Image display device and channel switching method therefor

Abstract

An image display device and a channel switching method therefor are disclosed. The channel switching method for the image display device may comprise the steps of: decoding the frames constituting received content of the current channel; and storing only some frames of received content of the previous channel or content of the next channel, and then performing decoding from some stored frames when switching channels, thereby enabling channel switching speed to be reduced.

Description

Video display device and channel switching method thereof

[0001] The present disclosure relates to a video display device capable of switching channels and a method for switching channels thereof, and more particularly, to a video display device capable of shortening a channel switching time and a method for switching channels thereof.

[0002] A video display device, for example, a television (hereinafter referred to as a TV), can decode received broadcast content and display it through a display unit.

[0003] In the case of video, such broadcast content consists of multiple video frames. The transmitting side compresses the multiple video frames into I (Intra) frames, P (Predicted) frames, and B (Bidirectional or Bidirectionally Predicted) frames in units of GOP (Group Of Pictures) and transmits them to a video display device. Here, the I frame, P frame, and B frame are also referred to as I picture, P picture, and B picture, and the GOP is also referred to as GOF (Group Of Frames). In the present disclosure, the terms frame and picture are used interchangeably and have the same meaning.

[0004] Here, I-frames are also called key frames. I-frames are frames that can be decoded independently, without reference to other frames. These I-frames can be assigned to every kth frame in a series of video frames, or they can be assigned to frames with higher scores based on inter-frame correlation. Specifically, I-frames are used at the beginning of broadcast content or for scene transitions.

[0005] A P-frame, also known as a forward prediction frame, is a frame that compares the current frame to the immediately preceding I-frame or P-frame and stores the differences between the two frames. Therefore, in a video display device, a P-frame is decoded when a reference to the I-frame or the preceding P-frame is available.

[0006] A B frame is a frame that contains the differences between the current frame and the previous or subsequent I frame and / or P frame. Therefore, in a video display device, a B frame is decoded when a reference to both the previous or subsequent I frame and / or P frame is possible.

[0007] And, GOP refers to an encoding unit that groups at least one I frame, one or more P frames, and one or more B frames, and one or more P frames and one or more B frames are included in a certain pattern between I frames.

[0008] Figure 1 is a diagram showing an example of a GOP structure. In Figure 1, the GOP structure is IBBPBBIBBPBBI.

[0009] At this time, the number of frames included in the GOP, the arrangement pattern of the frames, etc. may vary, and the compression ratio and transmission rate may vary depending on the number and arrangement pattern of the frames included in the GOP structure.

[0010] Typically, one GOP contains one I-frame, so Figure 1 can be viewed as an example of a two-GOP structure.

[0011] In this GOP structure, I frames are not dependent on any other frames and can be decoded independently, whereas P and B frames depend on previous and / or subsequent frames, which must be received and decoded first. In other words, B frames depend on I and P frames, and P frames depend on I frames.

[0012] Therefore, when a user requests to switch to another channel while watching broadcast content of a specific channel on a video display device, the video decompression operation (i.e., decoding) can begin only after receiving the next I frame in the channel where the channel switch occurred between I frames. For example, if the channel switch occurs in the middle of a GOP, the video of the switched channel will not be displayed until the I frame of the next GOP is received and decoded.

[0013] That is, the time interval between the I frames that make up the broadcast content affects the channel switching time, and the time waiting for the reception of these I frames (i.e., key picture frames) has a significant impact, typically accounting for more than 90 percent of the entire channel switching time. In other words, depending on the number of frames included in the GOP and the point in time when the channel switching request is performed within the GOP (i.e., the channel switching start position), the waiting time until the video is displayed on the switched channel may be longer.

[0014] Figures 2(a) to 2(c) are diagrams showing examples of waiting times that vary depending on the point in time when channel switching starts when the GOP structure is IPBBBPBBB.

[0015] In Fig. 2(a), when there is a channel switching request (or start) between the second P frame and the next B frame in the GOP, there is a wait of approximately 3 frames until the next I frame is received, and then the image is displayed.

[0016] In Fig. 2(b), when there is a channel switching request (or start) between the first P frame and the next B frame in the GOP, there is a wait of approximately 7 frames until the next I frame is received, and then the image is displayed.

[0017] In Fig. 2(c), when there is a channel switching request (or start) before the last B frame in the GOP, there is a wait of approximately one frame until the next I frame is received, and then the image is displayed.

[0018] When switching channels on a video display device (e.g., a TV), the time the TV waits for the next I-frame of the compressed video on the newly switched channel can be very long or very short. In other words, the channel switching time is greatly influenced by the time the TV waits to receive an I-frame, which has the disadvantage of increasing the waiting time when switching channels.

[0019] The present disclosure is proposed to solve the above-mentioned problems and various problems related thereto, and the purpose of the present disclosure is to provide a video display device and a channel switching method thereof for improving a channel switching speed.

[0020] However, the scope of the embodiments is not limited to the aforementioned technical tasks, and the scope of the embodiments may be expanded to other technical tasks that can be inferred by a person skilled in the art based on the entire contents of this document.

[0021] In order to achieve the above-described purpose and other advantages, a method for switching channels in a video display device comprises the steps of: receiving content of a current channel; receiving content of a previous channel based on the current channel; receiving content of a next channel based on the current channel; decoding frames constituting the content of the received current channel; displaying content of the current channel composed of the decoded frames on a screen; decoding frames constituting the content of the received previous channel or storing some of the frames constituting the content of the received previous channel and then starting decoding from some of the stored frames when channel down is selected from a remote control; displaying content of the previous channel including frames decoded in the step at the time channel down is selected from the remote control on the screen; decoding frames constituting the content of the received next channel or storing some of the frames constituting the content of the received next channel and then starting decoding from some of the stored frames when channel up is selected from the remote control; and including frames decoded in the step at the time channel up is selected from the remote control. It may include a step of displaying the content of the next channel on the above screen.

[0022] According to embodiments, the frames constituting the received content are grouped into GOP units, and each GOP may be composed of at least one I frame, one or more P frames, and one or more B frames.

[0023] According to embodiments, some frames of content of the previous channel stored in the decoding step of the previous channel may be frames within the most recently received GOP.

[0024] According to embodiments, when decoding frames constituting the content of a previous channel received in the decoding step of the previous channel, decoding of B frames may be omitted, and decoding of B frames may be performed from the time when channel down is selected from the remote control.

[0025] According to embodiments, some frames of the content of the next channel stored in the decoding step of the next channel may be frames within the most recently received GOP.

[0026] According to embodiments, when decoding frames constituting the content of the next channel received in the decoding step of the next channel, decoding of B frames may be omitted, and decoding of B frames may be performed from the time when channel up is selected from the remote control.

[0027] According to embodiments, when the content of the current channel is received from a server via a network, the method may further include a step of transmitting at least one of a channel change request to the previous channel and a channel change request to the next channel to the server in advance before changing the channel by the remote control.

[0028] According to embodiments, a video display device may include a remote control capable of selecting a channel down to a previous channel and a channel up to a next channel based on a current channel for channel switching, a first channel processing unit that receives content of the previous channel and stores some frames among frames constituting the content of the received previous channel, a second channel processing unit that receives content of the current channel, a third channel processing unit that receives content of the next channel and stores some frames among frames constituting the content of the received next channel, a selection unit that selects and outputs frames of content of one of the first channel processing units or the third channel processing units, a decoding unit that decodes frames of content output from the selection unit, a display processing unit that displays content composed of frames decoded by the decoding unit on a screen, and a control unit that controls the selection unit and the decoding unit such that decoding starts from some frames stored in the first channel processing unit or some frames stored in the third channel processing unit according to selection of a channel down or channel up by the remote control.

[0029] According to embodiments, the frames constituting the received content are grouped into GOP units, and each GOP may be composed of at least one I frame, one or more P frames, and one or more B frames.

[0030] According to embodiments, some frames of content of a previous channel stored in the first channel processing unit may be frames within the most recently received GOP.

[0031] According to embodiments, some frames of content of the next channel stored in the third channel processing unit may be frames within the most recently received GOP.

[0032] According to embodiments, when the content of the current channel is received from a server via a network, the control unit may transmit at least one of a channel change request to the previous channel and a channel change request to the next channel to the server in advance before the channel is changed by the remote control.

[0033] According to embodiments, a video display device may include a remote control capable of selecting a channel down to a previous channel and a channel up to a next channel based on a current channel for channel switching, a first channel processing unit that receives content of the previous channel and decodes frames constituting the content of the received previous channel, a second channel processing unit that receives content of the current channel and decodes frames constituting the content of the received current channel, a third channel processing unit that receives content of the next channel and decodes frames constituting the content of the received next channel, a selection unit that selects and outputs frames decoded by one of the channel processing units of the first channel processing unit to the third channel processing unit, a display processing unit that displays content composed of frames selected by the selection unit on a screen, and a control unit that controls the selection unit to select frames decoded by one of the channel processing units of the first channel processing unit to the third channel processing unit according to a channel down or channel up selection by the remote control.

[0034] According to embodiments, the frames constituting the received content are grouped into GOP units, and each GOP may be composed of at least one I frame, one or more P frames, and one or more B frames.

[0035] According to embodiments, the first channel processing unit may omit decoding of B frames when decoding frames constituting content of the received previous channel, and perform decoding of B frames from the time when channel down is selected from the remote control.

[0036] According to embodiments, the third channel processing unit may omit decoding of B frames when decoding frames constituting the content of the next channel received, and perform decoding of B frames from the time when channel up is selected from the remote control.

[0037] According to embodiments, when the content of the current channel is received from a server via a network, the control unit may transmit at least one of a channel change request to the previous channel and a channel change request to the next channel to the server in advance before changing the channel.

[0038] According to the device and method of the present disclosure, a plurality of receiving units and a plurality of decoding units are provided, and while the contents of the current channel are displayed on the screen, the contents of the previous channel and / or the contents of the next channel are simultaneously received and decoded using the remaining receiving units and decoding units, so that when a user switches channels using the channel up / down buttons of a remote control, the channel is switched to the contents of a new channel without a waiting time, thereby reducing the channel switching time.

[0039] According to the device and method of the present disclosure, a plurality of receivers and a plurality of storage units are provided, and while the contents of the current channel are displayed on the screen, the remaining receivers and storage units are simultaneously used to receive and store some frames including the most recent I frame of the contents of the previous channel and / or some frames including the most recent I frame of the contents of the next channel, so that when a user switches channels using the channel up / down buttons of a remote control, the channel is switched to the contents of a new channel without a waiting time, thereby reducing the channel switching time.

[0040] According to the device and method of the present disclosure, in an Internet-based video display device, a request for changing a channel to a previous channel and / or a request for changing a channel to a next channel is instructed in advance to a server while the content of the current channel is received through a network and displayed on a screen, thereby eliminating the waiting time for a network request and response for a new channel to be switched, thereby reducing the channel switching time.

[0041] In addition to the technical effects explicitly mentioned above, effects that are obvious to those skilled in the art can also be inferred from the entire description of this specification.

[0042] The drawings are included to further understand the embodiments, and the drawings illustrate the embodiments together with the description related to the embodiments.

[0043] Figure 1 is a drawing showing an example of compressed frames that constitute general content.

[0044] Figures 2(a) to 2(c) are diagrams showing examples of waiting times that vary depending on the point in time when channel switching starts when the GOP structure is IPBBBPBBB.

[0045] Figure 3 is a diagram showing examples of channel up / down buttons in a remote control.

[0046] FIG. 4 is a block diagram showing an example of a video display device according to the first embodiment of the present disclosure.

[0047] Fig. 5(a) is a drawing showing an example of a waiting time when switching channels in a conventional manner, and Fig. 5(b) is a drawing showing an example of a waiting time when switching channels in a manner according to the first embodiment.

[0048] FIG. 6 is a diagram showing an example of compressed frames that constitute content when the codec according to embodiments is the HEVC method.

[0049] FIG. 7 is a block diagram showing an example of a video display device according to a second embodiment of the present disclosure.

[0050] Fig. 8(a) is a drawing showing an example of a waiting time when switching channels in a conventional manner, and Fig. 8(b) is a drawing showing an example of a waiting time when switching channels in a manner according to the first embodiment.

[0051] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Regardless of the drawing numbers, identical or similar components will be assigned the same reference numbers, and redundant descriptions thereof will be omitted. It should be noted that the following embodiments are intended only to concretize the present disclosure and do not limit or restrict the scope of the present disclosure. Anything that a specialist in the technical field to which the present disclosure pertains can easily infer from the detailed description and embodiments of the present disclosure is interpreted as falling within the scope of the present document.

[0052] The detailed description in this document should not be construed in any way as restrictive, but rather as illustrative. The scope of this document should be determined by a reasonable interpretation of the appended claims, and all changes within the scope of equivalents herein are intended to be included within the scope of this document.

[0053] Meanwhile, the blocks of the attached block diagram or the steps of the flowchart may be implemented directly in hardware, implemented as software modules executed by hardware, or implemented by a combination of these. In addition, the blocks of the attached block diagram or the steps of the flowchart may be interpreted as computer program instructions that are loaded into the processor or memory of a data processing device such as a general-purpose computer, a special-purpose computer, a portable notebook computer, or a network computer to perform designated functions. Since these computer program instructions may be stored in a memory provided in a computer device or a computer-readable memory, the functions described in the blocks of the block diagram or the steps of the flowchart may be produced as a product that includes a command means for performing the same. In addition, each block or each step may represent a module, segment, or part of code that includes one or more executable instructions for performing a specific logical function(s). Furthermore, in some alternative embodiments, the functions mentioned in the blocks or steps may be executed out of the specified order. For example, two blocks or steps shown in succession may be performed substantially simultaneously, or may be performed in reverse order, or in some cases, some blocks or steps may be performed with some blocks or steps omitted.

[0054] In this disclosure, the most significant factor affecting channel switching time in a video display device, such as a TV, is the characteristics of the TV signal. The TV receives compressed content, which is comprised of multiple Groups of Programs (GOPs). Each GOP includes an I-frame (i.e., a key frame), one or more P-frames, and one or more B-frames. In this disclosure, "content" is used interchangeably with "broadcast content."

[0055] According to embodiments, the transmitting side can compress the video frames constituting the content into I frames, P frames, and B frames in units of GOP using various codecs and then transmit them to a video display device.

[0056] For example, codecs such as MPEG-4 AVC (Moving Picture Expert Group-4 Advanced Video Coding) (or H.264), HEVC (High Efficiency Video Coding) (or H.265), MPEG-2, VP9, ​​AV1, etc. can be used to compress the video frames that make up the content.

[0057] The present disclosure provides a method and device for improving channel switching speed in a video display device that receives and plays content (or broadcast content) having such characteristics.

[0058] In the present disclosure, the video display device may be implemented as various types of monitors capable of receiving digital broadcast signals, including TVs, smart phones, portable terminals, mobile terminals, Personal Digital Assistants (PDAs), computers, laptop computers, notepads, tablet PCs, smart TVs, and IPTVs (Internet Protocol TVs). However, it will be apparent to those skilled in the art that the video display device in the present disclosure is not limited to the above-described devices.

[0059] In the present disclosure, content may be a program of a specific channel, or may be an advertisement inserted at the beginning or end of a program or between programs.

[0060] Typically, channel switching in video display devices is performed by a remote controller (hereinafter referred to as a remote control).

[0061] In the present disclosure, any remote control capable of channel up and channel down functions may be used. According to embodiments, the channel up and channel down functions in the remote control may be implemented in the form of buttons and / or in the form of a wheel mouse (or mouse wheel).

[0062] For example, when a user presses the channel up button on a remote control, the current channel switches to the next channel. As another example, a user can move up or down a channel by scrolling up or down a wheel mouse mounted on a remote control. In general, scrolling a wheel mouse up or down occurs faster than pressing the up or down buttons on a remote control, so the user may be more bothered by the channel switching delay caused by the latency of the I-frame. In other words, the channel switching latency perceived by the user using the wheel mouse may feel longer than the channel switching latency using the button method.

[0063] FIG. 3 is a diagram showing examples of channel up / down buttons within a remote control. In the present disclosure, the channel up / down buttons within the remote control may have one of the examples in FIG. 3 or may have another shape.

[0064] For example, assuming that the current channel the user is watching is numbered 11-1, the previous channel is numbered 10-1, and the next channel is numbered 12-1, when the user presses the channel up button on the remote control, the channel changes to 10-1, and when the user presses the channel down button, the channel changes to 12-1.

[0065] For convenience of explanation, in this disclosure, the channel number that the user is currently watching is referred to as the current channel, the channel number with a number lower than the current channel (i.e., a number in a decreasing direction) is referred to as the previous channel (or down channel), and the channel number with a number higher than the current channel (i.e., a number in an increasing direction) is referred to as the next channel (or up channel).

[0066] At this point, the previous channel may be the channel number immediately preceding the current channel number, but it may not be, depending on settings. For example, if you've set up preferred channels or have configured certain channels to be viewable, the previous channel number may or may not be the channel number immediately preceding the current channel number. The same applies to the next channel.

[0067] In addition, the broadcast signal (or broadcast content) selected on the video display device according to the channel up or down signal transmitted from the remote control may include not only terrestrial, cable, and satellite signals, but also services provided by content providers by mapping the content to channels.

[0068] In this disclosure, considering the fact that the user scenario that is most commonly expected and actually most frequently occurring for a TV in terms of social conventions when the video display device is a TV is “channel up / down,” a method is proposed to improve the channel switching speed by switching the next channel and previous channel in advance in the background of the TV while the current channel is being watched.

[0069] That is, in this case, since multiple (e.g., two) receivers located in the TV background are already receiving I frames (i.e., key image frames) of the corresponding channels, when switching to the corresponding channel using the channel up / down button of the remote control, the waiting time for receiving the I frame can be eliminated, thereby shortening the channel switching time.

[0070] In the present disclosure, channel switching can be performed by dividing into the following two embodiments depending on whether pre-decoding is performed on pre-received frames.

[0071] The present disclosure, as a first embodiment, comprises a plurality of receivers and a plurality of decoders, and while a user is watching a current channel, simultaneously uses the remaining receivers and decoders to receive and decode at least the broadcast content of a previous channel and / or the broadcast content of a next channel, thereby enabling the user to immediately display the broadcast content of a new channel without a waiting time when switching channels using the channel up / down buttons of a remote control. In other words, the first embodiment also performs decoding in advance for data that has been received in advance. This first embodiment has the advantage of being simple and easy to control. The first embodiment can be applied to a scenario of switching between HDMI (High Definition Multimedia Interface) and RF (Radio Frequency) digital TV, and in this case, the channel switching time can be reduced by 20% compared to the existing method.

[0072] The present disclosure, as a second embodiment, comprises a plurality of receivers and a plurality of storage units, and while a user is watching a current channel, simultaneously uses the remaining receivers and storage units to receive and store at least the most recent I frame of broadcast content of a previous channel and / or the most recent I frame of broadcast content of a next channel, so that when the user changes channels using the channel up / down buttons of a remote control, the storage unit of the new channel already has the next I frame stored, so that the broadcast content of the new channel can be displayed immediately without waiting for the next I frame. At this time, each storage unit may store only the next I frame of the corresponding channel, or may store the entire GOP including the next I frame.

[0073] When channel switching is performed according to the first or second embodiment proposed in the present disclosure, the video of a new channel can be shown to the user immediately with almost no waiting time due to I-frames, not only in the button mode but also in a situation of rapid and repetitive channel switching using a wheel mouse.

[0074] Since this disclosure relates to video among broadcast contents, explanation of audio will be omitted.

[0075] FIG. 4 is a block diagram showing an example of a video display device according to the first embodiment of the present disclosure.

[0076] Each component of the video display device of FIG. 4 corresponds to hardware, software, a processor, and / or a combination thereof. The execution order of each block in FIG. 4 may be changed, some blocks may be omitted, and some new blocks may be added.

[0077] The video display device according to the first embodiment may include a video processing unit (210) for receiving, decoding, and displaying broadcast content, a control unit (250) for controlling the operation of each block in the video processing unit (210), and a remote control (270).

[0078] The above image processing unit (210) may include first to third receiving units (211-213), first to third decoding units (221-223), a multiplexing unit (230), and a display processing unit (240). If the image processing unit (210) includes two receiving units and two decoding units, one of them may be used for the current channel and the other for the next channel. As another example, one may be used for the current channel and the other for the previous channel.

[0079] In Fig. 4, when the video display device is a TV of the RF (Radio Frequency) type, each of the first to third receiving units (211-213) may include at least a tuner, a demodulator, and a parsing unit. Here, the tuner receives broadcast content of a specific channel under the control of the control unit (250), the demodulator demodulates the received broadcast content, and the parsing unit parses (or extracts) I frames, P frames, and B frames from the demodulated broadcast content in units of GOP.

[0080] According to embodiments, the parsing unit may perform processes such as packet analysis and audio / video separation to parse I frames, P frames, and B frames from demodulated broadcast content.

[0081] Depending on the embodiments, the parsing unit may not be included in the receiving unit and may be implemented as a separate device or component. Alternatively, some functions of the parsing unit may be included in the decoding unit.

[0082] According to embodiments, each of the first to third decoding units (221-223) can decode and restore compressed frames (e.g., I frames, P frames, B frames) constituting the corresponding broadcast content by applying a codec algorithm. For example, I frames are not decoded, the current P frame is decoded using the previous I frame or P frame as a reference frame, and the current B frame is decoded using the previous I frame or P frame and the subsequent I frame or P frame.

[0083] According to embodiments, the multiplexing unit (230) selects one of the outputs of the first to third decoding units (221-223) under the control of the control unit (250) and outputs it to the display processing unit (240).

[0084] According to embodiments, the display processing unit (240) performs the processing necessary to display the decoded broadcast content on the screen (or screen or display unit). That is, the display processing unit (240) performs format conversion, resolution conversion, frame rate conversion, scaling or cropping to adjust the frame to the screen, aspect ratio conversion, color space conversion, etc. on the decoded broadcast content of the current channel to fit the screen, and then displays it. This is one example, and various additional functions and optimizations may be performed in the display processing unit (240) depending on the specific implementation and requirements of the device and software.

[0085] According to embodiments, the remote control (270) can transmit and receive signals to and from the control unit (250) using a short-range communication network including infrared or Bluetooth. In addition, the remote control (270) includes a power on / off button for turning the power of the video display device on or off.

[0086] In the first embodiment, the first to third receiving units (211-213), the first to third decoding units (221-223), the multiplexing unit (230), and the display processing unit (240) always maintain an active (or on) state when power is supplied to the video display device.

[0087] At this time, a frame buffer (not shown) is required in the first to third decoding units (221-223) to decode the broadcast content of the previous channel, the broadcast content of the current channel, and the broadcast content of the next channel. The frame buffer can be allocated and used by a portion of memory. That is, the frame buffer is for storing reference frames (e.g., I frames, P frames, B frames) required to decode compressed frames (e.g., P frames, B frames) in the first to third decoding units (221-223). Here, the size of the frame buffer may vary depending on the size of the GOP, i.e., the number of P frames and B frames included between the I frame and the next I frame.

[0088] For convenience of explanation, the present disclosure assumes that the first receiver (211) receives broadcast content of the previous channel, the second receiver (212) receives broadcast content of the current channel, and the third receiver (213) receives broadcast content of the next channel. This is an example to help understand the explanation, and the first receiver (211) may receive broadcast content of the current channel, and one of the second receiver (212) and the third receiver (213) may receive broadcast content of the previous channel, and the other may receive broadcast content of the next channel.

[0089] Since the present disclosure assumes that the broadcast content of the current channel is received by the second receiving unit (212), the I frames, P frames, and B frames of the broadcast content received and parsed by the second receiving unit (212) are decoded by the second decoding unit (222) and then displayed on the screen (or screen) of the video display device through the multiplexing unit (230) and the display processing unit (240) under the control of the control unit (250).

[0090] At the same time, the first receiver (211) receives the broadcast content of the previous channel and parses I frames, P frames, and B frames, and the first decoding unit (221) decodes the parsed I frames, P frames, and B frames. In addition, the third receiver (213) receives the broadcast content of the next channel and parses I frames, P frames, and B frames, and the third decoding unit (223) decodes the parsed I frames, P frames, and B frames. That is, while the broadcast content of the current channel is decoded and displayed, the broadcast content of the previous channel and the broadcast content of the next channel are only decoded.

[0091] At this time, when the user presses one of the channel up / down buttons of the remote control (270) or scrolls the wheel mouse button up or down, the broadcast content of the previous channel being decoded in the first decoding unit (221) is displayed on the screen through the multiplexing unit (230) and the display processing unit (240) under the control of the control unit (250), or the broadcast content of the next channel being decoded in the third decoding unit (223) is displayed on the screen through the multiplexing unit (230) and the display processing unit (240) under the control of the control unit (250).

[0092] For example, when a user presses the channel down button on the remote control (270) or scrolls down the wheel mouse button, i.e., when the user selects to switch channels to the previous channel, the broadcast content of the previous channel being decoded in the first decoding unit (221) is displayed on the screen through the multiplexing unit (230) and the display processing unit (240) under the control of the control unit (250).

[0093] That is, while the broadcast content of the current channel is displayed on the screen, the first receiving unit (211) and the first decoding unit (221) have already received and decoded the broadcast content of the previous channel in the background, so when the channel switching to the previous channel begins, there is no need to wait for the next I frame in the new channel to which the channel has been switched. Accordingly, the channel switching speed to the previous channel is accelerated.

[0094] In this case, since the first receiver (211) and the first decoding unit (221) receive and decode the broadcast content of the current channel by channel switching, the second receiver (212) and the second decoding unit (222) receive and decode the broadcast content of the previous channel in the background under the control of the control unit (250). For example, if the current channel is 11-1 and the broadcast content of channel 11-1 is received and decoded through the second receiver (212) and the second decoding unit (222) and then displayed on the screen through the multiplexer (230) and the display processing unit (240), and the user selects channel down using the remote control (270), the broadcast content of channel 10-1, which was being received and decoded by the first receiver (211) and the first decoding unit (221), is displayed on the screen through the multiplexer (230) and the display processing unit (240). In this case, under the control of the control unit (250), the second receiver (212) and the second decoding unit (222) receive and decode the broadcast content of the previous channel (e.g., 9-1) in the background.

[0095] As another example, when a user presses the channel up button on the remote control (270) or scrolls the wheel mouse button upward, i.e., when the user selects to switch to the next channel, the broadcast content of the next channel being decoded in the third decoding unit (223) is displayed on the screen through the multiplexing unit (230) and the display processing unit (240) under the control of the control unit (250).

[0096] That is, while the broadcast content of the current channel is displayed on the screen, the third receiving unit (213) and the third decoding unit (223) have already received and decoded the broadcast content of the next channel in the background, so when the channel switching to the next channel begins, there is no need to wait for the next I frame in the new channel to which the channel has been switched. Accordingly, the channel switching speed to the next channel is accelerated.

[0097] In this case, since the third receiver (213) and the third decoding unit (223) receive and decode the broadcast content of the current channel by channel switching, the second receiver (212) and the second decoding unit (222) receive and decode the broadcast content of the next channel in the background under the control of the control unit (250). For example, if the current channel is 11-1, and the broadcast content of channel 11-1 is received and decoded by the second receiver (212) and the second decoding unit (222) and then displayed on the screen by the multiplexer (230) and the display processing unit (240), and then the user selects channel up using the remote control (270), the broadcast content of channel 12-1, which was being received and decoded by the third receiver (213) and the third decoding unit (223), is displayed on the screen by the multiplexer (230) and the display processing unit (240). In this case, under the control of the control unit (250), the second receiver (212) and the second decoding unit (222) receive and decode the broadcast content of the next channel (e.g., 13-1) in the background.

[0098] FIG. 5(a) and FIG. 5(b) are drawings showing an example of comparing the waiting time when switching channels in the manner according to the first embodiment with the waiting time when switching channels in the conventional manner.

[0099] That is, FIG. 5(a) is a drawing showing an example of a waiting time when switching channels in a conventional manner, and FIG. 5(b) is a drawing showing an example of a waiting time when switching channels in a manner according to the first embodiment.

[0100] Figure 5(a) is an example in which only one receiver is provided in the video display device.

[0101] For example, if a user selects channel down using a remote control (270) while the current channel (11-1) is displayed on a video display device, the receiver changes the tuning to the previous channel (10-1) and starts receiving broadcast content of the previous channel (10-1). If the time at which the user selects a channel change is position 511 of the previous channel (10-1), although the channel change starts at position 511, actual decoding waits until the next I-frame comes in and then decoding starts, and the decoded frames are displayed. That is, there is a wait of approximately 4 frames until the next I-frame comes in, and then the video of the previous channel (10-1) is displayed on the screen.

[0102] As another example, if a user selects channel up using a remote control (270) while the current channel (11-1) is displayed on a video display device, the receiver changes the tuning to the next channel (12-1) and starts receiving broadcast content of the next channel (12-1). If the time at which the user selects the channel change is position 512 of the next channel (12-1), although the channel change starts at position 512, actual decoding waits until the next I-frame comes in and then decoding starts, and the decoded frames are displayed. That is, there is a wait of approximately 5 frames until the next I-frame comes in, and then the video of the next channel (12-1) is displayed on the screen.

[0103] FIG. 5(b) illustrates an example in which a video display device is provided with at least three receivers and at least three decoders, all of which are maintained in an active state. For example, the three receivers / decoders of FIG. 5(b) may correspond to the first to third receivers (211-213) and the first to third decoders (221-223) of FIG. 4. That is, the three receivers / decoders each receive and decode broadcast content of a corresponding channel. For convenience of explanation, the illustration and description of the display processing unit in FIG. 5(b) are omitted.

[0104] For example, if the user selects channel down using the remote control (270) while the broadcast content of the current channel (11-1) received and decoded by the second receiver / decoder is being displayed on the screen through the multiplexer, the multiplexer selects the broadcast content of the previous channel (10-1) received and decoded by the first receiver / decoder, and the broadcast content of the selected previous channel (10-1) is displayed on the screen. If it is assumed that the time when the user selects the channel change is position 521 of the previous channel (10-1), since the reception and decoding of the broadcast content of the previous channel (10-1) has already been performed before, the first receiver / decoder does not need to wait for the next I frame, and the broadcast content of the previous channel (10-1) is displayed immediately with almost no waiting time when the channel change begins. That is, in Fig. 5(a), after the channel switching starts, there is a wait of approximately 4 frames and then the image of the previous channel (10-1) is displayed on the screen, whereas in Fig. 5(b), after the channel switching starts, the image of the previous channel (10-1) is displayed on the screen immediately with almost no wait.

[0105] As another example, if the user selects channel up using the remote control (270) while the broadcast content of the current channel (11-1) received and decoded by the second receiver / decoder is being displayed on the screen through the multiplexer, the multiplexer selects the broadcast content of the previous channel (12-1) received and decoded by the third receiver / decoder, and the broadcast content of the next selected channel (12-1) is displayed on the screen. If it is assumed that the time when the user selects the channel change is position 522 of the next channel (12-1), since the reception and decoding of the broadcast content of the next channel (12-1) has already been performed before, the third receiver / decoder does not need to wait for the next I frame, and the broadcast content of the next channel (12-1) is displayed immediately with almost no waiting time when the channel change begins. That is, in Fig. 5(a), after the channel switching starts, there is a wait of approximately 5 frames and then the image of the next channel (12-1) is displayed on the screen, whereas in Fig. 5(b), after the channel switching starts, the image of the next channel (12-1) is displayed on the screen immediately with almost no wait.

[0106] Meanwhile, among compressed frames (or compressed video frames), there may be frames that satisfy the conditions below depending on the codec and encoding method.

[0107] For example, if there are no frame(s) referencing it, and the decoding operation of the frame(s) referencing it occurs before its own decoding operation.

[0108] A frame that satisfies these conditions can be a B frame, as shown in Fig. 1, if the codec is MPEG-2. That is, an I frame is referenced by a P frame or a B frame, and a P frame is referenced by another P frame or a B frame. However, a B frame may or may not be referenced by another B frame. In Fig. 1, a B frame is not referenced by another frame.

[0109] If the codec is HEVC (H.265) and the HEVC (H.265) codec has temporal scalability, the frame constituting the highest temporal layer can be a frame that satisfies the above conditions.

[0110] FIG. 6 is a diagram showing an example of the structure of temporal scalability when the codec according to embodiments is HEVC.

[0111] In Fig. 6, frames that satisfy the above conditions can be frames corresponding to P1, P3, P5, and P7.

[0112] In the present disclosure, for frame(s) satisfying the above conditions, the decoding unit for decoding broadcast content of the previous channel and / or the decoding unit for decoding broadcast content of the next channel may not perform decoding, and may perform decoding at the moment when the current channel switches to the previous channel or the next channel. That is, when the frame(s) satisfying the above conditions are in the background position, decoding is not performed, and when the corresponding decoding unit moves to the foreground position due to the channel switch, the corresponding decoding unit performs decoding. Even in this way, the corresponding decoding unit can still maintain the channel switching speed gain without causing malfunction. By not performing decoding on frames where the channel switching speed does not slow down even if decoding is skipped in this way while the corresponding decoding unit is in the background, the increased load on the central processing unit (CPU) and increased memory bandwidth caused by multiple decoding units and multiplexing units operating simultaneously can be reduced.

[0113] Meanwhile, the second embodiment of the present disclosure performs decoding only on the broadcast content of the current channel, and does not decode the frames of the broadcast content of the previous channel and the frames of the broadcast content of the next channel that have been received in advance. Taking the previous channel as an example, at least one frame among the frames constituting the broadcast content of the previous channel is stored and not decoded. At this time, the frame to be stored may vary depending on memory capacity, system performance, etc. For example, the at least one frame to be stored may be the most recent I-frame, frames within a GOP including the most recent I-frame, or frames for a specific period of time (e.g., 1 second) from the most recent reference. That is, since broadcast content (i.e., TV signal) is continuously received, when receiving new inter-I-frame frames (i.e., video data), the frames (i.e., video data) between previous I-frames are discarded. Therefore, for the previous channel (or the next channel) in the background position, only the most recent inter-I-frame frames are always stored. And, when switching from the current channel to the next channel or the previous channel, the frames between the I frames of the next channel or the previous channel that were stored in advance are decoded and displayed on the screen. In this case, the two receivers located in the background (the receiver of the previous channel and the receiver of the next channel based on the current channel) have already received not only the I frames (i.e., key video frames) of the corresponding channel, but also the video frames that are not key videos (e.g., I frames, B frames), so the waiting time for receiving I frames can be eliminated. This allows the channel switching time to be shortened. In the case of audio data, since compressed audio data also has a key audio frame similar to compressed video data, a method similar to that for video data can be applied.

[0114] FIG. 7 is a block diagram showing an example of a video display device according to a second embodiment of the present disclosure.

[0115] Each component of the video display device of FIG. 7 corresponds to hardware, software, a processor, and / or a combination thereof. The execution order of each block in FIG. 7 may be changed, some blocks may be omitted, and some new blocks may be added.

[0116] The video display device according to the second embodiment may include a video processing unit (610) for receiving, decoding, and displaying broadcast content, a control unit (660) for controlling the operation of each block in the video processing unit (610), and a remote control (270).

[0117] The image processing unit (610) may include first to third receiving units (211-213), first to third storage units (621-623), a multiplexing unit (630), a decoding unit (640), and a display processing unit (650). If the image processing unit (610) includes two receiving units and two storage units, one of them may be used for the current channel and the other for the next channel. As another example, one may be used for the current channel and the other for the previous channel.

[0118] In Fig. 7, when the video display device is a TV based on RF (Radio Frequency), each of the first to third receiving units (211-213) may include at least a tuner, a demodulator, and a parsing unit. Here, the tuner receives broadcast content of a specific channel under the control of the control unit (660), the demodulator demodulates the received broadcast content, and the parsing unit parses (or extracts) I frames, P frames, and B frames from the demodulated broadcast content in units of GOP.

[0119] According to embodiments, the parsing unit may perform processes such as packet analysis and audio / video separation to parse I frames, P frames, and B frames from demodulated broadcast content.

[0120] Depending on the embodiments, the parsing unit may not be included in the receiving unit and may be implemented as a separate device or component. Alternatively, some functions of the parsing unit may be included in the decoding unit.

[0121] For convenience of explanation, the present disclosure assumes that the first receiver (211) receives broadcast content of the previous channel, the second receiver (212) receives broadcast content of the current channel, and the third receiver (213) receives broadcast content of the next channel. This is an example to help understand the explanation, and the first receiver (211) may receive broadcast content of the current channel, and one of the second receiver (212) and the third receiver (213) may receive broadcast content of the previous channel, and the other may receive broadcast content of the next channel.

[0122] In this case, the first storage unit (621) and the third storage unit (623) store only the most recent frames of the corresponding broadcast content, and the frames stored in the first storage unit (621) and the third storage unit (623) are not decoded. In contrast, the second storage unit (622) stores frames to be used as reference frames for decoding the broadcast content of the current channel, and the decoding unit (640) decodes the current frame by referring to the frames stored in the second storage unit (622) provided through the multiplexing unit (630). That is, the number and type of frames stored in the first storage unit (621) and the third storage unit (623) are different from the number and type of frames stored in the second storage unit (622). In other words, the frames stored in the first storage unit (621) and the third storage unit (623) are frames for decoding when switching channels, and the frames stored in the second storage unit (622) are frames for use as reference frames when decoding.

[0123] In the present disclosure, taking the previous channel as an example, the first storage unit (621) unconditionally stores the most recent I-frame among the frames of the broadcast content of the previous channel output from the first receiver unit (211). In addition, the first storage unit (621) may store all frames within a group of operations (GOP) including the most recent I-frame, or all frames between the most recent I-frame and the previous I-frame. As another example, the first storage unit (621) may store frames for the most recent period of time, or frames included in the most recent GOP. For example, the period of time may be the time for which one GOP is received or longer. According to embodiments, the period of time or the number of frames to be stored may vary depending on memory capacity, etc. This rule also applies to the third storage unit (623) that stores some frame(s) of the broadcast content of the next channel. If the receiving unit and the storage unit that receive and store the previous channel or the next channel are changed, the above rule may be applied equally to the changed storage unit.

[0124] According to embodiments, the multiplexing unit (630) selects the output of a storage unit that stores frames of broadcast content of the current channel under the control of the control unit (660) and outputs it to the decoding unit (640). For example, if the second storage unit (622) is a storage unit that stores frames of broadcast content of the current channel, the output of the second storage unit (622) is selected and outputted to the decoding unit (640).

[0125] According to embodiments, the decoding unit (640) decodes the current frame by using the frames stored in the second storage unit (622) as reference frames. That is, the decoding unit (640) can decode and restore compressed frames (e.g., I frame, P frame, B frame) constituting the broadcast content of the current channel by applying a codec algorithm. For example, the I frame is not decoded, the current P frame is decoded by using the previous I frame or P frame as a reference frame, and the current B frame is decoded by using the previous I frame or P frame and the subsequent I frame or P frame.

[0126] According to embodiments, the display processing unit (650) performs the processing necessary to display the decoded broadcast content of the current channel on the screen (or screen or display unit). That is, the display processing unit (650) performs format conversion, resolution conversion, frame rate conversion, scaling or cropping to adjust the frame to the screen, aspect ratio conversion, color space conversion, etc. on the decoded broadcast content of the current channel to fit the screen, and then displays it. This is one example, and various additional functions and optimizations may be performed in the display processing unit (650) depending on the specific implementation and requirements of the device and software.

[0127] According to embodiments, the remote control (270) can transmit and receive signals to and from the control unit (660) using a short-range communication network including infrared or Bluetooth. In addition, the remote control (270) includes a power on / off button for turning the power of the video display device on or off.

[0128] In the first embodiment, the first to third receiving units (211-213), the first to third storage units (621-623), the multiplexing unit (630), the decoding unit (640), and the display processing unit (650) always maintain an active (or on) state when power is supplied to the video display device. Since the present disclosure assumes that the second receiving unit (212) receives the broadcast content of the current channel, the I frames, P frames, and B frames of the broadcast content received and parsed by the second receiving unit (212) are decoded by the decoding unit (640) under the control of the control unit (660) and then displayed on the screen (or screen) of the video display device through the display processing unit (650).

[0129] At the same time, the first receiver (211) receives the broadcast content of the previous channel and parses I frames, P frames, and B frames, and the first storage unit (621) stores the most recent I frame among the parsed I frames, P frames, and B frames. In addition, the first storage unit (621) may further store some frames related to the most recent I frame. For example, the frames within the GOP including the most recent I frame (e.g., frames between the most recent I frame and the I frame) may further be stored. According to embodiments, when a new GOP including a new I frame comes in, the frames of the previously stored GOP are discarded and the new GOP is stored. In addition, the third receiver (213) receives the broadcast content of the next channel and parses I frames, P frames, and B frames, and the third storage unit (623) stores the most recent I frame among the parsed I frames, P frames, and B frames. Additionally, the third storage unit (623) may further store some frames related to the most recent I-frame. For example, it may further store frames within the GOP including the most recent I-frame (e.g., frames between the most recent I-frame and the I-frame). According to embodiments, when a new GOP including a new I-frame comes in, the frames of the previously stored GOP are discarded and the new GOP is stored. That is, while the broadcast content of the current channel is decoded and displayed, the broadcast content of the previous channel and the broadcast content of the next channel only store some frames including the most recent I-frame and do not perform decoding.

[0130] At this time, when the user presses one of the channel up / down buttons of the remote control (270) or scrolls the wheel mouse button up or down, the frames stored in the first storage unit (621) are provided to the decoding unit (640) through the multiplexing unit (630) under the control of the control unit (660) for decoding and then displayed on the screen through the display processing unit (650), or the frames stored in the third storage unit (623) are provided to the decoding unit (640) through the multiplexing unit (630) for decoding and then displayed on the screen through the display processing unit (650). If the frames stored in the first storage unit (621) or the third storage unit (623) are frames within the GOP including the most recent I frame of the corresponding broadcast content, the image displayed on the screen can be faster by at most one GOP (i.e., I frame time interval) than the GOP at the time of channel switching.

[0131] For example, when a user presses the channel down button on the remote control (270) or scrolls down (or pushes) the wheel mouse button, i.e., when the user selects to switch channels to the previous channel, frames of broadcast content of the previous channel stored in the first storage unit (621) are decoded in the decoding unit (640) and then displayed on the screen through the display processing unit (650).

[0132] That is, while the broadcast content of the current channel is displayed on the screen, the first receiver (211) and the first storage unit (621) receive the broadcast content of the previous channel in the background and store some frames including the most recent I frame among them, so that when the channel switching to the previous channel starts, there is no need to wait for the next I frame in the new channel to which the channel has been switched. Accordingly, the channel switching speed to the previous channel is accelerated.

[0133] In this case, since the first receiver (211) and the first storage unit (621) receive and store the broadcast content of the current channel by channel switching, the second receiver (212) and the second storage unit (622) receive the broadcast content of the previous channel in the background under the control of the control unit (660) and store some frames including the most recent I frame among them. For example, if the current channel is 11-1 and the broadcast content of channel 11-1 is received and stored through the second receiver (212) and the second storage (622) and then displayed on the screen through the multiplexer (630), the decoding unit (640), and the display processing unit (650), and if the user selects channel down using the remote control (270), the frames of the broadcast content of channel 10-1 that were received and stored in the first receiver (211) and the first storage (621) are decoded and then displayed on the screen through the display processing unit (650). In this case, under the control of the control unit (660), the second receiver (212) and the second decoding unit (222) receive the broadcast content of the previous channel (e.g., 9-1) in the background and store some frames including the most recent I frame.

[0134] As another example, when a user presses the channel up button on the remote control (270) or scrolls (or pushes) the wheel mouse button upward, i.e., when the user selects to change the channel to the next channel, frames of the broadcast content of the next channel stored in the third storage unit (623) are decoded in the decoding unit (640) and then displayed on the screen through the display processing unit (650).

[0135] That is, while the broadcast content of the current channel is displayed on the screen, the third receiver (213) and the third storage unit (623) receive the broadcast content of the next channel in the background and store some frames including the most recent I frame among them, so that when the channel switching to the next channel starts, there is no need to wait for the next I frame in the new channel to which the channel has been switched. Accordingly, the channel switching speed to the next channel is accelerated.

[0136] In this case, since the third receiver (213) and the third storage unit (623) receive and store the broadcast content of the current channel by channel switching, the second receiver (212) and the second storage unit (622) receive the broadcast content of the next channel in the background under the control of the control unit (660) and store some frames including the most recent I frame among them. For example, if the current channel is 11-1 and the broadcast content of channel 11-1 is received and stored through the second receiver (212) and the second storage (622) and then displayed on the screen through the multiplexer (630), the decoding unit (640), and the display processing unit (650), and if the user selects channel up using the remote control (270), the frames of the broadcast content of channel 12-1 that were received and stored in the third receiver (213) and the third storage (623) are decoded and then displayed on the screen through the display processing unit (650). In this case, under the control of the control unit (660), the second receiver (212) and the second decoding unit (222) receive the broadcast content of the next channel (e.g., 13-1) in the background and store some frames including the most recent I frame.

[0137] In this way, the second embodiment maintains a state of storing only some frames (e.g., the most recent GOP) including the most recent I frame among the frames continuously received for channels other than the current channel, for example, broadcast contents of the previous channel and broadcast contents of the next channel, so that when switching channels, decoding is performed immediately on already stored frames, thereby having the effect of shortening (or speeding up) the channel switching time. That is, since the video display device always stores the signals of adjacent channels, including the most recent I frame and the video signals between adjacent I frames, when switching channels, the time for waiting for I frame input can be eliminated, so that the video of the new channel to which the channel has been switched can be immediately displayed on the screen (i.e., the screen).

[0138] And, in the case of the second embodiment, since only a decoding unit for decoding the broadcast content of the current channel is required, that is, since only one decoding unit is required, the present disclosure can be applied even to a low-cost TV that supports only one VDEC (Video decoder) and one ADEC (Audio decoder), which are components of a video display device. In other words, in the case of the second embodiment, the two receiving units and storage units responsible for receiving the broadcast content of the previous channel and the next channel located in the TV background only need to receive and store the signals, and decoding is not required in the decoding unit.

[0139] If the second embodiment is applied to a video display device configured as in FIG. 4, only the decoding unit that decodes the broadcast content of the current channel remains on (i.e., active), and the decoding unit that decodes the broadcast content of the previous channel and the decoding unit that decodes the broadcast content of the next channel remain off (i.e., inactive). Then, when a channel change to the previous channel or the next channel occurs, only the decoding unit that decodes the broadcast content of the switched previous channel or the next channel changes to the on (i.e., active) state, and the remaining decoding units change to the off (i.e., inactive) state. Even in this case, the method of storing some frames of the broadcast content of the previous channel and some frames of the broadcast content of the next channel in the background position is the same as in the second embodiment.

[0140] FIG. 8(a) and FIG. 8(b) are drawings showing an example of comparing the waiting time when switching channels in a manner according to the second embodiment with the waiting time when switching channels in a conventional manner.

[0141] That is, Fig. 8(a) is a drawing showing an example of a waiting time when switching channels in a conventional manner, and Fig. 8(b) is a drawing showing an example of a waiting time when switching channels in a manner according to the second embodiment.

[0142] Figure 8(a) is an example in which only one receiver is provided in the video display device.

[0143] For example, if a user selects channel down using a remote control (270) while the current channel (11-1) is displayed on a video display device, the receiver changes the tuning to the previous channel (10-1) and starts receiving broadcast content of the previous channel (10-1). If the time at which the user selects a channel change is position 511 of the previous channel (10-1), although the channel change starts at position 511, actual decoding waits until the next I-frame comes in and then decoding starts, and the decoded frames are displayed. That is, there is a wait of approximately 4 frames until the next I-frame comes in, and then the video of the previous channel (10-1) is displayed on the screen.

[0144] As another example, if a user selects channel up using a remote control (270) while the current channel (11-1) is displayed on a video display device, the receiver changes the tuning to the next channel (12-1) and starts receiving broadcast content of the next channel (12-1). If the time at which the user selects the channel change is position 512 of the next channel (12-1), although the channel change starts at position 512, actual decoding waits until the next I-frame comes in and then decoding starts, and the decoded frames are displayed. That is, there is a wait of approximately 5 frames until the next I-frame comes in, and then the video of the next channel (12-1) is displayed on the screen.

[0145] Fig. 8(b) is an example in which a video display device is provided with at least three receivers and at least three storage units. For example, the three receivers / storages of Fig. 8(b) may correspond to the first to third receivers (211-213) and the first to third storage units (621-623) of Fig. 7. At this time, the decoding unit performs decoding only on the broadcast content of the current channel provided through the multiplexer. If at least three decoding units are provided for the previous channel, the current channel, and the next channel, only the decoding unit that decodes the broadcast content of the current channel remains on (i.e., active) and the remaining decoding units remain off (i.e., inactive). For convenience of explanation, the illustration and description of the display processing unit in Fig. 8(b) are omitted.

[0146] For example, when the broadcast content of the current channel (11-1) is received and decoded through the second receiver / storage unit, the multiplexer, and the decoding unit and is displayed on the screen, if the user selects channel down using the remote control (270), the multiplexer selects some frames (e.g., the most recent GOP) including the most recent I frame of the broadcast content of the previous channel (10-1) that is received and stored by the first receiver / storage unit and outputs them to the decoding unit, and the decoding unit starts decoding from the selected GOP (i.e., the most recent I frame) and displays the broadcast content of the previous channel (10-1) on the screen. If it is assumed that the time when the user selects a channel change is position 811 of the previous channel (10-1), the first storage unit stores the most recent GOP based on the time when the channel change is selected, and the decoding unit starts decoding from this GOP, so that the broadcast content of the previous channel (10-1) is displayed immediately with almost no waiting time when the channel change starts. That is, in Fig. 8(a), after the channel switching starts, there is a wait of approximately 4 frames and then the image of the previous channel (10-1) is displayed on the screen, whereas in Fig. 8(b), after the channel switching starts, the image of the previous channel (10-1) is displayed on the screen immediately with almost no wait.

[0147] As another example, when the broadcast content of the current channel (11-1) is received and decoded through the second receiver / storage unit, the multiplexer, and the decoding unit and is displayed on the screen, if the user selects channel up using the remote control (270), the multiplexer selects some frames (e.g., the most recent GOP) including the most recent I frame of the broadcast content of the next channel (12-1) that is received and stored by the third receiver / storage unit and outputs them to the decoding unit, and the decoding unit starts decoding from the selected GOP (i.e., the most recent I frame) and displays the broadcast content of the next channel (12-1) on the screen. If, assuming that the time at which the user selects a channel change is position 812 of the next channel (12-1), the third storage unit stores the most recent GOP (851) based on the time at which the channel change was selected, and the decoding unit starts decoding from the I frame of this GOP (851) (e.g., 852), the broadcast content of the next channel (12-1) is displayed immediately with almost no waiting time when the channel change starts. That is, in Fig. 8(a), there is a waiting time of approximately 5 frames after the channel change starts, and then the image of the next channel (12-1) is displayed on the screen, whereas in Fig. 8(b), the image of the next channel (12-1) is displayed on the screen with almost no waiting time after the channel change starts.

[0148] So far, we have described the channel switching method in RF-based video display devices.

[0149] Meanwhile, the video display device may be an Internet (or network)-based TV rather than an RF-based one. Such video display devices may include IPTVs and set-top boxes. If the Internet-based video display device provides content using adaptive streaming, a tuner is not required. Adaptive streaming in the present disclosure is a technology that dynamically adjusts video quality according to the user's network conditions and device (e.g., video display device) performance to provide the user with an optimal viewing experience. It mainly uses a protocol based on HTTP (Hyper Text Transfer Protocol), and major adaptive streaming protocols include MPEG-DASH (Dynamic Adaptive Streaming over HTTP) and HLS (HTTP Live Streaming).

[0150] In these Internet-based video display devices, the factor that significantly affects the channel switching time is not the I-frame, but the time it takes to request a channel change and receive the changed content in response to the request. In other words, in the case of Internet-based video display devices, when a channel change is requested, the server providing the content always provides the I-frame first, so there is no need to wait for the I-frame for decoding. Instead, there may be a waiting time between requesting a channel change to the server and receiving the content of the changed channel in response. In other words, in the case of video display devices that transmit TV signals over a network, another important factor in the channel switching time is the delay between the network request for the next channel and the network response to it when switching channels. In other words, the network response time of the previous and / or next channel determines the channel switching speed.

[0151] To address this, the present disclosure, in one embodiment, instructs a server in advance to request a channel change to a previous channel and / or a channel change to a next channel while broadcast content of the current channel is being received over a network, decoded, and displayed on a screen. In other words, while broadcast content of the current channel is being displayed, a request for data transmission of the previous channel and / or the next channel is made in advance.

[0152] Therefore, for network-based video display devices (e.g., IPTV), channel switching time can be shortened by eliminating the waiting time for network requests and responses for new channels to be switched.

[0153] That is, when a channel switch request is made to the previous or next channel, the network requests for the previous and next channels have already been made, so the delay time between the network request and response for the new channel to be switched to is eliminated, thereby accelerating the channel switch time.

[0154] In particular, in the case of network-based video display devices, since multiplexing and audio / video codecs are trending toward being implemented in software, there is less burden in increasing the number of receiving units and / or decoding units in the video display device than when these components are implemented in hardware.

[0155] In addition, if the video display device is Internet-based, the increase in the number of receivers and / or decoders may increase Internet traffic. To solve this problem, the present disclosure temporarily operates receivers / decoders in the background only when a motion movement of a remote control (e.g., a motion remote control) is detected that precedes a channel-switching operation, or when there is a high possibility that the operation will precede a subsequent channel up / down button press operation, for example, when the channel up / down button is pressed for the first time after a long period of no button press, or only for a few seconds immediately after the TV is turned on, when there is a high probability that a channel-switching operation will occur when considering TV usability, thereby minimizing the increase in Internet traffic.

[0156] For example, when the remote control is moved, the background receiver / decoder operates to prepare for the user's action of pressing the channel up / down button.

[0157] Each of the parts, modules, or units described above may be software, processors, or hardware parts that execute sequential execution processes stored in memory (or storage units). Each of the steps described in the embodiments described above may be performed by processors, software, or hardware parts. Each of the modules / blocks / units described in the embodiments described above may operate as a processor, software, or hardware. In addition, the methods presented in the embodiments may be implemented as code. This code may be written on a processor-readable storage medium and thus may be read by a processor provided by an apparatus.

[0158] For convenience of explanation, this specification has been described separately in each drawing. However, it is also possible to design new embodiments by combining the embodiments described in each drawing. Furthermore, designing a computer-readable recording medium containing a program for executing the previously described embodiments, as required by those skilled in the art, is also within the scope of the present disclosure.

[0159] The device and method according to the present disclosure are not limited to the configuration and method of the embodiments described above, but the embodiments may be configured by selectively combining all or part of each embodiment so that various modifications can be made.

[0160] In this disclosure, terms such as "first" and "second" may be used to describe various components of the disclosure. However, the various components according to the disclosure should not be interpreted in a limited manner by these terms. These terms are merely used to distinguish one component from another. For example, a first user input signal may be referred to as a "second user input signal." Similarly, a second user input signal may be referred to as a "first user input signal." The use of these terms should be interpreted as not departing from the scope of various embodiments. Although "first user input signal" and "second user input signal" are both user input signals, they do not necessarily mean the same user input signals unless the context clearly indicates otherwise.

[0161] The terminology used to describe the present disclosure is for the purpose of describing particular embodiments and is not intended to be limiting of the embodiments. As used in the description of the embodiments and in the claims, the singular is intended to include the plural unless the context clearly dictates otherwise. In addition, the term “and / or” is used to mean all possible combinations of terms. The term “comprises” or “includes” describes the presence of features, numbers, steps, elements, and / or components, but does not mean that additional features, numbers, steps, elements, and / or components are not included. Conditional expressions such as “if” or “when” used to describe the present disclosure are not intended to be limited to only optional cases. When a specific condition is satisfied, a related action is performed in response to a specific condition, or a related definition is intended to be interpreted.

[0162] The best mode for carrying out the invention has been specifically described.

[0163] It will be apparent to those skilled in the art that various modifications and variations can be made to the present embodiments without departing from the spirit or scope of the present embodiments. Accordingly, the present embodiments are intended to include modifications and variations of the present embodiments provided they come within the scope of the appended claims and their equivalents.

Claims

1. Step of receiving content of the current channel; A step of receiving content of a previous channel based on the current channel; A step of receiving content of the next channel based on the current channel; A step of decoding frames constituting the content of the current channel being received; A step of displaying the contents of the current channel composed of the above decoded frames on the screen; A step of decoding frames constituting the content of the previous channel received or storing some of the frames constituting the content of the previous channel received, and then starting decoding from some of the stored frames when channel down is selected from the remote control; A step of displaying the contents of the previous channel including the frames decoded in the step on the screen at the time when the channel down is selected from the remote control; A step of decoding frames constituting the content of the next channel received or storing some of the frames constituting the content of the next channel received, and then starting decoding from some of the stored frames when channel up is selected from the remote control; and A method for switching channels in a video display device, comprising the step of displaying content of a next channel including frames decoded in the step on the screen at a time when channel up is selected from the remote control.

2. In paragraph 1, A method for switching channels in a video display device, wherein frames constituting the above received content are grouped into GOP (Group Of Pictures) units, and each GOP consists of at least one I frame, one or more P frames, and one or more B frames.

3. A method for switching channels in a video display device, wherein some frames of the content of the previous channel stored in the decoding step of the previous channel in the second paragraph are frames within the most recently received GOP.

4. A method for switching channels in a video display device, wherein, in the second paragraph, when decoding frames constituting the content of the previous channel received in the decoding step of the previous channel, decoding of B frames is omitted, and decoding of B frames is performed from the time when channel down is selected from the remote control.

5. A method for switching channels in a video display device, wherein some frames of the content of the next channel stored in the decoding step of the next channel in the second paragraph are frames within the most recently received GOP.

6. A method for switching channels in a video display device, wherein, in the second paragraph, when decoding frames constituting the content of the next channel received in the decoding step of the next channel, decoding of B frames is omitted and decoding of B frames is performed from the time when channel up is selected from the remote control.

7. In paragraph 2, A method for switching channels in a video display device, further comprising the step of transmitting to the server in advance at least one of a channel change request to the previous channel and a channel change request to the next channel, prior to changing the channel by the remote control, when the content of the current channel is received from a server through a network.

8. Remote control to select channel down to previous channel and channel up to next channel based on current channel for channel switching; A first channel processing unit that receives content of the previous channel and stores some of the frames constituting the content of the received previous channel; A second channel processing unit for receiving content of the current channel; A third channel processing unit that receives content of the next channel and stores some of the frames constituting the content of the received next channel; A selection unit for selecting and outputting frames of content of one of the first to third channel processing units; A decoding unit that decodes frames of content output from the above selection unit; A display processing unit that displays content composed of frames decoded by the above decoding unit on a screen; and A video display device including a control unit that controls the selection unit and the decoding unit so that decoding starts from some frames stored in the first channel processing unit or some frames stored in the third channel processing unit according to channel down or channel up selection by the remote control.

9. In paragraph 8, A video display device in which the frames constituting the above received content are grouped into GOP (Group Of Pictures) units, and each GOP consists of at least one I frame, one or more P frames, and one or more B frames.

10. A video display device according to claim 9, wherein some frames of content of a previous channel stored in the first channel processing unit are frames within the most recently received GOP.

11. A video display device in accordance with claim 9, wherein some frames of content of the next channel stored in the third channel processing unit are frames within the most recently received GOP.

12. In paragraph 8, A video display device in which, when the content of the current channel is received from a server through a network, the control unit transmits at least one of a channel change request to the previous channel and a channel change request to the next channel to the server in advance before the channel is changed by the remote control.

13. Remote control to select channel down to previous channel and channel up to next channel based on current channel for channel switching; A first channel processing unit that receives content of the previous channel and decodes frames constituting the content of the received previous channel; A second channel processing unit that receives content of the current channel and decodes frames constituting the received content of the current channel; A third channel processing unit that receives content of the next channel and decodes frames constituting the content of the received next channel; A selection unit for selecting and outputting frames decoded by one of the first to third channel processing units; A display processing unit that displays content composed of frames selected from the above selection unit on a screen; and A video display device including a control unit that controls the selection unit to select frames decoded by one of the first channel processing unit to the third channel processing unit according to channel down or channel up selection by the remote control.

14. In paragraph 13, A video display device in which the frames constituting the above received content are grouped into GOP (Group Of Pictures) units, and each GOP consists of at least one I frame, one or more P frames, and one or more B frames.

15. In paragraph 14, A video display device in which the first channel processing unit omits decoding of B frames when decoding frames constituting the content of the received previous channel, and performs decoding of B frames from the time when channel down is selected from the remote control.

16. In paragraph 14, A video display device in which the third channel processing unit, when decoding frames constituting the content of the next channel received, omits decoding of B frames and performs decoding of B frames from the time when channel up is selected from the remote control.

17. In paragraph 13, A video display device in which, when the content of the current channel is received from a server through a network, the control unit transmits at least one of a channel change request to the previous channel and a channel change request to the next channel to the server in advance before changing the channel.

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