JP2010204344A - Video signal output device and method of outputting video signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video signal output device which outputs proper video signals according to an output device. <P>SOLUTION: When the device externally connected is a video signal recording and reproducing device 3 or the like, the switch 18 changes an output path to output the video signal D2 as it is to the video signal recording and reproducing device 3. On the other hand, when the connected device is a liquid crystal display 2 or the like, the switch 18 changes the path to output the video signal corrected by the video signal processor 19 to the liquid crystal display 2. Thus, high-quality video signals are faithfully output as they are, or the response speed to display the video signals can be effectively improved, according to the output device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a video signal output device and a video signal output method for outputting a video signal to another device.

  A hard disk video recorder compresses an input video signal (video signal), converts it into a compressed digital video signal (video compressed signal), records it on an HDD (Hard Disk Drive), and compresses the recorded video signal on the HDD. An apparatus for reproducing a digital video signal.

  In such a video signal recording / playback apparatus such as a hard disk video recorder, image quality is improved by converting the screen resolution from standard to HD (High Definition), or by converting the frame rate from standard to high frame rate. Has come to be realized. This allows the recorded video signal to be the same as the reproduced video signal, for example, when performing medical fields, artistic recordings, historical recordings, etc. that require fidelity to the video content recorded from the camera. Recording / reproduction using a certain lossless compression (lossless) codec can be performed.

  In this case, as a display (display device) for reproducing the video signal recorded in the video signal recording / reproducing apparatus, a display satisfying the screen resolution and frame rate at the time of display is used. That is, for the screen resolution, a display device having the number of pixels corresponding to the number of pixels of the video signal may be used, and for the frame rate, a display device capable of frame display corresponding to the number of frames of the video signal may be used.

  However, even a display capable of displaying a frame corresponding to the number of frames has a problem that an afterimage remains in a display device that does not have a sufficient response speed margin with respect to the frame rate. Specifically, a display device with a sufficiently fast response speed such as a CRT (Cathode Ray Tube) display device has few problems with such an afterimage, but a display with a relatively slow response speed such as a liquid crystal display device. In the apparatus, an afterimage remains.

  For this reason, particularly in a liquid crystal display device compatible with moving images, the response speed of liquid crystal is improved by incorporating an overdrive circuit into a liquid crystal drive circuit and performing overdrive processing (for example, Patent Document 1).

JP 2006-349952 A

  However, even in a liquid crystal display device or the like whose afterimage characteristics have been improved by the overdrive process as described above, if a sufficient margin cannot be secured for the frame rate intended for high image quality, the afterimage remains unremoved. It may end up.

  Under such circumstances, when a display device with a relatively slow response speed, such as a liquid crystal display device, is connected to a video signal recording / reproducing device with high image quality and high fidelity, the video signal has the original high image quality and high fidelity. There was a problem that the image was deteriorated with an afterimage because the image was not seen.

  That is, in a video recording / reproducing apparatus with high image quality and high fidelity, when it becomes a signal source of another video recording / reproducing apparatus, it is desired to reproduce and output a video signal with little or no deterioration (lossless). On the other hand, when a signal source such as a liquid crystal display device having a relatively low response speed is used, there is a problem that an afterimage remains when the output video signal is displayed as described above. Therefore, reproduction output of a video signal with little or no deterioration (lossless) is not always desired. Such a problem is not limited to a video signal recording / reproducing apparatus such as a hard disk video recorder, and can occur in all apparatuses (video signal output apparatuses) that output video signals.

  The present invention has been made in view of such problems, and an object thereof is to provide a video signal output device and a video signal output method capable of outputting an appropriate video signal according to an output destination device. is there.

  A video signal output device according to the present invention includes a switching unit for switching a video signal output path to an external connection device, and an overdrive executed in the liquid crystal display device when the connection device is a liquid crystal display device. And a correction unit that corrects the video signal by superimposing a correction value on the video signal in a direction in which the processing is further strengthened. In addition, when the connected device is a display device other than the video signal recording / reproducing device, the video signal recording device, or the liquid crystal display device, the switching unit outputs the video signal as it is to the connected device without passing through the correction unit. On the other hand, when the connected device is a liquid crystal display device, the output path is switched so that the corrected video signal is output to the connected device through the correction unit. ing.

  In the video signal output method of the present invention, when the video signal is output to an external connection device, the connection device is a display device other than the video signal recording / playback device, the video signal recording device, or the liquid crystal display device. On the other hand, the output path is switched so that the video signal is output to the connected device as it is. On the other hand, when the connected device is a liquid crystal display device, the overdrive process executed in the liquid crystal display device is more effective. In addition to correcting the video signal that superimposes the correction value on the video signal in the direction of strengthening, the output path is switched so that the corrected video signal is output to the connected device. Is.

  In the video signal output device and the video signal output method of the present invention, when the connection device is a display device other than the video signal recording / reproducing device, the video signal recording device, or the liquid crystal display device, the video signal is not corrected, It is output to the connected device as it is. On the other hand, when the connected device is a liquid crystal display device, the video signal is corrected and then output to the connected device. Specifically, the correction of the video signal is performed by superimposing the correction value on the video signal in the direction in which the overdrive processing executed in the liquid crystal display device becomes stronger. Are output to the connected device. As a result, when the connected device is a video signal recording / reproducing device or the like, there is no deterioration or little high quality video signal is output faithfully, while the connected device is a liquid crystal display device. Since the corrected video signal as described above is output, the response speed when displaying the video signal is effectively improved.

  According to the video signal output device and the video signal output method of the present invention, when the connected device is a video signal recording / reproducing device or the like, the output path is switched so that the video signal is directly output to the connected device. On the other hand, when the connected device is a liquid crystal display device, the output path is switched so that the corrected video signal is output to the connected device. It is possible to output video signals with high image quality as they are, or to effectively improve the response speed when displaying video signals, and to output appropriate video signals according to the output destination device. It becomes.

It is a block diagram showing the structure of the video signal output device (video signal recording / reproducing apparatus) which concerns on one embodiment of this invention. It is a schematic diagram showing an example of LUT used in the video signal correction | amendment part shown in FIG. It is a block diagram for demonstrating operation | movement at the time of connecting a liquid crystal display device as an output destination in the video signal output device (video signal recording / reproducing apparatus) which concerns on a comparative example. FIG. 4 is a timing waveform chart for explaining an example of overdrive processing in the liquid crystal display device shown in FIG. 3. FIG. 6 is a timing waveform diagram for explaining another example of overdrive processing in the liquid crystal display device shown in FIG. 3. FIG. 5 is a block diagram for explaining an operation when another video signal recording / reproducing apparatus is connected as an output destination in the video signal recording / reproducing apparatus shown in FIG. 1. FIG. 2 is a block diagram for explaining an operation when a liquid crystal display device is connected as an output destination in the video signal recording / reproducing apparatus shown in FIG. 1. FIG. 8 is a timing waveform diagram for describing an example of video signal correction processing in the case illustrated in FIG. 7. It is a characteristic view for demonstrating an example of the correction process of the video signal which concerns on the modification 2 of this invention. It is a characteristic view for demonstrating an example of the correction process of the video signal which concerns on the modification 4 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The description will be given in the following order.
1. Embodiment (example of correction processing using LUT)
2. Modified example Modified example 1 (example when thinning out masked low-order bits in the gradation of a video signal)
Modification 2 (example in which the correction value of the thinned gradation is calculated by interpolation processing)
Modification 3 (example in which a common correction value is applied to R, G, B signals)
Modification 4 (Example of correction processing using arithmetic expression (approximate curve))
Modification 5 (example in which correction processing is performed on Y, Cr, Cb signals)

<1. Embodiment>
[Example of overall configuration of video signal output device (video signal recording / playback device)]
FIG. 1 shows a block configuration of a video signal recording / reproducing apparatus 1 as a video signal output apparatus according to an embodiment of the present invention. The video signal recording / reproducing apparatus 1 compresses an externally input video signal (video signal) Din to generate a video compression signal (digital video signal) Sin, records it on the HDD, and records the recorded video compression signal Sout. It is reproduced and output to the outside as an output video signal Dout. The video signal recording / reproducing apparatus 1 includes a video signal input unit 10, a video signal encoding unit 11, and an HDD 12. The video signal recording / reproducing apparatus 1 also includes a video signal decoding unit 13, a synchronization signal generating unit 14, a video signal output unit 15, a system controller 16, a file system unit 17, a changeover switch 18, a video signal correction. Part 19. The video signal output method according to an embodiment of the present invention is embodied in the video signal output apparatus (video signal recording / reproducing apparatus 1) of the present embodiment, and will be described below.

  The video signal input unit 10 supplies an input video signal Din input from the outside to the video signal encoding unit 11. At this time, the video signal input unit 10 extracts information serving as a basis of a synchronization signal generated by a synchronization signal generation unit 14 described later from the input video signal Din.

  The video signal encoding unit 11 encodes the input video signal Din supplied from the video signal input unit 10 by performing compression processing (encoding processing) to generate a video compression signal Sin. Thereby, data is reduced in the video compression signal Sin compared to the original input video signal Din. As such a concord process, for example, an MPEG (Moving Picture Experts Group) system that compresses data using intra-frame compression and inter-frame correlation can be used. However, in the encoding process using the MPEG system or the like, although the compression rate is high, it is generally not reversible compression (lossless). On the contrary, in the encoding process using JPEG (Joint Photographic Experts Group) or JPEG2000 system, although the compression rate is low, it is lossless compression (lossless).

  The HDD 12 is a recording unit for holding the video compression signal Sin supplied from the video signal encoding unit 11. Such a recording unit is not limited to an HDD, and various types such as an optical, magneto-optical, and semiconductor recording medium can be used.

  The video signal decoding unit 13 decodes the video compression signal Sout read from the HDD 12 by performing a decompression process (decoding process) to generate a video signal D1.

  The synchronization signal generator 14 uses the information supplied from the video signal input unit 10 to generate a synchronization signal (vertical synchronization signal, horizontal synchronization signal, clock signal, etc.) for synchronizing with the input video signal Din. Is supplied to the video signal output unit.

  The video signal output unit 15 generates the video signal D2 by adding the synchronization signal supplied from the synchronization signal generation unit 14 to the video signal D1 supplied from the video signal decoding unit 13. . Thereby, in the video signal D2, a signal waveform similar to that of the input video signal Din can be obtained.

  The system controller 16 has a memory unit 16A which is a predetermined memory, and controls a series of recording / reproducing operations in the video signal recording / reproducing apparatus 1 as an OS (Operating System). Specifically, as shown in FIG. 1, the system controller 16 controls the operations of the video signal encoding unit 11, the video signal decoding unit 13, the synchronization signal generating unit 14, and the file system unit 17, respectively. Yes.

  The file system unit 17 controls the operation of recording the video compression signal Sin and reproducing the video compression signal Sout in the HDD 12 in accordance with control by the system controller 16.

  The changeover switch 18 has an input terminal and two output terminals 181 and 182, and is connected to an external connection device (FIG. 1) for the video signal D2 supplied from the video signal output unit 15 in accordance with the switching control signal CTL. This is for switching the output route to (not shown in the figure). Specifically, when the connected device is a display device other than the video signal recording / reproducing device, the video signal recording device, or the liquid crystal display device, the video signal D2 is directly transmitted without going through the video signal correction unit 19 described later. The output path is switched so that it is output to the connected device. That is, the switch state is switched so that the video signal D2 is output to the output terminal 181 side. Examples of such a video signal recording / reproducing apparatus include a hard disk video recorder and a DVD (Digital Versatile Disk) recorder. On the other hand, when the connected device is a liquid crystal display device, the output path is switched so that the corrected video signal is output to the connected device by the video signal D2 passing through the video signal correction unit 19. That is, the switch state is switched so that the video signal D2 is output to the output terminal 182 side. Here, such switching of the state of the switch is performed by, for example, a switching control signal CTL acquired in response to a user's operation of a remote controller or the like, or a switching control signal CTL acquired automatically. Yes. The case where the switching control signal CTL is automatically acquired is specifically, for example, by automatically recognizing the device type of the connected device via a cable of HDMI (High-Definition Multimedia Interface) standard, for example. For example, the switching control signal is acquired.

  When the connected device is a liquid crystal display device, the video signal correction unit 19 superimposes a correction value on the video signal D2 in a direction in which overdrive processing executed in the liquid crystal display device becomes stronger. Thus, the video signal D2 is corrected.

  Specifically, in the present embodiment, for example, as shown in FIG. 2, an LUT (Look Up Table) 19A in which correction values are set in advance according to the response characteristics of the liquid crystal in the connection target liquid crystal display device is used. Thus, the video signal D2 is corrected by real-time processing. In this LUT 19A, the correction value (the correction value of the gradation indicated by “−2” in the figure) is based on the gradation of the video signal of the previous frame and the gradation of the video signal of the current frame. It is prescribed. However, in FIG. 2, for the sake of simplification, correction values corresponding to some combinations of gradations are representatively shown. Here, as a specific example, when the video signal D2 is composed of an RGB standard video signal and the gradation of the video signal D2 is 8 bits, as shown in FIG. Both have 1 to 256 gradations. Accordingly, when individual correction values are held in the LUT 19A in signals corresponding to the three colors R (red), G (green), and B (blue), the entire LUT 19A has (256 × 256 × 3). ) Correction values are set. Details of the correction processing in the video signal correction unit 19 will be described later.

  Here, the HDD 12 corresponds to a specific example of “recording unit” in the invention. The changeover switch 18 corresponds to a specific example of the “switching unit” in the present invention, and the video signal correction unit 19 corresponds to a specific example of the “correction unit” in the present invention.

[Operation and effect of video signal output device (video signal recording / playback device)]
Next, operations and effects of the video signal recording / reproducing apparatus 1 of the present embodiment will be described.

(basic action)
First, the basic operation of the video signal recording / reproducing apparatus 1 will be described with reference to FIG.

  In this video signal recording / reproducing apparatus 1, an input video signal Din input from the outside is supplied to the video signal encoding unit 11 via the video signal input unit 10. The video signal encoding unit 11 encodes the input video signal Din by performing compression processing to generate a video compression signal Sin. The compressed video signal Sin is recorded in the HDD 12, whereby a video signal recording operation is performed under the control of the system controller 16 and the file system unit 17.

  On the other hand, the video compressed signal Sout read from the HDD 12 is decoded by the decompression process in the video signal decoding unit 13 to generate the video signal D1. Next, the video signal output unit 15 generates the video signal D2 by adding the synchronization signal supplied from the synchronization signal generation unit 14 to the video signal D1. The video signal D2 is output to the outside as an output video signal Dout through the changeover switch 18 and the video signal correction unit 19 depending on the case. Thereby, the reproduction operation of the video signal is performed under the control of the system controller 16 and the file system unit 17.

  In this manner, the video signal recording / reproducing apparatus 1 performs the recording / reproducing operation of the video signal with high image quality and high fidelity.

(Operation of characteristic part)
Next, referring to FIG. 3 to FIG. 8 in addition to FIG. 1 and FIG. 2, the operation of characteristic parts (switching / correction processing) in the video signal recording / reproducing apparatus 1 will be described in detail in comparison with the comparative example. To do. Here, FIG. 3 shows a block configuration of a video signal output apparatus (video signal recording / reproducing apparatus 101) according to a comparative example in a case where the liquid crystal display device 2 is connected as an output destination. 4 and 5 show an example of overdrive processing in the liquid crystal display device 2 using timing waveform diagrams. 6 and 7 show the case where another video signal recording / reproducing device 3 (FIG. 6) or liquid crystal display device 2 (FIG. 7) is connected as an output destination in the video signal recording / reproducing device 1 of the present embodiment. It represents the operation of. FIG. 8 shows an example of video signal correction processing in this embodiment using a timing waveform diagram. In these timing waveform diagrams, the waveform indicated by the broken line represents the waveform of the liquid crystal driving voltage corresponding to the video signal, and the waveform indicated by the solid line represents the response waveform of the actual liquid crystal.

(Comparative example)
First, in the video signal recording / reproducing apparatus 101 according to the comparative example shown in FIG. 3, unlike the video signal recording / reproducing apparatus 1 of the present embodiment shown in FIG. 1, a changeover switch 18 and a video signal correcting unit 19 are provided. It is not done. Therefore, the output signal from the video signal output unit 15 is output as it is as the output video signal Dout to the liquid crystal display device 2 which is an external connection device.

  In the liquid crystal display device 2, in order to improve the response characteristics of the liquid crystal, overdrive processing as shown in FIGS. 4A to 4C, for example, is performed on the input output video signal Dout. Later, video display is performed. Specifically, for example, in the case of a small gradation change from halftone to halftone, a situation where the actual gradation operation (solid line) cannot catch up with the liquid crystal drive voltage (broken line) exceeds the target gradation. Is applied for a certain period of time to speed up the gradation changing operation and increase the response speed. Here, in FIG. 4A, when there is a large gradation change from the black gradation (0 gradation) to the white gradation (255 gradation), the actual liquid crystal driving voltage (broken line) is This represents a situation in which the gradation operation (solid line) catches up within one frame period. In FIG. 4B, in the case of a small gradation change from the halftone Y1 to the halftone Y2, the actual gradation operation (solid line) is performed within one frame period with respect to the liquid crystal drive voltage (broken line). It represents a situation that has not caught up. Further, in FIG. 4C, in the case of a small gradation change from the halftone Y1 to the halftone Y2, as indicated by the arrow in the figure, the overdrive process is performed at the liquid crystal drive voltage ( (Broken line) represents a situation where the actual gradation operation (solid line) is catching up.

  Here, when such a video signal recording / reproducing apparatus 101 becomes a signal source of another video signal recording / reproducing apparatus or the like, reproduction of a video signal with little image quality degradation or desirably no image quality degradation (lossless). Output is desired.

  However, as shown in FIG. 3, a liquid crystal display with a relatively low response speed is used for such a video signal Dout (a video signal with high image quality and high fidelity) Dout with little or no image quality degradation (lossless). When outputting to the device 2, the following problems occur. That is, even in the liquid crystal display device 2 and the like whose afterimage characteristics have been improved by the overdrive process as described above, if a sufficient margin cannot be secured for the frame rate intended for high image quality, the afterimage remains without being removed. As a result, the display image quality deteriorates. Specifically, for example, in FIG. 5A, in the case of a small gradation change from the halftone Y1 to the halftone Y2, the actual gradation operation (solid line) with respect to the liquid crystal drive voltage (broken line) is Compared to FIG. 4 (B), this represents a situation in which it has not caught up within one frame period. In FIG. 5B, in the case of a small change in gradation from the halftone Y1 to the halftone Y2, overdrive processing is performed at the liquid crystal drive voltage as indicated by the arrows in the figure. Nevertheless, this represents a situation where the actual gradation operation (solid line) has not caught up (broken line).

  In this way, in the video recording / playback apparatus 101 with high image quality and high fidelity, when it becomes a signal source of another video recording / playback apparatus, playback output of a video signal with little or no degradation (lossless) is provided. Is desired. On the other hand, when a signal source such as the liquid crystal display device 2 having a relatively slow response speed is used, as described above, there is a problem that an afterimage remains when the output video signal is displayed. That is, since it is not always desirable to reproduce and output a video signal with little or no degradation (lossless), the video signal recording and reproducing device 101 according to this comparative example is connected to the liquid crystal display device 2 or the like. In some cases, the display image quality is deteriorated.

(This embodiment)
On the other hand, in the video signal recording / reproducing apparatus 1 according to the present embodiment, the change-over switch 18 applies the video signal D2 supplied from the video signal output unit 15 to an external connection device in accordance with the switching control signal CTL. The output path is switched. Then, in the video signal correction unit 19, when the connected device is the liquid crystal display device 2 or the like, the overdrive process executed in the liquid crystal display device 2 or the like is strengthened with respect to the video signal D2. The correction value is superimposed to correct the video signal D2.

  Specifically, for example, as shown in FIG. 6, when the external connection device is the video signal recording / reproducing device 3 or the like, the video signal D2 is not passed through the video signal correction unit 19 in the changeover switch 18. The output path is switched so that it is output to the video signal recording / reproducing apparatus 3 as it is. That is, in this case, as shown by the output path Pa in the figure, the video signal D2 is not corrected and is output to the video signal recording / reproducing apparatus 3 as it is. As a result, when the connected device is the video signal recording / reproducing apparatus 3 or the like, a high-quality video signal with no deterioration (lossless) or low quality is output as it is.

  On the other hand, for example, as shown in FIG. 7, when the external connection device is the liquid crystal display device 2 or the like, the corrected video signal is transmitted to the liquid crystal display device 2 through the video signal correction unit 19. The output path is switched so that the signal is output to. That is, in this case, as indicated by the output path Pb in the figure, the video signal D2 is corrected and then output to the liquid crystal display device 2. At this time, as described above, the video signal correction unit 19 superimposes the correction value on the video signal D2 in a direction in which the overdrive process executed in the liquid crystal display device 2 or the like is further strengthened. The video signal D2 is corrected.

  Specifically, for example, as shown in FIG. 8A, when the video signal D2 rises, as shown by an arrow P11 in the figure, a correction value (scale) is set with respect to the original video signal D2. The video signal D2 is corrected by adding (difference) ΔY1. On the other hand, as shown in FIG. 8B, when the video signal D2 falls, as shown by an arrow P21 in the figure, a correction value (tone difference) with respect to the original video signal D2. The video signal D2 is corrected by subtracting ΔY2. In these cases, the video signal correction unit 19 displays the response waveform (solid line) of the liquid crystal after overdrive processing (see arrows P12 and P22 in the figure) in the liquid crystal display device 2 within the unit frame period. Correction is performed so that the gradation Y2 after the transition is reached. In this way, when the connected device is the liquid crystal display device 2 or the like, such a corrected video signal is output as the output video signal Dout, thereby displaying the output video signal Dout. The response speed is effectively improved, and the image quality of the display image is improved as compared with the comparative example.

  As described above, in the present embodiment, when the externally connected device is the video signal recording / reproducing apparatus 3 or the like, the output path is switched so that the video signal D2 is output to the video signal recording / reproducing apparatus 3 as it is. On the other hand, when the connected device is the liquid crystal display device 2 or the like, the output path is switched so that the video signal corrected by the video signal processing unit 19 is output to the liquid crystal display device 2. Therefore, according to the output destination device, it is possible to faithfully output a high-quality video signal as it is, or to effectively improve the response speed when displaying the video signal, depending on the output destination device. Therefore, it is possible to output an appropriate video signal.

  In addition, since the video signal correction unit 19 corrects the video signal D2 using the LUT 19A in which a correction value is set in advance according to the response characteristics of the liquid crystal in the liquid crystal display device 2, the correction within the real time is performed. Correction processing can be facilitated.

<2. Modification>
Hereinafter, some modified examples of the present invention will be described. In addition, the same code | symbol is attached | subjected to the same thing as the component in the said embodiment, and description is abbreviate | omitted suitably.

(Modification 1)
In the first modification of the present invention, the LUT 19A used in the video signal correction unit 19 masks the lower bits in the gradation of the video signal D2, so that the correction value is thinned out and set for the gradation. That is, in the above embodiment, for example, when the video signal D2 is composed of RGB standard video signals, and the gray level of the video signal D2 is 8 bits, both the previous frame and the current frame are 1st to 256th floors. There are correction values corresponding to all of the tones. On the other hand, in this modification, the number of correction values to be held is reduced by masking lower bits without applying 8 bits as they are.

Specifically, when the lower 1 bit is masked, the gradation change is from 128 gradation levels of 2, 4, 6,... 256 to 128 gradation levels of 2, 4, 6,. The correction value is held for all changes. The same applies when the lower 2, 3, 4,... Bits are masked. Accordingly, when the lower bits are masked, assuming that individual correction values are held in the LUT 19A in signals corresponding to the three colors R (red), G (green), and B (blue), the correction values in the LUT 19A Will decrease as follows.
1 bit mask (128 x 128 x 3) 2 bit mask (64 x 64 x 3) 3 bit mask (32 x 32 x 3) 4 bit mask (16 x 16 x 3) )Pieces

  In this way, in the present modification, the LUT 19A masks the lower bits in the gradation of the video signal D2, so that the correction value is thinned out and set for the gradation, so that it is held in the LUT 19A. The number of correction values can be reduced, and the amount of memory for holding correction values can be reduced.

(Modification 2)
FIG. 9 shows an example of video signal correction processing according to the second modification of the present invention. In this modified example, in the first modified example, the correction value corresponding to the gradation thinned out in the LUT 19A is calculated by a predetermined interpolation process, and correction is performed using the calculated correction value. Yes.

  Specifically, in the video signal correction unit 19, for example, based on the gradation differences X1 and X2 shown in FIG. 9 and the correction values Z1 and Z2 corresponding thereto (see points P31 and P32 in the figure), the straight line G3. A linear interpolation process using is performed. Thereby, as indicated by a point P33 in the figure, the correction value Z3 corresponding to the thinned gradation difference X3 is calculated. Note that although linear interpolation processing has been described as an example here, other interpolation processing may be used.

  Thus, in this modification, the correction value corresponding to the gradation thinned out in the LUT 19A is calculated by a predetermined interpolation process, and correction is performed using the calculated correction value. Even when the amount of memory is reduced, the correction accuracy can be maintained.

(Modification 3)
In the third modification of the present invention, the video signal processing unit 19 performs correction by using a common (same) correction value for the R, G, and B signals. That is, in the above-described embodiment and the like, individual correction values are held in the LUT 19A for signals corresponding to the three colors R, G, and B, thereby performing individual correction. On the other hand, in this modification, the same correction value is used for the R, G, and B signals by assuming that the correction characteristics for the R, G, and B signals B are approximately the same. .

  As a result, in this modification, the number of correction values held in the LUT 19A can be reduced to 1/3, and the amount of memory for holding correction values can be reduced.

(Modification 4)
FIG. 10 shows an example of video signal correction processing according to the fourth modification of the present invention. In this modification, the video signal correction unit 19 performs a correction process using a predetermined salt calculation formula (approximate curve) instead of the LUT described so far. That is, the video signal D2 is corrected by calculating a correction value as needed using an arithmetic expression (approximate curve) defined in advance according to the response characteristics of the liquid crystal in the liquid crystal display device 2.

Specifically, for example, as shown in FIG. 10, the correction is performed using an approximate curve G4 indicating the following arithmetic expression (1) that associates the gradation difference X with the correction value Z. In addition, A0 to An in the arithmetic expression (1) each indicate a predetermined coefficient.
Z = (A0) + (A1) × X ¹ + (A2) × X ² + (A3) × X ³ +... (An) × X ⁿ
... (1)

  As a result, in this modification, it is possible to reduce the amount of memory used for correction, compared to the case where correction is performed using the LUT 19A.

(Modification 5)
In the fifth modification of the present invention, correction is performed on a YCrCb standard video signal, which is an intermediate signal when the input video signal Din is compressed, instead of the RGB standard video signal described so far. Yes.

  At this time, the video signal correction unit 19 superimposes a relatively large correction value on the Y (luminance) signal, while superimposing a relatively small correction value on the Cr, Cb (color difference) signal. It is desirable to do. This is because when a large correction value is superimposed on the color difference signal, the hue of the entire video changes greatly, and the display image quality deteriorates.

  In this way, in this modification, correction is performed on the video signal of the YCrCb standard, so the number of pixels is smaller than in the case of the video signal of the RGB standard, and accordingly, the correction is small. As a result, correction processing is facilitated.

  In the present modification, the video signal correction unit 19 may perform correction using a common (identical) correction value for the Cr and Cb (color difference) signals. In such a case, since the number of correction values can be reduced to ½, the amount of memory for holding correction values can be reduced.

  While the present invention has been described with reference to the embodiments and modifications, the present invention is not limited to these embodiments and the like, and various modifications can be made.

  For example, in the above-described embodiment and the like, the case where overdrive processing is performed in the liquid crystal display device 2 has been described. For example, when the overdrive processing is not performed in the liquid crystal display device 2, the video signal processing unit 19 performs the following. May be corrected. That is, correction corresponding to the overdrive process in the liquid crystal display device 2 is performed in the video signal processing unit 19. Thereby, the response characteristic in the liquid crystal display device 2 is improved, and the image quality is better than the original performance of the liquid crystal display device 2.

  In the above-described embodiments and the like, correction has been described for RGB standard video signals and YCrCb standard video signals. However, video signals of other standards may be corrected.

  Furthermore, in the above-described embodiments and the like, the video signal output device that includes the HDD 12 as a recording unit for holding the video signal and is configured as a video signal recording / playback device (or video signal playback device) has been described. However, this is not the case. That is, the present invention can also be applied to, for example, a rotating monostorage that supplies the output video signal Dout to the liquid crystal display device 2 and a video signal processing device that supplies a liquid crystal drive signal to the liquid crystal display device 2. It is.

  DESCRIPTION OF SYMBOLS 1 ... Video signal recording / reproducing apparatus, 10 ... Video signal input part, 11 ... Video signal encoding part, 12 ... HDD, 13 ... Video signal decoding part, 14 ... Synchronization signal generation part, 15 ... Video signal output part, 16 ... System Controller: 16A ... Memory unit, 17 ... File system unit, 18 ... Changeover switch, 181, 182 ... Output terminal, 19 ... Video signal correction unit, 19A ... LUT, 2 ... Liquid crystal display device, 3 ... Video signal recording / reproducing device, Din: input video signal, Dout: output video signal, D1, D2: video signal, Sin, Sout: video compression signal, CTL: switching control signal, Y0-Y3: gradation, ΔY1, ΔY2: gradation difference (correction amount) ), Pa, Pb: Video signal output path, X, X1-X3: Gradation difference (= current gradation-previous gradation), Z, Z1-Z3: Correction value, A0-An: Coefficient, G4: Approximation Curve (correction value calculation Line).

Claims (13)

A switching unit for switching the output path of the video signal to the external connection device;
When the connected device is a liquid crystal display device, the correction of the video signal is performed by superimposing the correction value on the video signal in a direction in which overdrive processing executed in the liquid crystal display device becomes stronger. And a correction unit to perform,
When the connected device is a display device other than a video signal recording / reproducing device, a video signal recording device, or a liquid crystal display device, the switching unit directly transmits the video signal to the connected device without passing through the correction unit. On the other hand, when the connected device is a liquid crystal display device, the output path is switched so that the corrected video signal is output to the connected device through the correction unit. A video signal output device. The correction unit is
When the video signal rises, the video signal is corrected by adding a correction value to the original video signal,
The video signal output device according to claim 1, wherein when the video signal falls, the video signal is corrected by subtracting a correction value from the original video signal. The correction unit adds or subtracts the correction value so that the response waveform of the liquid crystal reaches the gradation level after transition within a unit frame period when the video signal falls or falls. The video signal output device according to claim 2. 4. The correction unit corrects the video signal using an LUT (Look Up Table) in which a correction value is set in advance according to a response characteristic of liquid crystal in the liquid crystal display device. 5. The video signal output device according to claim 1. The video signal output device according to claim 4, wherein in the LUT, a low-order bit in the gradation of the video signal is masked to set a correction value for the gradation. The video signal output according to claim 5, wherein the correction unit calculates a correction value corresponding to the gradation thinned out in the LUT by a predetermined interpolation process, and performs correction using the calculated correction value. apparatus. The correction unit corrects the video signal by calculating a correction value as needed using an arithmetic expression defined in advance according to a response characteristic of liquid crystal in the liquid crystal display device. The video signal output device according to claim 1. The video signal is composed of RGB standard video signals,
The video signal output device according to claim 1, wherein the correction unit corrects the R, G, and B signals using a common correction value. The video signal output device according to claim 1, wherein the correction unit corrects a video signal of YCrCb standard that is an intermediate signal when the video signal is compressed. The video according to claim 9, wherein the correction unit superimposes a relatively large correction value on a Y (luminance) signal, and superimposes a relatively small correction value on a Cr, Cb (color difference) signal. Signal output device. The video signal output device according to claim 9, wherein the correction unit performs correction using a common correction value for the Cr and Cb signals. It has a recording unit to hold the video signal,
The video signal output device according to claim 1, wherein the video signal output device is configured as a video signal recording / playback device or a video signal playback device. When outputting video signals to external connected devices,
When the connected device is a display device other than a video signal recording / reproducing device, a video signal recording device, or a liquid crystal display device, the output path is switched so that the video signal is directly output to the connected device. ,
When the connected device is a liquid crystal display device, the video signal is corrected so that a correction value is superimposed on the video signal in a direction in which overdrive processing executed in the liquid crystal display device becomes stronger. And a video signal output method for switching the output path so that the corrected video signal is output to the connected device.

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