Video transmission method and video transmission apparatus

Abstract

To facilitate the process of switching the luminance dynamic range in a video reception apparatus.SOLUTION: A video transmission method includes: a generation step (S204, S201, S202) of generating a transmission signal 212B including first video data having a first luminance dynamic range and second video data having a second luminance dynamic range wider than the first luminance dynamic range; and a transmission step (S203) of transmitting the transmission signal 212B. In the generation step (204), during a transition period before the second video data starts to be displayed when the first video data is switched to the second video data, the level of the signal corresponding to the luminance value is limited to 0, which is the lower limit value.SELECTED DRAWING: Figure 20

Description

[Technical Field]

[0001] The present invention relates to a video transmission method, a video reception method, a video transmission device, and a video reception device. [Background technology]

[0002] HDR (High Dynamic Range) is attracting attention as a method that supports a brightness range with an expanded maximum brightness value in order to represent bright light, such as specular reflections, that cannot be expressed with current TV signals, in a more realistic brightness while maintaining the dark gradation of conventional images. Specifically, the brightness range method supported by current TV signals is called SDR (Standard Dynamic Range), which has a maximum brightness value of 100 nits, but HDR is expected to expand the maximum brightness value to over 1000 nits. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] ARIB STANDARD ARIB STD-B67 Version 1.0 July 3, 2015 [Non-patent document 2] BBC Research & Development White Paper WHP 283, July 2014 Summary of the Invention [Problem to be solved by the invention]

[0004] In transmitting or receiving video signals corresponding to a plurality of brightness dynamic ranges, it is desirable to facilitate the process of switching the brightness dynamic ranges in the video receiving device.

[0005] Therefore, an object of the present invention is to provide a video transmission method, a video reception method, a video transmission device, or a video reception device that can facilitate the process of switching the luminance dynamic range in a video reception device. [Means for solving the problem]

[0006] A video transmission method according to one embodiment of the present invention includes a generation step of generating a transmission signal including first video data of a first luminance dynamic range and second video data of a second dynamic range wider than the first luminance dynamic range, and a transmission step of transmitting the transmission signal, wherein in the generation step, during a transition period before the second video data starts to be displayed when switching from the first video data to the second video data, the level of a signal corresponding to a luminance value is limited to a lower limit value of 0.

[0007] A video receiving method according to one embodiment of the present invention is a video receiving method in a video receiving device having a display unit, and includes a receiving step of receiving a received signal including first video data of a first luminance dynamic range and second video data of a second dynamic range wider than the first luminance dynamic range, wherein in the received signal, during a transition period before the display of the second video data begins when switching from the first video data to the second video data, the level of a signal corresponding to a luminance value is limited to a lower limit value of 0.

[0008] These general or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or may be realized as any combination of a system, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0009] The present invention can provide a video transmission method, a video reception method, a video transmission device, or a video reception device that can facilitate the process of switching the luminance dynamic range in a video reception device. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram of a video receiving device according to the first embodiment. [Figure 2] FIG. 2 is a flowchart of processing by the display control unit according to the first embodiment. [Figure 3] FIG. 3 is a flowchart of the video reception process according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating an operation when the transfer characteristic changes according to the first embodiment. [Figure 5] FIG. 5 is a diagram illustrating an operation when the transfer characteristic changes according to the first embodiment. [Figure 6] FIG. 6 is a block diagram of the video transmitting device according to the first embodiment. [Figure 7] FIG. 7 is a flowchart of the video transmission process according to the first embodiment. [Figure 8] FIG. 8 is a diagram illustrating an abnormal operation when the transfer characteristic changes according to the second embodiment. [Figure 9] FIG. 9 is a block diagram of a video receiving device according to the second embodiment. [Figure 10] FIG. 10 is a flowchart of processing by the display control unit according to the first embodiment. [Figure 11] FIG. 11 is a diagram illustrating an example of a timestamp descriptor according to the third embodiment. [Figure 12] FIG. 12 is a diagram illustrating an example of an extended timestamp descriptor according to the third embodiment. [Figure 13] FIG. 13 is a diagram showing an example of a video component descriptor according to the third embodiment. [Figure 14] FIG. 14 is a flowchart of processing by the display control unit according to the third embodiment. [Figure 15] FIG. 15 is a flowchart of a video reception process according to the third embodiment. [Figure 16] FIG. 16 is a diagram illustrating an example of a curve showing the relationship between the electrical signal level and the luminance of HDR and SDR according to the fourth embodiment. [Figure 17] FIG. 17 is a diagram illustrating an operation when switching from SDR to HDR according to the fourth embodiment. [Figure 18] FIG. 18 is a diagram illustrating an operation when switching from HDR to SDR according to the fourth embodiment. [Figure 19] FIG. 19 is a block diagram of a video transmission device according to the fourth embodiment. [Figure 20] FIG. 20 is a flowchart of a video transmission process according to the fourth embodiment. [Figure 21] FIG. 21 is a block diagram of a video receiving device according to the fourth embodiment. [Figure 22] FIG. 22 is a flowchart of a video reception process according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Findings that form the basis of the present invention) In the video coding standards ITU-T H.265 | ISO / IEC 23008-2 HEVC, for example, the OETF (Optical-Electro Transfer Function) or EOTF (Electro-Optical Transfer Function) of a video signal is notified by a syntax called transfer characteristics in the Video Usability Information (VUI) in the Sequence Parameter Set (SPS). By using the transfer characteristics of this SPS, it is possible to notify switching of transfer characteristics (transfer functions) with frame accuracy. The video receiving device determines a control method for the video display unit based on the transfer characteristics.

[0012] The MPEG-2 TS (Transport Stream) standard, used for multiplexing and transmitting video and audio signals, such as those used in television broadcasts, includes the parameters and parameter-related information contained in the SPS in a Program-specific information (PSI) descriptor, allowing higher-level information related to the operation of video receiving devices to be transmitted. Regarding transmission characteristics, the PSI descriptor also allows video receiving devices to more easily determine how to control the video display. Generally, PSI is inserted into the multiplexed stream at regular intervals, and is therefore not synchronized with the video signal frames. The MPEG-H MMT standard also defines a mechanism similar to PSI as MMT-SI.

[0013] Transfer characteristics are specified in standards such as ITU-R BT.2020 (hereafter referred to as BT.2020), ARIB STD-B67 (hereafter referred to as STD-B67), and SMPTE ST2084 (hereafter referred to as ST2084). STD-B67 and ST2084 can handle video signals containing luminance 10 to 100 times higher than conventional BT.2020, known as high dynamic range (HDR). In contrast to HDR, conventional BT.2020 and other standards are known as standard dynamic range (SDR).

[0014] In HDR-compatible television broadcasts, HDR and SDR may coexist for each program or commercial, so video receivers must switch the display control depending on whether the program is HDR or SDR.

[0015] A video transmission method according to one embodiment of the present invention includes a generation step of generating a transmission signal including, in time series, first video data of a first luminance dynamic range and second video data of a second dynamic range wider than the first luminance dynamic range, and a transmission step of transmitting the transmission signal, wherein in the generation step, during a transition period when switching from one of the first video data and the second video data to the other, the level of a signal corresponding to a luminance value is limited to a value lower than a predetermined limit value.

[0016] This limits the signal level of the video data to a value lower than the limit value during the transition period when switching to video data with a different luminance dynamic range. This eliminates the need for the video receiving device to change the luminance dynamic range of the display unit, for example, on a frame-by-frame basis, and only requires changing the luminance dynamic range of the display unit during the transition period. This facilitates the process of switching the luminance dynamic range in the video receiving device.

[0017] For example, in the generating step, the level of a signal corresponding to a luminance value may be limited to a value lower than the limit value during a first transition period when the first video data is switched to the second video data.

[0018] For example, in the generating step, the level of the signal corresponding to the luminance value may not be limited to a value lower than the limit value during a second transition period when switching from the second video data to the first video data.

[0019] For example, the transmission signal may include first information for notifying switching of the luminance dynamic range during a first period immediately after the start of the transition period.

[0020] For example, the first period may be a period from immediately after the start of the transition period to a time before the switching time that is an allowable switching time, which is the time allowed for the brightness dynamic range switching process in a video receiving device that receives the transmission signal.

[0021] For example, the generating step may include an encoding step of generating a video signal by encoding the first video data and the second video data, and a multiplexing step of generating the transmission signal including the first information by multiplexing the generated video signal and audio signal.

[0022] For example, the transmission signal may include second information indicating the transition period.

[0023] Furthermore, a video receiving method according to one embodiment of the present invention is a video receiving method in a video receiving device having a display unit, and includes a receiving step of receiving a received signal including, in time series, first video data of a first luminance dynamic range and second video data of a second dynamic range wider than the first luminance dynamic range, wherein in the received signal, during a transition period when switching from one of the first video data and the second video data to the other, the level of a signal corresponding to a luminance value is limited to a value lower than a predetermined limit value, and the received signal includes first information for notifying switching of the luminance dynamic range during a first period immediately after the start of the transition period, and the video receiving method further includes a switching step of switching the luminance dynamic range of the display unit during a switching allowable time, which is the time allowed for a luminance dynamic range switching process, after acquiring the first information.

[0024] This limits the signal level of the video data to a value lower than the limit value during the transition period when switching to video data with a different luminance dynamic range. This eliminates the need for the video receiving device to change the luminance dynamic range of the display unit, for example, on a frame-by-frame basis, and only requires changing the luminance dynamic range of the display unit during the transition period. This facilitates the process of switching the luminance dynamic range in the video receiving device.

[0025] For example, the first period may be a period from immediately after the start of the transition period to a time that is the permissible switching time before the switching time.

[0026] For example, the video receiving method may further include a demultiplexing step of demultiplexing the received signal in which a video signal and an audio signal are multiplexed to obtain the video signal and the first information, and a decoding step of decoding the obtained video signal to obtain the first video data and the second video data.

[0027] For example, the received signal may include second information indicating the transition period.

[0028] In addition, a video transmission device according to one embodiment of the present invention includes a generation unit that generates a transmission signal including, in time series, first video data of a first luminance dynamic range and second video data of a second dynamic range wider than the first luminance dynamic range, and a transmission unit that transmits the transmission signal, wherein the generation unit limits the level of a signal corresponding to a luminance value to a value lower than a predetermined limit value during a transition period when switching from one of the first video data and the second video data to the other.

[0029] This limits the signal level of the video data to a value lower than the limit value during the transition period when switching to video data with a different luminance dynamic range. This eliminates the need for the video receiving device to change the luminance dynamic range of the display unit, for example, on a frame-by-frame basis, and only requires changing the luminance dynamic range of the display unit during the transition period. This facilitates the process of switching the luminance dynamic range in the video receiving device.

[0030] Furthermore, a video receiving device according to one embodiment of the present invention is a video receiving device having a display unit, the receiving unit receiving a received signal including, in time series, first video data of a first luminance dynamic range and second video data of a second dynamic range wider than the first luminance dynamic range, wherein in the received signal, during a transition period when switching from one of the first video data and the second video data to the other, the level of a signal corresponding to a luminance value is limited to a value lower than a predetermined limit value, and the received signal includes first information for notifying switching of the luminance dynamic range during a first period immediately after the start of the transition period, and the video receiving device further includes a display control unit that switches the luminance dynamic range of the display unit during a switching allowable time, which is the time allowed for the luminance dynamic range switching process after acquiring the first information.

[0031] This limits the signal level of the video data to a value lower than the limit value during the transition period when switching to video data with a different luminance dynamic range. This eliminates the need for the video receiving device to change the luminance dynamic range of the display unit, for example, on a frame-by-frame basis, and only requires changing the luminance dynamic range of the display unit during the transition period. This facilitates the process of switching the luminance dynamic range in the video receiving device.

[0032] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0033] It should be noted that the embodiments described below each illustrate a specific example of the present invention. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept are described as optional components.

[0034] (Embodiment 1) The video receiving device according to the present embodiment controls the luminance dynamic range of the display unit with frame accuracy using transfer characteristic information that indicates transfer characteristics with frame accuracy, thereby enabling the video receiving device to display more appropriate video.

[0035] First, the configuration of a video receiving device according to this embodiment will be described. Fig. 1 is a block diagram of video receiving device 100 according to this embodiment. Video receiving device 100 is, for example, a television or the like, and receives a reception signal 111 transmitted by broadcast waves and displays a video based on the received reception signal 111. Video receiving device 100 includes a receiving unit 101, a demultiplexing unit 102, a video decoding unit 103, a display control unit 104, and a display unit 105.

[0036] The receiving unit 101 receives a received signal 111. The received signal 111 is a system stream in which a video signal and an audio signal are multiplexed.

[0037] The demultiplexing unit 102 generates a video signal 112, which is a video stream, by demultiplexing (system decoding) the received signal 111. The demultiplexing unit 102 also outputs transfer characteristics acquired from a descriptor or the like included in the received signal 111 as first transfer characteristic information 113. In other words, the first transfer characteristic information 113 is included in a multiplexing layer.

[0038] The video decoding unit 103 generates video data 114 by decoding the video signal 112. Furthermore, the video decoding unit 103 outputs the transfer characteristic acquired from the SPS as second transfer characteristic information 115. That is, the second transfer characteristic information 115 is included in a video coding layer.

[0039] This second transfer characteristic information 115 is information for specifying a transfer function (OETF or EOTF) with frame accuracy corresponding to the luminance dynamic range of the video data 114. For example, this second transfer characteristic information 115 is information for specifying, with frame accuracy, a first transfer function corresponding to a first luminance dynamic range (SDR) or a second transfer function corresponding to a second dynamic range (HDR) wider than the first luminance dynamic range. In other words, the second transfer characteristic information 115 indicates whether the video data 114 is SDR or HDR. Furthermore, if there are multiple formats of HDR, the second transfer characteristic information 115 may indicate which format of HDR it is. In other words, the second transfer characteristic information 115 indicates the luminance dynamic range of the video data 114, and indicates, for example, one of multiple predetermined luminance dynamic ranges.

[0040] Moreover, the SPS is control information included in the video signal 112 in units of sequences (units of multiple frames).

[0041] The display control unit 104 generates control information 116 for controlling the display unit 105 in accordance with the first transfer characteristic information 113 and the second transfer characteristic information 115 .

[0042] The display unit 105 displays the video data 114 while controlling the luminance dynamic range with frame accuracy in accordance with the control information 116 (i.e., the first transfer characteristic information 113 and the second transfer characteristic information 115). The display unit 105 includes a video characteristic conversion unit 106 and a display device 107.

[0043] The image characteristic conversion unit 106 converts the image data 114 in accordance with the control information 116 to generate the input signal 117. Specifically, the image characteristic conversion unit 106 converts the image data 114 into the input signal 117 using a transfer function indicated by the first transfer characteristic information 113 or the second transfer characteristic information 115.

[0044] Display device 107 is, for example, a liquid crystal panel, and changes the luminance dynamic range of the image to be displayed in accordance with control information 116. For example, when display device 107 is a liquid crystal panel, display device 107 changes the maximum luminance of the backlight.

[0045] Next, the operation of the video receiving device 100 will be described. Although Fig. 1 shows a configuration using both the first transfer characteristic information 113 and the second transfer characteristic information 115, it is sufficient if at least the second transfer characteristic information 115 is used. Control using the second transfer characteristic information 115 will be described in detail below.

[0046] Fig. 2 is a flowchart of the display control process by the display control unit 104. The process shown in Fig. 2 is performed on a frame-by-frame basis or every time the second transfer characteristic information 115 is changed.

[0047] First, the display control unit 104 determines whether the second transfer characteristic information 115 indicates SDR or HDR (S101).

[0048] If the second transfer characteristic information 115 indicates HDR (Yes in S101), the display control unit 104 outputs control information 116 for HDR display (S102), which causes the display unit 105 to display video in a luminance dynamic range corresponding to HDR.

[0049] On the other hand, if the second transfer characteristic information 115 indicates SDR (No in S101), the display control unit 104 outputs control information 116 for SDR display (S103), which causes the display unit 105 to display video in a luminance dynamic range corresponding to SDR.

[0050] In this way, by switching the control information 116 in accordance with the second transfer characteristic information 115 notified with frame accuracy, the switching of the transfer characteristic and the control of the display unit 105 can be synchronized with frame accuracy.

[0051] If multiple HDR methods (for example, STD-B67 and ST2084) exist, identification information of the HDR method may be included in the HDR display control information 116. This allows the display unit 105 to display video images with the luminance dynamic range of the corresponding method.

[0052] 3 is a flowchart of the video reception process by the video receiving device 100. First, the receiving unit 101 receives the received signal 111 (S111). Next, the demultiplexing unit 102 demultiplexes the received signal 111 to generate a video signal 112 (S112). Next, the video decoding unit 103 decodes the video signal 112 to generate video data 114 and acquires second transfer characteristic information 115 (S113).

[0053] Next, the display control unit 104 controls the luminance dynamic range of the display unit 105 in accordance with the second transfer characteristic information 115. Specifically, the display control unit 104 determines whether each frame is HDR or SDR with frame accuracy based on the second transfer characteristic information 115 (S114). If it is HDR (Yes in S114), the display unit 105 displays the video in the luminance dynamic range of HDR (S115). If it is SDR (No in S114), the display unit 105 displays the video in the luminance dynamic range of SDR (S116).

[0054] Figure 4 shows what happens when switching from an SDR program to an HDR program. Figure 5 shows what happens when switching from an HDR program to an SDR program. As shown in Figures 4 and 5, the above processing allows appropriate switching between SDR and HDR with frame accuracy.

[0055] The following describes video transmitting device 200 that generates transmission signal 212 corresponding to the above-mentioned received signal 111. Fig. 6 is a block diagram of video transmitting device 200 according to this embodiment. Video transmitting device 200 shown in Fig. 6 includes generation unit 201 and transmission unit 202.

[0056] The generator 201 generates a transmission signal 212 including video data and second transfer characteristic information for specifying, with frame accuracy, a transfer function corresponding to the luminance dynamic range of the video data. The generator 201 includes a video encoder 203 and a multiplexer 204.

[0057] 7 is a flowchart of video transmission processing by video transmitting device 200. First, video encoding unit 203 generates video signal 211 by encoding video data and second transfer characteristic information (S201). This second transfer characteristic information corresponds to second transfer characteristic information 115 described above, and is information for specifying, with frame accuracy, a first transfer function corresponding to a first luminance dynamic range (e.g., SDR) or a second transfer function corresponding to a second dynamic range (e.g., HDR) wider than the first luminance dynamic range. In addition, the second transfer characteristic information is stored in an SPS included in video signal 211.

[0058] Next, the multiplexing unit 204 multiplexes the encoded video signal 211 and audio signal to generate a transmission signal 212 (S202). Next, the transmitting unit 202 transmits the generated transmission signal 212 (S203).

[0059] As a result, the video transmitting device 200 generates the transmission signal 212 including the second transfer characteristic information for specifying the transfer function with frame accuracy. This allows the video receiving device receiving the transmission signal 212 to control the luminance dynamic range of the display unit with frame accuracy, thereby displaying more appropriate video.

[0060] (Embodiment 2) In TV broadcasts, errors may occur due to the radio wave conditions of terrestrial or satellite broadcasts. FIG. 8 illustrates a situation in which a reception error occurs due to radio wave interference or the like. As shown in FIG. 8, when switching from SDR to HDR, it is assumed that after the video receiving device acquires the second transfer characteristic information 115 in the SPS, the video stream is lost due to radio wave interference or the like, and the first frame of HDR cannot be acquired. In this case, the video decoding unit 103 continues to display the previous frame to conceal the error. In other words, frames of the SDR program are repeatedly displayed.

[0061] In this case, this frame is referenced by subsequent frames, resulting in abnormal video being displayed as subsequent video, with video from past programs mixed in.

[0062] Furthermore, immediately after switching, the display's brightness dynamic range is set to HDR, so frames from SDR programs are displayed in the HDR brightness dynamic range, resulting in the problem of images being displayed at higher brightness than originally intended.

[0063] This embodiment describes a video receiving device that addresses this problem. Fig. 9 is a block diagram of video receiving device 100A according to this embodiment. Video receiving device 100A shown in Fig. 9 further comprises an abnormality detection unit 108 and a message superimposition unit 109 in display unit 105A in addition to the components of video receiving device 100 shown in Fig. 1. In addition, a function has been added to display control unit 104A.

[0064] The abnormality detection unit 108 determines whether the video data 114 (video signal 112) was correctly acquired. Specifically, the abnormality detection unit 108 detects packet loss based on the packet sequence number and analyzes the packet payload to acquire the start position of the frame data, thereby determining whether all of the frame data was acquired (normal) or whether only part of the frame data was acquired (abnormal). The abnormality detection unit 108 also outputs abnormality notification information 118 indicating the determination result to the display control unit 104A. In other words, the display control unit 104A is notified that an abnormality has occurred, or information for identifying the frame in which the abnormality has occurred.

[0065] The display control unit 104A generates control information 116 and a message 119 in accordance with the first transfer characteristic information 113 and the second transfer characteristic information 115, as well as the abnormality notification information 118. Specifically, when an abnormality is detected, the display control unit 104A generates a message 119 indicating that an abnormality exists, and also generates control information 116 for SDR display.

[0066] The message superimposing unit 109 generates an input signal 120 by superimposing the message 119 on the video data (input signal 117) in accordance with the control information 116 and the message 119, and outputs the generated input signal 120 to the display device 107. As a result, for example, a message such as "An error has occurred" is displayed on the display device 107, thereby informing the viewer that the problem is not due to a malfunction of the equipment.

[0067] 10 is a flowchart of the display control process by the display control unit 104A. First, the display control unit 104A determines whether the second transfer characteristic information 115 has been updated (S121). If the second transfer characteristic information 115 has been updated (Yes in S121), the display control unit 104A starts determining whether to switch the display control.

[0068] First, the display control unit 104A determines whether the video data has been correctly acquired. Specifically, the display control unit 104A determines whether the intra-coded frame has been successfully decoded based on the abnormality notification information 118 (S122). If the intra-coded frame has not been successfully decoded (No in S122), the display control unit 104A outputs control information 116 for SDR display (S123). This causes the display unit 105 to display video in a luminance dynamic range corresponding to SDR. In other words, if it is determined that the video data has not been correctly acquired, the display control unit 104A sets the luminance dynamic range of the display unit 105 to SDR (first luminance dynamic range).

[0069] If an error occurs during switching, the displayed frame may contain pixels from the frame before switching. In contrast, in this embodiment, in such a case, by setting the display control to SDR display, it is possible to prevent frames from an SDR program from being displayed with the high brightness setting of HDR.

[0070] Furthermore, if an intra-coded frame that guarantees interrupt playback, such as IDR or CRA of HEVC, is successfully decoded (Yes in S122), the display control is switched as in the first embodiment. That is, the display control unit 104A determines whether the updated second transfer characteristic information 115 indicates SDR or HDR (S124). If the second transfer characteristic information 115 indicates HDR (Yes in S124), the display control unit 104A outputs control information 116 for HDR display (S125). On the other hand, if the second transfer characteristic information 115 indicates SDR (No in S124), the display control unit 104A outputs control information 116 for SDR display (S126).

[0071] In this way, the video receiving device 100A according to the present embodiment can prevent an excessively bright video from being displayed when an error occurs by displaying a video in the luminance dynamic range of SDR when an error occurs.

[0072] (Embodiment 3) In this embodiment, a description will be given of the details of the first transfer characteristic information 113 and processing using the first transfer characteristic information 113. First, an example of a transfer characteristic acquired in the demultiplexing unit 102 will be described.

[0073] When MMT is used as the multiplexing method, the PTS and DTS of the first access unit (corresponding to a picture) in decoding order in a random access unit called an MPU (Media Processing Unit) can be transmitted using a descriptor. For example, in STD-B60 of the Association of Radio Industries and Business (ARIB), the PTS of the first access unit of an MPU, or the DTS of the first access unit of an MPU and the DTS and PTS of subsequent access units are transmitted as program control information using an MPU timestamp descriptor or an MPU extended timestamp descriptor.

[0074] Fig. 11 is a diagram showing an example of the syntax of an MPU timestamp descriptor (MPU_Timestamp_Discriptor) including HDR identification information 301. Fig. 12 is a diagram showing an example of the syntax of an MPU extended timestamp descriptor (MPU_Extended_Timestamp_Discriptor) including HDR identification information 301.

[0075] 11 or 12, by extending the MPU timestamp descriptor or the MPU extended timestamp descriptor, HDR identification information 301 (mpu_hdr_indicator) indicating whether the EOTF of the access unit that constitutes the MPU is HDR or SDR can be added to the transmission signal 212 (received signal 111). Note that when multiple HDR EOTFs exist, such as when both STD-B67 and SMPTE ST2084 are usable, the HDR identification information 301 may include information for identifying the type of HDR EOTF. Alternatively, other descriptors may be used as long as they can transmit EOTF identification information for each MPU.

[0076] When MPEG-2 TS is used as the multiplexing method, 13818-1 AMD6 (Delivery of Timeline for External Data) may be extended to associate the PTS or DTS of an access unit with the EOTF identification information. Alternatively, the EOTF identification information of a random access unit may be stored using a descriptor as in MMT, or the EOTF identification information of a random access unit may be signaled using the header information of a PES or TS.

[0077] In this way, the first transfer characteristic information 113 is included in the control information for each random access unit included in the transmission signal 212 (received signal 111). Here, a random access unit is a unit consisting of multiple access units (frames) in which arbitrary access is guaranteed.

[0078] The first transfer characteristic information 113 may be stored in information per program including multiple MPUs, rather than as information per MPU, such as an MPU timestamp descriptor. In ARIB, the resolution, aspect ratio, frame rate, etc. of a video stream are stored in a video component descriptor, which is information per program. Therefore, the first transfer characteristic information 113 can also be stored in this video component descriptor. However, since information per program is transmitted periodically, such as every 0.5 seconds or 0.1 seconds, it may not be possible to update the information per frame or random access. Therefore, in this case, transfer characteristic information that will become valid in the future is stored along with currently valid transfer characteristic information.

[0079] Figure 13 shows an example of the syntax of a video component descriptor. Current_EOTF (first information) indicates the currently valid EOTF (transfer function), and EOTF_update_flag (second information) indicates whether the EOTF will be changed in the future. In other words, EOTF_update_flag (second information) indicates whether the transfer function will be changed within the program.

[0080] When the EOTF_update_flag (second information) indicates that the EOTF will be switched, the video component descriptor includes new_EOTF (third information) indicating the EOTF after the switch, and new_EOTF_start_mpu_sequence_number (fourth information) indicating the sequence number of the MPU where the EOTF after the switch becomes valid. In other words, new_EOTF_start_mpu_sequence_number (fourth information) is information for specifying the random access unit for which the EOTF will be switched.

[0081] If there is only one type of HDR, it is sufficient to know whether it is HDR or SDR. In other words, the EOTF after switching can be determined only by the EOTF_update_flag, so the new_EOTF field may be omitted.

[0082] By transmitting the transfer characteristics as described above, the video receiving device can acquire the transfer characteristics of the access units that make up the MPU based only on the information in the multiplexing layer (attribute information of the multiplexed AV data and header information of the packets that store the AV data). Furthermore, in the conventional ARIB seamless connection, the PID of the TS packet that stores the video stream or the asset ID (or packet ID) of the MMT packet is switched before and after switching the resolution, etc., which has disadvantages such as difficulty in managing the STD (System Target Decoder) buffer for packets with the same ID, or temporary interruption of data supply on the sending side at the switching point. By using this method, these problems can be solved.

[0083] This method can also be applied to seamlessly switching between multiple audio codecs.

[0084] The configuration of the video receiving device 100A according to this embodiment is different from that of the second embodiment in that a function is added to the display control unit 104A in the configuration shown in FIG.

[0085] First, prior to decoding the video signal 112, the demultiplexing unit 102 acquires the above-mentioned transfer characteristics (HDR identification information 301, etc.) from the information of the multiplexing layer, and outputs first transfer characteristic information 113 for identifying the acquired transfer characteristics to the display control unit 104A.

[0086] In this way, the video receiving device 100A can acquire the first transfer characteristic information 113 prior to decoding the video signal 112, and can therefore acquire the first transfer characteristic information 113 earlier than the second transfer characteristic information 115. This makes it possible to lengthen the period from when the display control unit 104A acquires the transfer characteristic information until it actually controls the video characteristic conversion unit 106 and the display device 107. In particular, assuming that transfer characteristics are switched on an access unit basis, when acquiring transfer characteristics based on the decoding results, the time margin decreases as the frame rate increases, and therefore it is highly effective to acquire transfer characteristics in advance from the multiplexing layer.

[0087] Fig. 14 is a flowchart of the display control process by the display control unit 104 A. The process shown in Fig. 14 differs from the process shown in Fig. 10 in steps S121A and S124A.

[0088] In step S121A, the display control unit 104A determines whether the first transfer characteristic information 113 has been updated in addition to the second transfer characteristic information 115. Furthermore, since the first access unit of an MPU is an intra-coded frame, in step S122, when operating based on the first transfer characteristic information 113, the display control unit 104A operates based on the first transfer characteristic information 113 corresponding to the sequence number (mpu_sequence_number) of the same MPU and the decoding result of the intra-coded frame. Furthermore, in step S124A, the display control unit 104A operates based on the first transfer characteristic information 113 or the second transfer characteristic information 115.

[0089] Although FIG. 14 shows an example in which both the first transfer characteristic information 113 and the second transfer characteristic information 115 are used, only the first transfer characteristic information 113 may be used.

[0090] 15 is a flowchart of a video reception process by the video receiving device 100A according to this embodiment. First, the receiving unit 101 receives the received signal 111 (S111). Next, the demultiplexing unit 102 demultiplexes the received signal 111 to generate a video signal 112 and acquire first transfer characteristic information 113 (S112A).

[0091] Here, the first transfer characteristic information 113 is information for specifying a transfer function (OETF or EOTF) corresponding to the luminance dynamic range of the video data 114 (video signal 112) for each random access unit (MPU unit). For example, the first transfer characteristic information 113 is information for specifying, for each random access unit, a first transfer function corresponding to a first luminance dynamic range (SDR) or a first transfer function corresponding to a second dynamic range (HDR) wider than the first luminance dynamic range. In other words, the first transfer characteristic information 113 indicates whether the video data 114 is SDR or HDR. Furthermore, if there are multiple formats of HDR, the first transfer characteristic information 113 may indicate which format of HDR it is. In other words, the first transfer characteristic information 113 indicates the luminance dynamic range of the video data 114, and indicates, for example, one of multiple predetermined luminance dynamic ranges.

[0092] Next, the video decoding unit 103 generates video data 114 by decoding the video signal 112 (S113).

[0093] Next, display control unit 104A controls the luminance dynamic range of display unit 105 in accordance with first transfer characteristic information 113. Specifically, display control unit 104A determines whether each MPU is HDR or SDR on an MPU-by-MPU basis based on first transfer characteristic information 113 (S114A). If it is HDR (Yes in S114), display unit 105 displays video in the HDR luminance dynamic range (S115). If it is SDR (No in S114), display unit 105 displays video in the SDR luminance dynamic range (S116).

[0094] As a result, the video receiving device 100A can control the luminance dynamic range of the display unit 105 for each random access unit, thereby displaying more appropriate video. Furthermore, by using the first transfer characteristic information 113 included in the multiplexing layer, the video receiving device 100A can acquire the transfer characteristic prior to decoding the video signal 112, thereby facilitating the process of switching the transfer characteristic.

[0095] The configuration and operation of the video transmitting device 200 that generates the transmission signal 212 corresponding to the above-described reception signal 111 are generally similar to those of the first embodiment.

[0096] Specifically, in step S202 shown in FIG. 7, the multiplexer 204 generates the transmission signal 212 including the first transfer characteristic information 113.

[0097] In this way, the video transmitting device 200 generates a transmission signal 212 including first transfer characteristic information for specifying a transfer function for each random access unit. This allows the video receiving device receiving the transmission signal 212 to control the luminance dynamic range of the display unit for each random access unit, thereby displaying more appropriate video. Furthermore, since the multiplexing layer includes the first transfer characteristic information 113, the video receiving device can easily switch between transfer characteristics.

[0098] A modification of this embodiment will now be described.

[0099] In cases where a video receiving device such as an STB (Set Top Box), DVD device, or Blu-ray (registered trademark) device receives a system stream and outputs it to a display device such as a television, the video receiving device and the display device are connected via a communication protocol such as HDMI (registered trademark). Here, in HDMI (registered trademark) and the like, a protocol re-authentication procedure occurs when the resolution of the stream is changed, etc.

[0100] Therefore, when a resolution switch, such as between 2K (e.g., 1920 x 1080 pixels) and 4K (e.g., 3840 x 2160 pixels), occurs, it is desirable for the video receiving device to output a video signal at the maximum resolution when playback begins. In other words, when 2K and 4K are mixed, even when playback begins from a 2K stream, the receiving device upconverts the 2K stream to 4K and outputs it. In this way, even if the signal switches to 4K midway, the resolution remains 4K and no resolution switch occurs. For example, when a switch occurs between 2K SDR and 4K HDR, the video receiving device converts 2K SDR to 4K SDR and outputs it.

[0101] That is, the video signal (video data 114) is a video signal with a first resolution or a second resolution higher than the first resolution. When the resolution of the video signal switches between the first resolution and the second resolution, the video receiving device 100A converts the video signal with the first resolution into a video signal with the second resolution.

[0102] Furthermore, in broadcasting, identification information of the maximum resolution allowed in the broadcasting service is indicated by a descriptor or the like, so the video receiving device may operate to always adjust the output signal to HDMI (registered trademark) to the maximum resolution. For example, for UHD (Ultra High Definition) services, the maximum resolution is specified as either 4K or 8K. Furthermore, if the multiplexing method is TS, the maximum resolution is specified as 2K, and if the multiplexing method is MMT, the maximum resolution is specified as 4K. In this way, the video receiving device may always convert and output the video signal to the maximum resolution according to the multiplexing method.

[0103] That is, if the resolution of the video signal (video data 114) is lower than the maximum resolution defined by the broadcast service of the received signal 111, the video receiving device 100A converts the resolution of the video signal to the maximum resolution.

[0104] (Fourth embodiment) In this embodiment, the signal level of the video signal is limited when switching between SDR and HDR, which makes it possible to facilitate the process of switching the luminance dynamic range in the video receiving device.

[0105] First, we will explain the compatibility characteristics of STD-B67 that support HDR. From the perspective of device implementation, it is important to allow a certain amount of delay from the time the transfer characteristics are acquired until the time the video characteristics conversion unit 106 and the display device 107 are controlled. As an example of how this can be achieved, we have previously mentioned the use of a descriptor in the multiplexing layer to notify in advance of the switching of transfer characteristics.

[0106] However, even when the change in transfer characteristics is notified in advance, it is necessary to control the video characteristics conversion unit 106 and the display device 107 in synchronization with the frame in which the change occurs from SDR to HDR or from HDR to SDR.

[0107] On the other hand, if the brightness value at an electrical signal level of 1.0 is adjusted to approximately 400-500% for SDR (e.g., BT.2020) compared to 1200% for STD-B67 (HDR), the shape of the curve showing the relationship between electrical signal level and brightness for STD-B67 roughly matches the shape of the curve for SDR at low brightness levels.

[0108] FIG. 16 shows curves indicating the relationship between electrical signal level and brightness for HDR (STD-B67) and SDR (BT.2020). As shown in FIG. 16, the HDR and SDR curves generally coincide in the low brightness range. Therefore, if the brightness range of HDR video data converted by STD-B67 is equivalent to the brightness range where the curve shapes generally coincide, visually natural images can be reproduced even on a display device that only supports SDR. In other words, STD-B67 has compatibility characteristics with SDR and HDR. Hereinafter, the range of electrical signal levels corresponding to the brightness range where the curve shapes of SDR and HDR (STD-B67) generally coincide is referred to as the compatible region. In other words, the compatible region is a predetermined range of electrical signal levels, as shown in FIG. 16, that is, a range of electrical signal levels lower than a predetermined limit value.

[0109] For example, in Figure 16, electrical signal level A is included in the compatibility range, so the luminance values ​​are equivalent for STD-B67 and BT.2020. On the other hand, the luminance values ​​corresponding to electrical signal level B are n1 and n2 for BT.2020 and STD-B67, respectively, which are significantly different. This can cause a problem, for example, when switching from HDR to SDR, if a delay in switching the transfer characteristics in the video receiving device causes SDR pixels outside the compatibility range to be mistakenly played back as HDR, resulting in playback at an unreasonably high luminance value.

[0110] A method for providing a transition period when switching transfer characteristics according to this embodiment will be described below. By utilizing the compatibility characteristics described above, it is possible to display natural video even when the video receiving device does not switch transfer characteristics in synchronization with frames.

[0111] First, using Figure 17, we will explain the operation when switching from an SDR program to an HDR program. A certain period at the end of an SDR program is set as a transition period from SDR to HDR. During this transition period, video data is generated using an electrical signal level within the compatibility range. This ensures that during the transition period, images with visually equivalent brightness are reproduced regardless of whether the control settings for SDR display or HDR display are used. This prevents images from being mistakenly reproduced at an inappropriately high brightness.

[0112] This transfer characteristic change can be notified by multiplex layer information such as the video component descriptor shown in Figures 11 to 13. Here, if the transition period is T seconds and the allowable time for switching transfer characteristics in the video receiving device is S seconds, a descriptor notifying the change of transfer characteristics is transmitted within (TS) seconds from the start of the transition period. By switching the display control within S seconds after acquiring the descriptor, the video receiving device can complete the display control change before the start of the HDR program.

[0113] In this way, by providing a transition period and restricting the maximum screen brightness during that period, and by notifying the switching of transfer characteristics via the multiplexing layer, the video receiving device can switch display control based solely on the information in the multiplexing layer, without analyzing the video stream (video signal 112).

[0114] Although analysis of the video stream is required, the transition period may be notified as information on the video stream, such as an SEI message.

[0115] Next, we will explain the operation when switching from an HDR program to an SDR program. In this case, a transition period can be set, just like the operation when switching from an SDR program to an HDR program described above.

[0116] If HDR pixels outside the compatible brightness range are treated as SDR and played back, they will be played back with a lower brightness value than the actual value. Therefore, in this case, there is little risk of adverse effects on the viewer's health. Therefore, as shown in Figure 18, when switching from an HDR program to an SDR program, it is not necessary to limit the range of electrical signal levels to the compatible region during the transition period.

[0117] The above-mentioned compatible area is a predetermined range of electrical signal levels, that is, a range of electrical signal levels lower than a predetermined limit value. For example, the specification of these SDR and HDR curves is described in Non-Patent Document 2 (page 9, Figure 3, etc.). In other words, the lower limit of the compatible area is electrical signal level 0, i.e., black.

[0118] A video transmitting device and a video receiving device that realize the above functions will be described below. Fig. 19 is a block diagram of video transmitting device 200B according to this embodiment. Video transmitting device 200B includes generation unit 201B and transmission unit 202. Generation unit 201B generates transmission signal 212B that includes, in time series, first video data of a first luminance dynamic range (SDR) and video data of a second dynamic range (HDR) that is wider than the first luminance dynamic range (SDR). This generation unit 201B includes video data generation unit 205, video encoding unit 203, and multiplexing unit 204. Transmission unit 202 transmits transmission signal 212B.

[0119] 20 is a flowchart of the video transmission process by video transmission device 200B. First, video data generation unit 205 generates video data 213 (S204). At this time, as described above, video data generation unit 205 limits the level of the signal corresponding to the luminance value to within the compatible region during the transition period when switching from one of the first video data and the second video data to the other. In other words, video data generation unit 205 limits the level of the signal to a value lower than a predetermined limit value. The transition period is, for example, the period immediately before the switching time.

[0120] Furthermore, as described above, it is possible to limit the level only when switching from SDR to HDR, and not limit the level when switching from HDR to SDR. In other words, it is possible to limit the level of the signal corresponding to the luminance value to a value lower than the limit value during the first transition period when switching from the first video data (SDR) to the second video data (HDR), and not limit the level of the signal corresponding to the luminance value to a value lower than the limit value during the second transition period when switching from the second video data (HDR) to the first video data (SDR).

[0121] Next, the video encoding unit 203 generates a video signal 211B by encoding the video data 213 (S201). Next, the multiplexing unit 204 multiplexes the generated video signal 211B and an audio signal to generate a transmission signal 212B (S202). Then, the transmitting unit 202 transmits the transmission signal 212B (S203).

[0122] 17 and 18, the transmission signal 212B includes first information (switching notification descriptor) for notifying switching of the luminance dynamic range during a first period immediately after the start of the transition period. For example, this first period is a period from immediately after the start of the transition period to a time before the switching time that is an allowed switching time, which is the time allowed for switching processing of the luminance dynamic range in a video receiving device receiving the transmission signal 212B.

[0123] Furthermore, this first information (switching notification descriptor) is transmitted in the multiplexing layer. That is, the multiplexing unit 204 multiplexes the video signal 211B and the audio signal to generate a transmission signal 212B including the first information (switching notification descriptor). Furthermore, the transmission signal 212B may include second information indicating a transition period.

[0124] Fig. 21 is a block diagram of a video receiving device 100B according to this embodiment. This video receiving device 100B receives a received signal 111B, which is a transmitted signal 212B generated by the video transmitting device 200B shown in Fig. 19. Note that the basic configuration is the same as that of the video receiving device 100 shown in Fig. 1, but the function of the display control unit 104B is different from that of the display control unit 104.

[0125] 22 is a flowchart of video reception processing by video receiving device 100B. First, receiving unit 101 receives received signal 111B including, in time series, first video data of a first luminance dynamic range (SDR) and second video data of a second dynamic range (HDR) wider than the first luminance dynamic range (SDR) (S111). Here, as described above, in received signal 111B, during a transition period when switching from one of the first video data and the second video data to the other, the level of a signal corresponding to a luminance value is limited to a value lower than a predetermined limit value.

[0126] Next, the demultiplexer 102 demultiplexes the received signal 111B in which the video signal and the audio signal are multiplexed, thereby obtaining the video signal 112 (S112). The multiplex layer also includes a switching notification descriptor 121 (first information), and the demultiplexer 102 obtains the switching notification descriptor 121. Here, the switching notification descriptor 121 is information for notifying switching of the luminance dynamic range in the first period immediately after the start of the transition period.

[0127] If the switching notification descriptor 121 is received (Yes in S114B), the display control unit 104B switches the brightness dynamic range of the display unit 105 within the switching allowable time, which is the time allowed for the brightness dynamic range switching process, after acquiring the switching notification descriptor 121 (S115B).

[0128] Although not shown, in parallel with the processing of steps S114B and S115B, video decoding unit 103 decodes video signal 112 to obtain video data 114. Display unit 105 displays video data 114 within the currently set luminance dynamic range.

[0129] As described above, in this embodiment, during a transition period when switching to video data with a different luminance dynamic range, the signal level of the video data is limited to a value lower than the limit value. This eliminates the need for the video receiving device to change the luminance dynamic range of the display unit, for example, on a frame-by-frame basis, and allows the video receiving device to easily control the switching of the luminance dynamic range.

[0130] Although the video receiving device and the video transmitting device according to the embodiment of the present invention have been described above, the present invention is not limited to this embodiment.

[0131] Furthermore, each processing unit included in the video receiving device and the video transmitting device according to the above embodiments is typically realized as an LSI, which is an integrated circuit. These may be individually implemented as single chips, or some or all of them may be integrated into a single chip.

[0132] Furthermore, the integration is not limited to LSI, but may be realized by dedicated circuits or general-purpose processors. FPGAs (Field Programmable Gate Arrays), which can be programmed after LSI fabrication, or reconfigurable processors, which allow the connections and settings of circuit cells within LSIs to be reconfigured, may also be used.

[0133] In each of the above embodiments, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0134] The present invention may also be realized as a video receiving method or a video transmitting method executed by a video receiving device or a video transmitting device.

[0135] The division of functional blocks in the block diagram is an example, and multiple functional blocks may be realized as a single functional block, one functional block may be divided into multiple blocks, or some functions may be moved to another functional block.Furthermore, the functions of multiple functional blocks having similar functions may be processed in parallel or in time-sharing by a single piece of hardware or software.

[0136] The order in which the steps in the flowchart are executed is merely an example for specifically explaining the present invention, and an order other than the above may be used. Also, some of the steps may be executed simultaneously (in parallel) with other steps.

[0137] Although the video receiving device and the video transmitting device according to one or more aspects have been described based on the embodiments, the present invention is not limited to these embodiments. As long as they do not deviate from the spirit of the present invention, various modifications conceivable by those skilled in the art to the present embodiments and configurations constructed by combining components of different embodiments may also be included within the scope of one or more aspects. [Industrial Applicability]

[0138] The present invention can be applied to video receiving devices and video transmitting devices such as TVs. [Explanation of symbols]

[0139] 100, 100A, 100B Video receiving device 101 Receiving unit 102 Demultiplexer 103 Video Decoding Unit 104, 104A, 104B Display control unit 105, 105A display section 106 Video characteristics conversion unit 107 Display Devices 108 Abnormality detection unit 109 Message superposition unit 111, 111B received signal 112, 211, 211B video signal 113 First transmission characteristic information 114, 213 Video data 115 Second transfer characteristic information 116 Control Information 117, 120 Input signal 118 Abnormality notification information 119 Messages 121 Switch Notification Descriptor 200, 200B Video transmitter 201, 201B generation section 202 Transmission Unit 203 Video Encoding Unit 204 Multiplexer 205 Video data generation unit 212, 212B transmit signal 301 HDR Identification Information

Claims

1. generating a transmission signal including first video data having a first luminance dynamic range and second video data having a second dynamic range wider than the first luminance dynamic range; a transmitting step of transmitting the transmission signal, In the generating step, during a transition period before a display of the second video data starts when the first video data is switched to the second video data, a level of a signal corresponding to a luminance value is limited to a lower limit value of 0. Video transmission method.

2. a generator that generates a transmission signal including first video data having a first luminance dynamic range and second video data having a second dynamic range that is wider than the first luminance dynamic range; a transmitter that transmits the transmission signal, the generation unit limits a level of a signal corresponding to a luminance value to a lower limit value of 0 during a transition period before display of the second video data starts when switching from the first video data to the second video data. Video transmission device.

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