Data generation device, data output device, encoding device, and decoding device

Abstract

To provide a data generator capable of achieving backward compatibility.SOLUTION: The data generator generates a video elementary stream of a second luminance dynamic range wider than a first luminance dynamic range. The video elementary stream includes: first transfer function information for identifying a first OETF that is referred to by a first device when the first device decodes a video elementary stream; and a second transfer function information for identifying a second OETF that is referred to by a second device when the second device decodes the video elementary stream.SELECTED DRAWING: Figure 13

Description

Technical Field

[0001] The present invention relates to a data generation method, a data reproduction method, a data generation apparatus, and a data reproduction apparatus.

Background Art

[0002] As techniques for generating, encoding, and multiplexing video, there are the techniques described in Non-Patent Documents 1 to 3.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the generation of video data like this, although new methods are constantly being devised, it is desired to achieve backward compatibility with conventional devices.

[0005] Therefore, the present invention aims to provide a data generation method, a data reproduction method, a data generation device, or a data reproduction device that can achieve backward compatibility. [Means for solving the problem]

[0006] To achieve the above objective, a data generation device according to one aspect of the present invention is a data generation device that generates a video elemental stream having a second luminance dynamic range wider than a first luminance dynamic range, comprising an encoding unit that generates the video elemental stream by performing encoding in accordance with a video encoding standard, wherein the video elemental stream includes first transfer function information for identifying a first OETF referenced by the first device when the first device decodes the video elemental stream, and second transfer function information for identifying a second OETF referenced by the second device when the second device decodes the video elemental stream.

[0007] These general or specific embodiments may be implemented as a system, method, integrated circuit, computer program, or recording medium such as a computer-readable CD-ROM, or as any combination of a system, method, integrated circuit, computer program, and recording medium. [Effects of the Invention]

[0008] The present invention can provide a data generation method, a data playback method, a data generation device, or a data playback device that can achieve backward compatibility. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a diagram showing the configuration of the system according to the embodiment. [Figure 2] Figure 2 shows an example of an OETF according to an embodiment. [Figure 3] Figure 3 shows an example of the VUI configuration according to the embodiment. [Figure 4]Figure 4 shows an example of an OETF according to an embodiment. [Figure 5] Figure 5 shows an example of an extended OETF according to the embodiment. [Figure 6] Figure 6 shows an example of the configuration of an SEI message according to the embodiment. [Figure 7] Figure 7 shows an example of the configuration of an SEI message according to the embodiment. [Figure 8] Figure 8 shows an example of the configuration of the SPS according to the embodiment. [Figure 9] Figure 9 shows an example of the configuration of a hybrid descriptor according to an embodiment. [Figure 10] Figure 10 shows an example of the configuration of a hybrid descriptor according to an embodiment. [Figure 11] Figure 11 shows an example of the configuration of an HEVC descriptor according to an embodiment. [Figure 12] Figure 12 shows the operation of the stream and data playback device according to the embodiment. [Figure 13] Figure 13 is a flowchart showing the operation of the data generation device according to the embodiment. [Figure 14] Figure 14 is a flowchart showing the operation of the data playback device according to the embodiment. [Modes for carrying out the invention]

[0010] (Knowledge that formed the basis of this invention) HDR (High Dynamic Range) is attracting attention as a method that expands the maximum brightness range to express bright light, such as specular reflections that cannot be represented by current TV signals, with a brightness closer to reality, while maintaining the dark tone gradation of conventional images. Specifically, the brightness range supported by conventional TV signals is called SDR (Standard Dynamic Range), and the maximum brightness value was 100 nits, whereas HDR is expected to expand the maximum brightness value to 1000 nits or more.

[0011] On the other hand, it is desired that such video data corresponding to HDR can be played back even on a playback device that only supports conventional SDR. That is, video data that can be played back as HDR video on a playback device corresponding to HDR and as SDR video on a playback device corresponding to SDR is desired.

[0012] A data generation method according to an aspect of the present invention is a data generation method for generating video data having a second luminance dynamic range wider than a first luminance dynamic range, the video data being compatible with playback on a first device that does not support playback of video having the second luminance dynamic range and supports playback of video having the first luminance dynamic range, the method including: generating a video signal included in the video data using a second OETF (Opto-Electrical Transfer Function) referenced by a second device when the second device that supports playback of video having the second luminance dynamic range decodes the video data; storing first transfer function information for specifying a first OETF referenced by the first device when the first device decodes the video data in VUI (Video Usability Information) in the video data; and storing second transfer function information for specifying the second OETF in SEI (Supplemental enhancement information) in the video data.

[0013] According to this, on a device that only supports playback of video having a first luminance dynamic range, the video data can be played back using the first transfer function information, and on a device that supports playback of video having a second luminance dynamic range, the video data can be played back using the second function information. Thus, the data generation method can generate video data having backward compatibility.

[0014] For example, the data generation method may further include a step of storing, in a descriptor of a multiplexing layer, hybrid information indicating whether the video data is video data of the second luminance dynamic range.

[0015] According to this, in a data playback device that plays back video data, it is possible to prepare for switching the playback method in advance by using the hybrid information in the multiplexing layer. Thereby, the switching of the playback method in the data playback device can be smoothly performed.

[0016] For example, the first OETF may be an OETF defined by a linear term of the luminance of the video data in a first range of the luminance of the video data and defined by a power term of the luminance of the video data in a second range larger than the first range.

[0017] For example, the second OETF may be an OETF defined by a linear term of the luminance of the video data in a third range of the luminance of the video data, defined by a power term of the luminance of the video data in a fourth range larger than the third range, and defined by a logarithmic term of the luminance of the video data in a fifth range larger than the fourth range.

[0018] For example, the first OETF may be an OETF defined by a power term of the luminance of the video data.

[0019] For example, the second OETF may be an OETF defined by a power term of the luminance of the video data in a sixth range of the luminance of the video data and defined by a logarithmic term of the luminance of the video data in a seventh range larger than the sixth range.

[0020] For example, the first OETF may be an OETF defined by BT.709 or BT.2020, and the second OETF may be a hybrid gamma OETF.

[0021] For example, the data generation method may further include the step of storing dynamic range increase information, which indicates the difference between the luminance dynamic range of the video data and the first luminance dynamic range, in the SEI.

[0022] For example, the data generation method may further include the step of storing picture maximum average level information, which indicates the maximum average brightness value among the average brightness values ​​of each of the pictures included in the video sequence, in the SEI.

[0023] Furthermore, a data playback method according to one aspect of the present invention is a data playback method for playing video data having a second luminance dynamic range wider than a first luminance dynamic range, which does not support playback of video of the second luminance dynamic range, and is compatible with playback on a first device that supports playback of video of the first luminance dynamic range, wherein the video data includes VUI (Video Usability Information) which stores first transfer function information for identifying a first OETF (Opto-Electrical Transfer Function) referenced by the first device when the first device decodes the video data, and SEI (Supplemental enhancement information) which stores second transfer function information for identifying a second OETF referenced by the second device when the second device that supports playback of video of the second luminance dynamic range decodes the video data, and the data playback method includes the steps of acquiring the second transfer function information contained in the SEI, and playing video signals contained in the video data by referring to the second OETF identified by the acquired second transfer function information.

[0024] According to this, the data playback method can play video data that is backward compatible.

[0025] For example, the video data may further include hybrid information stored in a descriptor of the multiplexing layer indicating whether or not the video data is video data of the second luminance dynamic range, and the data playback method may further include the steps of acquiring the hybrid information from the video data, preparing to switch between playback of the first luminance dynamic range and playback of the second luminance dynamic range based on the acquired hybrid information, and switching between playback of the first luminance dynamic range and playback of the second luminance dynamic range at the timing when the video sequence switches.

[0026] According to this, hybrid information within the multiplexed layer can be used to prepare in advance for switching playback modes. This allows for a smoother switching of playback modes.

[0027] For example, the first OETF may be an OETF that is defined by a linear term of the luminance of the video data in a first range of luminance of the video data, and by a power term of the luminance of the video data in a second range greater than the first range.

[0028] For example, the second OETF may be an OETF defined by a linear term of the luminance of the video data in a third range of luminance of the video data, by a power term of the luminance of the video data in a fourth range greater than the third range, and by a logarithmic term of the luminance of the video data in a fifth range greater than the fourth range.

[0029] For example, the first OETF may be an OETF defined by a power of the luminance term of the video data.

[0030] For example, the second OETF may be an OETF that is defined by a power term of the luminance of the video data in the sixth range of luminance of the video data, and by a logarithmic term of the luminance of the video data in the seventh range which is greater than the sixth range.

[0031] For example, the first OETF may be an OETF defined in BT.709 or BT.2020, and the second OETF may be a hybrid gamma OETF.

[0032] For example, the data playback method may further include the step of obtaining dynamic range increase information from the SEI that indicates the difference between the luminance dynamic range of the video data and the first luminance dynamic range.

[0033] For example, the data playback method may further include the step of obtaining picture maximum average level information from the SEI, which indicates the maximum average brightness value among the average brightness values ​​of each of the pictures included in the video sequence.

[0034] Furthermore, a data generation device according to one aspect of the present invention is a data generation device that generates video data having a second luminance dynamic range wider than a first luminance dynamic range, which does not support playback of video in the second luminance dynamic range, and is compatible with playback on a first device that supports playback of video in the first luminance dynamic range, and includes a generation unit that generates video signals included in the video data using a second OETF (Opto-Electrical Transfer Function) that is referenced by the second device when the second device, which supports playback of video in the second luminance dynamic range, decodes the video data; a first storage unit that stores first transfer function information for identifying the first OETF referenced by the first device when the first device decodes the video data in VUI (Video Usability Information) within the video data; and a second storage unit that stores second transfer function information for identifying the second OETF in SEI (Supplemental enhancement information) within the video data.

[0035] According to this, a device that only supports playback of video with a first luminance dynamic range can reproduce video data using the first transfer function information, and a device that supports playback of video with a second luminance dynamic range can reproduce video data using the second function information. In this way, the data generation device can generate backward-compatible video data.

[0036] Furthermore, a data playback device according to one aspect of the present invention is a data playback device that plays video data having a second luminance dynamic range wider than a first luminance dynamic range, which does not support playback of video in the second luminance dynamic range, and is compatible with playback on a first device that supports playback of video in the first luminance dynamic range, wherein the video data includes VUI (Video Usability Information) which stores first transfer function information for identifying a first OETF (Opto-Electrical Transfer Function) referenced by the first device when the first device decodes the video data, and SEI (Supplemental enhancement information) which stores second transfer function information for identifying a second OETF referenced by the second device when the second device that supports playback of video in the second luminance dynamic range decodes the video data, and the data playback device includes an acquisition unit which acquires the second transfer function information contained in the SEI, and a playback unit which plays video signals contained in the video data by referring to the second OETF identified by the acquired second transfer function information.

[0037] According to this, the data playback device can play video data that is backward compatible.

[0038] These comprehensive or specific embodiments may be implemented as a system, method, integrated circuit, computer program, or recording medium such as a computer-readable CD-ROM, or as any combination of a system, method, integrated circuit, computer program, and recording medium.

[0039] The embodiments will be described in detail below with reference to the drawings.

[0040] The embodiments described below are all specific examples of the present invention. The numerical values, shapes, materials, components, arrangement and connection configurations of the components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, those components that are not described in the independent claim representing the highest-level concept will be described as optional components.

[0041] Furthermore, detailed explanations of terminology, data structure, and processing content may be omitted below, but examples of these specifics are similar to those described in Non-Patent Documents 1, 2, and 3.

[0042] First, the configuration of the system according to this embodiment will be described. Figure 1 is a block diagram showing the configuration of the system according to this embodiment. The system shown in Figure 1 includes a data generation device 110 and a data playback device 120.

[0043] The data generation device 110 generates video data with a second luminance dynamic range (e.g., HDR) that is wider than a first luminance dynamic range (e.g., SDR), which does not support playback of video with the second luminance dynamic range, but is compatible with playback on a first device that supports playback of video with the first luminance dynamic range.

[0044] This data generation device 110 comprises a video signal generation unit 111, an encoding unit 112, and a multiplexing unit 113.

[0045] The video signal generation unit 111 converts the luminance values ​​of the HDR-compatible source image into coded values ​​using OETF (Opto-Electrical Transfer Function). Here, OETF is a function for converting the luminance values ​​of the source image into coded values, as shown in Figure 2. Specifically, the video signal generation unit 111 uses an SDR-compatible HDR OETF. The details of this will be described later.

[0046] The encoding unit 112 generates a video elementary stream by encoding the obtained code value in accordance with a video encoding standard such as HEVC. The multiplexing unit 113 generates a transport stream (e.g., a DVB transport stream) by multiplexing the video elementary stream.

[0047] The generated transport stream is transmitted to the data playback device 120, for example, by broadcast waves. While this example uses broadcast waves, transmission may also occur via a network or a recording medium such as a BD disc.

[0048] The data playback device 120 plays back the video data generated by the data generation device 110. This data playback device 120 comprises a demultiplexing unit 121, a decoding unit 122, and a playback unit 123.

[0049] The demultiplexing unit 121 generates a video elementary stream by demultiplexing the video data (transport stream). The decoding unit 122 generates a code value by decoding the obtained video elementary stream in accordance with a video encoding standard such as HEVC.

[0050] The playback unit 123 restores the image by converting the obtained code values ​​into luminance values ​​using the EOTF (Electro-Optical Transfer Function) corresponding to the OETF. Here, EOTF is the inverse function of OETF and is a function for converting code values ​​into luminance values. The obtained image is displayed on a display unit provided by or connected to the data playback device 120.

[0051] The signaling of the transfer function (OETF) in this embodiment will be described below.

[0052] The transfer function is signaled using the transfer_characteristics within the VUI (Video Usability Information) included in the SPS (Sequence Parameter Set) of the HEVC and AVC video encoding standards.

[0053] Furthermore, only OETFs are signaled, while EOTFs are not.

[0054] Figure 3 shows the syntax of the VUI parameters. As shown in Figure 3, the VUI includes first transfer function information (transfer_characteristics). Figure 4 is a table showing the meaning of transfer_characteristics. Values ​​1 and 14 are assigned to the OETF of SDRs supported by DVB (Digital Video Broadcasting) UHD (Ultra HD) Phase 1 receivers.

[0055] As described in Non-Patent Document 1, etc., `transfer_characteristics` represents the opto-electrical transfer characteristics of the original image.

[0056] Signaling, in this context, means including a signal within the transmitted signal that identifies the desired information, or a signal that indicates the information itself, so that the receiving end can acquire the desired information. For example, in the examples in Figures 3 and 4, the transmitted signal includes transfer_characteristics to identify the OETF, and the receiving end identifies the OETF based on the received transfer_characteristics.

[0057] The following describes an example of an extension for a new OETF according to this embodiment.

[0058] The HEVC and AVC standards include a reserve value for further expansion. Therefore, this reserve value can be assigned to an SDR-compatible HDR OETF (hereinafter referred to as Hybrid OETF). For example, as shown in Figure 5, the Hybrid OETF is assigned to the reserve values ​​18-20.

[0059] However, in this case, older data playback devices (receivers) that do not support HDR cannot recognize this new value and mistakenly recognize it as a reserve value. This creates a problem where backward compatibility cannot be achieved when a new value is used for hybrid OETF. Here, hybrid OETF refers to an OETF that includes both a portion expressed as a power of luminance and a portion expressed as a logarithm of luminance, such as the BBC Hybrid Gamma OETF.

[0060] In this embodiment, the value of the first transfer function information (transfer_characteristics) is set to 1 (BT.709) or 14 (BT.2020), similar to conventional SDRs.

[0061] Furthermore, to identify the hybrid OETF, a second transfer function information (HDR_transfer_characteristic) is signaled separately from the first transfer function information. This allows data playback devices that do not support HDR to identify the SDR OETF using the first transfer function information (transfer_characteristics), while data playback devices that support HDR can identify the HDR OETF using the second transfer function information.

[0062] Here, the second transfer function information (HDR_transfer_characteristic) is used for signaling the OETF for HDR. Specifically, the OETF for HDR is compatible with the OETF for SDR, which is identified by the first transfer function information (transfer_characteristics).

[0063] For example, the second transfer function information (HDR_transfer_characteristic) indicates one of the three hybrid OETFs shown in Figure 5. The second transfer function information may also indicate whether or not a hybrid OETF is used. Furthermore, the number of selectable hybrid OETFs can be arbitrary, as long as it is one or more.

[0064] Furthermore, as shown in Figure 2, the characteristics of the hybrid OETF are almost identical to those of the SDR OETF in the low-luminance range. In other words, when a video signal generated using the hybrid OETF is played back using the hybrid OETF, the reproduced luminance is almost identical in the low-luminance range when played back using the SDR OETF. This reduces the difference in luminance values ​​between playback on HDR equipment and playback on SDR equipment, allowing for the reproduction of images with less noticeable distortion even when played back using the SDR OETF.

[0065] The following describes several methods for storing second transfer function information. Broadly speaking, there are two methods for storing second transfer function information: one in the video coding layer and the other in the multiplaxing layer.

[0066] First, we will explain how to store the second transfer function information in the video coding layer.

[0067] Figure 6 shows the syntax of the HDR hybrid gamma SEI message (hereinafter referred to as the hybrid SEI message) according to this embodiment. As shown in Figure 6, the hybrid SEI message includes second transfer function information (HDR_transfer_characteristic).

[0068] Hybrid SEI messages exist only within IRAP NAL units or I-pictures and are valid for subsequent encoded video sequences.

[0069] Hybrid SEI messages may also be prefix or suffix SEI messages.

[0070] Furthermore, the presence of this SEI message may be mandated within the application standardization document if HDR_transfer_characteristici is a predetermined fixed value.

[0071] Furthermore, as shown in Figure 7, the hybrid SEI message may include, in addition to or instead of, the second transfer function information described above, dynamic range increase information (dynamic_range_increase) and picture maximum average level information (maximum_average_picture_level).

[0072] The dynamic range increase information (dynamic_range_increase) is used in the calculation of the coefficient k and can only take values ​​of 0, 1, or 2. The coefficient k represents the difference from the dynamic range of SDR and is calculated using the following equation (Equation 1). Specifically, the coefficient k represents the ratio of the dynamic range of the image to the dynamic range of SDR.

[0073] k = 2 × dynamic_range_increase + 4 ... (Equation 1)

[0074] The maximum average picture level information (maximum_average_picture_level) indicates the highest average picture level among all pictures included in the video sequence. Here, the average picture level is the average value of the pixel brightness expressed as a percentage of the maximum brightness.

[0075] In this way, by using dynamic range increase information and picture maximum average level information, the difference from SDR can be set to any range.

[0076] Furthermore, the presence of this SEI message may be mandated within the application standardization document if k is a predetermined fixed value. For example, k=4 in DVB and k=8 in BDA.

[0077] Figure 8 shows the configuration of the extended SPS. As shown in Figure 8, dynamic range increase information (dynamic_range_increase) and picture maximum average level information (maximum_average_picture_level) may be included in the SPS.

[0078] Next, we will explain how to store the second transfer function information in the multiplexing layer.

[0079] Figure 9 shows the configuration of the hybrid descriptor (HDR_hybrid_gamma_descriptor), which is a new MPEG2-TS level descriptor according to this embodiment.

[0080] As shown in Figure 9, the hybrid descriptor includes a hybrid OETF flag (HDR_hybrid_gamma_OETF_flag) and second transfer function information (HDR_transfer_characteristic).

[0081] The hybrid OETF flag (HDR_hybrid_gamma_OETF_flag) indicates whether the content is HDR encoded using hybrid OETF. For example, if the hybrid OETF flag is 1, the content is HDR encoded using hybrid OETF.

[0082] Note that the hybrid OETF flag is not necessarily required, and only the second transfer function information may be used.

[0083] Furthermore, the hybrid descriptor is stored in at least one of the following: the Program Map Table (PMT) defined in MPEG, the Service Description Table (SDT) defined in DVB within the DVB-SI standard, and the Event Information Table (EIT) defined in DVB within the DVB-SI standard.

[0084] The PMT indicates the PID of a TS packet containing images or audio. The data playback device can extract the desired image or audio TS packet by obtaining the desired image or audio PID from the PMT.

[0085] SDT indicates the channel (service) name, the type of EIT transmitted on each channel, and digital copy control information, etc.

[0086] EIT indicates information related to the program, such as the program name, broadcast date and time, and broadcast content.

[0087] If the PMT contains a hybrid descriptor, the hybrid descriptor is only applied to the video elementary stream. However, in this case, the broadcaster needs to control the modification of the PMT, which can be difficult.

[0088] If an SDT includes a hybrid descriptor, the contents of the hybrid descriptor are not updated frequently. Therefore, it is preferable to apply the contents of the hybrid descriptor to the entire service.

[0089] If an EIT includes a hybrid descriptor, it has the advantage of allowing the contents of the hybrid descriptor to be modified on an event-by-event basis.

[0090] Figure 10 shows another configuration of the hybrid descriptor according to this embodiment. As shown in Figure 10, the hybrid descriptor may include dynamic range increase information (dynamic_range_increase) and picture maximum average level information (maximum_average_picture_level) in addition to, or instead of, the second transfer function information.

[0091] Figure 11 shows the configuration of the HEVC descriptor (HEVC_descriptor) according to this embodiment. The HEVC descriptor is an MPEG2-TS level descriptor. As shown in Figure 11, the reserved value of the HEVC descriptor is replaced with a hybrid coding flag (hdr_hybrid_gamma_coded_content_flag) and dynamic range increase information (dynamic_range_increase). The hybrid coding flag is the same flag as the hybrid OETF flag (HDR_hybrid_gamma_OETF_flag) described above. In addition, other information described above (second transfer function information and picture maximum average level information) may be included in the HEVC descriptor.

[0092] Alternatively, a similar extension may be applied to the AVC descriptor (AVC_video_descriptor).

[0093] Furthermore, the aforementioned hybrid descriptor (HDR_hybrid_gamma_descriptor) may be combined with OETF signaling to the video elementary stream (hybrid SEI message). This allows for smooth parameter switching in the data playback device.

[0094] The operation will be explained in detail below. Figure 12 shows the stream configuration and the operation of the data playback device.

[0095] A hybrid descriptor (HDR_hybrid_gamma_descriptor) containing the hybrid OETF flag (HDR_hybrid_gamma_OETF_flag) is sent shortly before the actual change. Upon receiving this hybrid OETF flag, the data regenerator prepares for the change between SDR and HDR.

[0096] Furthermore, to enable parameter changes, an EOS (End Of Sequence) is inserted into the video elementary stream to indicate the end of the video sequence. In addition, a hybrid SEI message adapted to the hybrid descriptor that was signaled immediately before the EOS may or may not be stored in the subsequent RAP (Random Access Point).

[0097] The data playback device detects whether EOS and hybrid SEI messages are present and makes changes according to the detection results.

[0098] In the example shown in Figure 12, the data playback device acquires a hybrid descriptor containing HDR_hybrid_gamma_OETF_flag=0 while in HDR operation. This causes the data playback device to begin preparing to switch from HDR to SDR operation. Next, the data playback device switches from HDR to SDR when it acquires EOS. Furthermore, since hybrid SEI messages do not exist in the SDR video elementary stream, the data playback device does not acquire hybrid SEI messages.

[0099] Next, while operating in SDR mode, the data playback device acquires a hybrid descriptor containing HDR_hybrid_gamma_OETF_flag=1. This causes the data playback device to begin preparing to switch from SDR to HDR mode. Then, the data playback device switches from SDR to HDR when it acquires EOS (End of Storage).

[0100] The operation of the data generation device 110 and the data playback device 120 based on the above will be described below.

[0101] Figure 13 is a flowchart of the operation of the data generation device 110 according to this embodiment. The data generation device 110 generates HDR video data that does not support HDR video playback but is compatible with playback on a first device that supports SDR video playback.

[0102] First, the video signal generation unit 111 generates a video signal by converting the luminance values ​​of the original image into coded values ​​using the second OETF (S101). Next, the encoding unit 112 generates a video elementary stream by encoding the video signal. At this time, the encoding unit 112 stores first transfer function information in the VUI within the video data (video elementary stream) to identify the first OETF that the first device, which supports only SDR, will refer to when playing back the video data. It also stores second transfer function information in the SEI within the video data to identify the second OETF that the second device, which supports HDR, will refer to when decoding the video data (S102).

[0103] Here, VUI and SEI belong to the video coding layer. Furthermore, the first OETF is, for example, the OETF specified in BT.709 or BT.2020, and the second OETF is, for example, the BBC Hybrid Gamma OETF.

[0104] Furthermore, the encoding unit 112 may store dynamic range increase information in the SEI, which indicates the difference between the luminance dynamic range of the video data and the luminance dynamic range of the SDR. The encoding unit 112 may also store picture maximum average level information in the SEI, which indicates the maximum average luminance value among the average luminance values ​​of each of the pictures included in the video sequence.

[0105] Next, the multiplexing unit 113 generates a transport stream by multiplexing the video elementary stream data. At this time, the multiplexing unit 113 stores hybrid information (hybrid OETF flag) indicating whether or not the video data is HDR video data in the hybrid descriptor of the multiplexing layer (S103).

[0106] In the example shown in Figure 12, the hybrid descriptor includes at least a hybrid OETF flag, but the hybrid descriptor may also include second transfer function information, dynamic range increase information, or picture maximum average level information.

[0107] Similarly, a hybrid SEI message may include at least one of the hybrid OETF flag, second transfer function information, dynamic range increase information, and picture maximum average level information.

[0108] Furthermore, although the above explanation describes the hybrid OETF flag and the second transfer function information as separate pieces of information, the second transfer function information may be used instead of the hybrid OETF flag. In other words, the hybrid OETF flag does not have to be used. For example, whether or not the second transfer function information is included in the video data can signal whether or not the video data is HDR video data (whether or not hybrid OETF is used). Alternatively, whether or not the video data is HDR video data can be signaled by whether or not hybrid OETF or SDR OETF is indicated by the second transfer function information.

[0109] In the above explanation, an example was given in which the hybrid OETF is shown using the second transfer function information. However, as shown in Figure 12, if HDR and SDR video data are mixed within the video data, the SDR OETF may also be shown using the second transfer function information for the SDR video. This means that a data playback device that supports HDR only needs to refer to the second transfer function information at all times, regardless of whether the video data is SDR or HDR. In other words, the data playback device does not need to refer to the first transfer function information. This simplifies the processing of the data playback device.

[0110] Figure 14 is a flowchart of the operation of the data playback device 120 according to this embodiment. The data playback device 120 plays HDR video data that does not support HDR video playback but is compatible with playback on a first device that supports SDR video playback. Here, this video data is, for example, video data generated by the data generation device 110.

[0111] First, the demultiplexing unit 121 generates a video elementary stream by demultiplexing the video data (transport stream). At this time, the demultiplexing unit 121 obtains hybrid information (e.g., hybrid OETF flag) from the hybrid descriptor of the video data (S121). The demultiplexing unit 121 may also obtain at least one of dynamic range increase information and picture maximum average level information from the hybrid descriptor.

[0112] Next, the data playback device 120 prepares to switch between SDR playback and HDR playback based on the acquired hybrid information (S122).

[0113] Next, the decoding unit 122 generates a video signal (code value) by decoding the video elementary stream. If the preceding hybrid OETF flag indicates that hybrid OETF is being used, the decoding unit 122 obtains the second transfer function information contained in the hybrid SEI within the video elementary stream (S123). The decoding unit 122 may also obtain at least one of the dynamic range increase information and the picture maximum average level information from the hybrid SEI.

[0114] The playback unit 123 plays back the video signal contained in the video data by referring to the second OETF identified by the acquired second transfer function information (S124). The playback unit 123 also switches between SDR playback and HDR playback at the timing when the video sequence changes. Specifically, the playback unit 123 plays back the data from EOS onward in the modified format. Furthermore, if dynamic range increase information or picture maximum average level information is acquired, playback is performed using this information.

[0115] If the preceding hybrid OETF flag indicates that a hybrid OETF is not being used, in step S123, the decoding unit 122 acquires the first transfer function information contained in the VUI within the video elementary stream. In step S124, the playback unit 123 plays back the video signal contained in the video data by referring to the second OETF identified by the acquired first transfer function information. As described above, if the second transfer function information selectively indicates either the first OETF or the second OETF, the decoding unit 122 may always acquire the second transfer function information, and the playback unit 123 may refer to the first OETF or the second OETF indicated by the second transfer function information.

[0116] As described above, in this embodiment, in addition to the first transfer function information stored in the VUI, the second transfer function information is stored in the SEI message. This makes it possible to realize HDR coding using hybrid OETF such as BBC Hybrid Gamma OETF.

[0117] Specifically, signaling to the multiplexing layer using descriptors can indicate whether the content is HDR encoded using hybrid OETF.

[0118] Furthermore, the combination of the new SEI message and new descriptor enables smooth switching between HDR and SDR by the data playback device.

[0119] Furthermore, the first OETF may be a function defined by (Equation 2) below.

[0120]

number

[0121] Here, L is the brightness of the image and is normalized to 0 ≤ L ≤ 1 with the reference white level. V is a numerical value corresponding to an electrical signal. Also, α, β, γ, δ, and ρ are constants, and specific numerical examples are α=4.5, β=0.018, γ=1.099, δ=0.45, and ρ=0.099.

[0122] In other words, as shown in (Equation 2), the first OETF may be an OETF that is defined by a linear term of the luminance of the video data in a first range of luminance of the video data, and by a power term of the luminance of the video data in a second range greater than the first range.

[0123] Furthermore, the first OETF may also be a function expressed by (Equation 3) below.

[0124]

number

[0125] Here, L is the brightness of the image, normalized between 0 and L ≤ 1. E is a value corresponding to the voltage normalized by the reference white level, and is proportional to the absolute light intensity detected in the reference camera color channel RGB. As a result, E' becomes a nonlinear signal. Also, α, β, γ, and δ are constants, and specific numerical examples are α=4.5, β=0.018 (for 10-bit system) or 0.0181 (for 12-bit system), γ=1.099 (for 10-bit system) or 1.0993 (for 12-bit system), δ=0.45, and ρ=0.099.

[0126] Furthermore, the second OETF may be a function defined by (Equation 4) below, in which the transformation function is defined by a logarithmic term at high brightness levels.

[0127]

number

[0128] Here, L is the brightness of the image, normalized to the reference white level. However, L can be greater than 1. That is, this conversion function also supports brightness levels greater than the reference white. V is a numerical value corresponding to an electrical signal. μ is the breakpoint between the gamma curve and the logarithmic curve, which determines the maximum value of L when V is less than or equal to 1. Also, α, β, γ, δ, and ρ are constants, and specific numerical examples are α=4.5, β=0.018, γ=1.099, δ=0.45, and ρ=0.099.

[0129] In other words, as shown in (Equation 4), the second OETF may be an OETF that is defined by a linear term of the luminance of the video data in the third range of luminance of the video data, by a power term of the luminance of the video data in the fourth range which is greater than the third range, and by a logarithmic term of the luminance of the video data in the fifth range which is greater than the fourth range.

[0130] Furthermore, the first OETF may be a function defined by (Equation 5) below.

[0131]

number

[0132] Here, L is the brightness of the image, normalized to 0 ≤ L ≤ 1 using the reference white level. V is a numerical value corresponding to an electrical signal. α is a constant, and a specific example of its numerical value is α = 0.5.

[0133] In other words, as shown in (Equation 5), the first OETF may be an OETF defined by a power of the luminance term of the video data.

[0134] Furthermore, the second OETF may be a function defined by (Equation 6) below. In this OETF, the transformation function is defined by a logarithmic term at high brightness levels.

[0135]

number

[0136] Furthermore, α is a constant, and a specific numerical example is α = 0.5.

[0137] In other words, as shown in (Equation 6), the second OETF may be an OETF that is defined by a power term of the luminance of the video data in the sixth range of luminance of the video data, and by a logarithmic term of the luminance of the video data in the seventh range which is greater than the sixth range.

[0138] Although a data generation device (data generation method) and a data reproduction device (data reproduction method) according to one or more embodiments have been described above based on embodiments, the present invention is not limited to these embodiments. Without departing from the spirit of the present invention, various modifications that a person skilled in the art can conceive of may be applied to these embodiments, and forms constructed by combining components from different embodiments may also be included within the scope of one or more embodiments.

[0139] For example, in each of the above embodiments, each component may be implemented by being composed of dedicated hardware such as a circuit, or by executing a software program suitable for each component. Each component may also be implemented 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. [Industrial applicability]

[0140] This invention can be applied to data transmission devices or data playback devices such as BD players. [Explanation of Symbols]

[0141] 110 Data Generation Device 111 Video signal generation unit 112 Encoding section 113 Multiplexer 120 Data Playback Device 121 Demultiplexer 122 Decoding section 123 Playback Department

Claims

1. A data generation device that generates a video elemental stream with a second luminance dynamic range wider than the first luminance dynamic range, The system includes an encoding unit that generates the video element stream by performing encoding in accordance with a video encoding standard, The aforementioned video elementary stream is First transfer function information for identifying the first OETF (Opto-Electrical Transfer Function) referenced by the first device when the first device decodes the video elementary stream, This includes second transfer function information for identifying a second OETF referenced by the second device when the second device decodes the video elemental stream. Data generation device.

2. A data output device for transmitting the video elementary stream described in claim 1 via broadcast waves or a network.

3. An encoding device that generates a video element stream with a second luminance dynamic range wider than a first luminance dynamic range, The system includes an encoding unit that generates the video element stream by performing encoding in accordance with a video encoding standard, The encoding unit stores in the video element stream first transfer function information for identifying the first OETF (Opto-Electrical Transfer Function) that the first device references when decoding the video element stream. The encoding unit stores in the video element stream second transfer function information for identifying the second OETF that the second device references when the second device decodes the video element stream. Encoding device.

4. A decoding device for decoding a video element stream with a second luminance dynamic range wider than a first luminance dynamic range, The system includes a decoding unit that decodes the video elementary stream by performing decoding in accordance with a video encoding standard, The aforementioned video elementary stream is First transfer function information for identifying the first OETF (Opto-Electrical Transfer Function) referenced by the first device when the first device decodes the video elementary stream, This includes second transfer function information for identifying a second OETF referenced by the second device when the second device decodes the video elemental stream. Decoding device.

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