JP7663953B2 - VIDEO ROUTING DEVICE, VIDEO ROUTING METHOD, AND PROGRAM - Google Patents

Description

The present invention relates to a video routing device, a video routing method, and a program.

Video transmission technology that transmits video recorded at multiple locations (hereinafter also referred to as "recording locations") to multiple other locations (hereinafter also referred to as "playback locations") where the video is played back has been known for some time (see, for example, Non-Patent Document 1). In this type of video transmission technology, a router (hereinafter also referred to as "video routing device") is deployed that collects video streams from each recording location and distributes the video streams to the playback locations corresponding to the recording locations.

Video stream routing software, Internet <URL: https://www.ntt-tx.co.jp/products/viaPlatz/MTS/>

However, at a certain playback point, there are cases where it is desired to switch the video being played at that playback point from one video to another video. In other words, there are cases where it is desired to switch the video stream being delivered to that playback point from a video stream from one recording point to a video stream from another recording point. In such cases, however, when switching the video, there may be a long interruption in the playback of the video at that playback point. This is because the video stream that was being delivered to the playback point before the switch is cut off at the point of switch, and a new video stream is delivered from the point of switch, causing the decoder to lose track of the syntax of the video stream and to be unable to correctly decode the switched video stream until the header of a picture that can be decoded by itself (hereinafter also referred to as a "key picture") appears.

One embodiment of the present invention has been made in consideration of the above points, and aims to reduce interruptions in video when switching between videos.

In order to achieve the above object, a video routing device according to one embodiment is a video routing device that distributes a video stream recorded at a first location to a second location, and includes a switching instruction receiving unit configured to receive a video switching instruction for switching the video stream to be distributed to the second location to another video stream, a search unit configured to search for a randomly accessible picture from the other video stream, a replacement unit configured to replace the picture immediately before the randomly accessible picture with a skip instruction bit stream for displaying a picture that has no difference from the previous picture, and a switching unit configured to switch the video stream to be distributed to the second location to the other video stream so as to switch to the previous picture.

This reduces the interruption of video when switching between videos.

FIG. 1 is a diagram showing a conventional example of video switching. 1A to 1C are diagrams illustrating an example of video switching according to the present embodiment. 1 is a diagram illustrating an example of the overall configuration of a video transmission system according to an embodiment of the present invention. 1 is a diagram illustrating an example of a functional configuration of a video routing device according to an embodiment of the present invention. 10 is a flowchart illustrating an example of a video switching process according to the embodiment.

One embodiment of the present invention is described below.

<Conventional video switching example>
First, a conventional example of video switching in switching a video played at a certain playback point from one video to another will be described with reference to FIG. 1. In the example shown in FIG. 1, the video before switching is "video A", its video stream is "video stream A", the video after switching is "video B", and its video stream is "video stream B". Each picture of video A is "F _k ⁽¹⁾ " (where k is an index or picture number representing a picture time), and each picture of video B is "F _l ⁽²⁾ " (where l is an index or picture number representing a picture time). Here, video streams are generally compressed (or coded) by differential compression (also called "differential coding"), and each picture is divided into key pictures representing randomly accessible pictures (i.e., pictures that can be played back independently) and non-key pictures other than those. A specific example of a key picture is, for example, an IRAP access unit (IRAP AU: Intra Random Access Point Access Unit) or the like. A picture may also be called a "frame."

At this time, when the video routing device receives a video switching instruction, it switches the video stream delivered to the playback base from video stream A to video stream B. Conventionally, when a video routing device receives a video switching instruction, it immediately executes this video switching. For example, as shown in FIG. 1, after receiving a video switching instruction at time _t1 , the video routing device executes video switching at time _t2 = _t1 + _Δ1 (where _Δ1 is an infinitesimal time required until the process for switching the video stream delivered to the playback base is executed). As a result, as shown in FIG. 1, the video stream is switched at time _t3 = _t2 + _Δ2 (where _Δ2 is an infinitesimal time required from the start of the process for switching the video stream delivered to the playback base to the completion), and thereafter, video stream B is delivered to the playback base.

However, since video stream B cannot be correctly decoded until the appearance of the key picture, there is a gap in the video from the start time of the picture in video A at the time when the video switching instruction is received to the start time of the picture represented by that key picture. For example, in the example shown in Figure 1, there is a gap in the video from the start time _t0 of picture FK ₊₁ ⁽¹⁾ in video A to the start time _t4 of picture FL ₊₉ ⁽²⁾ in video B, and during this period, no video is displayed at the playback location.

Thus, in the past, when the video stream was switched, a video interruption occurred at the playback location for a certain period of time. This was because when the video stream was switched, the decoder at the playback location lost track of the syntax of the video stream and was unable to correctly decode the switched video stream until the key picture appeared. Note that syntax refers to the rules for the bit string of the video stream, and is determined by the compression method (or encoding method) used to convert video data into a video stream.

To deal with the above-mentioned video interruptions, there is a method in which the video stream after switching is decoded once at the time of switching, returned to SDI (Serial Digital Interface), then switched, and then re-encoded, but this requires additional equipment such as a decoder, SDI switcher, and encoder. As a result, this method complicates the system configuration and increases costs.

Below, we will explain a method for video switching that can reduce interruptions in video at the playback location when switching videos, without adding the equipment described above.

<Video switching example according to this embodiment>
An example of video switching according to the present embodiment will be described with reference to Fig. 2. In the example shown in Fig. 2, a case will be described in which a video being played back at a certain playback site is switched from video A to video B, similar to Fig. 1.

At this time, when the video routing device according to this embodiment receives a video switching instruction, it searches for a key picture from video stream B after the time when this video switching instruction was issued. The video routing device according to this embodiment then replaces the picture immediately before this key picture with a picture (hereinafter also referred to as a "skipped picture") that represents a skip instruction to display the previous picture as is, and then executes video switching so that the picture is switched to.

For example, as shown in Fig. 2, when the video routing device according to this embodiment receives a video switching instruction, it searches for a key picture (a bit stream corresponding to picture F _L+9 ⁽²⁾ ) from video stream B after time t ₁ when this video switching instruction is made. Then, the video routing device according to this embodiment replaces the bit stream corresponding to picture F _L+8 ⁽²⁾ immediately before picture F _L+9 ⁽²⁾ with a skipped picture, and executes video switching so as to switch at picture F _L+8 ⁽²⁾ . As a result, as shown in Fig. 2, the video stream is switched at time t ₃ = t ₂ + Δ ₂ (where t ₂ is the time when the process for switching the video stream to be distributed to the playback base is executed, and Δ ₂ is an infinitesimal time required from the start to the completion of the process for switching the video stream to be distributed to the playback base), and thereafter, video stream B is distributed to the playback base. It should be noted that a skipped picture is a skip instruction bitstream for displaying a picture whose difference from the immediately preceding picture is zero (i.e., a picture identical to the immediately preceding picture), or a picture represented by such a skip instruction bitstream.

Therefore, in the video switching example according to this embodiment, video A is displayed at the playback base from start time _t0 of the picture of video _A at the time when the video switching instruction is received to start time _t2 ' of picture FK _{+ 8} ^{(1) to} which time t2 belongs (in other words, the end time of picture FK ₊₇ ⁽¹⁾ immediately preceding picture FK ₊₈ (1)), and the same picture as the immediately preceding picture (i.e., picture FK ₊₇ ⁽¹⁾ ) is displayed from time _t3 to start time _t4 of picture FL+9 ⁽²⁾ . Therefore, the time during which the video is interrupted during video switching is _t3 - _t2 ', which is at most the sum of the playback time of one picture and the infinitesimal time _Δ2 , making it possible to significantly reduce video interruptions compared to conventional video switching.

The following describes a video transmission system 1 that includes a video routing device 10 that performs video switching according to an example of video switching according to this embodiment.

<Example of Overall Configuration of Video Transmission System 1>
An example of the overall configuration of the video transmission system 1 according to this embodiment is shown in Fig. 3. As shown in Fig. 3, the video transmission system 1 according to this embodiment includes a video routing device 10, a terminal 20, a shooting device 30 and an encoder 40 arranged at each recording site, and a decoder 50 and a playback device 60 arranged at each playback site. Each encoder 40 and the video routing device 10 are communicatively connected via a collection NW 70, and similarly, each decoder 50 and the video routing device 10 are communicatively connected via a distribution NW 80. Here, the collection NW 70 and the distribution NW 80 are any communication networks.

The video routing device 10 collects video streams from the encoders 40 installed at each recording location and distributes the video streams to the playback locations corresponding to the recording locations. In addition, when the video routing device 10 receives a video switching instruction to switch the video being played at a certain playback location to another video, it switches the video stream being distributed to the decoder 50 at that playback location to the other video stream.

The terminal 20 transmits a video switching instruction to the video routing device 10 in response to a user operation using an input device (keyboard, mouse, touch panel, etc.) provided on the terminal 20.

The imaging device 30 captures the image within the imaging range and generates video data. The imaging device 30 is, for example, a video camera.

The encoder 40 encodes (compresses or codes) the video data generated by the imaging device 30 using a predetermined compression method (encoding method) to generate a video stream, and transmits the video stream to the video routing device 10.

The decoder 50 decodes (expands or decodes) the video stream received from the video routing device 10 using a specified compression method (encoding method) to generate video data, and transmits the video data to the playback device 60.

The playback device 60 plays back the video data generated by the decoder 50. The playback device 60 is, for example, a device or a group of devices that includes at least a display.

In the example shown in FIG. 3, "recording site A", "recording site B", and "recording site C" are shown as recording sites, with the recording site A being equipped with a camera 30A and an encoder 40A, the recording site B being equipped with a camera 30B and an encoder 40B, and the recording site C being equipped with a camera 30C and an encoder 40C. Similarly, in the example shown in FIG. 3, "playback site A", "playback site B", and "playback site C" are shown as playback sites, with the playback site A being equipped with a decoder 50A and a playback device 60A, the playback site B being equipped with a decoder 50B and a playback device 60B, and the playback site C being equipped with a decoder 50C and a playback device 60C. Note that although the example shown in FIG. 3 shows three recording sites and three playback sites, this is merely an example, and any number of recording sites and any number of playback sites may exist.

The overall configuration of the video transmission system 1 shown in FIG. 3 is an example and is not limited to this. For example, if the video routing device 10 is implemented as a PC (personal computer) or the like and video switching instructions can be given by user operation using an input device (keyboard, mouse, etc.) provided in this video routing device 10, the terminal 20 does not need to be included in the video transmission system 1. Also, for example, multiple shooting devices 30 and multiple encoders 40 may be arranged at each recording location, and similarly, multiple decoders 50 and multiple playback devices 60 may be arranged at each playback location.

<Example of Functional Configuration of Video Routing Device 10>
An example of the functional configuration of the video routing device 10 according to the present embodiment is shown in FIG. 4. As shown in FIG. 4, the video routing device 10 according to the present embodiment includes a stream transmitting/receiving unit 101, a switching instruction receiving unit 102, a searching unit 103, a replacing unit 104, and a switching unit 105. Each of these units is realized, for example, by a process in which one or more programs installed in the video routing device 10 are executed by a computing device such as a CPU (Central Processing Unit). In addition, the video routing device 10 according to the present embodiment includes a stream buffer unit 106 and a routing information storage unit 107. Each of these units is realized, for example, by a storage device such as an SSD (Solid State Drive) or an HDD (Hard Disk Drive).

The stream transmission/reception unit 101 collects video streams from the encoder 40 of each recording location and stores them in the stream buffer unit 106. The stream transmission/reception unit 101 also distributes the video streams stored in the stream buffer unit 106 to the decoder 50 of the playback location corresponding to the recording location according to the routing information stored in the routing information storage unit 107. Here, the routing information is information indicating which recording location's video stream is to be distributed to which playback location, and is represented by, for example, information indicating the playback location and information indicating the recording location in association with each other. For example, the information indicating the playback location or the information indicating the recording location can be the IP (Internet Protocol) address or MAC (Media Access Control) address of the decoder 50 located at the playback location or the encoder 40 located at the recording location, or a unique ID arbitrarily assigned to the playback location or the recording location. For example, multiple decoders 50 may be located at one playback location, or multiple encoders 40 may be located at one recording location, so the routing information may be represented by information that associates information indicating the decoder 50 with information indicating the encoder 50.

The switching instruction receiving unit 102 receives a video switching instruction transmitted from the terminal 20. Here, the video switching instruction includes, for example, information indicating the playback location to which the video is to be switched and information indicating the recording location where the video after switching will be recorded. Note that the switching instruction receiving unit 102 may also receive a video switching instruction inputted via an input device provided in the video routing device 10.

The search unit 103 searches for a key picture from the switched video stream stored in the stream buffer unit 106. Note that since the key picture has specific header information, the search unit 103 can search for the key picture by searching for a bit string that identifies this header information.

The replacement unit 104 replaces the picture immediately before the key picture found by the search unit 103 (i.e., the picture immediately before the key picture) with a skipped picture.

The switching unit 105 switches the video stream to be delivered to the decoder 50 of the playback base to the video stream after switching so as to switch to the picture immediately before the key picture searched for by the search unit 103. In addition, when the switching unit 105 switches the video stream to be delivered to the decoder 50 of a certain playback base, it updates the routing information.

The stream buffer unit 106 temporarily stores the video stream collected from the encoder 40 at each recording location. The stream buffer unit 106 stores a video stream of a certain length (for example, a video stream of a length of about one minute to several minutes) for each recording location (or for each encoder 40).

The routing information storage unit 107 stores routing information used for distributing video streams. In the routing information, for example, information indicating one playback location may be associated with information indicating multiple recording locations, or information indicating multiple playback locations may be associated with information indicating the same recording location. When information indicating one playback location is associated with information indicating multiple recording locations, this means that multiple video streams recorded at the multiple recording locations are distributed to one playback location. On the other hand, when information indicating multiple playback locations is associated with information indicating the same recording location, this means that video streams recorded at the same recording location are distributed to multiple playback locations.

<Video switching process>
The video switching process when switching the video being played at a certain playback location will be described below with reference to Fig. 5. It is assumed that the video streams from each recording location are collected in real time by the stream transmitting/receiving unit 101 and stored in the stream buffer unit 106. It is also assumed that the video streams in the stream buffer unit 106 are distributed to the playback location by the stream transmitting/receiving unit 101 according to routing information.

First, the switching instruction receiving unit 102 receives a video switching instruction (step S101). In the following, as an example, it is assumed that the video switching instruction includes information "playback location A" indicating the playback location to be switched and information "recording location B" indicating the recording location where the video after switching will be recorded. In addition, the video before switching (i.e., the video currently being played at playback location A) is "video A", its video stream is "video stream A", information indicating the recording location where video A is recorded is "recording location A", the video after switching (i.e., the video recorded at recording location B) is "video B", and its video stream is "video stream B".

Next, the search unit 103 searches the post-switching video stream B stored in the stream buffer unit 106 for key pictures that exist after the time the video switching instruction was received (step S102).

Next, the replacement unit 104 replaces the picture immediately before the key picture found in step S102 with a skipped picture (step S103). Note that, in general, the picture immediately before a key picture is a non-key picture.

Next, the switching unit 105 switches the video stream to be delivered to the decoder 50 at the playback location A from video stream A to video stream B so as to switch to the picture immediately before the key picture found in step S102 above (step S104).

Then, the switching unit 105 updates the routing information stored in the routing information storage unit 107 (step S105). That is, the switching unit 105 updates, for example, the information associated with "playback location A" in the routing information from "recording location A" to "recording location B." As a result, from then on, video stream B from recording location B will be distributed to playback location A.

<Summary>
As described above, when switching a video stream to be distributed to a certain playback point, the video routing device 10 included in the video transmission system 1 according to this embodiment replaces the picture immediately before the key picture in the switched video stream with a skipped picture, and then executes video switching so that the video is switched at that picture. As a result, the time during which the video is interrupted during video switching is at most the sum of the playback time of one picture and the very short time required from the start to the completion of the process for switching the video stream to be distributed to the playback point, and video interruptions can be significantly reduced compared to conventional video switching.

The present invention is not limited to the specifically disclosed embodiments above, and various modifications, changes, and combinations with known technologies are possible without departing from the scope of the claims.

Reference Signs List 1 Video transmission system 10 Video routing device 20 Terminal 30 Shooting device 40 Encoder 50 Decoder 60 Playback device 70 Concentration network
80 Distribution Network
101 Stream transmission/reception unit 102 Switching instruction reception unit 103 Search unit 104 Replacement unit 105 Switching unit 106 Stream buffer unit 107 Routing information storage unit

Claims (5)

A video routing device that distributes a video stream recorded at a first location to a second location,
a switching instruction receiving unit configured to receive a video switching instruction for switching the video stream to be distributed to the second location to another video stream;
a search unit configured to search for randomly accessible pictures from said other video stream;
a replacement unit configured to replace a picture immediately before the randomly accessible picture with a skip instruction bitstream for displaying a picture that has no difference from the immediately previous picture;
a switching unit configured to switch the video stream to be distributed to the second location to the other video stream so as to switch at the previous picture;
A video routing device having the above configuration. the randomly accessible picture is a key picture;
The search unit is
The video routing device of claim 1, configured to search for the randomly accessible picture by searching for a bit string for identifying header information contained in the key picture from the other video stream after the time when the video switching instruction is received. a storage unit configured to store routing information in which a first location where a video stream is recorded and a second location where the video stream is distributed are associated with each other;
The switching unit is
A video routing device as described in claim 1 or 2, which is configured so that when the video stream to be delivered to the second location is switched to the other video stream, the first location associated with the second location in the routing information is updated to the first location where the other video stream is recorded. A video routing device that distributes a video stream recorded at a first location to a second location,
a switching instruction receiving step of receiving a video switching instruction for switching the video stream to be distributed to the second location to another video stream;
a search step for searching said other video stream for randomly accessible pictures;
a replacement step of replacing a picture immediately before the randomly accessible picture with a skip instruction bit stream for displaying a picture that has no difference from the immediately previous picture;
a switching step of switching the video stream to be distributed to the second site to the other video stream so as to switch at the previous picture;
A video routing method that performs the above. A program that causes a computer to function as a video routing device according to any one of claims 1 to 3.

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