JP7846971B2 - Transmitter and receiver - Google Patents

Description

This invention relates to a transmitting device and a receiving device for a video transmission system.

In recent years, supplementary services in broadcasting have gained popularity, such as audio commentary using audio multiplexing technology and behind-the-scenes talk services as additional content. These audio supplementary services provide separate audio content using a different audio channel from the main service. This can help viewers with impaired vision understand the video and contribute to attracting new viewers by providing new content for programs.

On the other hand, broadcast video transmission generally uses a mode that transmits only one video signal per channel. Furthermore, multi-layer coding (also called hierarchical coding or scalable coding) is a coding technique used in video transmission. Multi-layer coding is a technique that transmits multiple layers of coded streams. While high-quality video can be reproduced by using all coded streams for decoding, lower-quality video can be reproduced even if only some of the coded streams (specifically, the base layer) are decoded.

Japanese Patent Publication No. 2017-135522

While technologies exist for simultaneously transmitting multiple programs, such as multi-programming technology, there is a problem in that supplementary services, such as the aforementioned secondary audio service, have not been implemented for video. Currently, broadcast services offer subtitle services as an add-on service, but these are implemented as data broadcasting, transmitting text information as data. This limits the handling of text information and simple icons, and explanatory broadcasts using subtitles, diagrams, and other visuals have not been realized. Furthermore, multilingual subtitle broadcasting has not been implemented because it would increase the amount of font data that receivers would need to support.

On the other hand, while the aforementioned multi-layer encoding technology can efficiently realize video services with different resolutions and qualities, and is used in video distribution services where different line qualities such as wireless and wired transmissions coexist, there is a problem in that its utilization is not being fully realized.

Therefore, the present invention aims to provide a transmitting device and a receiving device that realize a sub-video service in a video transmission system by utilizing multi-layer coding technology.

The first embodiment of the transmitting device is a transmitting device for a video transmission system, comprising: a superposition means for superimposing a sub-video signal of a sub-video service onto a video signal of a main video service; an encoding means for encoding the video signal as a base layer and encoding the sub-video signal output by the superposition means as an enhancement layer using multi-layer encoding technology; and a transmitting means for transmitting the encoded streams of the base layer and the enhancement layer output by the encoding means.

The second embodiment of the receiving device is a receiving device for a video transmission system using multilayer coding technology, comprising: receiving means for receiving the coding streams of the base layer and the enhancement layer, respectively; and decoding means for decoding the video signal of the main video service from the coding stream of the base layer when video playback of the sub-video service is not selected, wherein, when video playback of the sub-video service is selected, the decoding means decodes a video signal with sub-video superimposed on the main video signal from the coding streams of the base layer and the enhancement layer, respectively.

According to the present invention, a transmitting device and a receiving device can be provided that realize a sub-video service in a video transmission system by utilizing multi-layer coding technology.

This diagram shows the configuration of the transmitting device according to the embodiment. This figure shows an example of the operation of the subtitle overlay unit according to the embodiment. This figure shows an example of the configuration of the encoding unit according to the embodiment. This is a diagram showing the configuration of the receiving device according to the embodiment. This diagram shows the configuration of the transmitting device in the modified example. This figure shows an example of the operation of the overlay section for the explanatory video related to the changes.

The transmitting and receiving devices for the video transmission system according to the embodiment will be described with reference to the drawings. In the following drawings, identical or similar parts are denoted by the same or similar reference numerals.

(Transmitter)
First, the transmitting device according to this embodiment will be described. In this embodiment, an example of realizing a multilingual subtitle service as a secondary video service in a video transmission system will be described. Figure 1 is a diagram showing the configuration of the transmitting device 10 according to this embodiment.

As shown in Figure 1, the transmitting device 10 has k subtitle overlay units 11 (11#1 to 11#k), k encoding units 12 (12#1 to 12#k), and a transmitting unit 13. Here, k is an integer of 2 or more. In this embodiment, the subtitle overlay units 11 (11#1 to 11#k) correspond to overlay means, the encoding units 12 (12#1 to 12#k) correspond to encoding means, and the transmitting unit 13 corresponds to transmitting means.

The subtitle overlay units 11#1 to 11#k overlay the subtitle signals of the subtitle service related to the main video service onto the video signal of the main video service, and output a video signal with subtitles. The subtitle service is an example of a secondary video service, and the subtitle signal is an example of a secondary video signal.

In this embodiment, the subtitle overlay units 11#1 to 11#k overlay k distinct subtitle signals onto the video signal of the main video service, and output k subtitled video signals. Here, the k subtitle signals are video signals from subtitle services in k different languages.

Specifically, the subtitle overlay unit 11#1 overlays the subtitle signal #1 of the first language onto the video signal of the main video service and outputs the subtitled video signal #1 to the encoding unit 12#1. Similarly, the subtitle overlay unit 11#2 overlays the subtitle signal #2 of the second language onto the video signal of the main video service and outputs the subtitled video signal #2 to the encoding unit 12#2. The subtitle overlay unit 11#k overlays the subtitle signal #k of the kth language onto the video signal of the main video service and outputs the subtitled video signal #k to the encoding unit 12#k.

Figure 2 shows an example of the operation of the subtitle overlay unit 11 according to this embodiment. Here, an example where k = 3 is described. As shown in Figure 2(b), the subtitle overlay unit 11#1 overlays and outputs Japanese subtitle #1 onto the main video service video (main video) shown in Figure 2(a). As shown in Figure 2(c), the subtitle overlay unit 11#2 overlays and outputs English subtitle #2 onto the main video shown in Figure 2(a). As shown in Figure 2(d), the subtitle overlay unit 11#3 overlays and outputs French subtitle #3 onto the main video shown in Figure 2(a).

Returning to Figure 1, the encoding unit 12 (12#1 to 12#k) uses multi-layer encoding technology to encode the video signal of the main video service as the base layer, and also encodes the subtitled video signals #1 to #k output by the subtitle overlay unit 11 (11#1 to 11#k) as the enhancement layer.

Specifically, the encoding unit 12#1 encodes the video signal of the main video service as the base layer, and also encodes the subtitled video signal #1 output by the subtitle overlay unit 11#1 as enhancement layer #1, and outputs the encoded stream of the base layer and the encoded stream of enhancement layer #1 to the transmission unit 13. The encoding unit 12#2 encodes the subtitled video signal #2 output by the subtitle overlay unit 11#2 as enhancement layer #2, and outputs the encoded stream of enhancement layer #2 to the transmission unit 13. The encoding unit 12#k encodes the subtitled video signal #k output by the subtitle overlay unit 11#k as enhancement layer #k, and outputs the encoded stream of enhancement layer #k to the transmission unit 13. Encoding units 12#2 to 12#k share encoding control information related to the encoding of the base layer of encoding unit 12#1, enabling them to generate the same base layer as encoding unit 12#1. However, since the base layer stream is identical to that of encoding unit 12#1, it is not output to the transmission unit 13.

For multi-layer encoding, the Scaleable Main 10 profile in the HEVC (High Efficiency Video Coding) encoding scheme can be used. HEVC is the encoding scheme currently used in 4K/8K satellite broadcasting. In 4K/8K satellite broadcasting, a set of encoding tools called the Main 10 profile is used to efficiently compress and transmit video. The Scaleable Main 10 profile is an encoding mechanism that allows for the transmission of video equivalent to the Main 10 profile as the base layer, while adding an enhancement layer and superimposing it on the base layer video.

Alternatively, the Multilayer Main 10 profile in the latest encoding method called VVC (Versatile Video Coding) may be used for multilayer encoding. Similar to the Scaleable Main 10 profile described above, the Multilayer Main 10 profile enables the transmission of multiple layers relative to the Main 10 profile, allowing for the transmission of video across multiple layers.

In encoding technologies with such multi-layer functionality, the enhancement layer, which is a higher layer of video, can be superimposed on the base layer, which is the main video service. While HEVC's Scaleable Main 10 profile and VVC's Multilayer Main 10 profile were given as examples of multi-layer encoding, it is not limited to HEVC or VVC; other encoding methods may also be used.

Figure 3 shows an example configuration of the encoding unit 12#1 according to this embodiment. As shown in Figure 3, the encoding unit 12#1 includes a base layer encoding unit 121 that performs base layer encoding and an enhancement layer encoding unit 122 that performs encoding corresponding to the layer above the base layer.

The base layer encoding unit 121 includes an encoding processing unit 121a, an entropy encoding unit 121b, a decoding processing unit 121c, and a DPB (Decoded Picture Buffer) 121d.

The encoding processing unit 121a performs prediction processing on the video frame (original image) of the video signal of the main video service by referring to the DPB 121d. It then transforms and quantizes the prediction residual, which is the difference between the predicted image and the original image, and outputs the quantized transformation coefficients. Furthermore, the encoding processing unit 121a outputs information related to the prediction processing (e.g., motion vector information) as encoding control information to the enhancement layer encoding unit 122.

The entropy encoding unit 121b performs entropy encoding on the encoded information, such as quantization conversion coefficients and motion vector information, output by the encoding processing unit 121a, and outputs the encoded stream (bitstream) of the base layer.

The decoding processing unit 121c inversely quantizes and inversely transforms the quantization conversion coefficients output by the encoding processing unit 121a to restore the prediction residuals. Using encoding control information such as motion vector information, it synthesizes the restored prediction image and prediction residuals to restore (decode) the original image, and outputs the decoded image to the DPB 121d and the encoding processing unit 121a.

The DPB121d stores the decoded image output by the decoding processing unit 121c. The decoded image output by the DPB121d is used as a prediction reference image in the prediction processing of the encoding processing unit 121a. The DPB121d also outputs the decoded image to the enhancement layer encoding unit 122 as one of the prediction reference signals used by the encoding processing unit 122a.

The enhancement layer coding unit 122, like the base layer coding unit 121, includes an coding processing unit 122a, an entropy coding unit 122b, a decoding processing unit 122c, and a DPB 122d.

The DPB122d stores the decoded image output by the DPB121d of the base layer encoding unit 121 and the decoded image output by the decoding processing unit 122c as the predicted reference image of the enhancement layer.

The encoding processing unit 122a performs prediction processing on the video frame (original image) of the subtitled video signal #1 by referring to the DPB 122d. It then transforms and quantizes the prediction residual, which is the difference between the predicted image and the original image, and outputs the quantized transformation coefficients. Here, the encoding processing unit 122a uses the encoding control information (e.g., motion vector information) output by the base layer encoding unit 121 for the prediction processing.

The entropy coding unit 122b performs entropy coding on the coded information, such as quantization conversion coefficients and motion vector information, output by the coding processing unit 122a, and outputs the coded stream (bitstream) of enhancement layer #1.

The decoding processing unit 122c inversely quantizes and inversely transforms the quantization conversion coefficients output by the encoding processing unit 122a to reconstruct the prediction residuals. Using encoding control information such as motion vector information, it synthesizes the reconstructed prediction image and prediction residuals to reconstruct (decode) the original image, and outputs the decoded image to the DPB 122d.

Thus, the enhancement layer encoding unit 122 also uses the decoded image from the base layer for prediction processing and encodes the difference (prediction residual) between this decoded image and the subtitled video signal #1. Therefore, the enhancement layer encodes the difference signal between the decoded video and the original image, generally encoding a signal that compensates for encoding degradation. In this invention, by deliberately using a signal with subtitles different from those of the base layer video in the enhancement layer, the subtitle portion corresponds to the difference, and thus the subtitle portion is encoded solely by the enhancement layer.

Furthermore, multi-layer encoding, as in this embodiment, where the base layer and enhancement layer encode video at the same resolution, is generally called SNR (Signal to Noise Ratio) scalable encoding because it encodes information in the enhancement layer to compensate for encoding degradation in the base layer, resulting in different encoding qualities in each layer, thus transmitting signals of different qualities. However, in this embodiment, the enhancement layer encodes a subtitled video signal different from the video signal encoded by the base layer, which is different from general SNR scalable encoding. Additionally, it can improve video quality in areas other than the subtitles.

Here, an example configuration of the encoding unit 12#1 has been described. However, since encoding units 12#2 to 12#k receive encoding control information (i.e., information indicating how the base layer was encoded) and the decoded image from the base layer encoding unit 121 of encoding unit 12#1, they may have only the enhancement layer encoding unit 122 and not the base layer encoding unit 121. Furthermore, encoding unit 12#1 may incorporate not only the enhancement layer encoding unit 122 for enhancement layer #1, but also the enhancement layer encoding units 122 for enhancement layers #2 to #k.

Returning to Figure 1, the transmitting unit 13 transmits the encoded streams of the base layer and the k enhancement layers output by the encoding unit 12 (12#1 to 12#k) via the transmission path. Regarding the transmission path, for example, the encoded streams of the base layer and all enhancement layers may be transmitted via the same path using broadcast waves or a network, or they may be transmitted via different paths, such as transmitting some of the encoded streams via broadcast waves while transmitting the remaining encoded streams via a network.

The transmission unit 13 has a multiplexing unit 13a (multiplexing means) that multiplexes the base layer encoded stream and the k enhancement layer encoded streams. The multiplexing unit 13a assigns a service identification identifier to each of the base layer encoded stream and the k enhancement layer encoded streams, and transmits the multiple encoded streams synchronously using a synchronization function such as MPEG (Moving Picture Experts Group)-2/4 Transport Stream (TS) or MPEG Media Transport (MMT). While MPEG-2/4 TS and MMT are given as examples, the system is not limited to these and other synchronization functions may be used.

(Receiving device)
Next, the receiving device according to this embodiment will be described. Figure 4 is a diagram showing the configuration of the receiving device 20 according to this embodiment.

As shown in Figure 4, the receiving device 20 includes a receiving unit 21, a selection unit 22, an extraction unit 23, and a decoding unit 24. In this embodiment, the receiving unit 21 corresponds to the receiving means, the selection unit 22 corresponds to the selection means, the extraction unit 23 corresponds to the extraction means, and the decoding unit 24 corresponds to the decoding means.

The receiving unit 21 receives the base layer encoded stream and the encoded streams of each of the k enhancement layers from the transmitting device 10 via the transmission path, and outputs each received encoded stream to the extraction unit 23.

The selection unit 22 selects (tunes) the encoded stream to be played based on the viewer's input, and outputs an identifier indicating the selected encoded stream as control information to the extraction unit 23.

The extraction unit 23 extracts the desired encoded stream from the base layer's encoded stream and the encoded streams of each of the k enhancement layers, based on the identifier indicated by the control information output by the selection unit 22, and outputs the extracted encoded stream to the decoding unit 24.

If video playback of the subtitle service is not selected by the selection unit 22, the extraction unit 23 extracts only the encoded stream of the base layer and outputs only the encoded stream of the base layer to the decoding unit 24. On the other hand, if video playback of the subtitle service in any language is selected by the selection unit 22, the extraction unit 23 extracts the encoded stream of the base layer and the encoded stream of the enhancement layer corresponding to the selected subtitle service, and outputs the encoded stream of the base layer and the encoded stream of the selected enhancement layer to the decoding unit 24.

If the video playback of the subtitle service is not selected by the selection unit 22, the decoding unit 24 decodes (plays) the video signal of the main video service from the base layer encoded stream output by the extraction unit 23 and outputs the decoded video signal. On the other hand, if the video playback of the subtitle service in any language is selected by the selection unit 22, the decoding unit 24 decodes (plays) the subtitled video signal, in which the subtitle signal is superimposed on the video signal, from the base layer encoded stream output by the extraction unit 23 and the encoded stream of the selected enhancement layer, and outputs the decoded subtitled video signal.

(Effects/Mechanisms)
According to the video transmission system of this embodiment, a multi-layer coding profile that transmits video across multiple layers can be used to realize a multilingual subtitle service as an additional video service. This makes it possible to provide sub-services for video that are similar to those provided for audio, and in particular, it can realize advanced services for information-disadvantaged individuals who are visually or hearing impaired, or for those who have difficulty accessing information because Japanese is not their native language.

In conventional broadcasting, subtitle information is transmitted separately from the video as data. The receiver generates the subtitles internally using this data and overlays them onto the video. Therefore, different receivers may have different fonts and character placement, potentially making the base layer video (the basis for this service) difficult to view. Furthermore, the font set to be used for broadcasting must be predetermined, making it impossible to display custom-designed characters or images tailored to the video.

In contrast, the video transmission system according to this embodiment creates a secondary video with text and graphics positioned and designed to reflect the production intent of the main video, and encodes and transmits it as an enhancement layer. This avoids variations in appearance across different receivers and enables subtitle broadcasting that accurately manages the production intent. In this process, the base layer is used for prediction, and the video corresponding to the text and graphics is transmitted efficiently, allowing for the playback of subtitles and graphics without an extreme increase in the amount of information.

Furthermore, in multi-layer coding, the video from the base layer is used for signal prediction. By coding the video without subtitles as the base layer and the video with subtitles as the enhancement layer, the video including subtitles can be played back by receiving both the base layer and the enhancement layer. Here, within the limits of the transmission capacity, it is also possible to improve video quality by including a signal in the enhancement layer to compensate for coding degradation.

Conversely, when transmission capacity is low, it is possible to transmit only the encoding information (predictive difference information) of the smallest encoding unit including subtitles—specifically, the Coding Unit (CU) in HEVC and VVC—and limit other areas to only the minimum information specified by the encoding method, thereby effectively transmitting only the information within the subtitle data area.

(Example of change)
Regarding the modified embodiments, the differences from the embodiments described above will be explained primarily.

In the above embodiment, an example was described in which the secondary video service is a multilingual subtitle service. In contrast, the secondary video service in this modified example is an explanatory video service related to the primary video service. That is, in this modified example, an explanatory channel is implemented as an additional video service.

First, the transmission device 10 according to this modified example will be described. Figure 5 shows the configuration of the transmission device 10 according to this modified example. As shown in Figure 5, the transmission device 10 according to this modified example has an explanatory video overlay unit 11A, an encoding unit 12, and a transmission unit 13. In this modified example, the explanatory video overlay unit 11A corresponds to the overlay means, the encoding unit 12 corresponds to the encoding means, and the transmission unit 13 corresponds to the transmission means.

The explanatory video overlay unit 11A overlays the explanatory video signal of the explanatory video service related to the main video service onto the video signal of the main video service and outputs a video signal with explanatory video. Figure 6 shows an example of the operation of the explanatory video overlay unit 11A according to this modified example. In Figure 6, an example is shown where the explanatory video service is a sign language video service. As shown in Figure 6(b), the explanatory video overlay unit 11A overlays the sign language video as explanatory video onto the video of the main video service (main video) shown in Figure 6(a) and outputs it.

The encoding unit 12 uses multi-layer encoding technology to encode the video signal of the main video service as the base layer, and also encodes the video signal with explanatory video output by the explanatory video superimposition unit 11A as the enhancement layer. It then outputs the encoded stream of the base layer and the encoded stream of the enhancement layer to the transmission unit 13. The configuration of the encoding unit 12 is the same as that of the encoding unit 12#1 shown in Figure 3.

In multi-layer coding technology, the video from the enhancement layer, a higher layer, can be superimposed on the base layer, which is the main video service. In this process, the base layer's video can be used for prediction, allowing for higher quality with less information. However, it is also possible to overwrite the video using, for example, intra-mode, without using the base layer's video for prediction. Alternatively, the coding mode for the area where the video for commentary is superimposed could be set to an inter-prediction mode that does not refer to the base layer or areas outside that region, and a service could be implemented where only that area is overwritten with the enhancement layer's video.

The transmission unit 13 transmits the base layer encoded stream and the enhancement layer encoded stream output by the encoding unit 12 via the transmission path. The transmission unit 13 includes a multiplexing unit 13a that multiplexes the base layer encoded stream and the enhancement layer encoded stream. The multiplexing unit 13a assigns a service identification identifier to each of the base layer encoded stream and the enhancement layer encoded stream, and transmits the multiple encoded streams synchronously using a synchronization function such as MPEG-2/4 TS or MMT.

Next, the receiving device 20 according to this modified example will be described. The configuration of the receiving device 20 according to this modified example is the same as the configuration of the receiving device 20 according to the above embodiment (see Figure 4).

As shown in Figure 4, the receiving unit 21 receives the base layer encoded stream and the enhancement layer encoded stream from the transmitting device 10 via the transmission path, and outputs each received encoded stream to the extraction unit 23. The receiving unit 21 may also obtain an identifier for service identification and interpret the service of each encoded stream.

The selection unit 22 selects (tunes) the encoded stream to be played based on the viewer's input, and outputs an identifier indicating the selected encoded stream as control information to the extraction unit 23.

If the video playback of the explanatory video service is not selected by the selection unit 22, the extraction unit 23 extracts only the encoded stream of the base layer and outputs only the encoded stream of the base layer to the decoding unit 24. On the other hand, if the video playback of the explanatory video service is selected by the selection unit 22, the extraction unit 23 extracts the encoded stream of the base layer and the encoded stream of the enhancement layer corresponding to the explanatory video service, and outputs the encoded stream of the base layer and the encoded stream of the enhancement layer to the decoding unit 24. The extraction unit 23 may also have multiplexing means for separating predetermined encoded streams based on the service identification identifier acquired and interpreted by the receiving unit 21 and the identifier output by the selection unit 22.

If the video playback of the commentary video service is not selected by the selection unit 22, the decoding unit 24 decodes (plays back) the video signal of the main video service from the base layer encoded stream output by the extraction unit 23 and outputs the decoded video signal. On the other hand, if the video playback of the commentary video service is selected by the selection unit 22, the decoding unit 24 decodes (plays back) the video signal with the superimposed commentary video signal from the base layer encoded stream and the enhancement layer encoded stream output by the extraction unit 23, and outputs the decoded video signal with the commentary video.

According to this modified video transmission system, a multi-layer encoding profile that transmits video across multiple layers can be used to realize an additional video service: a commentary video service. This allows for the implementation of supplementary services for video, similar to those provided for audio, enabling advanced services, particularly for information-disadvantaged individuals with hearing impairments. It also enables new services, such as overlaying child-friendly commentary onto adult-oriented programs.

(Other embodiments)
In the above embodiment, the secondary video service is a multilingual subtitle service, and in the modified example, an example was described in which the secondary video service is an explanatory video service. However, it is not limited to multilingual subtitle services or explanatory video services, and it is possible to implement other secondary video services as well.

In the above embodiment, an example was described in which the extraction unit 23 provided in the receiving device 20 extracts the encoded stream of the base layer and the encoded stream of one enhancement layer and outputs them to the decoding unit 24 when the playback of the sub-video service is selected by the selection unit 22. However, the extraction unit 23 may output the encoded streams of multiple enhancement layers to the decoding unit 24.

A program may be provided that causes a computer to execute each process performed by the transmitting device 10. Similarly, a program may be provided that causes a computer to execute each process performed by the receiving device 20. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but for example, it may be a recording medium such as a CD-ROM or DVD-ROM.

The circuits that perform each process carried out by the transmitting device 10 may be integrated, and the transmitting device 10 may be configured as a semiconductor integrated circuit (chipset, SoC). The circuits that perform each process carried out by the receiving device 20 may be integrated, and the receiving device 20 may be configured as a semiconductor integrated circuit (chipset, SoC).

The embodiments have been described in detail above with reference to the drawings, but the specific configuration is not limited to those described above, and various design changes can be made without departing from the gist of the concept.

10: Transmitting device 11: Subtitle overlay unit 11A: Commentary video overlay unit 12: Encoding unit 13: Transmitting unit 13a: Multiplexing unit 20: Receiving device 21: Receiving unit 22: Selection unit 23: Extraction unit 24: Decoding unit 121: Base layer encoding unit 121a: Encoding processing unit 121b: Entropy encoding unit 121c: Decoding processing unit 121d: DPB
122: Enhancement layer coding unit 122a: Coding processing unit 122b: Entropy coding unit 122c: Decoding processing unit 122d: DPB

Claims (8)

A transmitting device for a video transmission system,
A superposition means for superimposing the secondary video signal of the secondary video service onto the video signal of the main video service,
An encoding means that encodes the video signal as a base layer using multi-layer encoding technology, and encodes the video signal with sub-image output by the superimposing means as an enhancement layer,
The system comprises a transmission means for transmitting the respective encoded streams of the base layer and the enhancement layer output by the encoding means ,
The transmission means is characterized by transmitting the enhanced layer's encoded stream after assigning a service identification identifier to it . The transmission device according to claim 1, characterized in that the sub-video service is a subtitle service or an explanatory video service related to the main video service. The superposition means superimposes k (k≧2) distinct sub-video signals onto the video signal.
The encoding means encodes each of the k video signals with sub-images output by the superimposing means as an enhancement layer.
The transmitting device according to claim 1 or 2, characterized in that the transmitting means transmits the encoded stream of the base layer and the encoded streams of k enhancement layers. The transmitting device according to claim 3, characterized in that the k sub-video signals are subtitle signals for a subtitle service in k different languages. A receiving device for a video transmission system using multilayer coding technology,
A receiving means for receiving the encoded streams of the base layer and the enhancement layer,
If video playback of the secondary video service is not selected, the system includes decoding means for decoding the video signal of the main video service from the encoded stream of the base layer,
When video playback of the sub-video service is selected, the decoding means decodes the sub-video signal superimposed on the video signal from the respective encoded streams of the base layer and the enhancement layer, thereby decoding the sub-video signal superimposed on the video signal .
An identifier for service identification is assigned to the encoded stream of the enhancement layer.
The receiving means is a receiving device characterized by obtaining the service identifier and interpreting the service of the enhancement layer . The receiving device according to claim 5 , characterized in that the secondary video service is a subtitle service or an explanatory video service relating to the main video service. When the receiving means receives the encoded stream of the base layer and the encoded streams of k enhancement layers, it includes an extraction means for extracting the encoded stream of one enhancement layer from among the k encoded streams of the enhancement layers.
The receiving device according to claim 5 or 6 , wherein the decoding means decodes the video signal with sub-video from the encoded stream of the base layer and the encoded stream of one enhancement layer output by the extraction means. The receiving device according to claim 7 , characterized in that the k sub-video signals are subtitle signals for a subtitle service in k languages.