Signal processing apparatus for video signals with a different display format

Abstract: The present invention has a function to process plural kinds of video signals and relates to a video signal processing apparatus used for displaying each one of the processed outputs of the plural kinds of video signals on the same screen. In the video signal processing apparatus, a memory used for a subtitle processing circuit and a memory used for a helper signal separation circuit are used in common by providing a switching means to switch according to an input video signal. The subtitle processing circuit magnifies a video signal with a letter box format like that a horizontally long picture is inserted in a picture with a 4:3 aspect ratio on a horizontally long screen with 2:1 or 16:9 aspect ratio. The helper signal separation circuit is used for receiving a television signal such as EDTV 2 system which has a helper signal to improve picture quality.

Description: The present invention relates to a video signal processing apparatus which provides a function to process plural kinds of video signals and is used when each processed video signal is displayed on the same display device. Especially, it relates to a subtitle processing circuit for magnifying a video signal with a letter box format which displays a horizontally long picture on a screen with a 4:3 aspect ratio into a video signal corresponding to a horizontal long screen having an aspect ratio such as 2:1 or 16:9 and a separation circuit for a helper signal such as a horizontal high frequency band helper signal used in a television system having a helper signal for picture quality improvement,such as an EDTV 2 system. Recently, beside a television system such as an NTSC system and a PAL system which are now practically and worldwidely used, various kinds of television systems which have compatibility with the current television systems and improved resolution and S/N ratio such as EDTV (Enhanced Definition TeleVision) 1 system, EDTV 2 system which is a second generation system of the EDTV system, IDTV (Improved Definition TeleVision) system, Improved PAL, Extended PAL, etc have been practically used or experimented. Because these new television systems always have compatibility in fundamental with a current television system, television receivers have to be able to receive signals of plural kinds of television systems. As an example which has no compatibility with a current television system and has high performance, there is an HDTV (High Definition TeleVision) system. However, receivers for the HDTV system are presumed to be a transient exsistence as single system receivers or to have a function to be able to receive a signal of a current television system beside an HDTV system. Thus, it will be desired more and more in the future that a picture for various different kinds of television systems is displayed on a same screen. It is necessary to convert video signals for various different kinds of television systems into a video signal which can display in common on a screen with an aspect ratio based on one of television systems. One of the problems, in this case, is a signal conversion of the television systems with different aspect ratios. In the case in which a video signal with a 16:9 aspect ratio is displayed on a screen with a 4:3 aspect ratio, for example, a video signal is often converted so that non-picture portions are generated at the upper and lower portions of the raster (this format is called letter box) as shown in FIG. 5(a) and the non-picture portions are used for superimposing a subtitle. When a video signal with such a letter box format is displayed on a horizontally long screen with a 16:9 aspect ratio shown in FIG. 5(b), if the raster is magnified so that the picture portion is full of the screen, the subtitle may be off the screen. Therefore, a subtitle processing circuit which moves the subtitle position as shown in FIG. 5(b) by storing a subtitle information in a memory is proposed, for example in Japanese Patent Laid-Open 2-179080. In this case, although the memory has to store all the video signal including the subtitle information, because the subtitle locates on the non-picture portion at the lower half of the picture, it is necessary to store maximum 910 pixels at 4fsc (fourfolds of subcarrier frequency) for about 130 lines at the lower half portion of the picture. That is, 910 (number of pixels per line) x 130 (number of lines) x 8 (number of gradations) = 946,400 bits = about 1 M bits is required as memory capacity. Usually in television systems such as EDTV 2 and Extended PAL systems, a helper signal which is necessary to improve the resolution is usually multiplexed and is demodulated at a receiver side and is used for improving the resolution. For example, in a EDTV 2 system, a horizontal high frequency band helper signal for improving horizontal resolution utilizing a frequency gap on the position which is symmetrical to a chrominance signal band is multiplexed on a video signal and transmitted. It is generally necessary to use a memory to separate such a helper signal at the receiver side and it is also necessary to process using a memory to separate a horizontal high frequency band helper signal of EDTV 2 system at the receiver side. For example, there is a circuit shown in FIGs. 4 and 14 on pages 137 of "multidimensional signal processing of television image" by Toshihiko Fukinuke published by Daily Industry Press Co.. In this case, the memory has to store all the video signal as much as one field color signal. Therefore, 455 (number of pixels per line) x 262.5 (number of lines) x 8 (number of gradations) = 955,500 bits = about 1 M bits is required as memory capacity. Therefore, two memories, a memory for a subtitle processing circuit and a memory for a horizontal high frequency band helper signal separation circuit are required. For an EDTV 2 signal having a 16:9 aspect ratio, a screen with a 16:9 aspect ratio is used. When a video signal with a letter box format is received at a receiver having a screen with an aspect ratio horizontally longer than 4:3, if only the picture portion is magnified and displayed as described above, the feature can be more displayed. Therefore, means to magnify and display only a picture portion is often used. However, to realize it, both helper signal processing for improving picture quality and subtitle processing are required and it is required to use two memories with about 1 M bits as described above. However, this method has a problem to be inferior in an economical point because of expensive memories. The present invention presents a video signal processing apparatus which can use a memory in common for subtitle processing and for helper signal processing to improve picture quality which is particular for the television system in question by switching. The present invention provides a signal processing apparatus for plural kinds of video signals comprising: memory means for storing a video signal; subtitle processing means for processing a first video signal constituting a subtitle of the input video signals using said memory means; first bidirectional switching means for connecting between an input and output terminal of said subtitle processing means and an output or input terminal of said memory means; helper signal separating means for processing a second video signal constituting a helper signal of the input video signals using said memory means; second bidirectional switching means for connecting between an input and output terminal of said helper signal separating means and an output and input terminal of said memory means; and control means for controlling said first bidirectional switching means and said second bidirectional switching means; and wherein said control means being arranged to turn on and off said first bidirectional switching means and said second bidirectional switching means whereby the memory means is used by either the subtitle processing means or the helper signal separation means depending on the content of the input video signal. From another aspect, the present invention provides A signal processing apparatus for plural kinds of video signals comprising: memory means for storing a video signal; subtitle processing means for processing a first video signal constituting a subtitle for input video signals using said memory means; first switching means for connecting between an output terminal of said subtitle processing means and an input terminal of said memory means; helper signal separating means for processing a second video signal constituting a helper signal for input video signals using said memory means; second switching means for connecting between an output terminal of said helper signal separating means and an input terminal of said memory means; control means for controlling said first switching means and said second switching means; and wherein an output terminal of said memory is connected to an input terminal of said subtitle processing means and an input terminal of said second signal processing means; and said control means being arranged to turn on and off said first switching means and said second switching means whereby the memory means is used by either the subtitle processing means or the helper signal separating means depending on the content of the input video signal. In order that the present invention be more readily understood, embodiments thereof will now be described by way of example with reference to the accompanying drawings, in which:- FIG. 1 is a block diagram of a signal processing apparatus for plural kinds of video signals in accordance with an exemplary embodiment of the present invention; FIG. 2 is timing charts for explaining performance of a signal processing apparatus for plural kinds of video signals in accordance with an exemplary embodiment of the present invention; FIG. 3 is a block diagram of a signal processing apparatus for plural kinds of video signals in accordance with another exemplary embodiment of the present invention; FIG. 4 is a block diagram of a signal processing apparatus in accordance with the present invention; and FIG. 5 illustrates displayed pictures on a screen. A block diagram of a signal processing apparatus for plural kinds of video signals in accordance with an exemplary embodiment of the present invention is shown in FIG. 1. The television receiver provides video signal input terminals for current television signals such as NTSC system and PAL system and for several television signals which are now under development for improving picture quality of the current television systems such as EDTV 1 system, EDTV 2 system, IDTV system, Improved PAL system, although they are not shown in the drawing. In FIG.1, the block 1 is a subtitle processing circuit for moving a subtitle, the block 2 is a horizontal high frequency band helper signal separation circuit for separating a horizontal high frequency band helper signal which is a helper signal multiplexed for improving picture quality, the block 3 is a first three state bus transceiver for selecting an input or output signal of the subtitle processing circuit 1 by a switching signal C1, the block 4 is a second three state bus transceiver for selecting an input or output signal of the horizontal high frequency band helper signal separation circuit 2 by a switching signal C2, the block 5 is a memory for storing either output of the first or second three state bus transceiver 3 or 4 and the block 6 is a switching circuit for generating switching signals C1 and C2. Performance of the signal processing apparatus for plural kinds of video signals is expalined with an example of a screen having a 16:9 aspect ratio used in EDTV 2 system. In the case of current NTSC system or PAL system, a video signal is often transmitted with a letter box format having a signal with a horizontally long aspect ratio such as 16:9 and having non-picture portion signal at the upper and lower portions of the screen and having no horizontal high frequency band helper signal which is a helper signal for improving picture quality. On the other hand, in the case of EDTV 2 system, IDTV system, Improved PAL system or Extended PAL system which are being developed for improving picture quality, the video signal is usually transmitted with a format having a signal with a horizontally long aspect ratio such as 16:9 and having no non-picture signal and having a horizontal high frequency band helper signal which is a helper signal for improving picture quality. Therefore, a discrimination signal indicating if there is a helper signal for improving picture quality in the input signal or not is detected by using means for discriminating kind of video signal (not shown in the drawing) and detects if a horizontal high frequency band helper signal is multiplexed in the input video signal or not. When a horizontal high frequency band helper signal is confirmed not to be multiplexed in the input video signal, a switching signal C1 is made level 0 (enable) and another switching signal C2 is made level 1 (disable) by a switching circuit 6 so that subtitle processing is performed. Thus, because processing of the horizontal high frequency band helper signal is unnecessary, a three state bus transceiver 4 is controlled to have a high impedance. A three state bus transceiver 3 is controlled to have a low impedance because processing of the subtitle signal is necessary, an output of a subtitle processing circuit 1 is written in a memory 5 passing through the three state bus transceiver 3 and the output of the memory 5 is read at the subtitle processing circuit 1. By this processing, only the picture portion is magnified and is displayed on the screen with a 16:9 aspect ratio and the subtitle located on the non-picture portion is moved to an appropriate position and is displayed. As a result, subtitles can be displayed appropriately as well as a larger picture display can be realized. In the case of a system such as EDTV 2, because a horizontal high frequency band helper signal is multiplexed, by detecting the horizontal high frequency band helper signal, the switching signal C1 is made level 1 (disable) and the switching signal C2 is made level 0 (enable) by the switching circuit 6 so that the horizontal high frequency band helper signal is separated. Thus, becaused subtitle processing is unnecessary, the three state bus transceiver 3 is controlled to have a high impedance. On the other hand, because processing of a horizontal high frequency band helper signal is necessary, the three state bus transceiver 4 is controlled to have a low impedance, an output of the horizontal high frequency band helper signal separation circuit 2 is written in the memory 5 passing through the three state bus transceiver 4 and an output of the memory 5 is read at the horizontal high frequency band helper signal separation circuit 2. By this processing, horizontal resolution is improved and this is one of features of an EDTV 2 system. The signals are illustrated in FIG. 2(a). Here, a is defined as input and output signals of the three state bus transceiver 3 and b is defined as input and output signals of the three state bus transceiver 4. If the video signal is difficult to be seen due to switching timing, a period during which both switching signals C1 and C2 are level 1 (disable) shown in FIG. 2(b). Although an example to detect a discrimination signal was described above as means for discriminating what kind of video signal it is, it is also possible to detect non-picture portion of the input video signal by detecting if a white signal exsists at every horizontal line and a black signal continuously exsists and discriminate if the input video signal is a signal with a letter box format or not. It is also possible to detect if the input video signal has a subtitle signal or not by detecting if the input video signal has a letter display on the non-picture portion. By detecting these, memory switching can be done more appropriately and the circuit group which is not necessary to perform can be automatically stopped and at the same time, the power consumption can be reduced. In the case of a video signal including a helper signal for improving picture quality, processing by the horizontal high frequency band helper signal separation circuit 2 is always necessary. In the case of a video signal not including a helper signal, processing by the subtitle processing circuit 1 is not always necessary. The subtitle processing circuit 1 is allowed to perform but what is necessay is a signal with a letter box format and it is restricted in the case in which a subtitle exsists. Although a three state bus transceiver was used as switching means of the memory 5, bidirectional switching means can be replaced presenting a similar effect. Although a switching circuit 6 was used as a control circuit of the switching means, any device having a bidirectional performance to control the switching means according to kind of the input video signal can be replaced presenting a similar effect. A block diagram of a signal processing apparatus for plural kinds of video signals in accordance with another exemplary embodiment of the present invention is shown in FIG. 3. In FIG. 3, the television receiver provides video signal input terminals for current television signals such as NTSC system and PAL system and for several television signals which are now under development for improving the picture quality of the current television systems such as EDTV 1 system, EDTV 2 system, IDTV system, Improved PAL system, although they are not shown in the drawing like in FIG. 1. In FIG. 3, the block 1 is a subtitle processing circuit for moving a subtitle, the block 2 is a horizontal high frequency band helper signal separation circuit for separating a horizontal high frequency band helper signal which is a helper signal multiplexed for improving picture quality, the block 5 is a memory and the above blocks are similar to those in FIG. 1. The block 7 is a switching device and the outputs of the subtitle processing circuit 1 and the horizontal high frequency band helper signal separation circuit 2 are inputted to the switching device 7 and the output of the switching device 7 is inputted to the memory 5. The block 8 is a control circuit for detecting a discriminating signal to judge if a horizontal high frequency band helper signal for improving picture quality is multiplexed or not using means (not shown in the drawung) to discriminate what kind of video signal the input video signal is and for controlling the switching device 7 according to the discrimination result. A read output of a memory 5 is inputted directly (without through a switch) to a subtitle processing circuit 1 and a horizontal high frequency band helper signal separation circuit 2. A switch 7 is switched according to a content of the input video signal similarly to the previous exemplary embodiment. When the subtitle processing circuit 1 is necessary, subtitle processing is made using the memory 5 through the switch 7 and when the horizontal high frequency band helper signal separation circuit 2 is necessary, helper signal processing is made using the memory 5 through the switch 7. Thus, the memory 5 can be used in common as well as processing which is appropriate to the input video signal is made. Although a current NTSC system and an EDTV 2 system which has a helper signal for improving picture quality and has a compatibility with the current NTSC system were described above, an HDTV system which has no compatibility presents a similar effect when the HDTV signal is displayed with signal switching, because the signal processing requires a memory particular to the system. According to a video signal processing apparatus in accordance with exemplary embodiments of the present invention, the memory capacity to be used can be reduced by detecting the features of the input video signals against plural kinds of input video signals and selecting which group of video signal processing circuits is made perform. In an EDTV system receiver providing a video signal processing apparatus in accordance with the present invention, when a signal with a letter box format is inputted, a first video signal processing circuit (for example, a subtitle procesing circuit) is selected and the video signal is processed using a memory and when an EDTV 2 signal is inputted, a second video signal processing circuit (for example, a horizontal high frequency band helper signal separation circuit) is selected and the video signal can be processed using the same memory by switching. Thus, a remarkable cost reduction can be realized by reducing a memory capacity.

Claims: A signal processing apparatus for plural kinds of video signals comprising: memory means (5) for storing a video signal; subtitle processing means (1) for processing a first video signal constituting a subtitle of the input video signals using said memory means (5); first bidirectional switching means (3) for connecting between an input and output terminal of said subtitle processing means (1) and an output or input terminal of said memory means (5); helper signal separating means (2) for processing a second video signal constituting a helper signal of the input video signals using said memory means (5); second bidirectional switching means (4) for connecting between an input and output terminal of said helper signal separating means (2) and an output and input terminal of said memory means (5); and control means (6) for controlling said first bidirectional switching means (3) and said second bidirectional switching means (4); and wherein said control means (6) being arranged to turn on and off said first bidirectional switching means (3) and said second bidirectional switching means (4) whereby the memory means (5) is used by either the subtitle processing means (1) or the helper signal separation means (2) depending on the content of the input video signal. A signal processing apparatus according to claim 1, wherein each of the bidirectional switching means (3,4) in the form of a three state bus transceiver means. A signal processing apparatus according to claim 1 or 2, wherein the subtitle processing means (1) is arranged to move a subtitle position, and said helper signal separating means is arranged to separate a horizontal high frequency band helper signal. A signal processing apparatus for plural kinds of video signals comprising: memory means (5) for storing a video signal; subtitle processing means (1) for processing a first video signal constituting a subtitle for input video signals using said memory means (5); first switching means (7) for connecting between an output terminal of said subtitle processing means (1) and an input terminal of said memory means (5); helper signal separating means (2) for processing a second video signal constituting a helper signal for input video signals using said memory means (5); second switching means (7) for connecting between an output terminal of said helper signal separating means (2) and an input terminal of said memory means (5); control means (8) for controlling said first switching means and said second switching means (7); and wherein an output terminal of said memory (5) is connected to an input terminal of said subtitle processing means (1) and an input terminal of said second signal processing means; and said control means being arranged to turn on and off said first switching means and said second switching means whereby the memory means (5) is used by either the subtitle processing means (1) or the helper signal separating means (2) depending on the content of the input video signal. A signal processing apparatus for plural kinds of video signals according to claim 4. wherein: said subtitle processing means is arranged to move a subtitle position; and said helper signal separating means is arranged to separate a helper signal for improving picture quality. A signal processing apparatus for plural kinds of video signals according to any one of the preceding claims, wherein: said control means provides a video signal discrimination means for discriminating kind of the video signal; when said video signal discrimination means discriminates that the input video signal includes a discrimination signal indicating that a helper signal is present, the first switching means (3,7) is made off and the second switching means (4,7) is made on, and when said video signal discrimination means discriminates that the input video signal does not include the discrimination signal, said first switching means (3,7) is made on and said second switching means (4,7) is made off. A signal processing apparatus for plural kinds of video signals as recited in claim 6, wherein: said video signal discrimination means of said control means (6,8) is arranged such that when the input video signal includes neither a horizontal high frequency band helper signal nor a subtitle signal, said first switching means (3,7) is made on and said subtitle processing means (1) is stopped working and said second switching means (4,7) is made off. A signal processing apparatus for plural kinds of video signals according to any one of the preceding claims, wherein said control means is arranged to turn off both said first switching means and said second switching means, when said first switching means and said second switching means are switched on and off.

Inventors: IZAWA YOSUKE, NIO YUTAKA, IZAWA, YOSUKE, NIO, YUTAKA
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1995
Main classification: H04N5
IPC codes: H04N5