Video signal processing device, video signal processing method and program

Abstract

A video signal processing device comprising an acquisition unit which acquires a first video signal by broadcast or communication via a network, an enlargement unit (111) which performs enlargement processing for enlarging the acquired first video signal according to a set first parameter, and a processor which (i) changes the first parameter in accordance with the resolution of the first video signal when the first video signal is a broadcast video signal obtained by broadcast and the resolution of the first video signal changes and (ii) sets the first parameter used for the enlargement processing performed by the enlargement unit to a fixed value when the first video signal is a communication video signal obtained by communication via a network.

Description

[Technical Field]

[0001] The present disclosure relates to a video signal processing device, a video signal processing method, and a program for improving image quality. [Background technology]

[0002] Patent document 1 discloses a video output device that, when a change in resolution of video content is detected, determines a scaling ratio for the video content after the change depending on the resolution before the change and the degree of reduction in resolution after the change, and enlarges the video content at the determined scaling ratio. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-67109 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a video signal processing device and the like that can suppress degradation in image quality when the resolution of an acquired video signal is changed, and can suppress the difference in image quality before and after the resolution change. [Means for solving the problem]

[0005] A video signal processing device according to an embodiment of the present disclosure includes: an acquisition unit that acquires a first video signal by broadcasting or communication via a network; an enlargement unit that performs enlargement processing to enlarge the acquired first video signal in accordance with a set first parameter; and a processor that (i) changes the first parameter in accordance with the resolution when the first video signal is a broadcast video signal acquired by the broadcast and the resolution of the first video signal has changed, and (ii) sets the first parameter to a fixed value when the first video signal is a communication video signal acquired by the communication. , the first parameter is the memory size of the frame memory .

[0006] A video signal processing method according to an aspect of the present disclosure includes acquiring a first video signal by broadcasting or communication via a network, performing enlargement processing to enlarge the acquired first video signal according to a set first parameter, and (i) if the first video signal is a broadcast video signal acquired by broadcasting and a resolution of the first video signal has changed, changing the first parameter according to the resolution, and (ii) if the first video signal is a communication video signal acquired by communication, setting the first parameter to a fixed value. The first parameter is the memory size of the frame memory. .

[0007] These general or specific aspects may be realized in a system, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM, or may be realized in any combination of an apparatus, a method, a system, an integrated circuit, a computer program, and a non-transitory recording medium. [Effects of the Invention]

[0008] The video signal processing device and the like according to the present disclosure can suppress degradation in image quality when the resolution of an acquired video signal is changed, and can suppress the difference in image quality before and after the change in resolution. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the appearance of a display device according to the present embodiment. [Figure 2] FIG. 2 is a block diagram showing an example of a hardware configuration of the display device according to the present embodiment. [Figure 3] FIG. 3 is a block diagram showing an example of the configuration of the control circuit according to this embodiment. [Figure 4A] FIG. 4A is a diagram for explaining enlargement processing for a broadcast video signal with 4K resolution. [Figure 4B] FIG. 4B is a diagram for explaining enlargement processing for a broadcast video signal with FHD resolution. [Figure 4C]FIG. 4C is a diagram for explaining enlargement processing for a broadcast video signal with SD resolution. [Figure 4D] FIG. 4D is a diagram for explaining enlargement processing for a communication video signal with FHD resolution. [Figure 4E] FIG. 4E is a diagram for explaining enlargement processing for a communication video signal with SD resolution. [Figure 5A] FIG. 5A is a diagram for explaining a first example of sharpness adjustment for a 4K resolution broadcast video signal. [Figure 5B] FIG. 5B is a diagram for explaining a first example of sharpness adjustment for a broadcast video signal with FHD resolution. [Figure 5C] FIG. 5C is a diagram for explaining a first example of sharpness adjustment for a broadcast video signal with SD resolution. [Figure 5D] FIG. 5D is a diagram for explaining sharpness adjustment for a communication video signal with 4K resolution. [Figure 5E] FIG. 5E is a diagram for explaining sharpness adjustment for a communication video signal with FHD resolution. [Figure 5F] FIG. 5F is a diagram for explaining sharpness adjustment for a communication video signal with SD resolution. [Figure 5G] FIG. 5G is a diagram for explaining a second example of sharpness adjustment for a 4K resolution broadcast video signal. [Figure 5H] FIG. 5H is a diagram for explaining a second example of sharpness adjustment for a broadcast video signal with FHD resolution. [Figure 5I] FIG. 5I is a diagram for explaining a second example of sharpness adjustment for a broadcast video signal with SD resolution. [Figure 6A] FIG. 6A is a table showing basic information about the second parameter. [Figure 6B] FIG. 6B is a table showing the difference between the second parameters for the communication video signal and the second parameters for the broadcast video signal. [Figure 6C]FIG. 6C is a table showing the second parameters when the difference is applied to the basic information. [Figure 7] FIG. 7 is a flowchart showing an example of the initial setting process performed by the display device. [Figure 8] FIG. 8 is a flowchart showing an example of video signal processing by the display device. [Figure 9] FIG. 9 is a flowchart showing an example of enlargement processing for a communication video signal. [Figure 10] FIG. 10 is a flowchart showing an example of the enlargement process for a broadcast video signal. [Figure 11] FIG. 11 is a flowchart showing an example of the resolution change process. [Figure 12] FIG. 12 is a flowchart showing an example of sharpness adjustment. [Figure 13A] FIG. 13A is a diagram for explaining a problem that occurs in enlargement processing of a broadcast video signal. [Figure 13B] FIG. 13B is a diagram for explaining a problem that occurs in enlargement processing of a broadcast video signal. [Figure 13C] FIG. 13C is a diagram for explaining a problem that occurs in enlargement processing of a broadcast video signal. [Figure 14A] FIG. 14A is a diagram for explaining a problem that occurs in enlargement processing of a communication video signal. [Figure 14B] FIG. 14B is a diagram for explaining a problem that occurs in enlargement processing of a communication video signal. [Figure 14C] FIG. 14C is a diagram for explaining a problem that occurs in enlargement processing of a communication video signal. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Knowledge that formed the basis of the invention) The present inventors have found that the video signal processing device described in the "Background Art" section has the following problems.

[0011] In a process (hereinafter referred to as "enlargement process") of interpolating pixels of an image that is lower than the display resolution of a display device to increase the resolution, an interpolation filter corresponding to the degree of resolution increase (enlargement ratio) is required. However, switching the interpolation filter takes a time equivalent to several frames, resulting in frames to which processing corresponding to the enlargement ratio has not been applied. In other words, since processing corresponding to the enlargement ratio is not applied to frames when the resolution is changed, the image quality of the image when the resolution is changed deteriorates (i.e., the image quality of the image immediately after the resolution change deteriorates), and the difference in image quality before and after the resolution change becomes large.

[0012] The number of pixels (hereinafter referred to as "resolution") in a video signal period, which is the period excluding blanking periods in one frame of a video signal format of a broadcast video signal or a video signal played back and input by an external playback device (hereinafter referred to as "broadcast video signal"), can vary for each program or input content (hereinafter referred to as "program"), but broadcast stations and content creators generally aim to maintain the resolution constant during a scene or program. In other words, for broadcast video signals, changes in resolution coincide with program changes. Therefore, even when a video signal processing device performs processing according to the magnification ratio, seamless video processing is not required. For example, by turning off the display of frames to which processing according to the magnification ratio has not been applied (i.e., muting the video), video signal processing can be performed so as to minimize the impact on the program. When the resolution of a broadcast video signal is changed, the video content itself changes, or the change occurs when a user changes channels. Therefore, turning off the display of frames (i.e., muting the video) during the resolution change process can prevent the user from feeling uncomfortable.

[0013] The resolution of video signals distributed via the Internet, such as online video or streaming video signals (hereinafter referred to as "communication video signals"), can change dynamically for each scene in a program to reduce the amount of data transmitted depending on the technical specifications of the distributor. It can also change for each program depending on the distributor's programming. Furthermore, the resolution of communication video signals can change depending on the amount of data that can be transmitted depending on the Internet communication conditions. Therefore, when displaying video based on communication video signals, seamless video processing is required even when the resolution is changed, so that the displayed video is not interrupted and the difference in image quality does not become too large.

[0014] That is, when the resolution of a communication video signal changes, the difference in the sense of detail or clarity before and after the change in resolution becomes large, resulting in a problem of a large difference in image quality.

[0015] For this reason, when seamless video processing is required and resolution changes can occur at any time, as in the case of displaying communication video signals, turning off the display of frames to which processing according to the magnification ratio has not been applied (i.e., muting the video), as in the case of broadcast video signals, can cause a sense of discomfort to the user. For this reason, when displaying communication video signals, video processing is required that does not turn off the display of frames to which processing according to the magnification ratio has not been applied. When this video processing is performed, the user will visually perceive a change in image quality due to a change in resolution, which poses a problem of degraded display quality.

[0016] The inventors have found the above-mentioned problems, and after extensive research, have come up with a video signal processing device that functions before and after a change in resolution.

[0017] A video signal processing device according to a first aspect of the present disclosure includes an acquisition unit that acquires a first video signal through broadcasting or communication via a network, an enlargement unit that performs an enlargement process to enlarge the acquired first video signal according to a set first parameter, and a processor that (i) changes the first parameter according to the resolution when the first video signal is a broadcast video signal obtained through the broadcasting and the resolution of the first video signal changes, and (ii) sets the first parameter to a fixed value when the first video signal is a communication video signal obtained through the communication.

[0018] According to this, when the resolution of the broadcast video signal changes, the first parameter of the enlargement process is changed according to the resolution. Since the resolution of the broadcast video signal changes only when the program changes, the video signal processing device can execute the enlargement process appropriate for the change in resolution so that the change is less likely to be affected during the program.

[0019] Furthermore, the video signal processing device sets the first parameter of the enlargement process to a fixed value (i.e., does not change the first parameter) regardless of changes in the resolution of the communication video signal. Since the resolution of the communication video signal may change even during a scene or a program, the video signal processing device performs a constant enlargement process regardless of changes in resolution, thereby preventing the occurrence of frames to which processing according to the enlargement ratio has not been applied when the resolution changes.

[0020] In this way, the video signal processing device can suppress degradation in image quality when the resolution of the acquired video signal changes.

[0021] A video signal processing device according to a second aspect of the present disclosure is a video signal processing device according to the first aspect, further comprising a sharpness adjustment unit that adjusts the sharpness of the second video signal after the enlargement processing according to a set second parameter, and the processor adjusts the second parameter so that, when the second video signal is a video signal after the enlargement processing of the communication video signal, the sharpness is emphasized more than when the second video signal is a video signal after the enlargement processing of the broadcast video signal.

[0022] For this reason, the second parameter of the sharpness adjustment is adjusted so that the sharpness of a communication video signal is emphasized more than that of a broadcast video signal. Therefore, by fixing the enlargement process regardless of the resolution, the image quality when a low-resolution video signal is input can be improved by sharpness adjustment using the second parameter.

[0023] A video signal processing device according to a third aspect of the present disclosure is the video signal processing device according to the second aspect, wherein the processor adjusts the second parameter so that the lower the resolution, the more sharpness is emphasized.

[0024] Therefore, the second parameter is adjusted so that the sharpness of the communication video signal is emphasized more than that of the broadcast video signal, and the lower the resolution, the more the sharpness is emphasized. In other words, because the sharpness of the communication video signal is adjusted according to the enlargement ratio, even if the enlargement processing is fixed regardless of the resolution, video signal processing appropriate for the resolution can be performed on the communication video signal. This reduces the difference in image quality that occurs before and after changing the resolution.

[0025] A video signal processing device according to a fourth aspect of the present disclosure is a video signal processing device according to the first or second aspect, wherein the processor adjusts the second parameter so that sharpness is emphasized in a first frequency band among the spatial frequency bands occupied by the first video signal, and the first frequency band is a higher frequency band among the spatial frequency bands.

[0026] This enhances the sharpness in the first frequency band, which is the higher frequency band of the spatial frequency band occupied by the first video signal in the second video signal, thereby effectively enhancing the sharpness of the second video signal.

[0027] A video signal processing device according to a fifth aspect of the present disclosure is a video signal processing device according to the fourth aspect, wherein the processor adjusts the second parameter to change the first frequency band to a higher frequency side when emphasizing the sharpness.

[0028] This emphasizes the sharpness of the first frequency band, which is a higher frequency band than the broadcast video signal within the spatial frequency band occupied by the first video signal in the second video signal, so that the sharpness of the second video signal can be effectively emphasized so that a sense of detail and clarity closer to that of a high-resolution video signal such as a 4K resolution video signal can be obtained compared to a low-resolution video signal such as an FHD resolution video signal or an SD resolution video signal.

[0029] A video signal processing device according to a sixth aspect of the present disclosure is a video signal processing device according to the fourth aspect, wherein the processor adjusts the second parameter so as to increase sharpness gain when emphasizing the sharpness.

[0030] According to this, the sharpness is enhanced by increasing the sharpness gain, so that the sharpness of the second video signal can be enhanced effectively.

[0031] A video signal processing device according to a seventh aspect of the present disclosure is a video signal processing device according to the fourth aspect, wherein when the sharpness is to be emphasized, the processor adjusts the second parameter so as to change the first frequency band to a higher frequency side and increase the sharpness gain.

[0032] This narrows the bandwidth of the first frequency band, which is the higher frequency band of the spatial frequency band occupied by the first video signal in the second video signal, and increases the sharpness gain to emphasize sharpness, thereby effectively emphasizing the sharpness of the second video signal.

[0033] A video signal processing method according to an eighth aspect of the present disclosure acquires a first video signal via broadcast or communication via a network, performs an enlargement process to enlarge the acquired first video signal according to a set first parameter, and (i) if the first video signal is a broadcast video signal obtained via broadcast and the resolution of the first video signal has changed, changes the first parameter according to the resolution, and (ii) if the first video signal is a communication video signal obtained via communication, sets the first parameter to a fixed value.

[0034] According to this, when the resolution of the broadcast video signal changes, the first parameter of the enlargement process is changed according to the resolution. Since the resolution of the broadcast video signal changes only when the program changes, the video signal processing device can execute the enlargement process appropriate for the change in resolution so that the change is less likely to be affected during the program.

[0035] Furthermore, the video signal processing device sets the first parameter of the enlargement process to a fixed value (i.e., does not change the first parameter) regardless of changes in the resolution of the communication video signal. Since the resolution of the communication video signal may change even during a scene or a program, the video signal processing device performs a constant enlargement process regardless of changes in resolution, thereby preventing the occurrence of frames to which processing according to the enlargement ratio has not been applied when the resolution changes.

[0036] A program according to a ninth aspect of the present disclosure is a program for causing a computer to execute the video signal processing method according to the eighth aspect.

[0037] These general or specific aspects may be realized in a system, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM, or in any combination of a system, an integrated circuit, a computer program, and a non-transitory recording medium.

[0038] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of well-known matters or redundant explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0039] The inventors have provided the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and do not intend for them to limit the subject matter described in the claims.

[0040] (Embodiment) Hereinafter, the embodiment will be described with reference to FIGS. 1 to 14C.

[0041] [1. Configuration] FIG. 1 is a diagram showing the appearance of a display device according to the present embodiment.

[0042] The display device 100 acquires a video signal and displays an image represented by the acquired video signal. The video signal may be, for example, a communication video signal or a broadcast video signal. The display device 100 has the appearance of a typical flat panel display, with a display device including a display panel housed in a housing. The display device 100 may be, for example, a liquid crystal display or an organic EL display.

[0043] The display device 100 is an example of a video signal processing device.

[0044] FIG. 2 is a block diagram showing an example of a hardware configuration of the display device according to the present embodiment.

[0045] As shown in FIG. 2, the display device 100 includes a tuner 101, a communication IF (Interface) 102, a decoder 103, an HDMI (registered trademark) (High-Definition Multimedia Interface) circuit 104, a memory 105, a control circuit 106, and a display device 107.

[0046] The tuner 101 converts the analog signal constituting the broadcast wave received by an antenna (not shown) into a coded signal (a coded signal of a video signal), which is a digital signal, and outputs the coded signal obtained by the conversion to the decoder 103.

[0047] The communication IF 102 is a communication interface that is communicatively connected to a network such as the Internet and transmits and receives information to and from a server via the network. The communication IF 102 acquires an encoded video signal from the server. The communication IF 102 may be, for example, an interface for wireless communication such as a wireless LAN interface or a Bluetooth (registered trademark) interface. The communication IF 102 may also be an interface for wired communication such as a USB (Universal Serial Bus) or a wired LAN interface.

[0048] The decoder 103 decodes the coded signal acquired from the tuner 101 or the communication IF 102, and outputs the video signal (first video signal) obtained by decoding to the control circuit 106. When the coded signal is multiplexed, the decoder 103 may decode the coded signal for video and the coded signal for audio obtained by demultiplexing the coded signal into a video signal and an audio signal, respectively.

[0049] The HDMI circuit 104 is an interface that acquires a video signal (first video signal) output by an external device connected to the HDMI circuit 104. The HDMI circuit 104 may also acquire an audio signal output by the external device together with the video signal.

[0050] Although the decoder 103 and the HDMI circuit 104 may acquire an audio signal as described above, the following description will be made of processing only for a video signal.

[0051] Here, the combination of the tuner 101, the communication IF 102, and the decoder 103 is an example of an acquisition unit. The HDMI circuit 104 may also be an example of an acquisition unit. That is, the combination of the tuner 101 and the decoder 103 acquires the first video signal through broadcasting. The combination of the communication IF 102 and the decoder 103 acquires the first video signal through communication via a network.

[0052] The control circuit 106 performs video signal processing on the first video signal output by the decoder 103 or the HDMI circuit 104. The first video signal is a video signal acquired by the display device 100. The first video signal includes a video signal acquired via the tuner 101, a video signal acquired via the communication IF 102, and a video signal acquired via the HDMI circuit 104.

[0053] Control circuit 106 outputs a video signal obtained by performing video signal processing on the first video signal to display device 107. Note that decoder 103 and control circuit 106 may be implemented as an integrated circuit. Control circuit 106 may also be implemented by a general-purpose processor such as a CPU that executes a predetermined program, or may be implemented by a dedicated circuit. In other words, the functions of display device 100, which will be described later, may be implemented by software or hardware.

[0054] The memory 105 may store a control program. The memory 105 may also store a display resolution based on the display device 107 or a display resolution specified by an application. The memory 105 may also store various parameters used in video signal processing executed by the control circuit 106. The parameters will be described later. The memory 105 includes, for example, a non-volatile memory and a volatile memory. The memory 105 also includes a frame memory (frame buffer) which will be described later. The frame memory is a volatile memory (for example, a RAM (Random Access Memory)).

[0055] The display device 107 displays an image based on the image signal output by the control circuit 106. The display device 107 is a display panel, and is configured by, for example, a liquid crystal panel, an organic EL panel, or the like.

[0056] FIG. 3 is a block diagram showing an example of the configuration of the control circuit according to this embodiment.

[0057] As shown in FIG. 3, the control circuit 106 includes an enlargement unit 111, a sharpness adjustment unit 112, and a CPU (Central Processing Unit) 113.

[0058] The enlargement unit 111 performs an enlargement process to enlarge the acquired first video signal in accordance with the first parameter stored (set) in the memory 105. The enlargement unit 111 enlarges the first video signal by converting the resolution of the first video signal to a higher resolution, and generates a second video signal whose resolution has been converted to be higher than that of the first video signal.

[0059] The enlargement process includes, for example, a mapping process and an interpolation process. The first parameters include parameters used in the enlargement process. For example, the first parameters may include parameters used in the mapping process or parameters used in the interpolation process. Note that the first parameters do not include an enlargement ratio for the enlargement process that enlarges the first video signal.

[0060] The mapping process is a process of mapping (arranging) a plurality of first pixels that constitute an image of the first video signal to a frame of the display resolution. The frame generated by the mapping process includes pixels to which the plurality of first pixels are mapped and pixels to which the plurality of first pixels are not mapped. The frame is formed in a frame memory included in memory 105.

[0061] The interpolation process is a process of generating pixel values ​​of pixels to which multiple first pixels are not mapped in a frame generated by the mapping process, using multiple first pixel values. In other words, the interpolation process is a process of calculating the pixel value of a pixel that is not mapped and does not have a pixel value, using multiple first pixel values ​​of multiple first pixels surrounding the pixel. For example, the interpolation process may be performed using an interpolation filter having filter coefficients. The filter coefficients are parameters used in the interpolation process and are an example of the first parameter. The memory size of the frame memory is also a parameter used in the interpolation process and is an example of the first parameter.

[0062] Generally, the mapping process and the interpolation process are performed in a single enlargement process. The filter coefficients of the interpolation filter are loaded in advance into the memory 105 for one frame. The enlargement unit 111 calculates the pixel value of the first pixel using the first pixel and the filter coefficients in the memory 105. When switching the filter coefficients of the interpolation filter process, it takes several frames to reload the filter coefficients.

[0063] When a broadcast video signal is input, the enlargement unit 111 performs both mapping and interpolation processes as enlargement processes on the first video signal to generate a second video signal. When enlarging the broadcast video signal, a frame memory according to the enlargement ratio is applied.

[0064] When a communication video signal is input, the enlargement unit 111 performs mapping and interpolation as enlargement processing on the first video signal to generate a second video signal. When enlarging the communication video signal, a frame memory according to the display resolution is applied regardless of the resolution.

[0065] In this way, a variable-size frame memory is used for enlarging broadcast video signals, while a fixed-size frame memory is used for enlarging communication video signals. Variable-size frame memory is used because efficient memory use is prioritized. Fixed-size frame memory is used because seamless display is prioritized. In other words, there is a trade-off between efficient memory use and seamless display.

[0066] When a first video signal having a resolution lower than the display resolution is input, the enlargement process generates a second video signal in which the resolution of the input first video signal is increased to the display resolution.

[0067] The sharpness adjustment unit 112 adjusts the sharpness of the second video signal after enlargement processing by the enlargement unit 111, according to the second parameters stored (set) in the memory 105. The sharpness adjustment processing can be achieved by adding high-frequency components of the second video signal extracted using a sharpness filter to the second video signal. The high-frequency components extracted using the sharpness filter are high-frequency components in the second video signal, and are high-frequency components in the frequency band of the spatial frequency included in the first video signal. The sharpness gain can be changed by changing the gain of the extracted high-frequency components of the second video signal and adding them to the second video signal. The sharpness adjustment may be performed using a sharpness filter specified by a cutoff frequency, a frequency band, and a gain. The cutoff frequency, the frequency band, and the gain are examples of the second parameters.

[0068] The sharpness adjustment unit 112 may be implemented using a neural network. In this case, a weight or bias value in the learning model of the neural network is an example of the second parameter. The weight or bias value is determined by learning in the neural network. Alternatively, the sharpness adjustment unit 112 may include a first configuration according to this embodiment and a second configuration implemented using a neural network, and may be configured to blend and output their outputs. In this case, the weight or bias value in the learning model of the neural network and the blending ratio between the first configuration and the second configuration are examples of the second parameter.

[0069] CPU 113 detects the resolution of the acquired first video signal. CPU 113 determines whether the acquired first video signal is a broadcast video signal or a communication video signal. CPU 113 sets a first parameter for enlargement processing in enlargement unit 111 and a second parameter for sharpness adjustment in sharpness adjustment unit 112 according to the detected resolution of the first video signal and whether the first video signal is a broadcast video signal or a communication video signal. In other words, CPU 113 sets parameters including the first parameter and the second parameter stored in memory 105 according to the resolution of the first video signal and the source from which the first video signal was acquired.

[0070] Specifically, when the first video signal is a broadcast video signal and the resolution of the first video signal has changed, the CPU 113 changes the first parameter used in the enlargement process in accordance with the resolution. When the first video signal is a communication video signal, the CPU 113 sets the first parameter used in the enlargement process to a fixed value.

[0071] 4A to 4C are diagrams illustrating the enlargement process for a broadcast video signal. FIG. 4A is a diagram illustrating the enlargement process for a 4K resolution video signal. FIG. 4B is a diagram illustrating the enlargement process for an FHD resolution video signal. FIG. 4C is a diagram illustrating the enlargement process for an SD resolution video signal. FIGS. 4A to 4C are diagrams illustrating the relationship between the signal level and the spatial frequency band occupied by the first video signal in the second video signal to be processed. Note that in FIGS. 4A to 4C, the shaded video signal band area indicates the frequency band included in the first video signal in the second video signal. In the case of a non-enlarged 4K signal → 4K signal, the frequency band included in the first video signal in the second video signal is the same. However, in the case of an enlarged signal, for example, an FHD signal → 4K signal, the spatial frequency band occupied by the first video signal in the second video signal is approximately 1 / 2. The thick solid line indicates the frequency characteristics of the interpolation filter.

[0072] As shown in FIGS. 4A to 4C, the frequency band of the spatial frequency occupied by the first video signal varies depending on the resolution of the first video signal. Specifically, the lower the resolution, the narrower the frequency band of the spatial frequency occupied by the first video signal, and the smaller its maximum frequency. If the first video signal is a broadcast video signal, the resolution changes when the program is switched, so CPU 113 sets the filter coefficients of the interpolation filter to filter coefficients according to the resolution. Therefore, enlargement unit 111 performs the enlargement process using an interpolation filter according to the resolution. The filter characteristics of the interpolation filter are set to be flat in the low frequency band and to have a relatively higher signal level in the high frequency band than in the low frequency band. In the high frequency band, the signal level is set to increase as the frequency increases up to the cutoff frequency, reach a maximum at the cutoff frequency, and decrease as the frequency increases beyond the cutoff frequency.

[0073] For example, as shown in Fig. 4A, the enlargement unit 111 performs enlargement processing on a broadcast video signal with 4K resolution using an interpolation filter (4K filter) corresponding to the 4K resolution. In this enlargement processing, since the processing is from 4K resolution to 4K resolution, the resolution of the video is not enlarged, but the signal level on the high frequency side of the video signal is relatively amplified due to the filter characteristics of the interpolation filter. Note that 4K resolution is an example of a display resolution (high resolution), and this enlargement processing is processing that is performed when a video signal with the same resolution as the display resolution is acquired.

[0074] 4B, the enlargement unit 111 performs an enlargement process on a broadcast video signal of FHD resolution using an interpolation filter (FHD filter) corresponding to the FHD resolution. This enlargement process is an enlargement process from FHD resolution to 4K resolution, in which the resolution of the video is enlarged and the signal level of the high frequency side of the video signal is relatively amplified. Note that the FHD resolution is an example of a first resolution (low resolution) lower than the display resolution, and this enlargement process is a process that is performed when a video signal of the first resolution is acquired.

[0075] 4C, the enlargement unit 111 performs an enlargement process on an SD resolution broadcast video signal using an interpolation filter (SD filter) corresponding to the SD resolution. This enlargement process is an enlargement process from SD resolution to 4K resolution, in which the video resolution is enlarged and the signal level on the high frequency side of the video signal is relatively amplified. Note that the SD resolution is an example of a second resolution (low resolution) lower than the first resolution, and this enlargement process is performed when a video signal of the second resolution is acquired.

[0076] The characteristics of each interpolation filter are determined by the filter coefficient values ​​and the algorithm of the enlargement unit 111. More specifically, the characteristics of the interpolation filter are determined so as to raise the signal level on the high-frequency side in accordance with the maximum frequency of the frequency band of the spatial frequency occupied by the first video signal. By appropriately setting the characteristics of the interpolation filter according to the enlargement ratio, it is possible to enhance the detail and clarity of the image. In this way, the enlargement unit 111 performs the enlargement process using an interpolation filter that raises the signal level on the high-frequency side of the frequency band of the spatial frequency occupied by the first video signal, so that when a broadcast video signal below the display resolution is input, the image can be effectively made high-resolution.

[0077] 4D and 4E are diagrams illustrating the enlargement process of a communication video signal. FIG. 4D is a diagram illustrating the enlargement process of an FHD resolution video signal. FIG. 4E is a diagram illustrating the enlargement process of an SD resolution video signal. FIGS. 4D and 4E are diagrams illustrating the relationship between the frequency band of the spatial frequency occupied by the first video signal to be processed and the signal level. Note that the enlargement process of a 4K resolution broadcast video signal is similar to the enlargement process of a 4K resolution communication video signal in FIG. 4A, and therefore is not illustrated. Note that the filter characteristics of the interpolation filter are set to be flat in the low frequency band and to have a relatively higher signal level in the high frequency band than in the low frequency band. In the high frequency band, the signal level increases as the frequency increases up to the cutoff frequency, reaches a maximum at the cutoff frequency, and decreases as the frequency increases beyond the cutoff frequency.

[0078] As described above, the frequency band of the spatial frequency included in the first video signal varies depending on the resolution of the first video signal. Specifically, the lower the resolution, the narrower the frequency band of the spatial frequency included in the first video signal, and the smaller its maximum frequency. When the first video signal is a communication video signal, the resolution may change even during a scene or a program, requiring a seamless display. For this reason, the enlargement unit 111 performs enlargement processing using an interpolation filter whose filter coefficients are fixed for 4K resolution, even when the resolution changes. In this way, a constant enlargement processing is performed regardless of a change in resolution, thereby preventing the occurrence of frames to which processing according to the enlargement ratio has not been applied when the resolution changes. The reason why frames to which processing according to the enlargement ratio has not been applied occurs is that when a change in resolution and a change in enlargement ratio are performed, the interpolation filter is switched with a delay of several frames, since it takes several frames' worth of time to switch the interpolation filter. If frames to which processing according to the enlargement ratio has not been applied are generated, the image displayed will appear unnatural.

[0079] Furthermore, when the second video signal after enlargement processing is a video signal after enlargement processing of a communication video signal, CPU 113 adjusts the second parameter so that sharpness is emphasized more than when the second video signal is a video signal after enlargement processing of a broadcast video signal. More specifically, when the second video signal after enlargement processing is a video signal after enlargement processing of a communication video signal, CPU 113 adjusts the second parameter so that sharpness is emphasized more than when the second video signal is a video signal after enlargement processing of the broadcast video signal at the same enlargement rate. In other words, the process of adjusting the second parameter is performed based on the case where the enlargement rate of the enlargement processing of the broadcast video signal is the same as the enlargement rate of the enlargement processing of the communication video signal. In this embodiment, the enlargement processing of the communication video signal and the enlargement processing of the broadcast video signal are performed to a common resolution (display resolution), so when the resolution of the input first video signal is the same, the enlargement rate of the enlargement processing of the broadcast video signal and the enlargement rate of the enlargement processing of the communication video signal are the same. In the case of broadcast video signals, sharpness is also enhanced by interpolation processing that applies an interpolation filter according to the magnification ratio, whereas in the case of communication video signals, sharpness enhancement is insufficient because interpolation processing is performed using an interpolation filter that is fixed compared to broadcast video signals.By adjusting the second parameter described above, it is possible to compensate for the insufficient sharpness enhancement in the case of communication video signals.

[0080] Furthermore, CPU 113 may adjust the second parameter so that sharpness is emphasized as the resolution becomes lower. CPU 113 may adjust the second parameter so that sharpness is emphasized in a first frequency band of the spatial frequency band occupied by the first video signal, for example. The first frequency band, which is the frequency band in which sharpness is emphasized, is a band on the high side of the spatial frequency band. For example, the high side of the spatial frequency band is a frequency band whose upper limit (upper limit frequency) is the maximum frequency of the spatial frequency band included in the first video signal and whose lower limit (lower limit frequency) is a frequency equal to or higher than the median of the spatial frequency band included in the first video signal. When emphasizing sharpness, CPU 113 may adjust the second parameter so that the frequency band of the first frequency band is shifted to a higher frequency range (higher side). Specifically, CPU 113 may shift the frequency band of the first frequency band to a higher frequency range (higher side) by setting a higher lower limit frequency without changing the upper limit frequency of the first frequency band. Furthermore, when enhancing sharpness, the CPU 113 may adjust the second parameter so as to increase the sharpness gain.

[0081] Figures 5A to 5C are diagrams illustrating a first example of sharpness adjustment of a broadcast video signal. Figure 5A is a diagram illustrating a first example of sharpness adjustment for a 4K resolution video signal. Figure 5B is a diagram illustrating a first example of sharpness adjustment for a FHD resolution video signal. Figure 5C is a diagram illustrating a first example of sharpness adjustment for a SD resolution video signal. Figures 5A to 5C are diagrams illustrating the relationship between the frequency band of spatial frequencies occupied by the first video signal to be processed and the signal level.

[0082] As described above regarding the relationship between the resolution and spatial frequency of the first video signal, the frequency band of the spatial frequency occupied by the first video signal varies depending on the resolution of the first video signal. Specifically, the lower the resolution, the narrower the frequency band of the spatial frequency occupied by the first video signal, and the smaller its maximum frequency. CPU 113 sets the second parameter so that sharpness is enhanced in a first frequency band, which is the higher band of the spatial frequency band occupied by the first video signal. Specifically, CPU 113 determines the cutoff frequency of the sharpness adjustment filter so that the first frequency band is the target of sharpness adjustment. CPU 113 determines a gain to adjust the degree of sharpness enhancement.

[0083] The CPU 113 determines a cutoff frequency according to the resolution of the first video signal. For example, the CPU 113 may determine a higher frequency band of the spatial frequency band occupied by the first video signal as a first frequency band to be subjected to sharpness adjustment, and determine the cutoff frequency based on the determined first frequency band. This determines a sharpness filter for a contour enhancement band for adjusting sharpness. Alternatively, a bandpass filter on the higher frequency side may be selected from among a plurality of bandpass filters with different cutoff frequencies. Alternatively, a lowpass filter or a highpass filter may be used instead of a bandpass filter. The cutoff frequency may be determined to be a frequency at the center of the first frequency band, or may be determined to be a frequency other than the center of the first frequency band. The CPU 113 may also determine a gain to be a constant value regardless of the resolution of the first video signal.

[0084] For this reason, the sharpness adjustment unit 112 performs sharpness adjustment according to the resolution. For example, as shown in Fig. 5A, the sharpness adjustment unit 112 performs sharpness adjustment on a 4K resolution second video signal obtained by performing an enlargement process on an acquired 4K resolution broadcast video signal (first video signal) using a sharpness filter (4K sharpness filter) with a contour correction band corresponding to the resolution of the acquired first video signal (4K resolution in this case). Also, for example, as shown in Fig. 5B, the sharpness adjustment unit 112 performs sharpness adjustment on a 4K resolution second video signal obtained by performing an enlargement process on an acquired FHD resolution broadcast video signal (first video signal) using a sharpness filter (FHD sharpness filter) with a contour correction band corresponding to the resolution of the acquired first video signal (FHD resolution in this case). 5C, the sharpness adjustment unit 112 performs sharpness adjustment on a 4K resolution second video signal obtained by performing enlargement processing on the acquired SD resolution broadcast video signal (first video signal) using a sharpness filter (SD sharpness filter) with a contour correction band corresponding to the resolution of the acquired first video signal (SD resolution in this case). In this way, the sharpness adjustment unit 112 performs sharpness adjustment using a sharpness filter that improves the signal level of the frequency band of the spatial frequency occupied by the first video signal, so that when a broadcast video signal below the display resolution is input, it is possible to effectively achieve high image quality of the video.

[0085] 5D to 5F are diagrams illustrating sharpness adjustment of a communication video signal. FIG. 5D is a diagram illustrating sharpness adjustment for a 4K resolution video signal. FIG. 5E is a diagram illustrating sharpness adjustment for a FHD resolution video signal. FIG. 5F is a diagram illustrating sharpness adjustment for a SD resolution video signal. FIG. 5D to 5F are diagrams illustrating the relationship between the frequency band of spatial frequencies occupied by the first video signal to be processed and the signal level.

[0086] As described above, the spatial frequency band occupied by the first video signal varies depending on the resolution of the first video signal. Specifically, the lower the resolution, the narrower the spatial frequency band occupied by the first video signal, and the smaller its maximum frequency. CPU 113 sets the second parameter so that sharpness is emphasized in the first frequency band, which is the higher band of the spatial frequency band occupied by the first video signal. Furthermore, when the enlarged second video signal is a video signal obtained by enlarging a communication video signal, CPU 113 adjusts the second parameter so that sharpness is emphasized more than when the second video signal is a video signal obtained by enlarging a broadcast video signal. Specifically, CPU 113 determines the cutoff frequency of the sharpness adjustment filter so that the first frequency band is the target of sharpness adjustment. The sharpness adjustment filter referred to here is a so-called band-pass filter that can extract a video signal of a predetermined frequency band. The cutoff frequency refers to the center frequency of the predetermined frequency band, and the first frequency band refers to the predetermined frequency band. In this example, the filter is configured with a single bandpass filter, but it may be configured with multiple bandpass filters with different cutoff frequencies and frequency bands. The CPU 113 determines the gain to adjust the degree of sharpness enhancement. The CPU 113 determines the gain so that the gain for the communication video signal is greater than the gain for the broadcast video signal.

[0087] The CPU 113 determines the cutoff frequency according to the resolution of the first video signal, as in the case of a broadcast video signal. Alternatively, the CPU 113 may determine the gain to be a constant value regardless of the resolution of the first video signal.

[0088] For this reason, the sharpness adjustment unit 112 performs sharpness adjustment according to the resolution. For example, as shown in FIG. 5D, the sharpness adjustment unit 112 performs sharpness adjustment on a 4K resolution broadcast video signal using a sharpness filter (4K sharpness filter) according to the 4K resolution. In this sharpness adjustment, a larger gain is set than in the sharpness adjustment for the 4K resolution broadcast video signal shown in FIG. 5A. In addition, in this sharpness adjustment, the first frequency band is set so that the lower limit frequency F11 of the 4K sharpness filter shown in FIG. 5D is higher than the lower limit frequency F1 of the 4K sharpness filter shown in FIG. 5A. As a result, the first frequency band of the 4K sharpness filter shown in FIG. 5D is set in a region higher than the first frequency band of the 4K sharpness filter shown in FIG. 5A.

[0089] 5E, for example, the sharpness adjustment unit 112 performs sharpness adjustment on a broadcast video signal with FHD resolution using a sharpness filter (FHD sharpness filter) corresponding to the FHD resolution. In this sharpness adjustment, a sharpness filter with a higher cutoff frequency and a larger gain are set than in the sharpness adjustment for the broadcast video signal with FHD resolution shown in FIG. 5B. In this sharpness adjustment, the first frequency band is set so that the lower limit frequency F12 of the FHD sharpness filter shown in FIG. 5E is higher than the lower limit frequency F2 of the FHD sharpness filter shown in FIG. 5B. As a result, the first frequency band of the FHD sharpness filter shown in FIG. 5E is set in a higher frequency range than the first frequency band of the FHD sharpness filter shown in FIG. 5B.

[0090] Also, for example, as shown in FIG. 5F, the sharpness adjustment unit 112 performs sharpness adjustment on an SD resolution broadcast video signal using a sharpness filter (SD sharpness filter) corresponding to the SD resolution. In this sharpness adjustment, a sharpness filter with a higher cutoff frequency and a larger gain are set than in the sharpness adjustment for the SD resolution broadcast video signal shown in FIG. 5C. In this sharpness adjustment, the first frequency band is set so that the lower limit frequency F13 of the SD sharpness filter shown in FIG. 5F is higher than the lower limit frequency F3 of the SD sharpness filter shown in FIG. 5C. As a result, the first frequency band of the SD sharpness filter shown in FIG. 5F is set in a higher frequency range than the first frequency band of the SD sharpness filter shown in FIG. 5C.

[0091] In these cutoff frequency and gain setting controls, multiple band-pass filters with different cutoff frequencies are used, and the gain of the video signal extracted by each band-pass filter can be set, and the gain can be increased by selecting the side with a higher cutoff frequency. It is sufficient to emphasize the sharpness of the higher frequency range compared to the broadcast video signal.

[0092] 5G to 5I are diagrams illustrating a second example of sharpness adjustment of a broadcast video signal. FIG. 5G is a diagram illustrating a second example of sharpness adjustment for a 4K resolution video signal. FIG. 5H is a diagram illustrating a second example of sharpness adjustment for an FHD resolution video signal. FIG. 5I is a diagram illustrating a second example of sharpness adjustment for an SD resolution video signal. FIG. 5G to 5I are diagrams illustrating the relationship between the frequency band of spatial frequencies occupied by the first video signal to be processed and the signal level.

[0093] As shown in FIG. 5G, the sharpness adjustment unit 112 performs sharpness adjustment on a 4K resolution broadcast video signal using a 4K sharpness filter in which the 4K sharpness filter in FIG. 5D is arranged on the low-pass side. In other words, the 4K sharpness filter in FIG. 5D is a sharpness filter in which the 4K sharpness filter in FIG. 5G is moved to the high-pass side. The cutoff frequency of the 4K sharpness filter in FIG. 5D is higher than the cutoff frequency of the 4K sharpness filter in FIG. 5G. The first frequency band of the 4K sharpness filter in FIG. 5D is the same frequency band as the first frequency band of the 4K sharpness filter in FIG. 5G.

[0094] Furthermore, the sharpness adjustment unit 112 performs sharpness adjustment on the FHD resolution broadcast video signal using an FHD sharpness filter in which the FHD sharpness filter in FIG. 5E is arranged on the low-pass side, as shown in FIG. 5H. In other words, the FHD sharpness filter in FIG. 5E is a sharpness filter in which the FHD sharpness filter in FIG. 5H is moved to the high-pass side. The cutoff frequency of the FHD sharpness filter in FIG. 5E is higher than the cutoff frequency of the FHD sharpness filter in FIG. 5H. The first frequency band of the FHD sharpness filter in FIG. 5E is the same frequency band as the first frequency band of the FHD sharpness filter in FIG. 5H.

[0095] Furthermore, the sharpness adjustment unit 112 performs sharpness adjustment on an SD resolution broadcast video signal using an SD sharpness filter in which the SD sharpness filter in FIG. 5F is arranged on the low-pass side, as shown in FIG. 5I. In other words, the SD sharpness filter in FIG. 5F is a sharpness filter in which the SD sharpness filter in FIG. 5I is moved to the high-pass side. The cutoff frequency of the SD sharpness filter in FIG. 5F is higher than the cutoff frequency of the SD sharpness filter in FIG. 5I. The first frequency band of the SD sharpness filter in FIG. 5F is the same frequency band as the first frequency band of the SD sharpness filter in FIG. 5I.

[0096] In this way, when the second example sharpness adjustment is performed on a broadcast video signal, the second parameter of the sharpness adjustment on the communication video signal is adjusted so that the width of the frequency band to which the sharpness filter for the sharpness adjustment on the communication video signal is applied is the same as the width of the frequency band to which the sharpness filter for the sharpness adjustment on the broadcast video signal is applied, and the frequency band to which the sharpness filter for the sharpness adjustment on the communication video signal is applied is changed to a higher range (higher frequency side) than the frequency band to which the sharpness filter for the sharpness adjustment on the broadcast video signal is applied.

[0097] In this way, when a communication video signal having a resolution lower than the display resolution is input, the sharpness adjustment unit 112 performs sharpness adjustment with a larger gain using a sharpness filter that improves the signal level of the frequency band in which the spatial frequency occupied by the first video signal is higher than when a broadcast video signal having a resolution lower than the display resolution is input. Therefore, when a communication video signal having a resolution lower than the display resolution is input, the definition and clarity of the video can be effectively increased, thereby achieving high image quality. For example, it is possible to perform contour correction on low-resolution video signals such as FHD resolution video signals and SD resolution video signals to have characteristics closer to those of high-resolution video signals such as 4K resolution video signals, and it is possible to effectively emphasize the sharpness of the second video signal so as to obtain definition and clarity closer to those of high-resolution video signals.

[0098] Note that CPU 113 may determine the gain so that the lower the resolution, the more emphasized the sharpness, regardless of whether the video signal is a broadcast video signal or a communication video signal. In other words, CPU 113 may determine the gain so that the lower the resolution, the greater the gain of the sharpness adjustment. Even in this case, when the second video signal after enlargement processing is a video signal after enlargement processing of a communication video signal, CPU 113 may determine the cutoff frequency, frequency band, and gain of the sharpness filter for sharpness adjustment so that higher high-frequency components are extracted and the gain is greater than when the second video signal is a video signal after enlargement processing of a broadcast video signal.

[0099] Furthermore, when the second video signal after enlargement processing is a video signal after enlargement processing of a broadcast video signal, CPU 113 sets the filter coefficients of the interpolation filter to filter coefficients according to the resolution when the resolution changes in accordance with the resolution of the first video signal, but this is not limited to this. The filter coefficients of the interpolation filter do not have to be set to filter coefficients according to the resolution, and CPU 113 may set the filter coefficients of the interpolation filter to the same as when the second video signal after enlargement processing is a video signal after enlargement processing of a communication video signal.

[0100] Furthermore, when the second video signal after enlargement processing is a video signal after enlargement processing of a communication video signal, CPU 113 determines the second parameter so that sharpness is emphasized more than when the second video signal is a video signal after enlargement processing of a broadcast video signal, but this is not limited to this. CPU 113 may set the same cutoff frequency of the sharpness filter, the same frequency band of the sharpness filter, or the same gain, for the second video signal after enlargement processing of a communication video signal and the second video signal after enlargement processing of a broadcast video signal, and may determine the second parameter so that sharpness adjustment is performed so that either is the same.

[0101] The second parameters may be stored in memory 105 in the manners shown in Figures 6A and 6B. Figure 6A is a table showing basic information about the second parameters. Figure 6B is a table showing the differences between the second parameters for communication video signals and the second parameters for broadcast video signals.

[0102] As shown in Fig. 6A, the cutoff frequency for sharpness adjustment and the sharpness gain as the second parameters are determined according to each of the communication video signal and the broadcast video signal and the resolution of the first video signal. In Fig. 6A, the same values ​​are set as the second parameters for the communication video signal and the broadcast video signal.

[0103] The second parameter is set for the communication video signal so that sharpness is emphasized more than for the broadcast video signal. For this reason, as shown in Fig. 6B, a difference between the second parameter for the communication video signal and the second parameter for the broadcast video signal is determined. The second parameter for the communication video signal is calculated by adding the difference shown in Fig. 6B to the second parameter of the basic information shown in Fig. 6A.

[0104] Fig. 6C is a table showing the second parameters when the difference is applied to the basic information. CPU 113 calculates the second parameters for the communication video signal as shown in Fig. 6C by adding the difference shown in Fig. 6B to the second parameters of the basic information shown in Fig. 6A. Note that in Fig. 6C, nothing is added to the broadcast video signal, so the same value as in Fig. 6A is determined as the second parameter.

[0105] [2. Operation] Next, the operation of the display device 100 will be described.

[0106] FIG. 7 is a flowchart showing an example of the initial setting process performed by the display device.

[0107] The initial setting process is executed, for example, when the display device 100 is started (powered on). Note that the initial setting process may also be executed when the acquired first video signal is switched from a broadcast video signal to a communication video signal. Also, the initial setting process may also be executed when the acquired first video signal is switched from a communication video signal to a broadcast video signal.

[0108] The CPU 113 of the control circuit 106 of the display device 100 detects the resolution of the first video signal (S1).

[0109] Next, CPU 113 mutes the video (S2). Specifically, CPU 113 may output a video signal or a control signal for displaying a black screen to display device 107 without outputting a video signal based on the first video signal.

[0110] Next, CPU 113 sets an enlargement ratio and a first parameter for the communication video signal (S3). The enlargement ratio is set to an enlargement ratio according to the resolution of the detected first video signal. The first parameter for the communication video signal is set to a fixed parameter. The set enlargement ratio and first parameter are stored in memory 105. Note that in step S3, the first parameter for the communication video signal is set unconditionally, but if the acquired first video signal is a broadcast video signal, the first parameter for the broadcast video signal is set in step S14 of the flowchart in FIG. 8, which will be described later.

[0111] Next, CPU 113 cancels the mute of the video (S4). Specifically, CPU 113 controls enlargement unit 111 and sharpness adjustment unit 112 to stop outputting a video signal or a control signal for displaying a black screen to display device 107, and to output a processed video signal obtained by performing video signal processing on the first video signal to display device 107.

[0112] FIG. 8 is a flowchart showing an example of video signal processing by the display device.

[0113] The tuner 101, the communication IF 102 or the decoder 103 of the display device 100 acquires the first video signal (S11).

[0114] The CPU 113 of the control circuit 106 of the display device 100 determines whether the first video signal is a communication video signal (S12). That is, the CPU 113 determines whether the first video signal is a communication video signal or a broadcast video signal.

[0115] If the CPU 113 determines that the first video signal is a communication video signal (Yes in S12), it executes step S13, and if the CPU 113 determines that the first video signal is a broadcast video signal (No in S12), it executes step S14.

[0116] In step S13, the CPU 113 and the enlargement unit 111 execute enlargement processing for the communication video signal (S13). Details of step S13 will now be described with reference to FIG.

[0117] FIG. 9 is a flowchart showing an example of enlargement processing for a communication video signal.

[0118] The CPU 113 detects the resolution of the first video signal (S21).

[0119] The CPU 113 determines whether the resolution of the first video signal has changed (S22). If the CPU 113 determines that the resolution of the first video signal has changed (Yes in S22), it executes step S23, and if the CPU 113 determines that the resolution of the first video signal has not changed (No in S22), it executes step S24.

[0120] In step S23, CPU 113 detects that the resolution of the first video signal has changed, and therefore changes the enlargement ratio for enlarging the resolution of the first video signal to the display resolution (S23). At this time, CPU 113 sets the enlargement ratio for the enlargement process in accordance with the fact that the first video signal is a communication video signal and the resolution of the first video signal.

[0121] In step S24, the enlargement unit 111 reads out the first parameters for the communication video signal from the memory 105, and performs enlargement processing using the read out first parameters (S24).

[0122] Returning to the explanation of Figure 8.

[0123] In step S14, the CPU 113 and the enlargement unit 111 execute enlargement processing for the broadcast video signal (S14). Details of step S14 will now be described with reference to FIG.

[0124] FIG. 10 is a flowchart showing an example of the enlargement process for a broadcast video signal.

[0125] The CPU 113 detects the resolution of the first video signal (S31).

[0126] CPU 113 determines whether the resolution of the first video signal has changed (S32). If CPU 113 determines that the resolution of the first video signal has changed (Yes in S32), it executes step S33, and if CPU 113 determines that the resolution of the first video signal has not changed (No in S32), it executes step S34.

[0127] In step S33, the CPU 113 starts the resolution change process (S33). Once the resolution change process has started, the process proceeds to the next step S34 without waiting for the resolution change process to end. Details of the resolution change process will be described later with reference to FIG.

[0128] In step S34, the enlargement unit 111 reads out from the memory 105 the first parameters for the broadcast video signal that were set in the resolution change process described below, and performs the enlargement process using the read out first parameters (S34).

[0129] Next, the resolution change process started in step S33 will be described with reference to FIG.

[0130] FIG. 11 is a flowchart showing an example of the resolution change process.

[0131] CPU 113 mutes the video (S41). Specifically, CPU 113 may output a video signal or a control signal to display device 107 for displaying a black screen, without outputting a video signal based on the first video signal.

[0132] Next, CPU 113 sets the enlargement ratio and first parameters (S42). At this time, CPU 113 sets the first parameters for the enlargement process in accordance with the fact that the first video signal is a broadcast video signal and the resolution of the first video signal. The specific method for setting the first parameters is as explained in the explanation of enlargement unit 111 and CPU 113. The set first parameters are stored in memory 105. Note that the process of step S34 may be executed before the process of step S42 is completed. In this case, the enlargement process may be executed with inappropriate first parameters, but this will not be visible to the user because the video is muted.

[0133] CPU 113 cancels the mute of the video (S43). Specifically, CPU 113 controls enlargement unit 111 and sharpness adjustment unit 112 to stop outputting a video signal or a control signal for displaying a black screen to display device 107, and to output a processed video signal obtained by performing video signal processing on the first video signal to display device 107.

[0134] Returning to the explanation of Figure 8.

[0135] In step S15, the CPU 113 and the sharpness adjustment unit 112 perform sharpness adjustment (S15). Details of step S15 will now be described with reference to FIG.

[0136] FIG. 12 is a flowchart showing an example of sharpness adjustment.

[0137] The CPU 113 detects the resolution of the first video signal (S51).

[0138] CPU 113 determines whether the resolution of the first video signal has changed (S52). If CPU 113 determines that the resolution of the first video signal has changed (Yes in S52), it executes step S53, and if CPU 113 determines that the resolution of the first video signal has not changed (No in S52), it executes step S54.

[0139] In step S53, CPU 113 sets a second parameter for sharpness adjustment (S53). Specifically, CPU 113 sets the second parameter for sharpness adjustment in sharpness adjustment unit 112 according to the detected resolution of the first video signal and whether the second video signal is a broadcast video signal or a communication video signal. The set second parameter is stored in memory 105.

[0140] The sharpness adjustment unit 112 reads the set second parameter from the memory 105 and performs sharpness adjustment using the read second parameter (S54). As a result, the adjusted video signal is output from the control circuit 106 to the display device 107.

[0141] Returning to the explanation of Figure 8.

[0142] In step S16, the display device 107 displays an image based on the adjusted video signal (S16).

[0143] [3. Issues and Effects] 13A to 13C and 14A to 14C are diagrams illustrating problems that arise in enlargement processing. 13A to 13C are diagrams illustrating enlargement processing of broadcast video signals. 13A shows an example of enlarging an SD resolution video signal to output 4K video, 13B shows an example of enlarging an FHD resolution video signal to output 4K video, and 13C shows an example of enlarging a 4K resolution video signal to output 4K video.

[0144] As shown in Figures 13A and 13B, when the acquired first video signal is a broadcast video signal and its resolution is lower than the display resolution, the size of the frame memory in which the first video signal is temporarily stored is set according to the resolution. That is, when the resolution of the first video signal is SD resolution, the size of the frame memory is set to 1 / 6 of the size of the frame memory for the second video signal with 4K resolution, as shown in Figure 13A. When the resolution of the first video signal is FHD resolution, the size of the frame memory is set to 1 / 4 of the size of the frame memory for the second video signal with 4K resolution, as shown in Figure 13B. When the resolution of the first video signal is 4K resolution, the size of the frame memory is set to the same size as the size of the frame memory for the second video signal with 4K resolution, as shown in Figure 13C. The display resolution is, for example, the maximum resolution (the resolution of the display device 107) or a resolution specified by an application, and is 4K resolution in this embodiment.

[0145] As described above, when the resolution of the first video signal changes, the mapping of the frame memory is changed. It takes several frames for the changed mapping to be applied, resulting in frames to which processing according to the enlargement ratio matching the resolution has not been applied. However, as described above, in broadcast video signals, the time when the resolution changes coincides with the time when the program switches. Therefore, even if the video signal processing device performs processing according to the enlargement ratio, seamless video processing is not required. For example, by turning off the display of frames to which processing according to the enlargement ratio has not been applied (i.e., muting the video), the video signal processing device can perform video signal processing so as to minimize the impact on the program. In other words, when the first video signal is a broadcast video signal, enlargement processing according to the enlargement ratio of the first video signal can be performed.

[0146] 14A to 14C are diagrams illustrating the enlargement process of a communication video signal. Fig. 14A shows an example of performing the enlargement process on an SD resolution video signal to output 4K video, Fig. 14B shows an example of performing the enlargement process on an FHD resolution video signal to output 4K video, and Fig. 14C shows an example of performing the enlargement process on a 4K resolution video signal to output 4K video.

[0147] If the acquired first video signal is a communication video signal, a frame memory corresponding to the display resolution is used regardless of the resolution of the first video signal. The communication video signal is composed of a video signal in which frames with a resolution lower than the display resolution are embedded within frames with the display resolution. In other words, in a communication video signal, even if the resolution of the first video signal is lower than the display resolution, one frame has the display resolution. If the resolution of the first video signal is lower than the display resolution, the frame memory includes an area with pixel values ​​and an area without pixel values. In this way, since one frame of the communication video signal has the display resolution, a frame memory of a size corresponding to the display resolution is uniformly used regardless of the resolution of the first video signal. Therefore, even if the resolution changes, the size of the frame memory does not change, enabling seamless video processing. The display device 100 (video signal processing device) according to this embodiment includes a tuner 101, a communication IF 102, a decoder 103 (acquisition unit), an enlargement unit 111, and a CPU 113 (processor). The tuner 101, the communication IF 102, and the decoder 103 (acquisition unit) acquire the first video signal via broadcast or communication via a network. The enlargement unit 111 performs an enlargement process to enlarge the acquired first video signal according to the set first parameter. The CPU 113 (processor) (i) changes the first parameter according to the resolution when the first video signal is a broadcast video signal obtained by broadcasting and the resolution of the first video signal has changed, and (ii) sets the first parameter to a fixed value when the first video signal is a communication video signal obtained by communication.

[0148] According to this, when the resolution of the broadcast video signal changes, the first parameter of the enlargement process is changed according to the resolution. Since the resolution of the broadcast video signal changes only when the program changes, the display device 100 (video signal processing device) can perform enlargement process appropriate for the change in resolution so that the change is less likely to be affected during the program.

[0149] Furthermore, the display device 100 (video signal processing device) sets the first parameter of the enlargement process to a fixed value (i.e., does not change the first parameter) regardless of changes in the resolution of the communication video signal. Since the resolution of the communication video signal may change even during a scene or a program, the display device 100 (video signal processing device) performs a constant enlargement process regardless of changes in resolution, thereby preventing the occurrence of frames to which processing according to the enlargement ratio has not been applied when the resolution changes.

[0150] In this way, the display device 100 (video signal processing device) can suppress degradation in image quality when the resolution of the acquired video signal changes.

[0151] Moreover, display device 100 (video signal processing device) according to this embodiment further includes sharpness adjustment unit 112. Sharpness adjustment unit 112 adjusts the sharpness of the enlarged second video signal according to the set second parameter. When the second video signal is a video signal obtained by enlarging a communication video signal, CPU 113 (processor) adjusts the second parameter so that the sharpness is emphasized more than when the second video signal is a video signal obtained by enlarging a broadcast video signal.

[0152] For this reason, the second parameter of the sharpness adjustment is adjusted so that the sharpness of a communication video signal is emphasized more than that of a broadcast video signal. Therefore, by fixing the enlargement process regardless of the resolution, the image quality when a low-resolution video signal is input can be improved by sharpness adjustment using the second parameter.

[0153] Furthermore, in the display device 100 (video signal processing device) according to the present embodiment, the CPU 113 (processor) adjusts the second parameter so that the lower the resolution, the more the sharpness is emphasized.

[0154] Therefore, for communication video signals, the second parameter is adjusted so that sharpness is emphasized more than for broadcast video signals, and the lower the resolution, the more sharpness is emphasized. In other words, because sharpness adjustment is performed on the communication video signal according to the resolution, even if the enlargement processing is fixed regardless of the resolution, video signal processing appropriate for the resolution can be performed on the communication video signal. Therefore, the difference in image quality that occurs before and after a change in resolution can be reduced.

[0155] Furthermore, in display device 100 (video signal processing device) according to the present embodiment, CPU 113 (processor) adjusts the second parameter so that sharpness is emphasized in a first frequency band of the spatial frequency band occupied by the first video signal. The first frequency band is a band on the higher side of the spatial frequency band. The higher side of the spatial frequency band is a frequency band whose upper limit is the maximum frequency of the spatial frequency band occupied by the first video signal in the second video signal, and whose lower limit is a frequency equal to or higher than the median of the spatial frequency band occupied by the first video signal in the second video signal.

[0156] This enhances the sharpness in the first frequency band, which is the higher frequency band of the spatial frequency band occupied by the first video signal in the second video signal, thereby effectively enhancing the sharpness of the second video signal.

[0157] Furthermore, in the display device 100 (video signal processing device) according to this embodiment, when sharpness is to be enhanced, the CPU 113 (processor) adjusts the second parameter so as to change the first frequency band to a high frequency range.

[0158] According to this, the sharpness is enhanced by the sharpness filter extracting a higher frequency band from the spatial frequency band occupied by the first video signal than that of a broadcast video signal as the first frequency band, which makes it possible to effectively enhance the sharpness of the second video signal so that a sense of detail and clarity closer to that of a high-resolution video signal such as a 4K resolution video signal can be obtained for a low-resolution video signal such as an FHD resolution video signal or an SD resolution video signal.

[0159] Furthermore, in the display device 100 (video signal processing device) according to the present embodiment, the CPU 113 (processor) adjusts the second parameter so as to increase the sharpness gain when sharpness is to be enhanced.

[0160] According to this, the sharpness is enhanced by increasing the sharpness gain, so that the sharpness of the second video signal can be enhanced effectively.

[0161] Furthermore, in the display device 100 (video signal processing device) according to this embodiment, the CPU 113 (processor) executes two processes when enhancing sharpness: a process of adjusting the second parameter so as to shift the first frequency band to a high-frequency region, and a process of adjusting the second parameter so as to increase the sharpness gain. This makes it possible to effectively enhance the sharpness of the second video signal.

[0162] [4. Modifications] In the above embodiment, when emphasizing sharpness, CPU 113 performs two processes, namely, a process of adjusting the second parameter so as to change the band of the first frequency band to a higher frequency range, and a process of adjusting the second parameter so as to increase the sharpness gain, but sharpness may be emphasized by performing only one of the two cases.

[0163] As described above, the embodiments have been described as examples of the technology in the present disclosure, and for that purpose, the accompanying drawings and detailed description have been provided.

[0164] Therefore, the components shown in the accompanying drawings and detailed description may include not only essential components for solving the problem, but also components that are not essential for solving the problem in order to illustrate the above technology. Therefore, the fact that these non-essential components are shown in the accompanying drawings or detailed description should not be interpreted as immediately indicating that these non-essential components are essential.

[0165] Furthermore, since the above-described embodiments are intended to illustrate the technology of the present disclosure, various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents. [Industrial Applicability]

[0166] The present disclosure is useful as an image processing device, an image processing method, an image generating device, an image generating method, a program, and the like that can suppress the amplification of noise caused by increasing the sharpness gain. [Explanation of symbols]

[0167] 100 display device 101 Tuner 102 Communication Interface 103 Decoder 104 HDMI circuit 105 memory 106 Control circuit 107 Display Devices 111 Enlarged section 112 Sharpness adjustment section 113 CPU

Claims

1. an acquisition unit that acquires a first video signal through broadcasting or communication via a network; an enlargement unit that performs an enlargement process to enlarge the acquired first video signal in accordance with a set first parameter; (i) when the first video signal is a broadcast video signal obtained by the broadcast and the resolution of the first video signal has changed, changing the first parameter in accordance with the resolution, and (ii) when the first video signal is a communication video signal obtained by the communication, setting the first parameter to a fixed value, The first parameter is the memory size of the frame memory. Video signal processing device.

2. moreover, a sharpness adjustment unit that adjusts sharpness of the second video signal after the enlargement process in accordance with the set second parameter; The processor: When the second video signal is the video signal obtained by the enlargement processing of the communication video signal, the second parameter is adjusted so that sharpness is emphasized more than when the second video signal is the video signal obtained by the enlargement processing of the broadcast video signal.

2. The video signal processing device according to claim 1.

3. The processor adjusts the second parameter so that the lower the resolution, the more sharpness is emphasized.

3. The video signal processing device according to claim 2.

4. the processor adjusts the second parameter so that sharpness is enhanced in a first frequency band among spatial frequency bands occupied by the first video signal; The first frequency band is a band on the higher side of the spatial frequency band.

4. A video signal processing device according to claim 2 or 3.

5. When the sharpness is to be enhanced, the processor adjusts the second parameter to shift the first frequency band to a higher frequency band.

5. The video signal processing device according to claim 4.

6. When the sharpness is to be enhanced, the processor adjusts the second parameter to increase the sharpness gain.

5. The video signal processing device according to claim 4.

7. When the sharpness is to be enhanced, the processor adjusts the second parameter so as to shift the first frequency band to a higher frequency side and increase a sharpness gain.

5. The video signal processing device according to claim 4.

8. moreover, a sharpness adjustment unit that adjusts sharpness of the second video signal after the enlargement processing; The sharpness adjustment unit A first sharpness adjustment process using a sharpness filter and a second sharpness adjustment process using a neural network are executed; blending the result of the first sharpness adjustment process and the result of the second sharpness adjustment process at a predetermined ratio; The processor adjusts the predetermined ratio so that the lower the resolution of the first video signal, the more sharpness is emphasized.

2. The video signal processing device according to claim 1.

9. acquiring a first video signal by broadcasting or communication via a network; performing an enlargement process for enlarging the acquired first video signal in accordance with a set first parameter; (i) when the first video signal is a broadcast video signal obtained by broadcasting and the resolution of the first video signal changes, the first parameter is changed according to the resolution; (ii) when the first video signal is a communication video signal obtained by communication, the first parameter is set to a fixed value; The first parameter is the memory size of the frame memory. Video signal processing method.

10. A program for causing a computer to execute the video signal processing method according to claim 9.

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