Apparatus for recording and reproducing a video signal

Abstract: A recording and reproducing apparatus prevents deterioration of the picture quality from being caused by overshoot, ringing or a noise component when, using a video tape recorder which can process two kinds of video signals having different aspect ratios, a video signal having a larger one of the aspect ratios is displayed on a television set. The recording and reproducing apparatus comprises a peaking circuit (19) for adding an overshoot or a ringing to a video signal, a noise canceller circuit (21) for cancelling noise from the video signal, and a comb line filter (22) for removing noise from the video signal. The peaking circuit, the noise canceller circuit and the comb line filter are capable of changing over the peaking frequency, the noise cancelling characteristic and the comb line filter characteristic thereof, respectively, in accordance with the aspect ratio of the video signal.

Description: This invention relates to recording and reproducing apparatus. Conventionally, television sets normally have an aspect ratio of 4:3 as shown in Fig. 9(a) of the accompanying drawings. Accordingly, video apparatuses which are connected in use to a television set, such as, for example, video tape recorders, are produced so as to match the aspect ratio. On the other hand, high definition television sets which have been developed recently include a number of scanning lines equal to twice that of conventional television sets and have a different aspect ratio, namely 16:9, as shown in Fig. 9(b) of the accompanying drawings. Accordingly, a video image which is of high picture quality and provides the feeling of presence can be obtained on a high definition television set. However, since high definition television sets are considerably expensive at the present time, television sets having the same number of scanning lines (e.g. 525) as that of conventional television sets, but having the different aspect ratio of 16:9, are produced. Consequently, video tape recorders are also required to process a video signal wherein the number of scanning lines is (for example) 525 and the aspect ratio is 16:9. However, since television sets having the aspect ratio of 4:3 prevail at the present time, video tape recorders which can record and reproduce both a video signal having the aspect ratio of 4:3 and another video signal having the aspect ratio of 16:9 are produced. In a video tape recorder of the type just described, aspect ratio information for distinguishing between the aspect ratios of 4:3 and 16:9 is recorded in a superimposed condition at a control portion or a vertical blanking portion of a video signal. A video tape recorder which can record and reproduce two different video signals having the different aspect ratios in this manner is normally constructed such that video signals having the different aspect ratios are processed in the same transmission band. In a video tape recorder of the type described above, when a video signal having the aspect ratio of 4:3 as seen in Fig. 9(a) is to be recorded, a predetermined overshoot is added in order to emphasize a contour of an image as seen from Fig. 10(a). On the other hand, when another video signal having the aspect ratio of 16:9 as seen in Fig. 9(b) is to be recorded, since it is recorded in the same transmission band as a video signal having the aspect ratio of 4:3 as described above, the video signal is reduced in the horizontal direction as seen from Fig. 10(b) and an overshoot similar to that which is added to a video signal having the aspect ratio of 4:3 is added to the video signal. As seen in Fig. 11(a), the width A of an overshoot when a video signal having the aspect ratio of 4:3 is reflected on a television set is set to a value at which the picture quality is not deteriorated. However, if a video signal having the aspect ratio of 16:9 is reflected in this condition on the television set as seen in Fig. 11(b), the image is expanded in the horizontal direction, and also the width B of the overshoot is expanded in the horizontal direction. Consequently, the picture quality is deteriorated. A similar phenomenon occurs not only in overshoot but also in any other factor of the picture quality such as a ringing or a noise component. According to one aspect of the invention there is provided a recording and reproducing apparatus for recording and reproducing a video signal having a first aspect ratio and another video signal having a second aspect ratio higher than the first aspect ratio, which comprises reproducing means for reproducing a video signal, means for detecting a brightness signal of the reproduced video signal, reproducing and detecting means for reproducing and detecting aspect ratio information, and peaking means for adding an overshoot or a ringing to the detected brightness signal with a predetermined peaking frequency, the peaking means being capable of changing over the peaking frequency in accordance with the aspect ratio information from the reproducing and detecting means. Thus, the width of an overshoot or a ringing applied to a video signal having the second aspect ratio may be made smaller than the width of an overshoot or a ringing applied to another video signal having the first aspect ratio. In the above recording and reproducing apparatus, the peaking frequency of the peaking means is changed over in accordance with an aspect ratio represented by the aspect ratio information of the video signal. Consequently, when the video signal has the second aspect ratio higher than the first ratio, the width of an overshoot or a ringing applied to the video signal can be reduced. Consequently, even when the video signal is displayed on a television set, the overshoot or the ringing appears within a suitable width. As a result, otherwise possible deterioration of the picture quality caused by overshoot or ringing can be prevented. According to another aspect of the invention there is provided a recording and reproducing apparatus for recording and reproducing a video signal having a first aspect ratio and another video signal having a second aspect ratio higher than the first aspect ratio, which comprises reproducing means for reproducing a video signal, means for detecting a brightness signal of the reproduced video signal, reproducing and detecting means for reproducing and detecting aspect ratio information, and noise cancelling means for cancelling noise components of the detected brightness signal, the noise cancelling means being capable of changing over the noise cancelling characteristic thereof in accordance with the aspect ratio information from the reproducing and detecting means. Thus, the width of noise components of a video signal having the second aspect ratio may be made smaller than the width of noise components of another video signal having the first aspect ratio. With the above recording and reproducing apparatus, the noise cancelling characteristic of the noise cancelling means is changed over in accordance with an aspect ratio represented by the aspect ratio information of the video image so that the width of noise components of a video signal having the second aspect ratio higher than the first aspect ratio may be made smaller than the width of noise components of another video signal having the first aspect ratio. Consequently, even when a video signal having the second aspect ratio higher than the first aspect ratio is displayed on a television set, the width of noise components of the image is small and the noise components are not emphasized. As a result, otherwise possible deterioration of the picture quality by noise can be prevented. According to a further aspect of the invention there is provided a recording and reproducing apparatus for recording and reproducing a video signal having a first aspect ratio and another video signal having a second aspect ratio higher than the first aspect ratio, which comprises reproducing means for reproducing a video signal, means for detecting a brightness signal of the reproduced video signal, reproducing and detecting means for reproducing and detecting aspect ratio information, and comb line filter means for removing noise components of the detected brightness signal, the comb line filter means being capable of changing over the comb line filter characteristic thereof in accordance with the aspect ratio information from the reproducing and detecting means. Thus, the width of noise components of a video signal having the second aspect ratio may be made smaller than the width of noise components of another video signal having the first aspect ratio. With the above recording and reproducing apparatus, the comb line filter characteristic of the comb line filter means is changed over in accordance with an aspect ratio represented by the aspect ratio information of the video image so that the width of noise components of a video signal having the second aspect ratio higher than the first aspect ratio may be made smaller than the width of noise components of another video signal having the first aspect ratio. Consequently, even when a video signal having the second aspect ratio higher than the first aspect ratio is displayed on a television set, the width of noise components of the image can be made small and the noise components are not emphasized. As a result, otherwise possible deterioration of the picture quality by noise can be prevented. Embodiments of the invention thus provide recording and reproducing apparatus which can prevent deterioration of picture quality from being caused by overshoot, ringing or a noise component when, using a video tape recorder which can process two kinds of video signals having different aspect ratios, a video signal having a greater one of the aspect ratios is displayed on a television set. The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawings, in which like parts or elements are denoted by like reference signs throughout, and in which: Fig. 1 is a block diagram of a recording system of a video tape recorder to which a recording and reproducing apparatus embodying the invention is applied; Fig. 2 is a block diagram of a reproducing system of the video tape recorder; Fig. 3 is a circuit diagram of a peaking circuit; Fig. 4 is a diagram showing a resonance frequency of the peaking circuit; Fig. 5 is a block diagram of a noise canceller; Fig. 6 is a diagram showing a characteristic of a high-pass filter; Fig. 7 is a block diagram of a comb line filter; Fig. 8 is a diagram showing a characteristic of the comb line filter; Figs. 9(a) and 9(b) are diagrammatic views showing aspect ratios of television sets; Figs. 10(a) and 10(b) are diagrams illustrating video signals of the aspect ratios; and Figs. 11(a) and 11(b) are diagrammatic views showing overshoots. Referring first to Fig. 1, there is shown a recording system of a video tape recorder to which a recording and reproducing apparatus embodying the present invention is applied. The recording system includes an AGC (automatic gain control) circuit 1 which receives a brightness signal Y of a video signal inputted, for example, from a video camera not shown and controls the gain of the brightness signal Y. The brightness signal Y is then supplied by way of a low-pass filter (LPF) 2 to an emphasis (EMPH) circuit 3, at which predetermined emphasis is applied to the brightness signal Y. The brightness signal Y is then FM modulated by an FM (frequency modulation) modulating circuit 4 and supplied to a mixing circuit 6 by way of a high-pass filter (HPF) 5. Meanwhile, a color signal C of the video signal is supplied by way of a band-pass filter (BPF) 7 to an ACC circuit 8, at which the amplitude of the color signal C is adjusted. The color signal C is then frequency converted by a frequency converting circuit (CONV) 9 and then supplied to the mixing circuit 6 by way of a low-pass filter (LPF) 10. The brightness signal Y and the color signal C are mixed at the mixing circuit 6, and the mixture signal is supplied by way of a recording amplifier 11 to a video head 12, by which the mixture signal, i.e., a video signal, is recorded onto a video track of a record tape T. Further, in the video tape recorder, aspect ratio information representing whether the aspect ratio of the input video signal is 4:3 or 16:9 is supplied by way of a control signal controlling circuit 13 to a control head 14, by which it is recorded onto a control track of the record tape T. Here, the aspect ratio information is set such that the high signal level represents the aspect ratio of 4:3 and the low signal level represents the aspect ratio of 16:9. Referring now to Fig. 2, there is shown a reproducing system of the video tape recorder. The video signal recorded on the record tape T is reproduced by the video head 12 and amplified by a reproduction amplifier 15. The brightness signal Y of the video signal is supplied by way of a high-pass filter (HPF) 16 to an FM demodulating circuit 17, at which it is detected. The thus demodulated brightness signal Y is supplied by way of a low-pass filter (LPF) 18 to a peaking circuit 18, at which an overshoot is added to the brightness signal Y. In the embodiment shown, the width of the overshoot can be varied by varying the center frequency of the peaking circuit 19 in accordance with the aspect ratio of the video signal as hereinafter described. The brightness signal Y outputted from the peaking circuit 19 is outputted to the outside by way of a de-emphasis circuit 20, a noise canceller 21 and a comb line filter 22. Meanwhile, the color signal C of the video signal from the reproduction amplifier 15 is outputted to the outside by way of a low-pass filter (LPF) 23, an ACC circuit 24, a frequency converting circuit (CONV) 25 and a band-pass filter (BPF) 26. Meanwhile, the control signal recorded on the control track of the record tape T is reproduced by the control head 14 and supplied to a detector (DETECT) 28 by way of an amplifier 27. At the detector 28, the aspect ratio information included in the control signal is detected. The aspect ratio information thus detected is on one hand supplied to the peaking circuit 19 and on the other hand introduced to a connecting terminal not shown to the outside. Referring now to Fig. 3, detailed construction of the peaking circuit 19 is shown. The peaking circuit 19 shown receives an input brightness signal Y at a resistor R1. The input brightness signal Y from the resistor R1 is amplified by a PNP transistor Q1. Meanwhile, aspect ratio information is supplied to another PNP transistor Q2 by way of another resistor R2. Here, when the aspect ratio is 4:3, a high level signal is supplied, and consequently, the PNP transistor Q2 is turned on. On the other hand, when the aspect ratio is 16:9, a low level signal is supplied so that the PNP transistor Q2 is turned off. Consequently, when the aspect ratio is 4:3, a resonance circuit is constructed wherein a coil L, a pair of capacitors C1 and C2 and a resistor R3 are connected in parallel. If it is assumed that the reference characters applied to the individual elements represent respective values of them, then the resonance frequency f1 of the resonance circuit is given by f1 = 1/2π(L(C1 + C2)) 1/2 In the present peaking circuit 19, the resonance circuit is constructed so that the resonance frequency f1 thereof may be 2 MHz as seen from Fig. 4. The resonance frequency f1 generated by the resonance circuit is superimposed by way of a resistor R3 (Fig. 3) on the brightness signal Y to make an overshoot and then forwarded to the de-emphasize circuit 20 (Fig. 2). The width of the overshoot then is set so that a video image reflected on a television set may not look ugly. On the other hand, when the aspect ratio is 16:9, since the PNP transistor Q2 presents an off state, the resonance circuit is constructed except the capacitor C2, and the resonance frequency f2 of the resonance circuit then is given by f2 = 1/2π(L x C1) 1/2 > f1 In the present peaking circuit 19, the resonance circuit is constructed so that the resonance frequency f2 thereof may be 4 MHz as seen from Fig. 4. Consequently, the width of an overshoot when a video image having the aspect ratio is 16:9 is reproduced is smaller than that of an overshoot when a video signal having the aspect ratio of 4:3 is reproduced. Consequently, when a video signal having the aspect ratio of 16:9 is to be reproduced and reflected on a television set, even if an overshoot added by a video tape recorder is expanded in the horizontal direction, it will have an extent substantially similar to that of an overshoot of a video image having the aspect ratio of 4:3. Accordingly, otherwise possible deterioration by the overshoot can be prevented. It is to be noted that also a ringing is processed similarly as in processing of an overshoot. With the above apparatus, deterioration of the picture quality by expansion of a noise component when a video image having a higher aspect ratio is reproduced and displayed on a television set can be prevented by changing over the characteristic of the noise canceller 21 of the video tape recorder described above in accordance with an aspect ratio. Referring now to Fig. 5, detailed construction of the noise canceller 21 is shown. A brightness signal Y inputted to the noise canceller 21 is supplied to a subtractor 31 and also to a pair of high-pass filters (HPF1, HPF2) 32A and 32B, at which high frequency components of the brightness signal Y are extracted. The characteristics of the high-pass filters 32A and 32B are set in such a manner as shown in Fig. 6. In particular, referring to Fig. 6, the high-pass filter 32A in the present noise canceller 21 has a pass band of 1 MHz or more while the other high-pass filter 32B has another pass band of 2 MHz or more. The outputs of the high-pass filters 32A and 32B are selectively changed over in response to an aspect ratio by means of a change-over switch 33. In particular, when the aspect ratio is 4:3, the switch 33 is changed over to the high-pass filter 32A side, but when the aspect ratio is 16:9, the switch 33 is changed over to the high-pass filter 32B side. The high frequency components outputted from the high-pass filter 32A or the high-pass filter 32B in this manner are supplied to a limiter (LIM) 34, at which amplitude variations are removed from the high frequency components to extract noise components. The noise components are supplied by way of a low-pass filter 35 to a gain controller 36. A gain of the noise components is set to a predetermined value at the gain controller 36, and then, the noise components are supplied to the subtractor 31. The noise components are subtracted from the brightness signal Y at the subtractor 31. Consequently, the noise components are removed from the video signal. Where the noise canceller 21 constructed in such a manner as described above is employed, when a video signal having the aspect ratio of 16:9 is reproduced, noise components on the higher frequency side than those when a video signal having the aspect ratio of 4:3 is reproduced are removed. Consequently, even if the video signal is expanded in the horizontal direction when it is reflected on a television set, no striking noise can be observed on the image. It is to be noted that, while the high-pass filter 32A and the high-pass filter 32B which have different characteristics from each other are selectively used in accordance with an aspect ratio, the characteristic of the gain controller 36 may be varied simultaneously in accordance with the aspect ratio. According to the present apparatus, the characteristic 22 of the comb line filter (COMB) 22 which is provided to reduce noise components may be varied in accordance with an aspect ratio. Fig. 7 shows detailed construction of the comb line filter 22. Referring to Fig. 7, a video signal supplied from the noise canceller 21 to the comb line filter 22 is then supplied by way of a subtractor 40 to a pair of subtractors 41 and 42 and a 1H delay circuit 43. At the subtractor 41, a video image of last frame supplied thereto from the 1H delay circuit 43 is subtracted from another video image of the present frame to extract high frequency components, and the high frequency components pass through a limiter 44 to extract noise components. The noise components are supplied to a pair of gain amplifiers 45A and 45B, at which they are individually set to different predetermined gains. The outputs of the gain amplifiers 45A and 45B are selectively supplied by way of a change-over switch 46 to the subtractor 42, at which the selected output is subtracted from the video signal at present. Consequently, a video image in which noise components have been reduced can be obtained. Here, the gain amplifier 45B is set so that it has a gain higher than the gain of the other gain amplifier 45A. The change-over switch 46 is changed over in accordance with aspect ratio information. In particular, the change-over switch 46 is changed over to the gain amplifier 45 side when the aspect ratio is 4:3, but when the aspect ratio is 16:9, the change-over switch 46 is changed over to the gain amplifier 45B side. Accordingly, when the aspect ratio is 16:9, a video signal outputted from the subtractor 42 has a smaller amplitude at a predetermined frequency than the amplitude of a video image when the aspect ratio is 4:3 as seen from Fig. 8. Consequently, even when a video signal having the aspect ratio of 16:9 is reproduced, no striking noise can be observed on the screen of a television set. It is to be noted that, in the comb line filter 22 shown in Fig. 7, the output of the limiter 44 is fed back to the subtractor 40 side, and a pair of gain amplifiers 47A and 47B are interposed in the feedback circuit and the outputs thereof are selectively changed over by a change-over switch 48. Thus, similarly as described above, when the aspect ratio is 16:9, the change-over switch 48 is changed over to the gain amplifier 47B side having a higher gain, but when the aspect ratio is 4:3, the change-over switch 48 is changed over to the gain amplifier 47A side having a lower gain. Consequently, a video signal in which noise has been further reduced can be obtained.

Claims: A recording and reproducing apparatus for recording and reproducing a video signal having a first aspect ratio and another video signal having a second aspect ratio higher than the first aspect ratio, comprising: reproducing means for reproducing a video signal; means for detecting a brightness signal of the reproduced video signal; reproducing and detecting means for reproducing and detecting aspect ratio information; and peaking means for adding an overshoot or a ringing to the detected brightness signal with a predetermined peaking frequency, said peaking means being capable of changing over the peaking frequency in accordance with the aspect ratio information from said reproducing and detecting means. A recording and reproducing apparatus according to claim 1, wherein said peaking means includes a first transistor for receiving a brightness signal, a resonance circuit connected to said first transistor and consisting of a plurality of elements connected in parallel, and a second transistor for receiving aspect ratio information from said reproducing and detecting means and rendering a particular one of said elements of said resonance circuit effective or ineffective in response to said aspect ratio information so that, when the aspect ratio information represents the second aspect ratio, said resonance circuit may resonate at a frequency higher than the frequency at which said resonance circuit resonates when the aspect ratio information represents the first aspect ratio. A recording and reproducing apparatus for recording and reproducing a video signal having a first aspect ratio and another video signal having a second aspect ratio higher than the first aspect ratio, comprising: reproducing means for reproducing a video signal; means for detecting a brightness signal of the reproduced video signal; reproducing and detecting means for reproducing and detecting aspect ratio information; and noise cancelling means for cancelling noise components of the detected brightness signal, said noise cancelling means being capable of changing over the noise cancelling characteristic thereof in accordance with the aspect ratio information from said reproducing and detecting means. A recording and reproducing apparatus according to claim 3, wherein said noise cancelling means includes first and second high-pass filters having lower and higher pass bands for receiving a brightness signal, noise extracting means for extracting noise components from the output of a selected one of said first and second high-pass filters, subtracting means for subtracting the extracted noise components from the brightness signal, and switching means for selectively coupling the outputs of said first and second high-pass filters to said noise extracting means. A recording and reproducing apparatus for recording and reproducing a video signal having a first aspect ratio and another video signal having a second aspect ratio higher than the first aspect ratio, comprising: reproducing means for reproducing a video signal; means for detecting a brightness signal of the reproduced video signal; reproducing and detecting means for reproducing and detecting aspect ratio information; and comb line filter means for removing noise components of the detected brightness signal, said comb line filter means being capable of changing over the comb line filter characteristic thereof in accordance with the aspect ratio information from said reproducing and detecting means. A recording and reproducing apparatus according to claim 5, wherein said comb line filter means includes means for extracting high frequency components from a video signal from said reproducing and detecting means, means for extracting noise components from the extracted high frequency components, a pair of gain amplifiers for amplifying the extracted noise components, subtracting means for subtracting the amplified noise components from a selected one of said gain amplifiers from the video signal, and switching means for selectively coupling the outputs of said gain amplifiers to said subtracting means so that, when the aspect ratio information represents the second aspect ratio, the extracted noise components amplified at a higher gain than the gain at which the extracted noise components are amplified when the aspect ratio information represents the first aspect ratio may be supplied to said subtracting means. A recording and reproducing apparatus according to claim 6, wherein said comb line filter means further includes a pair of second gain amplifiers for amplifying the extracted noise components, and second switching means for selectively coupling the outputs of said second gain amplifiers to the input sides of said high frequency component extracting means and said subtracting means so that, when the aspect ratio information represents the second aspect ratio, the extracted noise components amplified at a higher gain than the gain at which the extracted noise components are amplified when the aspect ratio information represents the first aspect ratio may be fed back to the input sides.

Inventors: EZAKI TADASHI, EZAKI, TADASHI, EZAKI, TADASHI, SONY CORPORATION
Applicants: SONY CORP, SONY CORPORATION
Application year: 1992
Main classification: H04N9
IPC codes: H04N5, G11B20, H04N9