of the apparatus, the first device selects the second signal, and the fourth device selects the fourth signal.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a signal processing circuit for separating a sync signal from a video signal. The signal processing circuit of this invention can be used in a magnetic recording apparatus. This invention also relates to a signal processing apparatus. 
     2. Description of the Related Art 
     Some video tape recorders (VTR&#39;s) are based on a standard format referred to as a VHS format. There is an S-VHS format which improves over the VHS format. A VTR of the S-VHS standard can record and reproduce a video signal which is wider in frequency band and higher in picture quality than a video signal handled by a VTR of the VHS standard. 
     To provide compatibility with the VHS VTR, the S-VHS VTR is designed to record and reproduce a video signal in any one of the S-VHS format and the VHS format. During the VHS recording mode of operation of the VTR, the video signal is processed according to the VHS format. On the other hand, during the S-VHS recording mode of operation of the VTR, the video signal is processed according to the S-VHS format. If the S-VHS processing of the video signal includes a step of sub emphasis, it tends to be difficult to correctly separate a sync signal from the sub-emphasis-resultant video signal. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide a signal processing circuit for correctly separating a sync signal from a video signal. 
     It is another object of this invention to provide an improved signal processing apparatus. 
     A first aspect of this invention provides a signal processing circuit for use in a recording apparatus which operates in any one of a standard mode and a high-quality mode, the apparatus recording a video signal of a standard format during the standard mode of operation, the apparatus recording a video signal of a high-quality format during the high-quality mode of operation, wherein the video signal of the high-quality format is wider in frequency band than the video signal of the standard format. The circuit comprises first means for subjecting a first signal to a nonlinear emphasis process to convert the first signal into a second signal; second means for selecting one of the first signal and the second signal in response to whether the apparatus operates in the standard mode or the high-quality mode, and for outputting the selected signal as a third signal; third means for subjecting the third signal to a nonlinear de-emphasis process to convert the third signal into a fourth signal, the nonlinear de-emphasis process being inverse with respect to the nonlinear emphasis process; fourth means for selecting one of the third signal and the fourth signal in response to whether the apparatus operates in the standard mode or the high-quality mode, and for outputting the selected signal as a fifth signal; and fifth means for separating a sync signal from the fifth signal; wherein during the standard mode of operation of the apparatus, the first means selects the first signal, and the fourth means selects the third signal; and wherein during the high-quality mode of operation of the apparatus, the first means selects the second signal, and the fourth means selects the fourth signal. 
     A second aspect of this invention provides a signal processing circuit comprising first means for subjecting a first video signal to a nonlinear emphasis process to convert the first video signal into a second video signal; second means for selecting one of the first video signal and the second video signal, and for outputting the selected video signal as a third video signal; third means for subjecting the third video signal to a nonlinear de-emphasis process to convert the third video signal into a fourth video signal, the nonlinear de-emphasis process being inverse with respect to the nonlinear emphasis process; fourth means for selecting the third video signal when the second means selects the first video signal, for selecting the fourth video signal when the second means selects the second video signal, and for outputting the selected signal as a fifth video signal; and fifth means for separating a sync signal from the fifth video signal. 
     A third aspect of this invention provides a video signal processing apparatus comprising a first video signal processing circuit; and a second video signal processing circuit connectable to the first video signal processing circuit; wherein the first video signal processing circuit and the second video signal processing circuit comprise means for processing either a video signal of a standard format or a video signal of a high-quality format into a record signal in the presence of the second video signal processing circuit connected to the first video signal processing circuit, and the video signal of the high-quality format is higher in picture quality than the video signal of the standard format and is wider in frequency band than the video signal of the standard format; wherein the first video signal processing circuit comprises means for processing a video signal of the standard format into a record signal in the absence of the second video signal processing circuit; wherein the second video signal processing circuit comprises means for subjecting the video signal of the high-quality format to a nonlinear emphasis process to convert the video signal of the high-quality format into a first processing-resultant signal; and wherein the first video signal processing circuit comprises means for subjecting the first processing-resultant signal to a nonlinear de-emphasis process to convert the first processing-resultant signal into a second processing-resultant signal, and means for separating a sync signal from the second processing-resultant signal, the nonlinear de-emphasis process being inverse with respect to the nonlinear emphasis process. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a background-art signal processing circuit which is not prior art against this invention. 
     FIG. 2 is a time-domain diagram of a sync-pulse-added portion of a white signal, and a sync signal derived therefrom. 
     FIG. 3 is a time-domain diagram of a sync-pulse-added portion of a black signal, and a sync signal derived therefrom. 
     FIG. 4 is a block diagram of a signal processing circuit according to an embodiment of this invention. 
     FIG. 5 is a diagram of the relation among the mode of operation of the recording side of a magnetic recording and reproducing apparatus and the positions of switches in FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A background-art signal processing circuit which is not prior art against this invention will be explained below for a better understanding of this invention. 
     With reference to FIG. 1, the background-art signal processing circuit has a main signal processing portion  1  and an auxiliary signal processing portion (an added signal processing portion or an optional signal processing portion)  2 . 
     The main signal processing portion  1  implements video-signal processing for record according to the VHS format. When the auxiliary signal processing portion  2  is combined with the main signal processing portion  1 , it is possible to implement video-signal processing for record according to any one of the VHS format and the S-VHS format. 
     The main signal processing portion  1  includes a switch  3 , a sync separation circuit  4 , and a record processing circuit  5 . The auxiliary signal processing portion  2  includes a switch  6 , a sub emphasis circuit  7 , and a switch  8 . 
     In the case where the main signal processing portion  1  is used singly, a composite video signal is transmitted via the switch  3  to the sync separation circuit  4  and the record processing circuit  5 . The sync separation circuit  4  separates a sync signal from the composite video signal. The sync separation circuit  4  outputs the separated sync signal to the record processing circuit  5 . The sync separation circuit  4  outputs the separated sync signal also to an external. The record processing circuit  5  separates the composite video signal into a luminance signal and chrominance signals. The record processing circuit  5  processes the luminance signal. The record processing circuit  5  processes the chrominance signals. The record processing circuit  5  combines the processing-resultant luminance signal and the processing-resultant chrominance signals into a frequency-division multiplexed signal. The record processing circuit  5  outputs the frequency-division multiplexed signal as a record signal (a signal to be recorded). 
     In the case where the auxiliary signal processing portion  2  is combined with the main signal processing portion  1 , the switch  6  selects one of a composite video signal and a set of component video signals. When the switch  6  selects the composite video signal, the composite video signal is transmitted via the switch  6  to the sub emphasis circuit  7  and the switch  8 . In this case, the sub emphasis circuit  7  subjects the composite video signal (specifically, luminance components of the composite video signal) to a sub emphasis process including a nonlinear emphasis process. The sub emphasis circuit  7  outputs the sub-emphasis-resultant composite video signal to the switch  8 . When the switch  6  selects the set of the component video signals, the set of the component video signals is transmitted via the switch  6  to the sub emphasis circuit  7  and the switch  8 . In this case, the sub emphasis circuit  7  subjects the component video signals (specifically, a luminance signal among the component video signals) to the sub emphasis process. The sub emphasis circuit  7  outputs the set of the sub-emphasis-resultant component video signals to the switch  8 . 
     Operation of the combination of the main signal processing circuit  1  and the auxiliary signal processing circuit  2  can be changed between a VHS mode and an S-VHS mode. During the VHS mode of operation, the switch  8  selects the output signal of the switch  6  and transmits the selected signal to the switch  3 . The output signal of the switch  8  is transmitted via the switch  3  to the sync separation circuit  4  and the record processing circuit  5 . The sync separation circuit  4  separates a sync signal from the output signal of the switch  3 . The sync separation circuit  4  outputs the separated sync signal to the record processing circuit  5 . The sync separation circuit  4  outputs the separated sync signal also to the external. The record processing circuit  5  separates the output signal of the switch  3  into a luminance signal and chrominance signals. The record processing circuit  5  processes the luminance signal. The record processing circuit  5  processes the chrominance signals. The record processing circuit  5  combines the processing-resultant luminance signal and the processing-resultant chrominance signals into a frequency-division multiplexed signal. The record processing circuit  5  outputs the frequency-division multiplexed signal as a record signal (a signal to be recorded). 
     During the S-VHS mode of operation, the switch  8  selects the output signal of the sub emphasis circuit  7  and transmits the selected signal to the switch  3 . The output signal of the switch  8  is transmitted via the switch  3  to the sync separation circuit  4  and the record processing circuit  5 . The sync separation circuit  4  separates a sync signal from the output signal of the switch  3 . The sync separation circuit  4  outputs the separated sync signal to the record processing circuit  5 . The sync separation circuit  4  outputs the separated sync signal also to the external. The record processing circuit  5  separates the output signal of the switch  3  into a luminance signal and chrominance signals. The record processing circuit  5  processes the luminance signal. The record processing circuit  5  processes the chrominance signals. The record processing circuit  5  combines the processing-resultant luminance signal and the processing-resultant chrominance signals into a frequency-division multiplexed signal. The record processing circuit  5  outputs the frequency-division multiplexed signal as a record signal (a signal to be recorded). 
     In the sync separation circuit  4 , the output signal of the switch  3  is compared with a slice level to derive every sync pulse therefrom. During the S-VHS mode of operation, the output signal of the sub emphasis circuit  7  is transmitted to the sync separation circuit  4  via the switches  3  and  8 . Thus, during the S-VHS mode of operation, the signal inputted into the sync separation circuit  4  from the switch  3  results from the sub emphasis process. 
     FIG. 2 shows the waveform of a sync-pulse-added portion of a white signal inputted into the sync separation circuit  4  from the switch  3 . FIG. 3 shows the waveform of a sync-pulse-added portion of a black signal inputted into the sync separation circuit  4  from the switch  3 . The waveform of the sync-pulse-added portion of the white signal and the waveform of the sync-pulse-added portion of the black signal are different from each other. This difference is caused by a nonlinear emphasis characteristic of the sub emphasis circuit  7 . A greater-level signal is subjected to stronger emphasis by the sub emphasis circuit  7 . 
     As shown in FIG. 2, a separated sync pulse generated by comparing the white signal with the slice level has a relatively small width and a retarded start timing. As shown in FIG. 3, a separated sync pulse generated by comparing the black signal with the slice level has a relatively great width and an advanced start timing. 
     Accordingly, during the S-VHS mode of operation, pulses of the sync signal separated by the sync separation circuit  4  tend to have different widths and different start timings. Thus, the separated sync signal tends to be unreliable. 
     Embodiment of the Invention 
     A signal processing circuit according to an embodiment of this invention improves over the background-art signal processing circuit in FIG.  1 . Generally, the signal processing circuit of the embodiment of this invention is used in the recording side of a magnetic recording and reproducing apparatus capable of operating in any one of a VHS mode and an S-VHS mode. The magnetic recording and reproducing apparatus will be shortened to the apparatus hereinafter. During the VHS mode of operation of the apparatus, the recording side thereof processes an input video signal into a video signal of a VHS format. During the S-VHS mode of operation of the apparatus, the recording side thereof processes an input video signal into a video signal of an S-VHS format. The video signal of the S-VHS format is wider in frequency band and higher in picture quality than the video signal of the VHS format. 
     FIG. 4 shows the signal processing circuit of the embodiment of this invention. As shown in FIG. 4, the signal processing circuit includes a VHS signal processing portion  20 . An S-VHS signal processing portion  60  can be connected to the VHS signal processing portion  20 . It is preferable to provide the VHS signal processing portion  20  and the S-VHS signal processing portion  60  on separate printed circuit boards, respectively. 
     The S-VHS signal processing portion  60  may be omitted from the recording side of the apparatus. In the absence of the S-VHS signal processing portion  60 , the recording side of the apparatus is able to implement the processing of a VHS video signal only. On the other hand, in the presence of the S-VHS signal processing portion  60 , the recording side of the apparatus is able to implement the processing of a VHS video signal and also the processing of an S-VHS video signal. 
     As shown in FIG. 4, the VHS signal processing portion  20  includes switches SW 1 , SW 2 , SW 3 , and SW 4  while the S-VHS signal processing portion  60  includes switches SW 5 , SW 6 , SW 7 , and SW 8 . Each of the switches SW 1 -SW 8  has a movable contact, and first and second fixed contacts. Each of the switches SW 1 -SW 8  can change between a first position (a position ({circle around ( 1 )}) and a second position (a position {circle around ( 2 )}). In each of the switches SW 1 -SW 8 , the first and second fixed contacts are assigned to the first switch position (the switch position ({circle around ( 1 )}) and the second switch position (the switch position {circle around ( 2 )}) respectively. When each of the switches SW 1 -SW 8  assumes its first position, the movable contact thereof is connected to the first fixed contact thereof and is disconnected from the second fixed contact thereof. When each of the switches SW 1 -SW 8  assumes its second position, the movable contact thereof is connected to the second fixed contact thereof and is disconnected from the first fixed contact thereof. 
     With reference to FIG. 4, the VHS signal processing portion  20  includes the switch SW 1  and an AGC circuit  10 . The switch SW 1  is connected among an input terminal InV, the AGC circuit  10 , and a connection point “A”. The connection point “A” is provided between the VHS signal processing portion  20  and the S-VHS signal processing portion  60 . A composite video signal is applied to the switch SW 1  via the input terminal InV. The switch SW 1  transmits the composite video signal to either the AGC circuit  10  or the connection point “A”. 
     The AGC circuit  10  automatically adjusts the level of the composite video signal at a suitable level. In the VHS signal processing portion  20 , the AGC circuit  10  is followed by a low pass filter (LPF)  11  and the switch SW 4 . The AGC circuit  10  outputs the level-adjustment-resultant video signal to the low pass filter  11  and the switch SW 4 . The low pass filter  11  extracts a luminance signal from the output signal of the AGC circuit  10 . The cutoff frequency of the low pass filter  11  is set to 3 MHz (3 MHz or lower in passband) or lower. 
     The VHS signal processing portion  20  includes the switches SW 2  and SW 3 , a luminance signal processing circuit  12 , a chrominance signal processing circuit  13 , a sub de-emphasis circuit  14 , a sync separation circuit  15 , an adder  16 , and a recording amplifier  17 . 
     In the VHS signal processing portion  20 , the switch SW 2  is connected among the low pass filter  11 , a connection point “C”, the luminance signal processing circuit  12 , the sub de-emphasis circuit  14 , and the switch SW 3 . The connection point “C” is provided between the VHS signal processing portion  20  and the S-VHS signal processing portion  60 . The low pass filter  11  outputs the luminance signal to the switch SW 2 . A luminance signal can be transmitted from the S-VHS signal processing portion  60  to the switch SW 2  via the connection point “C”. The switch SW 2  selects one of the luminance signal from the low pass filter  11  and the luminance signal from the S-VHS signal processing portion  60 , and transmits the selected luminance signal to the luminance signal processing circuit  12 , the sub de-emphasis circuit  14 , and the switch SW 3 . 
     The sub de-emphasis circuit  14  is connected to the switch SW 3 . The sub de-emphasis circuit  14  subjects the luminance signal to a sub de-emphasis process including a nonlinear de-emphasis process. The sub de-emphasis circuit  14  outputs the resultant luminance signal to the switch SW 3 . 
     In the VHS signal processing portion  20 , the switch SW 3  is connected among the switch SW 2 , the sub de-emphasis circuit  14 , and the sync separation circuit  15 . The switch SW 3  selects one of the luminance signal from the switch SW 2  and the luminance signal from the sub de-emphasis circuit  14 , and transmits the selected luminance signal to the sync separation circuit  15 . The sync separation circuit  15  separates a sync signal from the luminance signal fed via the switch SW 3 . The sync separation circuit  15  is connected to the luminance signal processing circuit  12  and the chrominance signal processing circuit  13 . Also, the sync separation circuit  15  is connected to an output terminal for a sync signal. The sync separation circuit  15  outputs the separated sync signal to the luminance signal processing circuit  12  and the chrominance signal processing circuit  13 . The separated sync signal can be transmitted from the sync separation circuit  15  to an external device. 
     The luminance signal processing circuit  12  subjects the luminance signal from the switch SW 2  to various processes responsive to the sync signal fed from the sync separation circuit  15 . The processes by the luminance signal processing circuit  12  include a noise reduction process, a main emphasis process, a white/dark clipping process, and a frequency modulation process. The luminance signal processing circuit  12  outputs the resultant luminance signal (the FM modulated luminance signal). 
     In the VHS signal processing portion  20 , the switch SW 4  is connected among the AGC circuit  10 , a connection point “B”, and the chrominance signal processing circuit  13 . The connection point “B” is provided between the VHS signal processing portion  20  and the S-VHS signal processing portion  60 . A color signal can be transmitted from the S-VHS signal processing portion  60  to the switch SW 4  via the connection point “B”. The switch SW 4  selects one of the video signal from the AGC circuit  10  and the color signal from the S-VHS signal processing portion  60 , and transmits the selected signal to the chrominance signal processing circuit  13 . The chrominance signal processing circuit  13  processes the received signal in response to the sync signal fed from the sync separation circuit  15 . Specifically, the chrominance signal processing circuit  13  extracts components from the received signal which have frequencies in a given band assigned to chrominance. In other words, the chrominance signal processing circuit  13  extracts chrominance components from the received signal. The chrominance signal processing circuit  13  implements frequency down conversion of the chrominance components, and thereby generates frequency-down-converted chrominance signals. The chrominance signal processing circuit  13  outputs the frequency-down-converted chrominance signals. 
     The adder  16  follows the luminance signal processing circuit  12  and the chrominance signal processing circuit  13 . The adder  16  receives the FM modulated luminance signal from the luminance signal processing circuit  12 . The adder  16  receives the frequency-down-converted chrominance signals from the chrominance signal processing circuit  13 . The adder  16  multiplexes or combines the FM modulated luminance signal and the frequency-down-converted chrominance signals into a composite video signal on a frequency division basis. The adder  16  outputs the composite video signal to a recording current equalizer (not shown). The recording current equalizer processes the output signal of the adder  16  to compensate for variations in frequency response characteristics of parts including magnetic heads. The recording current equalizer outputs the resultant video signal to the recording amplifier  17 . The recording amplifier  17  enlarges the output signal of the recording current equalizer to a level suited to signal recording on a magnetic tape. The recording amplifier  17  outputs the resultant video signal. The output signal of the recording amplifier  17  is transmitted via rotary transformers to magnetic heads before being recorded on the magnetic tape by the magnetic heads. 
     In the absence of the S-VHS signal processing portion  60 , the switch SW 1  is fixed to a position {circle around ( 2 )} at which the AGC circuit  10  is connected to the input terminal InV, and the switch SW 2  is fixed to a position {circle around ( 2 )} at which the luminance signal processing circuit  12  and the switch SW 3  are connected to the low pass filter  11 . In addition, the switch SW 3  is fixed to a position {circle around ( 2 )} at which the sync separation circuit  15  is connected to the switch SW 2 , that is, connected to the low pass filter  11 . Furthermore, the switch SW 4  is fixed to a position {circle around ( 2 )} at which the chrominance signal processing circuit  13  is connected to the AGC circuit  10 . 
     In the absence of the S-VHS signal processing portion  60 , the composite video signal fed via the input terminal InV is processed by the AGC circuit  10 . The output signal of the AGC circuit  10  is processed into the luminance signal by the low pass filter  11 . The luminance signal is transmitted from the low pass filter  11  to the luminance signal processing circuit  12  and the sync separation circuit  15  via the switches SW 2  and SW 3 . The sync separation circuit  15  separates a sync signal from the luminance signal. In this case, since the luminance signal inputted into the sync separation circuit  15  differs from one which have been subjected to a nonlinear emphasis process (a sub emphasis process), the sync signal separated by the sync separation circuit  15  is correct and reliable. The sync separation circuit  15  outputs the separated sync signal to the luminance signal processing circuit  12  and the chrominance signal processing circuit  13 . The sync separation circuit  15  can also output the separated sync signal to an external device. The luminance signal processing circuit  12  processes the luminance signal into an FM modulated luminance signal in response to the sync signal fed from the sync separation circuit  15 . The luminance signal processing circuit  12  outputs the FM modulated luminance signal to the adder  16 . On the other hand, the output signal of the AGC circuit  110  is processed into frequency-down-converted chrominance signals by the chrominance signal processing circuit  13  in response to the sync signal fed from the sync separation circuit  15 . The chrominance signal processing circuit  13  outputs the frequency-down-converted chrominance signals to the adder  16 . The adder  16  combines the FM modulated luminance signal and the frequency-down-converted chrominance signals into a composite video signal. The composite video signal is transmitted from the adder  16  to an external device via the recording amplifier  17  as a record signal (a signal to be recorded). 
     The combination of the VHS signal processing portion  20  and the S-VHS signal processing portion  60  is able to implement the processing of an S-VHS video signal in addition to the processing of a VHS video signal. 
     As shown in FIG. 4, the S-VHS signal processing portion  60  includes the switches SW 5 , SW 6 , SW 7 , and SW 8 , an AGC circuit  50 , a Y/C separation circuit  51 , a low pass filter (LPF)  52 , a sub emphasis circuit  53 , and a low pass filter (LPF)  54 . 
     The switch SW 5  is connected among an input terminal InY, the connection point “A”, and the AGC circuit  50 . A luminance signal is applied to the switch SW 5  via the input terminal InY. A composite video signal can be transmitted from the VHS signal processing portion  20  to the switch SW 5  via the connection point “A”. The switch SW 5  selects one of the luminance signal from the input terminal InY and the composite video signal from the VHS signal processing portion  20 , and transmits the selected signal to the AGC circuit  50 . 
     The AGC circuit  50  automatically adjusts the level of the signal from the switch SW 5  at a suitable level. In the S-VHS signal processing portion  60 , the AGC circuit  50  is followed by the Y/C separation circuit  51  and the switch SW 6 . The AGC circuit  50  outputs the level-adjustment-resultant video signal to the Y/C separation circuit  51  and the switch SW 6 . The Y/C separation circuit  51  divides the output signal of the AGC circuit  50  into a luminance signal and a color signal. 
     In the S-VHS signal processing portion  60 , the switch SW 6  is connected among the AGC circuit  50 , the Y/C separation circuit  51 , and the low pass filters  52  and  54 . The Y/C separation circuit  51  outputs the luminance signal to the switch SW 6 . On the other hand, the luminance signal fed via the input terminal InY is transmitted to the switch SW 6  via the switch SW 5  and the AGC circuit  50 . The switch SW 6  selects one of the luminance signal from the Y/C separation circuit  51  and the luminance signal from the AGC circuit  50 , and transmits the selected luminance signal to the low pass filters  52  and  54 . 
     The low pass filter  52  processes the received luminance signal with a cutoff frequency of 5 MHz (5 MHz or lower in passband) or lower which matches with an S-VHS video signal. The low pass filter  52  is followed by the sub emphasis circuit  53 . The low pass filter  52  outputs the processing-resultant luminance signal to the sub emphasis circuit  53 . The sub emphasis circuit  53  subjects the luminance signal to a sub emphasis process including a nonlinear emphasis process. Specifically, the sub emphasis circuit  53  emphasizes high-frequency components of the luminance signal to enhance the luminance S/N. The sub emphasis circuit  53  outputs the resultant luminance signal. 
     The sub emphasis process by the sub emphasis circuit  53  in the S-VHS signal processing portion  60  and the sub de-emphasis process by the sub de-emphasis circuit  14  in the VHS signal processing portion  20  are inverse with respect to each other. 
     In the S-VHS signal processing portion  60 , the low pass filter  54  processes the received luminance signal with a cutoff frequency of 4 MHz or lower which matches with a VHS video signal. The low pass filter  54  outputs the processing-resultant luminance signal. 
     The switch SW 8  is connected among the sub emphasis circuit  53 , the low pass filter  54 , and the connection point “C”. The switch SW 8  receives the luminance signal from the sub emphasis circuit  53 . The switch SW 8  receives the luminance signal from the low pass filter  54 . The switch SW 8  selects one of the luminance signal from the sub emphasis circuit  53  and the luminance signal from the low pass filter  54 , and transmits the selected luminance signal to the VHS signal processing portion  20  via the connection point “C”. 
     The switch SW 7  is connected among an input terminal InC, the Y/C separation circuit  51 , and the connection point “B”. A color signal is applied to the switch SW 7  via the input terminal InC. The Y/C separation circuit  51  outputs the color signal to the switch SW 7 . The switch SW 7  selects one of the color signal from the input terminal InC and the color signal from the Y/C separation circuit  51 , and transmits the selected color signal to the VHS signal processing portion  20  via the connection terminal “B”. 
     In the presence of the S-VHS signal processing portion  60 , the composite video signal is transmitted from the switch SW 1  in the VHS signal processing portion  20  to the switch SW 5  in the S-VHS signal processing portion  60  via the connection point “A”. In addition, the luminance signal is transmitted from the switch SW 8  in the S-VHS signal processing portion  60  to the switch SW 2  in the VHS signal processing portion  20  via the connection point “C”. Furthermore, the color signal is transmitted from the switch SW 7  in the S-VHS signal processing portion  60  to the switch SW 4  in the VHS signal processing portion  20  via the connection point “B”. 
     In the presence of the S-VHS signal processing portion  60 , the recording side of the apparatus is able to implement the processing of a VHS video signal and also the processing of an S-VHS video signal. The recording side of the apparatus can handle the composite video signal fed via the input terminal InV, and also the component video signals, that is, the luminance signal and the color signal fed via the input terminals InY and InC. 
     In the presence of the S-VHS signal processing portion  60 , the recording side of the apparatus operates in a mode which can be changed among a composite VHS mode, a component VHS mode, a composite S-VHS mode, and a component S-VHS mode. As shown in FIG. 5, the positions of the switches SW 1 -SW 8  in the VHS signal processing portion  20  and the S-VHS signal processing portion  60  depend on the mode of operation of the recording side of the apparatus. 
     During the composite VHS mode of operation, the switch SW 1  in the VHS signal processing portion  20  is fixed to a position {circle around ( 1 )} at which a VHS composite video signal is transmitted from the input terminal InV to the switch SW 5  in the S-VHS signal processing portion  60  via the connection point “A”. The switch SW 2  in the VHS signal processing portion  20  is fixed to a position {circle around ( 1 )} at which the luminance signal is transmitted from the switch SW 8  in the S-VHS signal processing portion  60  to the luminance signal processing circuit  12  and the switch SW 3  in the VHS signal processing portion  20  via the connection point “C”. The switch SW 3  in the VHS signal processing portion  20  is fixed to a position {circle around ( 1 )} at which the sync separation circuit  15  is connected to the switch SW 2 , that is, connected to the switch SW 8  in the S-VHS signal processing portion  60 . The switch SW 4  in the VHS signal processing portion  20  is fixed to a position {circle around ( 3 )} at which the color signal is transmitted from the switch SW 7  in the S-VHS signal processing portion  60  to the chrominance signal processing circuit  13  in the VHS signal processing portion  20  via the connection point “B”. The switch SW 5  in the S-VHS signal processing portion  60  is fixed to a position {circle around ( 2 )} at which the composite video signal is transmitted from the switch SW 1  in the VHS signal processing portion  20  to the AGC circuit  50  in the S-VHS signal processing portion  60 . The switch SW 6  in the S-VHS signal processing portion  60  is fixed to a position {circle around ( 1 )} at which the low pass filters  52  and  54  are connected to the Y/C separation circuit  51 . The switch SW 7  in the S-VHS signal processing portion  60  is fixed to a position {circle around ( 1 )} at which the color signal is transmitted from the Y/C separation circuit  51  in the S-VHS signal processing portion  60  to the switch SW 4  in the VHS signal processing portion  20  via the connection point “B”. The switch SW 8  in the S-VHS signal processing portion  60  is fixed to a position {circle around ( 2 )} at which the luminance signal is transmitted from the low pass filter  54  to the switch SW 2  in the VHS signal processing portion  20  via the connection point “C”. 
     During the composite VHS mode of operation, a VHS composite video signal fed via the input terminal InV is transmitted to the AGC circuit  50  via the switches SW 1  and SW 5 . The composite video signal is successively processed by the AGC circuit  50  and the Y/C separation circuit  51 . The composite video signal is divided into a luminance signal and a color signal by the Y/C separation circuit  51 . The luminance signal is transmitted from the Y/C separation circuit  51  to the low pass filter  54  via the switch SW 6 . The luminance signal is processed by the low pass filter  54 . The processing-resultant luminance signal is transmitted from the low pass filter  54  to the luminance signal processing circuit  12  and the switch SW 3  via the switches SW 8  and SW 2 . Then, the luminance signal is transmitted via the switch SW 3  to the sync separation circuit  15 . The sync separation circuit  15  separates a sync signal from the luminance signal. In this case, since the luminance signal inputted into the sync separation circuit  15  differs from the output signal of the sub emphasis circuit  53 , the sync signal separated by the sync separation circuit  15  is correct and reliable. The sync separation circuit  15  outputs the separated sync signal to the luminance signal processing circuit  12  and the chrominance signal processing circuit  13 . The sync separation circuit  15  can also output the separated sync signal to an external device. The luminance signal processing circuit  12  processes the luminance signal into an FM modulated luminance signal in response to the sync signal fed from the sync separation circuit  15 . On the other hand, the color signal is transmitted from the Y/C separation circuit  51  to the chrominance signal processing circuit  13  via the switches SW 7  and SW 4 . The color signal is processed into frequency-down-converted chrominance signals by the chrominance signal processing circuit  13  in response to the sync signal fed from the sync separation circuit  15 . 
     During the component VHS mode of operation, the switch SW 1  in the VHS signal processing portion  20  is fixed to the position {circle around ( 1 )} at which the connection point “A” is connected to the input terminal InV. The switch SW 2  in the VHS signal processing portion  20  is fixed to the position {circle around ( 1 )} at which the luminance signal is transmitted from the switch SW 8  in the S-VHS signal processing portion  60  to the luminance signal processing circuit  12  and the switch SW 3  in the VHS signal processing portion  20  via the connection point “C”. The switch SW 3  in the VHS signal processing portion  20  is fixed to the position {circle around ( 2 )} at which the sync separation circuit  15  is connected to the switch SW 2 , that is, connected to the switch SW 8  in the S-VHS signal processing portion  60 . The switch SW 4  in the VHS signal processing portion  20  is fixed to the position {circle around ( 1 )} at which the color signal is transmitted from the switch SW 7  in the S-VHS signal processing portion  60  to the chrominance signal processing circuit  13  in the VHS signal processing portion  20  via the connection point “B”. The switch SW 5  in the S-VHS signal processing portion  60  is fixed to a position {circle around ( 1 )} at which a VHS luminance signal is transmitted from the input terminal InY to the AGC circuit  50  in the S-VHS signal processing portion  60 . The switch SW 6  in the S-VHS signal processing portion  60  is fixed to a position {circle around ( 2 )} at which the low pass filters  52  and  54  are connected to the AGC circuit  50  in the S-VHS signal processing portion  60 . The switch SW 7  in the S-VHS signal processing portion  60  is fixed to a position {circle around ( 2 )} at which a VHS color signal is transmitted from the input terminal InC to the switch SW 4  in the VHS signal processing portion  20  via the connection point “B”. The switch SW 8  in the S-VHS signal processing portion  60  is fixed to the position {circle around ( 2 )} at which the luminance signal is transmitted from the low pass filter  54  to the switch SW 2  in the VHS signal processing portion  20  via the connection point “C”. 
     During the component VHS mode of operation, a VHS luminance signal fed via the input terminal InY is transmitted to the AGC circuit  50  via the switch SW 5 . The luminance signal is processed by the AGC circuit  50 . The resultant luminance signal is transmitted from the AGC circuit  50  to the low pass filter  54  via the switch SW 6 . The luminance signal is processed by the low pass filter  54 . The processing-resultant luminance signal is transmitted from the low pass filter  54  to the luminance signal processing circuit  12  and the switch SW 3  via the switches SW 8  and SW 2 . Then, the luminance signal is transmitted via the switch SW 3  to the sync separation circuit  15 . The sync separation circuit  15  separates a sync signal from the luminance signal. In this case, since the luminance signal inputted into the sync separation circuit  15  differs from the output signal of the sub emphasis circuit  53 , the sync signal separated by the sync separation circuit  15  is correct and reliable. The sync separation circuit  15  outputs the separated sync signal to the luminance signal processing circuit  12  and the chrominance signal processing circuit  13 . The sync separation circuit  15  can also output the separated sync signal to an external device. The luminance signal processing circuit  12  processes the luminance signal into an FM modulated luminance signal in response to the sync signal fed from the sync separation circuit  15 . On the other hand, a VHS color signal fed via the input terminal InC is transmitted to the chrominance signal processing circuit  13  via the switches SW 7  and SW 4 . The color signal is processed into frequency-down-converted chrominance signals by the chrominance signal processing circuit  13  in response to the sync signal fed from the sync separation circuit  15 . 
     During the composite S-VHS mode of operation, the switch SW 1  in the VHS signal processing portion  20  is fixed to the position {circle around ( 1 )} at which an S-VHS composite video signal is transmitted from the input terminal InV to the switch SW 5  in the S-VHS signal processing portion  60  via the connection point “A”. The switch SW 2  in the VHS signal processing portion  20  is fixed to the position {circle around ( 1 )} at which the luminance signal is transmitted from the switch SW 8  in the S-VHS signal processing portion  60  to the luminance signal processing circuit  12  and the sub de-emphasis circuit  14  in the VHS signal processing portion  20  via the connection point “C”. The switch SW 3  in the VHS signal processing portion  20  is fixed to a position {circle around ( 1 )} at which the sync separation circuit  15  is connected to the sub de-emphasis circuit  14 . The switch SW 4  in the VHS signal processing portion  20  is fixed to the position {circle around ( 1 )} at which the color signal is transmitted from the switch SW 7  in the S-VHS signal processing portion  60  to the chrominance signal processing circuit  13  in the VHS signal processing portion  20  via the connection point “B”. The switch SW 5  in the S-VHS signal processing portion  60  is fixed to the position {circle around ( 2 )} at which the composite video signal is transmitted from the switch SW 1  in the VHS signal processing portion  20  to the AGC circuit  50  in the S-VHS signal processing portion  60 . The switch SW 6  in the S-VHS signal processing portion  60  is fixed to the position {circle around ( 1 )} at which the low pass filters  52  and  54  are connected to the Y/C separation circuit  51 . The switch SW 7  in the S-VHS signal processing portion  60  is fixed to the position {circle around ( 1 )} at which the color signal is transmitted from the Y/C separation circuit  51  in the S-VHS signal processing portion  60  to the switch SW 4  in the VHS signal processing portion  20  via the connection point “B”. The switch SW 8  in the S-VHS signal processing portion  60  is fixed to a position {circle around ( 1 )} at which the luminance signal is transmitted from the sub emphasis circuit  53  to the switch SW 2  in the VHS signal processing portion  20  via the connection point “C”. 
     During the composite S-VHS mode of operation, an S-VHS composite video signal fed via the input terminal InV is transmitted to the AGC circuit  50  via the switches SW 1  and SW 5 . The composite video signal is successively processed by the AGC circuit  50  and the Y/C separation circuit  51 . The composite video signal is divided into a luminance signal and a color signal by the Y/C separation circuit  51 . The luminance signal is transmitted from the Y/C separation circuit  51  to the low pass filter  52  via the switch SW 6 . The luminance signal is successively processed by the low pass filter  52  and the sub emphasis circuit  53 . Specifically, the sub emphasis circuit  53  subjects the output signal of the low pass filter  52  to the sub emphasis process. The processing-resultant luminance signal is transmitted from the sub emphasis circuit  53  to the luminance signal processing circuit  12  and the sub de-emphasis circuit  14  via the switches SW 8  and SW 2 . The sub de-emphasis circuit  14  subjects the luminance signal to a sub de-emphasis process inverse with respect to the sub emphasis process by the sub emphasis circuit  53 . Accordingly, the sub de-emphasis circuit  14  cancels the sub emphasis process by the sub emphasis circuit  53 . The sub de-emphasis circuit  14  outputs the resultant luminance signal to the switch SW 3 . The output signal of the sub de-emphasis circuit  14  is equivalent to the output signal of the low pass filter  52 . The luminance signal is transmitted via the switch SW 3  to the sync separation circuit  15 . The sync separation circuit  15  separates a sync signal from the luminance signal. In this case, since the sub emphasis process by the sub emphasis circuit  53  is canceled by the sub de-emphasis circuit  14  regarding the luminance signal, the sync signal separated by the sync separation circuit  15  is correct and reliable. The sync separation circuit  15  outputs the separated sync signal to the luminance signal processing circuit  12  and the chrominance signal processing circuit  13 . The sync separation circuit  15  can also output the separated sync signal to an external device. The luminance signal processing circuit  12  processes the luminance signal into an FM modulated luminance signal in response to the sync signal fed from the sync separation circuit  15 . On the other hand, the color signal is transmitted from the Y/C separation circuit  51  to the chrominance signal processing circuit  13  via the switches SW 7  and the SW 4 . The color signal is processed into frequency-down-converted chrominance signals by the chrominance signal processing circuit  13  in response to the sync signal fed from the sync separation circuit  15 . 
     During the component S-VHS mode of operation, the switch SW 1  in the VHS signal processing portion  20  is fixed to the position {circle around ( 1 )} at which the connection point “A” is connected to the input terminal InV. The switch SW 2  in the VHS signal processing portion  20  is fixed to the position {circle around ( 1 )} at which the luminance signal is transmitted from the switch SW 8  in the S-VHS signal processing portion  60  to the luminance signal processing circuit  12  and the sub de-emphasis circuit  14  in the VHS signal processing portion  20  via the connection point “C”. The switch SW 3  in the VHS signal processing portion  20  is fixed to the position {circle around ( 1 )} at which the sync separation circuit  15  is connected to the sub de-emphasis circuit  14 . The switch SW 4  in the VHS signal processing portion  20  is fixed to the position {circle around ( 1 )} at which the color signal is transmitted from the switch SW 7  in the S-VHS signal processing portion  60  to the chrominance signal processing circuit  13  in the VHS signal processing portion  20  via the connection point “B”. The switch SW 5  in the S-VHS signal processing portion  60  is fixed to the position {circle around ( 1 )} at which an S-VHS luminance signal is transmitted from the input terminal InY to the AGC circuit  50  in the S-VHS signal processing portion  60 . The switch SW 6  in the S-VHS signal processing portion  60  is fixed to the position {circle around ( 2 )} at which the low pass filters  52  and  54  are connected to the AGC circuit  50  in the S-VHS signal processing portion  60 . The switch SW 7  in the S-VHS signal processing portion  60  is fixed to the position {circle around ( 2 )} at which an S-VHS color signal is transmitted from the input terminal InC to the switch SW 4  in the VHS signal processing portion  20  via the connection point “B”. The switch SW 8  in the S-VHS signal processing portion  60  is fixed to the position {circle around ( 1 )} at which the luminance signal is transmitted from the sub emphasis circuit  53  to the switch SW 2  in the VHS signal processing portion  20  via the connection point “C”. 
     During the component S-VHS mode of operation, an S-VHS luminance signal fed via the input terminal InY is transmitted to the AGC circuit  50  via the switch SW 5 . The luminance signal is processed by the AGC circuit  50 . The resultant luminance signal is transmitted from the AGC circuit  50  to the low pass filter  52  via the switch SW 6 . The luminance signal is successively processed by the low pass filter  52  and the sub emphasis circuit  53 . Specifically, the sub emphasis circuit  53  subjects the output signal of the low pass filter  52  to the sub emphasis process. The processing-resultant luminance signal is transmitted from the sub emphasis circuit  53  to the luminance signal processing circuit  12  and the sub de-emphasis circuit  14  via the switches SW 8  and SW 2 . The sub de-emphasis circuit  14  subjects the luminance signal to the sub de-emphasis process inverse with respect to the sub emphasis process by the sub emphasis circuit  53 . Accordingly, the sub de-emphasis circuit  14  cancels the sub emphasis process by the sub emphasis circuit  53 . The sub de-emphasis circuit  14  outputs the resultant luminance signal to the switch SW 3 . The output signal of the sub de-emphasis circuit  14  is equivalent to the output signal of the low pass filter  52 . The luminance signal is transmitted via the switch SW 3  to the sync separation circuit  15 . The sync separation circuit  15  separates a sync signal from the luminance signal. In this case, since the sub emphasis process by the sub emphasis circuit  53  is canceled by the sub de-emphasis circuit  14  regarding the luminance signal, the sync signal separated by the sync separation circuit  15  is correct and reliable. The sync separation circuit  15  outputs the separated sync signal to the luminance signal processing circuit  12  and the chrominance signal processing circuit  13 . The sync separation circuit  15  can also output the separated sync signal to an external device. The luminance signal processing circuit  12  processes the luminance signal into an FM modulated luminance signal in response to the sync signal fed from the sync separation circuit  15 . On the other hand, an S-VHS color signal fed via the input terminal InC is transmitted to the chrominance signal processing circuit  13  via the switches SW 7  and SW 4 . The color signal is processed into frequency-down-converted chrominance signals by the chrominance signal processing circuit  13  in response to the sync signal fed from the sync separation circuit  15 . 
     During the composite VHS mode of operation, the component VHS mode of operation, the composite S-VHS mode of operation, and the component S-VHS mode of operation, the luminance signal processing circuit  12  outputs the FM modulated luminance signal to the adder  16 . On the other hand, the chrominance signal processing circuit  13  outputs the frequency-down-converted chrominance signals to the adder  16 . The adder  16  multiplexes or combines the FM modulated luminance signal and the frequency-down-converted chrominance signals into a composite video signal on a frequency division basis. The adder  16  outputs the composite video signal to the recording current equalizer (not shown). The recording current equalizer processes the output signal of the adder  16 , and outputs the resultant video signal to the recording amplifier  17 . The recording amplifier  17  enlarges the output signal of the recording current equalizer to the level suited to the signal recording on the magnetic tape. The recording amplifier  17  outputs the resultant video signal. The output signal of the recording amplifier  17  is transmitted via the rotary transformers to the magnetic heads before being recorded on the magnetic tape by the magnetic heads. 
     Preferably, the passband width of the VHS low pass filter  54  in the S-VHS signal processing portion  60  is slightly greater than that of the low pass filter  11  in the VHS signal processing portion  20 . 
     According to a first example, the switches SW 1 -SW 8  are changed in response to control signals generated via manually-operated buttons or keys. According to a second example, a decoder (not shown) including a ROM generates control signals in response to information representing the mode of operation of the apparatus. In the second example, the switches SW 1 -SW 8  are changed in response to the control signals generated by the decoder.