JP2024007248A - Distribution server, receiving device, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow streaming content in a low-delay segment format to be reproduced even by a receiving device that is not compatible with the low-delay segment format.

SOLUTION: A distribution server 10 includes: a segment conversion unit 14 that converts a low-delay segment having chunks that do not include intra frames into a normal segment in which all chunks include intra frames; a low-delay segment format compatibility determination unit 18 that determines whether a receiving device that requests a segment is compatible with the low-delay segment format; and a segment transmitting unit 19 that transmits a low-delay segment when the receiving device is compatible with the low-delay segment format, and transmits a normal segment when the receiving device is not compatible with the low-delay segment format.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

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

2. Description of the Related Art In recent streaming video distribution on the Internet, the mainstream is a method of streaming video distribution using a general-purpose Web server using the HTTP protocol. An example of such a streaming distribution method (adaptive streaming) using the HTTP protocol is the international standard MPEG-DASH (ISO/IEC23009-1).

In MPEG-DASH, a manifest file that describes initialization segments, media segments, their URLs, and video content attributes is prepared on the Web server. A media segment is a segment in which a stream of video content encoded with one or more qualities (parameters such as screen size and bit rate) is divided into files each having a length of several seconds to several tens of seconds. The initialization segment includes metadata necessary for presenting the segment, such as generation parameters related to encoding and encryption of each stream. The receiving device receives segments one after another, selecting the quality at the appropriate time, taking into account the screen size of the receiving device and the state of the network band of the transmission path, etc. from the manifest file, and connects them into one video content for playback. (For example, see Non-Patent Document 1).

The ISO-BMFF (ISO-Base Media File Format) format is mainly used as the media container format for segments, but the CMAF (Common Media Application Format) has been standardized (for example, see Non-Patent Document 2).

FIG. 6 shows a comparison between a conventional segment and a CMAF segment (CMAF segment). mdat (Media Data Box) is a box that stores media data such as video and audio, and moof (Movie Fragment Box) is a box that stores meta information of the immediately following mdat. A set of moof and mdat is called a "chunk".

In conventional segments, when the media data is video, one chunk within a segment is composed of a group of pictures (GOP), which is a group of intra frames and multiple inter frames that follow, or multiple GOPs. It was common. FIG. 6 shows an example in which one chunk is configured in units of 2 GOPs as a conventional segment. On the other hand, in a CMAF segment, one chunk (CMAF chunk) is composed of one to several frames. That is, a CMAF segment is composed of a plurality of CMAF chunks. The CMAF segment shown in FIG. 6 is composed of CMAF chunks a and c that include intra frames and CMAF chunks b and d that do not include intra frames.

In the conventional segment shown in Figure 6, the segment could not be delivered until the last byte of mdat has been encoded, whereas by using the CMAF segment format, the last byte of mdat in the first CMAF chunk can be encoded. Since distribution of segments can be started sequentially from the time of completion, live distribution with lower delay is possible (for example, see Non-Patent Document 3).

Furthermore, Patent Document 1 states that by converting an MMT (MPEG Media Transport) stream that applies CMAF as a media container format to MMT that does not apply CMAF, it can be played even on a receiver that does not support MMT streams that apply CMAF. A multiplex signal conversion device is disclosed.

Japanese Patent Application Publication No. 2021-197584

Mitsuhiro Hirabayashi, “Next generation video distribution technology “MPEG-DASH” technology overview, standardization and related technology trends”, Journal of the Institute of Image Information and Television Engineers, Vol.67, No.2, 2013, p.109-115 “ISO/IEC 23000-19:2020 Information technology - Multimedia application format (MPEG-A) - Part 19: Common media application format(CMAF) for segmented media”, International Organization for Standardization, March 2020 Yuhki Hanada, April 5, 2018, “CMAF and realization of low-latency LIVE distribution using CMAF”, [online], [searched on June 20, 2022], Internet <URL: https://www.akamai .com/ja/blog/performance/cmaf-cmaf-low-lalatency-live>

Due to the increasing demand for low-latency video distribution, low-latency segment format streaming distribution using CMAF and the like is expected to become more popular in the future. However, devices that have been compatible with streaming distribution in the conventional segment format from an early stage may not be able to play back streaming distribution in the low-delay segment format that includes chunks that do not include intra frames in the mdat. For receiving devices that are not compatible with such a low-delay segment format, it is possible to perform streaming distribution using the conventional segment format, but encoding of two types of streams is always required. Note that the technique disclosed in Patent Document 1 also did not solve this problem.

An object of the present invention, made in view of such circumstances, is to provide a distribution server, a receiving device, and a program that allow streaming content in a low-latency segment format to be played back even on a receiving device that is not compatible with the low-latency segment format. It is in.

In order to solve the above problems, a distribution server according to one embodiment is a distribution server that distributes content consisting of a plurality of segments to a receiving device segment by segment, and includes low-latency segments having chunks that do not include intraframes. a segment conversion unit that converts the above into normal segments in which all chunks include intra frames; a low-latency segment format compatibility determining unit that determines whether a receiving device requesting the segment is compatible with the low-latency segment format; a segment transmitter that transmits the low delay segment when the receiving device supports the low delay segment format, and transmits the normal segment when the receiving device does not support the low delay segment format; Equipped with

Furthermore, in the distribution server according to one embodiment, the segment conversion unit determines whether the first frame of the chunk is an intra frame based on the meta information of the received chunk, and determines whether the first frame is an intra frame. The normal segment may be generated by combining a certain chunk with a subsequent chunk whose first frame is not an intra frame.

In order to solve the above problems, a receiving device according to one embodiment is a receiving device that receives content consisting of a plurality of segments segment by segment from a distribution server, and has a low-latency chunk that does not include an intra frame. a segment conversion unit that converts a segment into a normal segment in which all chunks include intra frames; a low-latency segment format compatibility determination unit that determines whether the receiving device is compatible with the low-latency segment format; and the receiving device decoding to decode and reproduce the low delay segment if the receiving device supports the low delay segment format, and to decode and reproduce the normal segment if the receiving device does not support the low delay segment format;・Equipped with a playback section.

Furthermore, in the receiving device according to one embodiment, the segment conversion unit determines whether or not the first frame of the chunk is an intra frame based on the meta information of the received chunk, and the segment conversion unit determines whether the first frame of the chunk is an intra frame. The normal segment may be generated by combining a certain chunk with a subsequent chunk whose first frame is not an intra frame.

Moreover, in order to solve the above-mentioned problem, a program according to one embodiment causes a computer to function as the above-mentioned distribution server.

Moreover, in order to solve the above-mentioned problem, a program according to an embodiment causes a computer to function as the above-mentioned receiving device.

According to the present invention, streaming content in a low-delay segment format can be played back even by a receiving device that is not compatible with the low-delay segment format. Therefore, it is possible to efficiently achieve low-latency delivery while ensuring backward compatibility.

FIG. 1 is a block diagram illustrating a configuration example of a distribution system according to a first embodiment. FIG. 2 is a block diagram showing a configuration example of a distribution server according to the first embodiment. 5 is a flowchart illustrating an example of processing by a segment conversion unit in the distribution server according to the first embodiment. FIG. 2 is a block diagram showing a configuration example of a distribution system according to a second embodiment. FIG. 2 is a block diagram illustrating a configuration example of a receiving device according to a second embodiment. FIG. 3 is a diagram showing a comparison between a conventional segment and a segment based on CMAF.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In this specification, a "low delay segment" is a segment that constitutes one chunk in units of one to several frames, such as the CMAF segment shown in FIG. 6, and is a segment that has chunks that do not include intra frames. Say something. Furthermore, a "normal segment" is a segment that constitutes one chunk in units of one or more GOPs, such as the conventional segment shown in FIG. 6, and is a segment that does not have a chunk that does not include an intra frame. means.

<First embodiment>
(Content distribution system)
FIG. 1 is a diagram showing a configuration example of a content distribution system according to a first embodiment of the present invention. The content distribution system 1 shown in FIG. 1 includes a distribution server 10, a live encoder 20, a first receiving device 30, and a second receiving device 40. Although only one first receiving device 30 and one second receiving device 40 are shown in FIG. 1 for convenience of drawing, the content distribution system 1 includes at least one first receiving device 30 and one or more second receiving devices 40, respectively.

Distribution server 10 and live encoder 20 are connected via communication network NW1. The communication network NW1 may be a dedicated local network or the Internet. The distribution server 10, the first receiving device 30, and the second receiving device 40 are connected via a communication network NW2 such as the Internet.

The live encoder 20 encodes the input video in a low-delay segment format such as CMAF, and sequentially outputs the encoded low-delay segments to the distribution server 10. The encoding is H. 264 | MPEG-4 AVC (Advanced Video Coding), H.264 | This is performed using an existing video encoding method such as H.265|MPEG-H HEVC (High Efficiency Video Coding). The live encoder 20 establishes a session with the distribution server 10 in the HTTP/1.1 Chunked Transfer Encoding format in units of segments, for example, and transmits low-latency segments in units of chunks.

The distribution server 10 distributes content composed of a plurality of segments segment by segment to the first receiving device 30 and second receiving device 40 that request the segment.

The first receiving device 30 is a receiving device compatible with a low-latency segment format (segment type streaming method such as MPEG-DASH), and is a terminal that sequentially requests and acquires segments from the distribution server 10, and decodes and plays them. . The first receiving device 30 establishes a session with the distribution server 10 in units of segments, for example in the HTTP/1.1 Chunked Transfer Encoding format, and receives segments in units of chunks.

The second receiving device 40 has the same basic configuration as the first receiving device 30, but is a receiving device that is not compatible with the low delay segment format. That is, the second receiving device 40 is not capable of decoding and reproducing chunks that do not include intra frames (for example, CMAF chunks).

(Distribution server)
Next, details of the distribution server 10 will be explained. FIG. 2 is a block diagram showing a configuration example of the distribution server 10. As shown in FIG. The distribution server 10 shown in FIG. 2 includes a first communication I/F 11, a segment reception section 12, a low-delay segment buffer 13, a segment conversion section 14, a normal segment buffer 15, and a second communication I/F 16. , a request receiving section 17 , a low-delay segment format compatibility determining section 18 , and a segment transmitting section 19 . Note that when the communication network NW1 and the communication network NW2 are common, the first communication I/F 11 and the second communication I/F 16 may be common.

The segment receiving unit 12 sequentially receives low-delay segments from the live encoder 20 via the first communication I/F 11 and outputs them to the low-delay segment buffer 13 . From the live encoder 20, a session is established in units of segments using, for example, the HTTP/1.1 Chunked Transfer Encoding format, and low-latency segments are received in units of chunks. The segment receiving unit 12 outputs chunks to the low-delay segment buffer 13 without waiting for completion of segment reception. It is also simultaneously output to the segment conversion unit 14 in chunks.

The segment conversion unit 14 converts the low-delay segment input from the segment reception unit 12 into a normal segment in which all chunks include intra frames, and outputs the converted normal segment to the normal segment buffer 15.

The segment conversion unit 14 determines whether the first frame of the chunk is an intra frame based on the meta information of the received chunk, and converts the chunk whose first frame is an intra frame into a subsequent chunk whose first frame is not an intra frame. The chunks are combined to generate regular segments. Details of the processing by the segment conversion unit 14 will be described later.

The request receiving unit 17 receives a segment request from the first receiving device 30 or the second receiving device 40 via the second communication I/F 16, and receives the segment URL included in the request and the first receiving device 30. Alternatively, the terminal information of the second receiving device 40 is notified to the low delay segment format compatibility determination unit 18. As the terminal information, for example, User-Agent information included in the HTTP request can be used, but the terminal information is not limited to this.

The low-delay segment format compatibility determining unit 18 determines whether the receiving device that requests the segment is compatible with the low-delay segment format, based on the terminal information input from the request receiving unit 17 . Compatible with low-latency segment format means that low-latency segments can be decoded and played back. The low-latency segment format compatibility determination unit 18 creates a compatibility list (or non-compatibility list) in advance according to the browser, OS, model of the receiving device, etc., and compares it with the information included in the terminal information. It may also be determined whether the low-delay segment format is supported.

When the low-latency segment format compatibility determining unit 18 determines that the receiving device is compatible with the low-latency segment format, the low-latency segment format corresponding to the URL of the segment input from the request receiving unit 17 is set as the low-latency segment for the low-latency segment. It is acquired from the buffer 13 and output to the segment transmitter 19. On the other hand, when it is determined that the receiving device does not support the low-latency segment format, the low-latency segment format compatibility determination unit 18 acquires the regular segment corresponding to the URL of the segment from the regular segment buffer 15, and It is output to the transmitter 19.

The segment transmitting unit 19 outputs the low-latency segment input from the low-latency segment format compatibility determining unit 18 to the first receiving device 30 via the second communication I/F 16, and outputs the low-latency segment input from the low-latency segment format compatibility determining unit 18 to the first receiving device 30. The normal segment is output to the second receiving device 40 via the second communication I/F 16. That is, the segment transmitter 19 transmits a low delay segment when the receiving device supports the low delay segment format, and transmits a normal segment when the receiving device does not support the low delay segment format. .

(Segment conversion method)
Next, a method of converting one segment's worth of low-delay segments by the segment conversion unit 14 will be described with reference to the flowchart shown in FIG. 3. Here, it is assumed that the media container format of the low-latency segment follows ISO-BMFF or CMAF.

In step S001, the segment converter 14 receives one chunk from the segment receiver 12.

In step S002, the segment conversion unit 14 analyzes the moof box of the received chunk and obtains meta information of the media data included in the mdat box. The meta information includes, for example, the decoding time of the first frame (baseMediaDecodeTime), the number of frames in the chunk (sample_count), the time length of each frame (sample_duration), the data size (sample_size), the flag (sample_flag), and the time offset value ( sample_composition_time_offset).

In step S003, the segment conversion unit 14 determines whether the first frame of the received chunk is an intra frame based on the meta information. For example, if the sample_depends_on value in sample_flag of the first frame in the meta information is 2, it is determined that the first frame is an intra frame. If the segment conversion unit 14 determines that the first frame is not an intra frame (step S003-NO), the process proceeds to step S004; if it determines that the first frame is an intra frame (step S003-YES), the segment conversion unit 14 advances the process to step S004. ), the process advances to step S006.

In step S004, the segment converter 14 stores the meta information and mdat of the received chunk in the primary buffer within the segment converter 14. Note that the primary buffer may be located outside the segment converter 14.

In step S005, the segment conversion unit 14 determines whether the chunk stored in the primary buffer is the last chunk in one low delay segment. If the stored chunk is not the last chunk of the low-latency segment (step S005-NO), the process returns to step S001, and if the stored chunk is the last chunk of the low-latency segment (step S005-YES). ), the process advances to step S007.

In step S006, the segment conversion unit 14 checks whether data is stored in the primary buffer. If no data is stored in the primary buffer (step S006-NO), the process proceeds to step S004, and if data is stored in the primary buffer (step S006-YES), the process proceeds to step S007. Proceed.

In step S007, the segment conversion unit 14 extracts the data stored in the primary buffer. Then, the media data included in the mdat for each chunk is concatenated in the order in which they were stored in the primary buffer, and a reconfigured mdat is generated according to the ISO-BMFF specifications. Thereby, it is possible to generate mdat including an intra frame.

In step S008, the segment conversion unit 14 generates a moof corresponding to mdat according to the ISO-BMFF specifications based on the meta information for each chunk stored in the primary buffer.

In step S009, the segment conversion unit 14 concatenates the generated moof and mdat to generate a chunk in the normal segment format, and stores the chunk in the secondary buffer within the segment conversion unit 14. Note that the secondary buffer may be located outside the segment converter 14.

In step S010, the segment conversion unit 14 determines whether processing of all chunks within one low delay segment has been completed. If the processing of all chunks in the low delay segment has been completed (step S010-YES), the process advances to step S011. If there is a chunk for which processing has not been completed within the low delay segment (S010-NO), the process returns to step S004, and the meta information and mdat of the received chunk are stored in the primary buffer.

In step S011, the segment conversion unit 14 extracts the chunk in the normal segment format stored in the secondary buffer. Then, the segments are combined in the order stored in the secondary buffer to generate a normal segment, which is output to the normal segment buffer 15, and the process ends.

In this way, the distribution server 10 converts the low-delay segment output from the live encoder 20 into a normal segment, and then transmits the normal segment to the second receiving device 40 that is not compatible with the low-delay segment format. Therefore, the second receiving device 40 can also perform decoding and reproduction.

<Second embodiment>
Next, a second embodiment of the present invention will be described. FIG. 4 is a diagram showing an example of the configuration of a content distribution system according to the second embodiment of the present invention. The content distribution system 2 shown in FIG. 4 includes a distribution server 10a, a live encoder 20, and a receiving device 50. Although only one receiving device 50 is shown in FIG. 4 for convenience of drawing, the content distribution system 2 includes one or more receiving devices 50. Note that the distribution server 10a and the live encoder 20 may be a single device configured as an integrated unit.

In FIG. 4, live encoder 20 and distribution server 10a are connected via communication network NW1. The communication network NW1 may be a dedicated local network or the Internet. The distribution server 10a and the receiving device 50 are connected via a communication network NW2 such as the Internet.

The live encoder 20 is the same as in the first embodiment, and transmits low-delay segments in chunks to the distribution server 10a.

The distribution server 10a buffers the low delay segment received from the live encoder 20. The distribution server 10a then distributes the low-delay segment to the receiving device 50 in response to a segment request from the receiving device 50.

The receiving device 50 sequentially requests segments from the distribution server 10a according to a segment-based streaming method such as MPEG-DASH. Then, content composed of a plurality of segments is received segment by segment from the distribution server 10a.

(Receiving device)
Next, details of the receiving device 50 will be explained. FIG. 5 is a block diagram showing a configuration example of the receiving device 50. As shown in FIG. The receiving device 50 shown in FIG. 5 includes a communication I/F 51, a segment request section 52, a segment receiving section 53, a low delay segment format compatibility determining section 54, a buffer 55, a segment converting section 56, and a decoding/reproducing section. 57.

The segment request unit 52 establishes a session with the distribution server 10a for each segment using, for example, the HTTP/1.1 Chunked Transfer Encoding format, and requests the distribution server 10a to send a request including the URL of a desired segment.

The segment receiving unit 53 receives a low-delay segment corresponding to the URL of a desired segment from the distribution server 10a via the first communication I/F 11, and outputs it to the low-delay segment format correspondence determination unit 54.

The low-delay segment format compatibility determining unit 54 determines whether the decoding/reproducing unit 57 in the receiving device 50 is compatible with the low-delay segment format. For example, the determination may be made based on the browser, OS, terminal model, etc. of the receiving device 50. Alternatively, the low delay segment may be input in advance to the decoding/reproducing unit 57 via a buffer, and it may be verified whether or not an error occurs, and the determination may be made based on the result.

When determining that the decoding/reproducing unit 57 is compatible with the low delay segment format, the low delay segment format compatibility determining unit 54 outputs the low delay segment input from the segment receiving unit 53 to the buffer 55. On the other hand, if the low-delay segment format compatibility determination unit 54 determines that the decoding/playback unit 57 is not compatible with the low-delay segment format, it outputs the low-delay segment to the segment conversion unit 56 .

Similarly to the first embodiment (see FIG. 3), the segment conversion unit 56 converts a low-delay segment having a chunk that does not include an intra frame into a normal segment in which all chunks include an intra frame, and buffers the normal segment. 55.

The buffer 55 outputs the segment input from the low-delay segment format correspondence determination section 54 or the normal segment input from the segment conversion section 56 to the decoding/reproducing section 57.

The decoding/reproducing unit 57 decodes and reproduces the low delay segment or normal segment input from the buffer 55. That is, the decoding/reproducing unit 57 decodes and reproduces the low delay segment when the receiving device 50 supports the low delay segment format, and decodes and plays the low delay segment when the receiving device 50 does not support the low delay segment format. normally decodes and plays the segment.

Through the above processing, the receiving device 50 is able to receive and play the low-latency segment from the distribution server 10a, regardless of whether the decoding/playback unit 57 supports the low-latency segment format. .

Note that the segment converter 56 can be implemented as software such as JavaScript. Therefore, it is not necessary to be installed at the time of shipment of the receiving device 50, and it is possible to obtain and execute the content from an external website or the like prior to receiving the content from the distribution server 10a. Therefore, it is possible to efficiently realize low-delay delivery while ensuring backward compatibility.

(program)
In order to function as the above-mentioned distribution server 10 and receiving device 50, it is also possible to use computers that can execute program instructions, respectively. Here, the computer may be a general-purpose computer, a dedicated computer, a workstation, a PC (Personal Computer), an electronic notepad, or the like. Program instructions may be program code, code segments, etc. to perform necessary tasks.

The computer includes a processor, a storage section, an input section, an output section, and a communication interface. Processors include CPUs (Central Processing Units), MPUs (Micro Processing Units), GPUs (Graphics Processing Units), DSPs (Digital Signal Processors), and SoCs (System on a Chip). may be configured. The processor controls each of the above components and performs various calculation processes by reading and executing programs from the storage unit. Note that at least a part of these processing contents may be realized by hardware.

The program may be recorded on a computer readable recording medium. Using such a recording medium, it is possible to install a program on a computer. Here, the recording medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a CD-ROM, a DVD-ROM, a USB (Universal Serial Bus) memory, or the like. Further, this program may be downloaded from an external device via a network.

For example, a program for functioning as the distribution server 10 includes the steps of converting a low-latency segment into a normal segment, determining whether a receiving device requesting a segment supports the low-latency segment format, and receiving A computer is caused to perform the steps of transmitting a low delay segment if the device supports the low delay segment format, and transmitting a normal segment if the receiving device does not support the low delay segment format.

For example, a program for functioning as the receiving device 50 includes a step of converting a low delay segment into a normal segment, a step of determining whether the receiving device 50 supports the low delay segment format, and a step of determining whether the receiving device 50 supports the low delay segment format. a step of decoding and playing the low delay segment if the receiving device 50 supports the low delay segment format, and decoding and playing the normal segment if the receiving device 50 does not support the low delay segment format; have it executed.

Furthermore, the above-described distribution server 10 and receiving device 50 may each be configured with one or more semiconductor chips. This semiconductor chip may be equipped with a CPU that executes a program that describes processing contents for realizing each function of the distribution server 10 and the receiving device 50.

Although the embodiments described above have been described as representative examples, it will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the invention. Therefore, the present invention should not be construed as being limited to the above-described embodiments, and various modifications and changes can be made without departing from the scope of the claims. For example, it is possible to integrate a plurality of configuration blocks described in the configuration diagram of the embodiment, or to divide one configuration block.

1, 2 Content distribution system 10, 10a Distribution server 11 1st communication I/F
16 Second communication I/F
12 Segment receiving section 13 Low delay segment buffer 14,56 Segment converting section 15 Normal segment buffer 16 Communication I/F
17 Request receiving unit 18, 54 Low delay segment format compatibility determining unit 19 Segment transmitting unit 20 Live encoder 30 First receiving device 40 Second receiving device 50 Receiving device 51 Communication I/F
52 Segment request section 53 Segment reception section 55 Buffer 57 Decoding/playback section

Claims (6)

A distribution server that distributes content consisting of a plurality of segments to a receiving device segment by segment,
a segment conversion unit that converts a low-latency segment having chunks that do not include intra frames into a normal segment in which all chunks include intra frames;
a low-latency segment format compatibility determination unit that determines whether a receiving device requesting a segment is compatible with the low-latency segment format;
a segment transmitter that transmits the low delay segment when the receiving device supports the low delay segment format, and transmits the normal segment when the receiving device does not support the low delay segment format; ,
A distribution server equipped with. The segment conversion unit determines whether the first frame of the chunk is an intra frame based on the meta information of the received chunk, and converts the chunk whose first frame is an intra frame into a subsequent chunk whose first frame is not an intra frame. The distribution server according to claim 1, wherein the distribution server generates the regular segment by combining chunks of . A receiving device that receives content consisting of a plurality of segments segment by segment from a distribution server,
a segment conversion unit that converts a low-latency segment having chunks that do not include intra frames into a normal segment in which all chunks include intra frames;
a low-latency segment format compatibility determination unit that determines whether the receiving device is compatible with the low-latency segment format;
If the receiving device supports the low delay segment format, the low delay segment is decoded and played back, and if the receiving device is not compatible with the low delay segment format, the normal segment is decoded. a decoding/reproducing unit for reproducing;
A receiving device comprising: The segment conversion unit determines whether the first frame of the chunk is an intra frame based on the meta information of the received chunk, and converts the chunk whose first frame is an intra frame into a subsequent chunk whose first frame is not an intra frame. 4. The receiving device according to claim 3, wherein the normal segment is generated by combining chunks of . A program for causing a computer to function as the distribution server according to claim 1 or 2. A program for causing a computer to function as the receiving device according to claim 3 or 4.

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