JP6289900B2 - Broadcast signal transmitter - Google Patents

Description

The present embodiment relates to a broadcast signal transmitting apparatus.

  In the current television broadcasting based on the ARIB standard, the color gamut used for transmission of image signals is defined by BT.709. The color gamut defined by BT.709 is narrower than the natural color gamut. Therefore, with the current equipment, images with a natural color gamut are taken and transmitted after being reduced to the BT.709 color gamut.

  By the way, display of a wider color gamut than BT.709 has become possible with the progress of display panels of televisions. In this case, if the display is performed according to the BT.709 standard, a display panel having a wide color gamut is displayed in the BT.709 color gamut. Considering this point, among the signals reduced to the color gamut of BT.709, the signal close to the color gamut limit is estimated to be the signal that is outside the range of BT.709. It is also possible to estimate and restore (gamut expansion) a signal in a color gamut state wider than that of BT.709 before the signal of .709 is reduced to BT.709. Even an image signal transmitted by BT.709 can be displayed in a wider color gamut than BT.709 within the displayable range of the display panel, and a colorful image can be enjoyed.

  On the other hand, the next-generation broadcasting standard considering 4K broadcasting may adopt BT.2020, which can express a wider color gamut than BT.709. In the case of video content produced with equipment that can shoot in a wide color gamut, if the image signal is transmitted using the BT.2020 standard, the display panel can display an image with a color gamut wider than BT.709. A colorful image with a wide color gamut can be enjoyed without such a color gamut expansion process.

  Whether to transmit in the BT.709 color gamut or BT.2020 color gamut is specified in the ARIB standard B32, as indicated by the parameter transfer_characteristics in the VUI in the video stream. (Refer to “ARIB Standard STD-B32_2.8 Version 5.1.2.3 (2) VUI Middle”).

  However, there are many video contents that were shot in the past without the equipment that can shoot and record in a wide color gamut like BT.2020 and expressed in BT.709. Since the BT.2020 standard covers the color gamut of BT.709, it can be transmitted according to the BT.2020 standard. In this case, only a part of the color gamut that can be expressed by the BT.2020 standard is used for transmission. If this is the case, a vivid image can be enjoyed by displaying using the above-described color gamut expansion technology.

  However, the image signal transmitted by BT.2020 is transmitted using only a part of the color gamut that can be expressed by the standard of BT.2020, or used up to the color gamut exceeding the range of BT.709. Since there is no means for determining whether the signal is a color signal, it is not possible to determine whether or not to perform color gamut expansion processing. As a result, while high-definition broadcasts that are currently defined for transmission using BT.709 can perform color gamut expansion processing and enjoy colorful images, 4K broadcasts that use the BT.2020 standard In the case of, BT.709 content cannot be restored, and the color of the high-definition broadcast looks more vivid than the 4K broadcast, which should have adopted a wider color gamut standard. , And so on.

JP 2006-180477 A

  As described above, the image processing device in the conventional high-definition broadcasting system can perform color gamut expansion processing and enjoy colorful images in the high-definition broadcasting that is currently defined for transmission using BT.709. On the other hand, in the case of 4K broadcasting that adopts the BT.2020 standard, content shot with BT.709 cannot restore the color gamut, and uses a wider color gamut standard. There is a possibility that the color of the high-definition broadcast looks more vivid than the expected 4K broadcast.

  The present embodiment has been made in view of the above problems. Whether the image signal transmitted by BT.2020 is transmission using only a part of the color gamut that can be expressed by the BT.2020 standard, or BT.2020. It is possible to determine whether the signal is used up to a color gamut that exceeds the .709 range, whether or not to perform color gamut expansion processing, and whether or not a 4K broadcast that uses the BT.2020 standard has been adopted. In this case, an object of the present invention is to provide an image processing apparatus, an image processing method, and an image processing program that can restore the color gamut of content captured by BT.709.

In order to solve the above-described problem, the broadcast signal transmission apparatus according to the present embodiment is referred to for a video encoder that outputs a video stream including a compression-coded video signal, and for decoding and displaying the video signal. In a broadcast signal transmission device, comprising: an information processing device that generates a PMT; a multiplexing device that multiplexes the video stream and the PMT; and a modulation device that modulates the output of the multiplexing device and outputs a broadcast signal ,
The information processing apparatus includes:
Including the first PMT, the first data having the same color gamut as the color gamut designated by the transfer characteristics (transfer_characteristics) in the video stream, In the characteristic (transfer_characteristics), second data indicating the original color gamut of the video signal is described .

1 is a block diagram showing a schematic configuration of a digital television (hereinafter referred to as TV) broadcasting system to which an embodiment is applied. The block diagram which shows schematic structure of the broadcast equipment shown in FIG. The block diagram which shows schematic structure of the broadcast receiver shown in FIG. 2 is a color gamut chart showing the color gamut distribution of the display panel used in the broadcast receiving apparatus shown in FIG. 1 in comparison with the T.709 standard and the BT.2020 standard. The figure which shows the example which an imaging camera image | photographs in the gamut of BT.709 in the system shown in FIG. In the system shown in FIG. 1, as an example in which the imaging camera shoots in the color gamut of BT.709, when the display panel can display a wider color gamut than BT.709, the image processing circuit of the receiving device uses the color gamut of the display panel The figure which shows the example which performs color gamut expansion according to. In the system shown in FIG. 1, when the transmission line can transmit in a wide color gamut of BT.2020 and the camera can shoot in a wide color gamut of about BT.2020, The figure which shows the example which can reproduce correctly the color gamut which the range of the color gamut image | photographed with the camera. In the system shown in Fig. 1, when content with only the BT.709 color gamut taken with a high-definition camera is sent over the BT.2020 transmission line, it is displayed as it is and displayed correctly. Figure. In the system shown in FIG. 1, even if a signal having a transmission path in the BT.2020 color gamut and only using the BT.709 color gamut is passed there, the receiving device performs color gamut expansion processing to represent the display panel. The figure which shows the example displayed using all the color gamuts which can be performed. The figure which shows the data structure of PMT in the system shown in FIG. The figure which shows the structure of a video decoding control descriptor in the system shown in FIG. The figure which shows the structure of an original color gamut descriptor in the system shown in FIG. The figure which shows the example in the case of putting a flag in a video stream in the system shown in FIG.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a digital television (hereinafter referred to as TV) broadcasting system to which the embodiment is applied. This system includes a broadcast facility 100 having the configuration shown in FIG. 2 and a broadcast receiving apparatus 200 shown in FIG. 3, and both are connected via a transmission path. The transmission path is not limited to a wireless transmission path using broadcast waves, but also includes a wired transmission path using cables.

  A broadcast facility 100 shown in FIG. 2 includes an imaging camera 101. The video content shot by the imaging camera 101 is recorded in the video recording / playback apparatus 102. The video content recorded in the video recording / reproducing device 102 is subjected to editing processing such as addition of an audio signal by the editing device 103 and re-recorded in the device 102 as program content. The program content read from the video recording / reproducing apparatus 102 in accordance with the program organization is sent to the audio encoder 104, the video encoder 105, the caption information processing apparatus 106, the program information processing apparatus 107, and the descriptor insertion apparatus 108. The audio encoder 104 and the video encoder 105 respectively compress and encode audio data (sound) and video data (video) of the program content. The caption information processing device 106 generates caption information to be inserted in real time in the video of the program content. The program information processing apparatus 107 generates various information for introducing program content effects and program contents using SI / PSI (Service Information / Program Specific Information). The descriptor insertion device 108 sends a descriptor relating to the color gamut to the program information processing device 107 when the program content is reproduced, and is incorporated into the SI / PSI as one piece of program information. Audio data, video data, caption information, and program information (including descriptors) obtained by the audio encoder 104, the video encoder 105, the caption information processing device 106, and the program information processing device 107 are multiplexed by a multiplexing device 109 to be broadcast programs. It becomes data. The broadcast program data is modulated for transmission by the modulation device 110 and output to the transmission line as a broadcast signal. The output of the imaging camera 101 may be sent directly to the video encoder 105 when broadcasting in real time.

  A broadcast receiving apparatus 200 shown in FIG. 3 includes a tuner 201 that receives a broadcast signal transmitted from the broadcast facility 100 through a transmission path by a channel selection operation. The broadcast signal is demodulated by the demodulator 202 and then separated into audio data, video data, caption information, and SI / PSI multiplexed by the demultiplexer 203, and an audio decoder 204 and a video decoder 205, respectively. Are sent to the caption information decoder 206 and the SI / PSI processing device 207. The audio decoder 204, the video decoder 205, the caption information decoder 206, and the SI / PSI processing device 207 extract the audio signal, video signal, caption information, and SI / PSI information from the input data, respectively, and return them to their original formats. Is sent to the screen composition device 209 to compose the screen, and then subjected to appropriate image processing by the image processing device 210 and displayed on the display panel 211.

  Here, the SI / PSI information obtained by the SI / PSI processing device 207 is sent to the descriptor separation device 208. The descriptor separation device 208 separates the descriptor including the original color gamut information described from the input SI / PSI information, determines the color gamut information, and sends it to the image processing device 210. As a result, the image processing apparatus 210 adjusts the color gamut of the input image based on the color gamut information.

  In the system configured as described above, the color gamut control processing will be described with reference to FIGS.

  4 is a chromaticity diagram, where a is the color gamut of the display panel 211, b is the color gamut defined by BT.2020, and c is the color gamut defined by BT.709. Here, with the performance of the liquid crystal display panel at the initial stage of sales, a wide color gamut could not be displayed, and only a color gamut equivalent to BT.709 could be displayed. However, recently, it has become possible to display in a color gamut wider than that, for example, as indicated by a wider than c.

  In the above system, in the case of live broadcasting or the like, an image captured by the imaging camera 101 is compression encoded by the audio encoder 104 or the video encoder 105. In the case of a recorded program, the video signal and audio signal obtained by the imaging camera 101 are once recorded in the video recording / reproducing apparatus 102 together with the signal color gamut information (for example, BT.709 and BT.2020). Is edited and re-recorded by the editing device 103, is reproduced by the video recording / reproducing device 102 at the broadcast time, and is compressed and encoded by the audio encoder 104 and the video encoder 105.

  Here, the video encoder 105 encodes the color gamut indicated by the color signal of the video signal as BT.2020. A parameter called transfer_characteristics in the encoded stream indicates BT.2020. The color gamut standards include BT.601, BT.709, sRGB, BT.2020, AdobeRGB, and those defined by DCI (Digital Cinema Initiatives).

  When the color gamut of the imaging camera 101 is not BT.2020, a descriptor indicating the original color gamut is set by the descriptor insertion device 108, and is entered in the PMT (Program Map Table) of SI / PSI information. The data structure of the PMT is shown in FIG. In this data structure, a descriptor is described where a descriptor is described.

  That is, in the present embodiment, “on the transmission side, the image encoding / sending device is provided with multiplexing means for multiplexing the original color gamut information of the content in addition to the transmission color gamut information. The original color gamut information is separated from the received signal, and when the color gamut of the original content is narrower than the color gamut of the display panel, a color gamut expansion process is performed. ”

Here, “the original color gamut information of the content is multiplexed and transmitted. According to the original color gamut information, switching whether or not to execute the color gamut restoration process” is a new concept that has never been seen before. .
Therefore, the place where the original color gamut information is multiplexed is described in the video decode control descriptor of the PMT (specifically, “ARIB standard TR-B14 5.3 edition (second volume) Part 3 table operation See section 30.3.3.6 Video Decode Control Descriptor for details).

Here is 2bit reserved_future_use. This is currently used as '11'. This is defined as follows, for example.
11: The original content has the same color gamut as that defined in transfer_characteristics in the video stream.
10: Original content has the same color gamut as BT.709.
01: The original content has the same color gamut as that defined by DCI (Digital Cinema Initiative).

  The place where the original color gamut information is multiplexed may be described by adding a new descriptor to the PMT descriptor.

In addition, a parameter of “original content color gamut” is added as an encoding parameter in the video stream.
11: The original content has the same color gamut as that defined in transfer_characteristics in the video stream.
10: Original content has the same color gamut as BT.709.
01: The original content has the same color gamut as that defined by DCI (Digital Cinema Initiative).

In addition, there is a method for describing the original color gamut in the video decode control descriptor. FIG. 11 shows the data structure of the video decode control descriptor. In this data structure, reserved_future_use has 2 bits. Here, a 2-bit code defined as follows is described.
11: The original content has the same color gamut as that defined in transfer_characteristics in the video stream.
10: Original content has the same color gamut as BT.709.
01: The original content has the same color gamut as that defined by DCI (Digital Cinema Initiative).

  Here, the information related to the program is called SI / PSI in the MPEG or ARIB standard, and is multiplexed and transmitted by the multiplexer 109 together with the compression-coded video audio signal.

  FIGS. 5 to 9 show the flow of processing in the natural color gamut → camera color gamut → editing device color gamut → transmission channel color gamut → reception device color gamut → display panel color gamut (horizontal axis). FIG. 5 shows an example of how the color gamut (vertical axis: for example, a value along the vector of the color gamut in FIG. 3) changes.

(Example of FIG. 5)
In normal high-definition broadcasting, signals in a wide color gamut in nature are reduced to the BT.709 color gamut before transmission. This figure shows an example in which the camera 101 captures an image in the BT.709 color gamut. When the color gamut of the camera 101 is wide and the editing apparatus 103 narrows the color gamut, it becomes like a dotted line. If the display panel 211 can only display the color gamut of BT.709, the viewer will enjoy the color gamut of BT.709.

(Example of FIG. 6)
Signals with a wide natural color gamut are reduced to the BT.709 color gamut before transmission. This figure shows an example in which the camera 101 captures an image in the BT.709 color gamut. If the display panel 211 can display a color gamut wider than BT.709, the image processing device 210 of the receiving device 200 performs color gamut expansion in accordance with the color gamut of the display panel 211. Thus, the viewer can enjoy the color gamut of the display panel 211.

(Example of FIG. 7)
When the transmission path can transmit in a wide color gamut such as BT.2020, if the camera 101 can capture an image in a color gamut as wide as BT.2020, the signal is transmitted as it is, and the image processing apparatus 210 of the receiving apparatus 200 displays the display panel The color gamut is adjusted according to the color gamut 211, and if the color gamut of the display panel 211 is narrower than BT.2020, the color gamut is reduced and displayed. Thereby, in the color gamut range of the display panel 211, the color gamut photographed by the camera 101 can be correctly reproduced.

(Example of FIG. 8)
If you try to edit content shot with a camera in the high-definition era with the BT.2020 color gamut editing device 103 or transmit it over the BT.2020 color gamut transmission path, the device cannot handle a wide color gamut. But only a part of it is used. The receiving apparatus 200 must assume that a signal in the color gamut will be received as long as it is transmitted through the BT.2020 transmission path. For this reason, if a color gamut signal exceeding BT.709 is transmitted if the color gamut expansion processing is performed, there will be a problem that the signal overflows. Even so, it is displayed as it is. In the range of BT.709, correct color display is performed.

(Example of FIG. 9)
Even if the transmission path is in the BT.2020 color gamut and a signal that uses only the BT.709 color gamut is passed there, it is clearly notified to the receiving apparatus 200 with additional information such as SI / PSI. For example, the receiving apparatus 200 can perform display using all the color gamuts that can be expressed by the display panel 211 by performing the color gamut expansion processing in the image processing apparatus 210.

Another way to indicate the original color gamut is to add a single new descriptor and describe it there. FIG. 12 shows the structure of the original color gamut descriptor. A code having the following definition is described in 3 bits of original_color_gamut in FIG.
111: The original content has the same color gamut as that defined in transfer_characteristics in the video stream.
100: The original content has the same color gamut as adobeRGB.
011: The original content has the same color gamut as BT.601.
010: The original content has the same color gamut as BT.709.
001: The original content has the same color gamut as that defined by DCI (Digital Cinema Initiative).
Note that the location of the descriptor need not be limited to the PSI as in the PMT, but may be located in the SI such as EIT (program guide).

Further, when the color gamut of the camera 101 is not BT.2020, a bit parameter of original_vcolor_gamut may be added and transmitted separately from the parameter of transfer_characteristics in the encoded stream. For example, if it is 4bit,
1111: The original content has the same color gamut as that defined in transfer_characteristics in the video stream.
0100: The original content has the same color gamut as adobeRGB.
0011: The original content has the same color gamut as that of BT.601.
[0010] The original content has the same color gamut as that of BT.709.
0001: The original content has the same color gamut as that defined by DCI (Digital Cinema Initiative).

  Another way to indicate the original color gamut is to put a flag instead of a parameter in the encoded video stream. FIG. 13 shows a structure in which an original color gamut descriptor flag is added to transfer_characteristics.

  As described above, according to the configuration of the above embodiment, the original color gamut information of the content is separated from the received signal, and the color gamut expansion processing is performed when the color gamut of the original content is narrower than the color gamut of the display panel. carry out. As a result, even if content with a narrow color gamut is transmitted using a data format with a wide color gamut, a colorful image can be enjoyed by performing color gamut expansion processing on the receiving device side. Even if the content of a wide color gamut is transmitted using the data format of the wide color gamut, the correct color can be displayed without performing the color gamut expansion processing on the receiving device side. In this way, regardless of whether the color gamut of the content is BT.709 or BT.2020, it is possible to enjoy colorful display using the color gamut of the display panel effectively. In other words, when an image signal with a BT.709 color gamut or an image signal with a BT.2020 color gamut is transmitted in a wide color gamut format such as BT.2020, As the original color gamut is BT.709, color gamut restoration processing can be added to enjoy colorful images. In the case of BT.2020, the original color gamut can be displayed without performing color gamut restoration processing.

  Note that the present embodiment is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 100 ... Broadcast equipment, 101 ... Imaging camera, 102 ... Video recording / reproducing apparatus, 103 ... Editing apparatus, 104 ... Audio encoder, 105 ... Video encoder, 106 ... Subtitle information processing apparatus, 107 ... Program information processing apparatus, 108 ... Descriptor insertion 200, broadcast receiver, 201, tuner, 202, demodulator, 203 ... demultiplexer, 204 ... audio decoder, 205 ... video decoder, 206 ... subtitle information decoder, 207 ... SI / PSI processor, 208 ... descriptor Separation device, 209... Screen composition device, 210... Screen composition device, 211.

Claims (3)

A video encoder that outputs a video stream including a compression-encoded video signal;
An information processing device for generating a PMT referred to for decoding and displaying the video signal ;
A multiplexing device for multiplexing the video stream and the PMT;
A modulator that modulates the output of the multiplexer and outputs a broadcast signal;
In a broadcast signal transmission apparatus having
The information processing apparatus includes:
In the PMT, the first data having a constant meaning that the color gamut is the same as the color gamut specified by transfer characteristics (transfer_characteristics) in the video stream is described.
In the transfer characteristics (transfer_characteristics), second data indicating an original color gamut of the video signal is described.
A broadcast signal transmitter characterized by the above.   2. The broadcast signal transmitting apparatus according to claim 1, wherein the first data is data having the same content regardless of whether the second data is content indicating BT.709 or content indicating BT.2020. .   The broadcast signal transmitting apparatus according to claim 1, wherein the first data is data described in a video decode control descriptor that is transmitted by being included in a PMT.

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