JP6970143B2 - Distribution server, distribution method and program - Google Patents

Description

The present invention relates to a distribution server, a distribution method and a program.

In recent years, cameras capable of shooting 360-degree images in all directions of up, down, left, and right have been known, and the images taken by such cameras are panoramic images (or "panoramic moving images", "360-degree panoramic images", and ". It can be viewed as "VR (Virtual Reality) video", "VR video", etc.).

Further, for example, a video distribution server may stream a panoramic video to a terminal so that the panoramic video can be viewed on the terminal. However, in panoramic images, the amount of data required for distribution is often large. On the other hand, the range displayed on the terminal (hereinafter, also referred to as "field of view range") is delivered with normal image quality, and the range not displayed on the terminal is delivered with low image quality, which is required for the delivery of panoramic video. A technique for reducing the amount of data is known (see, for example, Patent Document 1).

Further, HLS (HTTP Live Streaming) is known as a protocol for a video distribution server to stream video to a terminal (client). In HLS, the video and audio taken by the camera are divided into multiple segment files in MPEG-2 TS (Transport Stream) format and stored in the video distribution server, and the location, playback time, and playback order of each segment file are stored. Generate a playlist file that records etc. and install it in the specified location. The client can acquire and play a desired segment file by acquiring the playlist file from the video distribution server.

Japanese Unexamined Patent Publication No. 2016-15705

Here, for example, in a concert, a sports competition, or the like, a plurality of cameras are installed at a plurality of points, and then a panoramic image is taken by each of the plurality of cameras. At this time, the user can generally switch the panoramic image taken by each of the plurality of cameras and display it on the terminal.

However, when the panoramic video is distributed by HLS, the playlist file corresponding to the camera after switching is acquired every time the panoramic video displayed on the terminal is switched (that is, each time the camera of the panoramic video displayed on the terminal is switched). There is a need to. Therefore, the reproduction of the panoramic image may be delayed.

The embodiment of the present invention has been made in view of the above points, and an object of the present invention is to prevent the occurrence of a reproduction delay due to switching of panoramic images taken by a plurality of cameras.

In order to achieve the above object, the distribution server according to the embodiment of the present invention is a distribution server that distributes a panoramic image taken by each of a plurality of cameras by HTTP Live Streaming to a client, and is a camera that identifies the camera. Upon receiving the first request including the identification information from the client, the transmission means for transmitting the playlist for reproducing the panoramic image taken by each of the plurality of cameras to the client, and the playlist are described. When transmitted to the client, the video distribution means includes a video distribution means for delivering the panoramic image taken by the camera identified by the camera identification information included in the first request to the client, and the video distribution means is the first. Upon receiving the second request including the camera identification information different from the camera identification information included in the first request, the client receives a panoramic image taken by the camera identified by the camera identification information included in the second request. It is characterized by delivering to.

It is possible to prevent the occurrence of playback delay due to switching of panoramic images taken by a plurality of cameras.

It is a figure for demonstrating an example of a panoramic image. It is a figure for demonstrating HLS. It is a figure for demonstrating an example of panoramic video distribution by HLS. It is a figure for demonstrating an example of panoramic image distribution at the time of switching a camera when there are a plurality of cameras. It is a figure which shows an example of the whole structure of the video distribution system which concerns on this embodiment. It is a figure (the 1) for demonstrating an example of the data structure of a video content. It is a figure (the 2) for demonstrating an example of the data structure of a video content. It is a sequence diagram which shows an example of the panoramic video distribution processing which concerns on this embodiment. It is a sequence diagram which shows an example of the communication processing which concerns on the playlist acquisition which concerns on this embodiment.

Hereinafter, an embodiment of the present invention (hereinafter, also referred to as “the present embodiment”) will be described. In the present embodiment, a video distribution system 1 that can prevent the occurrence of playback delay due to switching of panoramic video shot by a plurality of cameras will be described.

<Explanation of conventional technology>
First, the prior art and the like necessary for explaining the video distribution system 1 according to the present embodiment will be described.

(Panorama video)
As described above, the panoramic image is also referred to as "panoramic image", "360 degree panoramic image", "VR image", "VR image" and the like. The panoramic image is represented by an all-sky projection sphere, for example, as shown in FIG. In a panoramic image expressed by an all-sky projection sphere, the center of the all-sky projection sphere is set as the observation position, and the range taken by the pseudo camera at this observation position at a predetermined angle of view is the field of view (that is, the terminal). The range displayed in). Further, the panoramic image represented by the stereographic projection sphere can be represented by an equirectangular projection in which the vertical angle θ is 0 to π and the horizontal angle φ is 0 to 2π. At this time, for example, in the technique described in Patent Document 1 above, the partial area data including the visual field range of the panoramic image expressed by the equirectangular projection is "high resolution tile", and the entire panoramic image is compressed. Is delivered to the terminal as a "low resolution tile". In other words, the partial area including the visual field range is delivered to the terminal as a high-resolution tile with a high bit rate, and the entire panoramic image is delivered to the terminal as a low-resolution tile with a low bit rate.

As a result, the amount of data required for distribution of the panoramic image can be reduced, high-quality images can be viewed in the field of view, and the image is not interrupted even when the field of view is moved. It can be made viewable. Note that compression means reduction of the image size.

The video distribution system 1 according to the present embodiment also uses the technique described in the above-mentioned Patent Document 1 to distribute high-resolution tiles and low-resolution tiles to a terminal (client), thereby performing a panorama on the client. The video shall be played.

(HLS)
As described above, HLS is a protocol for a distribution server to stream a video to a client. For example, as shown in FIG. 2, the video signal output from the camera is encoded to create an encoded video, and the distribution server divides the encoded video into a plurality of segment files and generates a playlist file. Install (store) in the specified place. The segment file is a file in the ".ts" format (that is, the MPEG-2 transport stream format), and the playlist file is a file in the ".m3u8" format. FIG. 2 shows, as an example, a case where the encoded video is divided into “TS-00.ts” to “TS-NN.ts”.

At this time, in HLS, the client can acquire and play a desired segment file by acquiring the playlist file from the distribution server.

(Panorama video distribution by HLS)
When serving panoramic image by HLS, the distribution server for each predetermined time unit t _c, are stored low resolution tiles, the high resolution tiles each predetermined plurality of visual field range as a segment file. For example, as shown in FIG. 3, the low-resolution tile LT per _{t c,} high resolution tiles each _{t c} in the first field range HT1, high resolution tiles each _{t c} in the second field of view HT2, third high-resolution tiles HT3 like for each t _c is stored in the field of view. Here, in the example shown in FIG. 3, the first visual field range has the upper left coordinate of the visual field range (0, 0), and the second visual field range has the upper left coordinate of the visual field range (S _x , 0). ), The third visual field range is the range in which the upper left coordinate of the visual field range is (2S _x , 0). S _x is a predetermined horizontal angle (x-axis direction) shift amount.

_{The shift amount S y of} the vertical angle (y-axis direction) is also determined in advance, and the high-resolution tiles are generally set to p = 0, ..., P, q = 0, ..., Q, and are generally in the field of view. It is stored for each range in which the upper left coordinate is (p × S _x , q × S _y). Hereinafter, it is assumed that M = P × Q, and M high-resolution tiles for each field of view range are stored for each _{t c.}

Thus, in the panoramic image, the low-resolution tile for each t _c, and the high resolution tiles each t _c at a plurality of visual field range determined in advance is stored in the distribution server as a segment file.

Then, when playing back the panoramic video, the client can acquire the low-resolution tile and the high-resolution tile in the desired viewing range by acquiring the playlist from the distribution server. This allows the client to reproduce the panoramic image using the low resolution tile and the high resolution tile.

For example, if the viewing range of the client is _{moved by Sx} minutes to a horizontal angle every _{3t c} , the client will be given LT1-LT3 and HT1-1-1 to HT1- between _{the first 3t c} , as shown in FIG. 3 and 3 are delivered in order, LT4 to LT6 and HT2-4 to HT2-6 are delivered in order between _{the next 3t c} , and LT7 to LT9 and HT3-7 to HT3-9 are further delivered between the _{next 3t c.} And are delivered in order.

Although t _c is arbitrarily set, it may be set to about 0.5 [seconds], for example. Further, S _x and S _y are arbitrarily set according to the number of pixels of the panoramic image and the like. For example, when the panoramic image expressed by the equirectangular projection has 4000 × 2000 pixels, S _x = 100. , S _y = 50 and the like. The _{larger S x} and S _y , the smaller the number of high-resolution tiles held by the distribution server, but the smoothness when the field of view is switched is reduced (that is, the viewing quality of the user is reduced). On the other hand, as S _x and S _y are smaller, the number of high-resolution tiles held by the distribution server increases, but the smoothness when the field of view is switched is improved (that is, the viewing quality of the user is improved).

(Panorama video distribution by HLS when there are multiple cameras)
For example, in concerts, sports competitions, etc., a plurality of cameras are installed at a plurality of points, and then a panoramic image is taken by each of the plurality of cameras. At this time, it is general that the client can switchably display the panoramic images taken by each of the plurality of cameras.

At this time, when the panoramic video is distributed by HLS, the playlist and the segment file are stored in the distribution server for each camera. For example, as shown in FIG. 4, when there are N cameras of cameras 1 to N, the distribution server has a panoramic image taken by the camera 1 (that is, an encoding in which the image signal of the camera 1 is encoded). The camera 1 content indicating the image), the camera 2 content indicating the panoramic image taken by the camera 2, ..., The camera N content indicating the panoramic image taken by the camera N are stored. That is, the distribution server stores a playlist and a segment file for reproducing the panoramic image taken by this camera for each camera.

Therefore, as shown in FIG. 4, when playing back the panoramic image taken by the camera 1, the client acquires the playlist for the camera 1 content and the low resolution tile (LT: Low) of the camera 1 content. -resolution Tile) and high-resolution tile (HT: High-resolution Tile) of camera 1 content are acquired. Similarly, when the client reproduces the panoramic image shot by the camera N, the client acquires a playlist for the camera N content and sets the low resolution tile of the camera N content and the high resolution tile of the camera N content. get.

That is, the client needs to acquire the playlist file corresponding to this camera each time the camera of the panoramic image to be reproduced is switched. Therefore, the client needs to communicate with the distribution server each time the camera of the panoramic image to be reproduced is switched, which may cause a delay in the reproduction of the panoramic image.

Therefore, in the video distribution system 1 according to the present embodiment described below, the communication (communication for acquiring a playlist) when the camera of the panoramic image to be reproduced by the client is switched is eliminated, so that the panoramic image can be reproduced. Prevent delays from occurring.

<Overall configuration of video distribution system 1>
The overall configuration of the video distribution system 1 according to the present embodiment will be described with reference to FIG. FIG. 5 is a diagram showing an example of the overall configuration of the video distribution system 1 according to the present embodiment.

As shown in FIG. 5, the video distribution system 1 according to the present embodiment includes a distribution server 10, a client 20, a plurality of cameras 30, and an encoding device 40. Communication is possible between the camera 30 and the encoding device 40, between the encoding device 40 and the distribution server 10, and between the distribution server 10 and the client 20 via an arbitrary communication network.

The distribution server 10 is a computer or a computer system that distributes a panoramic image to the client 20 by HLS. At this time, the distribution server 10 distributes the panoramic image captured by the camera 30 desired by the client 20 to the client 20 among the panoramic images captured by the plurality of cameras 30 respectively.

The client 20 is a computer that receives (acquires) a panoramic image from the distribution server 10 by HLS and reproduces the panoramic image. The client 20 can select one or more cameras 30 from the plurality of cameras 30 and reproduce the panoramic image of the selected camera 30 (that is, the client 20 switches the camera 30 of the panoramic image to be reproduced. be able to.).

As the client 20, for example, a PC (personal computer), a smartphone, a tablet terminal, a head mounted display (HMD: Head Mounted Display), a wearable device, a game device, or the like can be used.

The camera 30 is an image pickup device installed at a predetermined point or position. Therefore, the plurality of cameras 30 are installed at a plurality of points or positions, respectively. In the following, when the total number of cameras 30 is N (where N is an integer of 2 or more) and each of the plurality of cameras 30 is distinguished, "camera 30 ₁ ", "camera 30 ₂ ", ... -Represented as "camera 30 _N " or the like.

The encoding device 40 is a computer that encodes the video signal of the camera 30 to create an encoded video. The encoded video created by the encoding device 40 is transmitted to the distribution server 10.

Here, the distribution server 10 according to the present embodiment has a distribution processing unit 110 and a storage unit 120. The distribution processing unit 110 is realized by processing one or more programs installed in the distribution server 10 to be executed by a processor such as a CPU (Central Processing Unit). Further, the storage unit 120 can be realized by using an auxiliary storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive), for example. The storage unit 120 may be realized by using a storage device or the like connected to the distribution server 10 via a communication network.

The distribution processing unit 110 distributes the contents of the corresponding camera 30 (that is, low-resolution tiles and high-resolution tiles) to the client 20 in response to a request from the client 20.

The storage unit 120 stores video content showing a panoramic image taken by a plurality of cameras 30. Here, the video content includes a playlist common to all camera 30 content and content of each camera 30 (that is, "camera 1 content", "camera 2 content", ..., "Camera N content". ) And is included. Further, the content of each camera 30, as a segment files, low resolution tile for each t _c, includes a high-resolution tile for each t _c at a plurality of visual field range determined in advance. It should be noted that the camera n content is content indicating a panoramic image taken by the _{camera 30 n, where n = 1, ..., N.}

As described above, in the storage unit 120 of the distribution server 10 according to the present embodiment, _{the playlist common to the camera n contents of the camera 30 n} (n = 1, ..., N) and the camera 30 _n (n =). The camera n contents (low resolution tiles and high resolution tiles) of 1, ..., N) are stored. Therefore, even if the client 20 switches the camera 30 after acquiring the playlist once, it is not necessary to acquire the playlist again, and the communication for acquiring the playlist can be reduced. The details of the data structure of the video content will be described later.

Further, the client 20 according to the present embodiment has a viewing processing unit 210. The viewing processing unit 210 is realized by processing one or more programs installed in the client 20 to be executed by a processor such as a CPU.

The viewing processing unit 210 transmits various requests (for example, a video distribution request, etc.) to the distribution server 10, and receives the contents (low-resolution tiles and high-resolution tiles) of the corresponding camera 30 from the distribution server 10. Then, the panoramic image is reproduced by the content.

The overall configuration of the video distribution system 1 shown in FIG. 1 is an example, and may be another configuration. For example, the encoding device 40 may be integrated with the distribution server 10. In this case, the video signal is encoded by the distribution server 10.

<Data structure of video content>
Next, the data structure of the video content stored in the storage unit 120 of the distribution server 10 according to the present embodiment will be described.

(Example 1)
The data structure of the video content in the first embodiment will be described with reference to FIG. FIG. 6 is a diagram (No. 1) for explaining an example of the data structure of the video content.

As shown in FIG. 6, in the first embodiment, a playlist (also referred to as “Conent.m3u8”), a Conf folder, and a Media folder are arranged directly under the content folder. Further, in the Conf folder, a metadata list (also referred to as "Play.ini") and placement information (this is also referred to as "Rendering.ini") are arranged.

On the other hand, in the Media folder, each folder in which the camera 1 content is stored (0 folder, 1 folder, 2 folder, ..., M folder) and each folder in which the camera 2 content is stored (M + 1 folder, M + 2). Folders, ..., 2M + 1 folders), ..., Each folder in which camera N contents are stored are arranged.

Here, i = 1, · · ·, as M-1, the n (i + 1) -1 folder, high resolution tiles of the field-of-view range of the i camera 30 _n are arranged. Specifically, for example, 0 to the folder, the high resolution tiles each t _c in the first field of view of the camera 30 ₁ is disposed. In the example shown in FIG. 6, the high resolution tiles between the first of the high-resolution tile between t _c "0.ts", the high resolution tiles between the next t _c "1.ts", further the next t _c "2.ts" and the like are arranged. Similarly, the 1 folder, high resolution tiles each t _c in the second field of view of the camera 30 ₂ is disposed.

On the other hand, with i = M, low resolution tiles for each t _{c of the camera 30 n are arranged in the n (M + 1) -1 folder.} Specifically, for example, the M folder, a low-resolution tile camera 30 _each of t _c are arranged. In the example shown in FIG. 6, the low-resolution tiles between the first _{t c} "0.ts" low resolution tile "1.ts" between the next _{t c,} further low-resolution tile between the next _{t c} "2. "ts" etc. are arranged. A playlist for media (also referred to as "LT.m3u8") is also arranged in the n (M + 1) -1 folder.

As described above, in the video content of the first embodiment, the content for each camera 30 is stored in the Media folder.

In addition, Content. In order to distinguish the playlist represented by m3u8 from the playlist for media, the playlist for content, which is also referred to as a "playlist for content" hereafter, is used to transmit, for example, communication session information and a segment file. Required information etc. are described.

On the other hand, a playlist for media (LT.m3u8) is also referred to as a "playlist for media". For example, the length (playback time) of each segment file is described in the playlist for media.

Further, the metadata list describes information about the codec, information on the size of each tile, information on the number of cameras 30, and the like. More specifically, the metadata list describes information on the number of cameras 30, information on the codec for each camera 30, information on the tile size for each camera 30, and the like.

Further, in the arrangement information, information regarding the arrangement of the high-resolution tiles (that is, information regarding the coordinates of the visual field range for each high-resolution tile) and the like are described. More specifically, in the arrangement information, information regarding the arrangement of high-resolution tiles for each camera 30 and the like are described.

(Example 2)
The data structure of the video content in the second embodiment will be described with reference to FIG. 7. FIG. 7 is a diagram (No. 2) for explaining an example of the data structure of the video content.

As shown in FIG. 7, in the second embodiment, a playlist for contents, a Conf folder, and a Media folder for each camera 30 (that is, a Media_1 folder, a Media_2 folder, ..., a Media_N folder) are provided directly under the content folder. Is placed. In the Conf folder, the metadata list and the arrangement information are arranged as in the first embodiment.

As n = 1, ..., N, the camera n contents are stored in the Media_n folder. That is, Media_n folder 0 folders, 1 folder, · · ·, M folder are arranged respectively, i = 0, · · ·, as M-1, the i folder, the camera 30 _n of the i + 1 High resolution tiles in the field of view are arranged. Specifically, for example, to 0 folder Media_1 folder, high resolution tiles each _{t c} in the first field of view of the camera 30 ₁ is disposed. In the example shown in FIG. 7, the high resolution tiles between the first of the high-resolution tile between t _c "0.ts", the high resolution tiles between the next t _c "1.ts", further the next t _c "2.ts" and the like are arranged. Similarly, the 1 folder Media_1 folder, high resolution tiles each _{t c} in the second field of view of the camera 30 ₁ is disposed.

On the other hand, low resolution tiles for each t _{c of the camera 30 n} are arranged in the M folder of the Media_n folder. Specifically, for example, the M folder Media_1 folder, low-resolution tile camera 30 _each of _{t c} are arranged. In the example shown in FIG. 7, the low-resolution tiles between the first _{t c} "0.ts" low resolution tile "1.ts" between the next _{t c,} low resolution tile "2 further between the next _{t c.} "ts" etc. are arranged. A playlist for media is also arranged in the M folder.

As described above, in the video content of the second embodiment, the media folder for each camera 30 is arranged directly under the content folder, and the content of the corresponding camera 30 is stored in each media folder.

<Panorama video distribution processing>
Next, the panoramic video distribution process according to the present embodiment will be described with reference to FIG. FIG. 8 is a sequence diagram showing an example of the panoramic video distribution process according to the present embodiment. In the following, the information that identifies the camera 30 will be used as the camera number, and the camera 30 ₁ with the camera number n = 1 will be used as the default camera 30. Then, when displaying a panoramic image on the client 20 is assumed to default camera 30 ₁ panorama image is first reproduced.

First, when the viewing processing unit 210 of the client 20 starts playing the panoramic video, the video distribution request is transmitted to the distribution server 10 (step S101). Here, the distribution request of the video include the camera ID n = 1 the default camera 30 _1. In addition, the distribution request of the video includes the current time or the time specified by the user. Hereinafter, the current time or the time specified by the user is also referred to as a “playback time”. For example, in the case of live distribution or the like, the current time is often included as the reproduction time, and in the case of on-demand distribution or the like, the time specified by the user is often included as the reproduction time.

In the present embodiment, the request transmitted in step S101 is referred to as a "video distribution request", but this request may be referred to as, for example, a "video distribution start request".

Next, the distribution server 10 and the client 20 perform a communication process related to playlist acquisition (that is, a process of transmitting a content playlist, a media playlist, or the like from the distribution server 10 to the client 20) (step S102). As a result, the client 20 can acquire playlists for contents, playlists for media, and the like. The details of the communication process related to the playlist acquisition will be described later.

Next, the distribution processing unit 110 of the distribution server 10 has a low-resolution tile corresponding to the reproduction time and a high-resolution tile corresponding to the reproduction time in the default viewing range among the low-resolution tiles and the high-resolution tiles of the camera 1 content. Is read from the storage unit 120 (step S103). The low-resolution tile and the high-resolution tile corresponding to the reproduction time are, for example, tiles in which the reproduction time includes the reproduction time of the low-resolution tile and the high-resolution tile.

Then, the distribution processing unit 110 of the distribution server 10 distributes (transmits) the low-resolution tile and the high-resolution tile read in the above step S103 to the client 20 (step S104).

Upon receiving the low-resolution tile and the high-resolution tile, the viewing processing unit 210 of the client 20 synthesizes the low-resolution tile and the high-resolution tile (step S105). That is, the viewing processing unit 210 superimposes the high-resolution tile on the corresponding area of the low-resolution tile based on the arrangement information acquired in step S102 above, so that the low-resolution tile and the high-resolution tile are superimposed. Synthesize tiles. As a result, a panoramic image having a high-resolution visual field range and a low-resolution panoramic image is created in an area other than the visual field range.

Then, the viewing processing unit 210 of the client 20 reproduces the panoramic image created by synthesizing the low-resolution tile and the high-resolution tile in step S105 above (step S106). The viewing processing unit 210 reproduces the panoramic video according to, for example, the information regarding the codec described in the metadata list.

Subsequent steps S107 to S111 describe processing when the field of view of the client 20 is changed when the panoramic image of the _{camera 30 n is being reproduced.} In the client 20, for example, a change in the line-of-sight direction is detected by a gyro sensor or the like, and the visual field range is also changed according to the change in the line-of-sight direction. However, the change in the line-of-sight direction is not limited to the case where it is detected by a gyro sensor or the like, and the line-of-sight direction may be changed by, for example, operating the touch panel of the client 20 with a user's finger.

The viewing processing unit 210 of the client 20 transmits the line-of-sight direction information indicating the changed line-of-sight direction to the distribution server 10 (step S107). At this time, the viewing processing unit 210 may also transmit the reproduction time to the distribution server 10.

When the distribution processing unit 110 of the distribution server 10 receives the line-of-sight direction information, the low resolution tile and the high resolution tile of the camera n content correspond to the playback time (that is, the current time or the time specified by the user). The resolution tile and the high-resolution tile corresponding to the reproduction time in the visual field range in the line-of-sight direction indicated by the line-of-sight direction information are read out from the storage unit 120 (step S108). The visual field range is specified as, for example, a range taken by a pseudo camera at the observation position toward the line-of-sight direction when the panoramic image is represented by an all-sky projection sphere.

Then, the distribution processing unit 110 of the distribution server 10 distributes (transmits) the low-resolution tiles and high-resolution tiles read in step S108 to the client 20 (step S109).

Upon receiving the low-resolution tile and the high-resolution tile, the viewing processing unit 210 of the client 20 synthesizes the low-resolution tile and the high-resolution tile in the same manner as in step S105 above (step S110).

Then, the viewing processing unit 210 of the client 20 reproduces the panoramic image created by synthesizing the low-resolution tile and the high-resolution tile in step S110 above (step S111).

Subsequent steps S112 to S116 describe processing when the panoramic image to be reproduced by the client 20 is switched (that is, when the camera 30 is switched). The user of the client 20 can switch the panoramic image to be reproduced by the client 20 by performing a predetermined operation (for example, pressing the camera switching button). As an example, a case of switching to a panoramic image taken by _{a camera 30 k} with a camera number n = k will be described.

_{When the operation of switching to the panoramic image captured by the camera 30 k} with the camera number n = k is performed, the viewing processing unit 210 of the client 20 transmits the image distribution request to the distribution server 10 (step S112). Here, the distribution request for the video includes the camera number n = k. At this time, the viewing processing unit 210 may also transmit the reproduction time to the distribution server 10. In the present embodiment, the request transmitted in step S112 is referred to as a "video distribution request", but this request may be referred to as, for example, a "camera switching request" or a "panoramic video switching request". good.

The distribution processing unit 110 of the distribution server 10 stores low-resolution tiles corresponding to the reproduction time and high-resolution tiles corresponding to the reproduction time in the default viewing range among the low-resolution tiles and high-resolution tiles of the camera k-content. Read from unit 120 (step S113).

Then, the distribution processing unit 110 of the distribution server 10 distributes (transmits) the low-resolution tiles and high-resolution tiles read in step S113 to the client 20 (step S114).

Upon receiving the low-resolution tile and the high-resolution tile, the viewing processing unit 210 of the client 20 synthesizes the low-resolution tile and the high-resolution tile in the same manner as in step S105 above (step S115).

Then, the viewing processing unit 210 of the client 20 reproduces the panoramic image created by synthesizing the low-resolution tile and the high-resolution tile in step S115 above (step S116).

As described above, in the video distribution system 1 according to the present embodiment, even if the camera 30 for shooting the panoramic video to be reproduced by the client 20 is switched, if the playlist is once acquired in step S102 above. , No need to get the playlist again. Therefore, since it is not necessary to perform the communication process related to the playlist acquisition again, it is possible to prevent the reproduction delay of the panoramic video.

In the present embodiment, a panoramic field of view of the image after switching the camera 30 _k was assumed to be a default field of view of the camera 30 _k (above step S113) is not limited thereto. For example, the coordinates for specifying the visual field range after switching may be the same as the coordinates for specifying the visual field range before switching.

Further, for example, when a certain object (for example, a specific singer in the case of a concert, a specific player in the case of sports, etc.) is included in the visual field range before switching, the same object is included. The included range may be used as the viewing range after switching. As a result, the user can view the same object shot from different angles, different positions, or the like by switching the plurality of cameras 30.

Further, for example, the field of view range to be focused on may be specified in advance for each camera 30 according to the reproduction time and contents of the panoramic image. Specifically, for example, during reproduction time is "0:00" - "5:00" is field of view 1 when switching to camera 30 _1, field of view 3 when switched to the camera 30 _2, a camera When switching to 30 ₃ , it is conceivable to set the field of view range 2 or the like in advance. Similarly, for example, when the contents of the panoramic image (content) is "concert", when switching the camera 30 ₁ is viewing range 2, when switching the camera 30 ₂ is switched to the viewing range 2, the camera 30 ₃ while the field-of-view range 1 and the like when, when the contents of the panoramic image is "sports", the field of view range 1 when switching field-of-view range 1, to the camera 30 ₂ when he switched to the camera 30 _1, camera 30 _{When it is switched to 3} , it is conceivable to set the field of view range 3 or the like in advance. This makes it possible to view the viewing range designated by the camera 30 after switching according to the reproduction time and contents of the panoramic image.

Here, the details of the communication process related to the playlist acquisition in the above step S102 will be described with reference to FIG. 9. FIG. 9 is a sequence diagram showing an example of communication processing related to playlist acquisition according to the present embodiment.

First, the viewing processing unit 210 of the client 20 transmits a Master Playlist request to the distribution server 10 (step S201). The Master Playlist request is a request for acquiring a playlist for contents.

Upon receiving the Master Playlist request, the distribution processing unit 110 of the distribution server 10 reads out the playlist for contents from the storage unit 120 (step S202).

Then, the distribution processing unit 110 of the distribution server 10 transmits the content playlist (that is, Content.m3u8) read in step S202 to the client 20 (step S203). As a result, the client 20 can acquire the playlist for the content.

Upon receiving the content playlist, the distribution processing unit 110 of the client 20 transmits a Media Playlist request to the distribution server 10 (step S204). The Media Playlist request is a request for acquiring a playlist for media and the like.

Upon receiving the Media Playlist request, the distribution processing unit 110 of the distribution server 10 receives a media playlist (that is, LT.m3u8), a metadata list (that is, Play.ini), and placement information (that is, Rendering.ini). ) And from the storage unit 120 (step S205).

Then, the distribution processing unit 110 of the distribution server 10 transmits the media playlist, the metadata list, and the arrangement information read in step S205 to the client 20 (step S206). As a result, the client 20 can acquire the playlist for media, the metadata list, and the arrangement information.

The present invention is not limited to the above-described embodiment disclosed specifically, and various modifications, changes, combinations, and the like can be made without departing from the scope of claims.

1 Video distribution system 10 Distribution server 20 Client 30 Camera 40 Encoding device 110 Distribution processing unit 120 Storage unit 210 Viewing processing unit

Claims (7)

A distribution server that distributes panoramic images taken by each of multiple cameras by HTTP Live Streaming to clients.
When a first request including camera identification information for identifying the camera is received from the client, a transmission means for transmitting a playlist for reproducing a panoramic image taken by each of the plurality of cameras to the client is used. ,
When the playlist is transmitted to the client, it has a video distribution means for distributing a panoramic image taken by a camera identified by the camera identification information included in the first request to the client.
The video distribution means is
Upon receiving the second request including the camera identification information different from the camera identification information included in the first request, the panoramic image taken by the camera identified by the camera identification information included in the second request is displayed. A distribution server characterized in that it distributes to the client. The transmission means is
The delivery according to claim 1, wherein when the second request including the camera identification information different from the camera identification information included in the first request is received, the playlist is not transmitted to the client. server. The first request is a request to start distribution of a panoramic image taken by a camera set as a default among the plurality of cameras.
The distribution server according to claim 1 or 2, wherein the second request is a camera switching request. Each camera has a storage means for storing the contents of the panoramic image taken by the camera as a segment file.
The video distribution means is
The distribution server according to any one of claims 1 to 3, wherein a segment file of a panoramic image taken by a camera identified by the camera identification information is distributed to the client. The segment file includes low-resolution data indicating data obtained by compressing a panoramic image having a predetermined time width to a low resolution, and high-resolution data indicating a predetermined image area included in the panoramic image having the time width. The distribution server according to claim 4, wherein the distribution server is characterized by the above. A computer that delivers panoramic video taken by each of multiple cameras by HTTP Live Streaming to the client,
When a first request including camera identification information for identifying the camera is received from the client, a transmission procedure for transmitting a playlist for playing a panoramic image taken by each of the plurality of cameras to the client is provided. ,
When the playlist is transmitted to the client, a video distribution procedure of distributing a panoramic image taken by a camera identified by the camera identification information included in the first request to the client is executed.
The video distribution procedure is
Upon receiving the second request including the camera identification information different from the camera identification information included in the first request, the panoramic image taken by the camera identified by the camera identification information included in the second request is displayed. A delivery method characterized by delivering to the client. A program for making a computer function as each means in the distribution server according to any one of claims 1 to 5.

Images