KR20150047081A

KR20150047081A - Apparatus and Method for Payloading to Reduce MMT Overhead

Info

Publication number: KR20150047081A
Application number: KR1020140087791A
Authority: KR
Inventors: 김창기; 유정주; 홍진우; 서광덕; 이홍래
Original assignee: 한국전자통신연구원; 연세대학교 원주산학협력단
Priority date: 2013-10-23
Filing date: 2014-07-11
Publication date: 2015-05-04

Abstract

The present invention relates to an MMT overhead-reducing payloading apparatus comprising: a type categorizing unit for categorizing the type of inputted media processing unit (MPU) fragments; a size comparison unit for comparing the size of an aggregated packet with the size of a maximum transmission unit (MTU), when the categorized MPU fragment type and another MPU fragment of a different type are aggregated; a payload generation unit for generating an MMT payload by aggregating two or more different types of MPU fragments, according to the result of size comparison; and a header generation unit for adding a header to the generated payload.

Description

Technical Field [0001] The present invention relates to an MMT overhead reduction type payloading apparatus and method,

The present invention relates to a media transmission service technology based on an MPEG media transmission system, and more particularly, to an MMT payload generation apparatus and method for reducing overhead.

MMT (MPEG Media Transport) is a new media transmission standard technology that began development in 2010 in the ISO / IEC WG11 (MPEG) system sub-working group.

2. Description of the Related Art Conventional MPEG-2 systems have standardized MPEG-2 transport stream (TS) technology as a standard for packetization, synchronization, and multiplexing necessary for transmitting AV (Audio Video) contents in a broadcasting network and are now widely used. However, MPEG-2 TS is inefficient in packet transmission environments where the network is based on IP (Internet Protocol).

In ISO / IEC WG 11 MPEG, the need for a new media transmission standard was recognized in consideration of the new media transmission environment and the anticipated media transmission environment, and MMT standardization was started.

In the MMT standardization, the types of the three kinds of MPU fragments are separately separated and loaded in the MMT payload as the payloading method.

However, in the case of the MPU file, the number of media samples included in the MPU varies depending on the length of the time interval covered by the MPU, and movie fragment metadata, which is one of the three types of MPU fragments, In case of small size, when payload is mapped to one MMT packet, the size of the payload compared to the size of the entire header of the MMT packet becomes very small, and the overhead increases seriously. Such an increase in overhead may cause a congestion in the transport channel since the number of packets required to transmit all the MPU fragments increases.

The present invention provides an MMT overhead reduction type payload apparatus and method capable of reducing congestion in a transmission channel due to an increase in overhead.

The present invention relates to an MMT overhead reduction type payload device, which comprises a type classification unit for classifying an input media processing unit (MPU) fragment type, and a type classification unit for combining the classified MPU fragment type with other types of MPU fragments A size comparing unit for comparing the size of the unified packet and the size of a maximum transmission unit (MTU) when the size of the MMU payload is smaller than the size of the unified packet, and a size comparing unit for creating an MMT payload by combining two or more different types of MPU fragments And a header generating unit for adding a header to the generated payload.

The present invention relates to an MMT overhead reduction type payload method in a transport function layer of an MMT system, the method comprising: classifying an input media processing unit (MPU) fragment type; Comparing a size of a combined packet and a size of a maximum transmission unit (MTU) when integrating the MPU fragment with another MPU fragment of the MMT, and combining the two or more different types of MPU fragments according to the size comparison result, Creating a payload, and adding a header to the generated payload.

According to the present invention, since the movie fragment metadata of a small size is integrated with the MPU metadata or the MFU and is mapped to the MMT payload, the packet overhead can be reduced by the increase of the payload size, thereby transmitting the entire MPU file The number of MMT packets to be consumed can be reduced.

In addition, the congestion in the network can be reduced by the number of MMT packets reduced, and the media transmission throughput such as FEC (forward error correction) can be increased due to the increased weight of the payload.

1 is a diagram showing a hierarchical structure of an MMT system.
2 shows an internal structure of an MMT packet.
3 is a diagram for explaining the principle of MMT payload loading.
4 is a view for explaining the principle of MMT overhead reduction type payloading according to an embodiment of the present invention.
5 is a block diagram illustrating an MMT overhead reduction type payload device according to an embodiment of the present invention.
6 shows the structure of the MMT payload header.
7 is a flowchart illustrating an MMT overhead reduction type payloading method according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In addition, the terms described below are defined in consideration of the functions of the present invention, which may vary depending on the intention of the user, the operator, or the custom. Therefore, the definition should be based on the contents throughout this specification.

1 is a diagram showing a hierarchical structure of an MMT system.

1, the MMT layer is composed of four functional areas including an encapsulation layer, a delivery layer, a signaling layer, and a composition layer. .

The encapsulation layer generates coded media data or stored media data as input and generates a data fragment that is a small unit for the MMT service. An access unit for the MMT service using the data fragment is used as an encapsulation layer, Lt; / RTI > The Encapsulation Layer also creates a packet format for creation and storage and delivery of composite content by combining and / or splitting access units.

The delivery layer translates the data unit (s) output from the encapsulation layer into the MMT payload format, adds the MMT transport packet header to the MMT transport packet, Or RTP packets using an existing transmission protocol RTP (Real-time Protocol).

Packets configured in the Delivery Layer are finally IP packetized in the Internet Protocol (IP) layer via a transport protocol layer such as UDP (User Datagram Protocol) or TCP (Transport Control Protocol). A signaling layer generates control information or signaling information necessary for data transmission, adds the control information or signaling information to the data, or transmits the data through separate signaling means.

The MMT payload format generated at the Delivery Layer defines the logical structure of the media unit (s) to be delivered by the MMT protocol or RTP. The MMT payload is specified by a payload format for conveying encapsulated data units and other information by MMT layer protocols or other existing Application Transport Protocols. The MMT payload provides information about streaming and information about file transfers. In streaming, the data unit may be an MMT Media Fragment Unit (MFU) or a Media Processing Unit (MPU).

Here, the MFU is a general container format that is independent of any specific media codec, including coded media data that can be independently processed by a media decoder. The MFU represents a fraction of the fragmented data of the MPU, which is the minimum unit that can be independently decoded. As an example, when encoding is performed using one frame as an access unit, the MFU can be one video frame, and in other cases, it can be one slice included in one frame.

An MPU is a container format that includes one or more MFUs and additional delivery and processing related information, and may include various numbers of MFUs generated from a plurality of different access units. The MPU refers to an encoded media data unit that can be completely and independently processed by an MMT compliant entity. The MPU can be a specific size (for example, 1 GOP (Group of Pictures) in the case of video, ). As an example, the MPU may be composed of a plurality of picture frames constituting one GOP (one-second video, for example), and the MFU may include each picture frame. The MPU contains header fields according to a given definition, at least some of which may be necessary for the processing of the MPU.

2 is an internal structure diagram of an MMT packet.

Referring to FIG. 2, the MMT packet generates an MMT payload in the delivery function layer 130 based on the MPU file 210 generated in the encapsulation function layer 120. The header information 220 and 230 are identified by identifying at least one multimedia data, and the header information and at least one multimedia data are combined to form a multimedia data packet.

The present invention is directed to a payloading scheme that can reduce the overhead generated by the transfer function layer 130 as shown in FIG.

Currently, the MMT payload scheme, which is considered in the MPEG system division, separates three types of MPU fragments separately into MMT payloads.

The types of the three MPU fragments consist of MPU metadata including MPU metadata, foup, mmpu, and moov box, Movie fragment metadata including the rest of the media data of moof box and mdat box, and an mdat box containing media data. And a media fragment unit (MFU).

3 is a diagram for explaining the principle of MMT payload loading.

Referring to FIG. 3, each type of three types of MPU fragments is separately separated into payloads of MMT packets. That is, the MPU metadata 310, the movie fragment metadata 320, and the MFU 330 are not integrated into one MMT payload but are separately loaded into the MMT packet.

However, in the case of the MPU file, the number of media samples included in the MPU varies depending on the length of the time interval covered by the MPU, and thus the size of the MPU metadata and the number of media samples included in the mdat box are different . That is, when the temporal length of the MPU is large, the size of the MPU metadata and the size of the mdat box increase.

On the other hand, if the size of the MPU file is large, it can be divided into moofs (movie fragments) of fragments through fragmentation. In this case, the size of the generated moof box increases as the number of media samples included in the moof increases. Unlike the realtime streaming service based on UDP and RTP / RTCP, TCP-based progressive streaming service reduces service latency by continuously transmitting segment fragments of small size. To do this, a relatively small number of media samples are split into moofs. In this case, the size of the movie fragment metadata shown in FIG. 3 is considerably reduced. When payloading a very small size movie fragment metadata in one MMT packet, the overhead is seriously increased because the size of the payload compared to the size of the entire header of the MMT packet becomes very small . As the overhead increases, the number of packets required to transmit all the MPU fragments increases, which may cause a congestion in the transmission channel.

Accordingly, when the data size of the moof box is significantly smaller than the MTU size of the network to prevent congestion in the transmission channel, the movie fragment metadata is integrated with the adjacent MPU metadata or MFU and mapped to the MMT payload.

4 is a view for explaining the principle of MMT overhead reduction type payloading according to an embodiment of the present invention.

Referring to FIG. 4, the MMT overhead reduction type payloading principle according to an embodiment of the present invention integrates one or more MPU fragments according to size size to generate one MMT payload. More specifically, the following three cases are possible within a range in which the integrated packet size when the movie fragment metadata is integrated with at least one of the MPU metadata and the MFU does not exceed the MTU.

CASE 1: Movie fragment metadata is integrated with MPU metadata for payload loading

CASE 2: Movie fragment metadata integrated with MFU for payload loading

CASE 3: Movie fragment metadata is integrated with MFU as well as MPU metadata and payloaded

5 is a block diagram illustrating an MMT overhead reduction type payload device according to an embodiment of the present invention. Here, the MMT overhead reduction type payload device is included in the transfer function layer 130 among the layers in FIG.

Referring to FIG. 5, the MMT overhead reduction type payload device includes a type classification unit 610, a size comparison unit 620, a payload generation unit 630, and a header generation unit 640.

The type classification unit 610 classifies input MPU fragment types. As described above, the types of the three MPU fragments include MPU metadata including the ftyp, mmpu, and moov boxes of the MPU file, Movie fragment metadata including the remainder excluding the media data of the moof box and the mdat box, and an MFU (media fragment unit) composed of an mdat box.

The size comparing unit 620 compares the size of the packet and the size of the MTU when integrating the MPU fragment with other types of MPU fragments according to the classified MPU fragment type. That is, it is checked whether the integrated packet size when the movie fragment metadata is integrated with at least one of the MPU metadata and the MFU does not exceed the MTU.

The payload generating unit 630 maps the movie fragment metadata to at least one of the MPU metadata and the MFU, and maps the movie fragment metadata to the MMT payload according to the size comparison result. That is, when the size of the unified packet is smaller than the MTU size, the movie fragment metadata is mapped with the MPU metadata according to the corresponding conditions, and when the movie fragment metadata is mapped with the MFU, However, if the MFU is integrated with the MFU, it is determined to be one of the mapping units and the payload is loaded.

The header generation unit 640 adds a header to the generated payload, and notifies the three integrated packets according to an embodiment of the present invention. This will be described in detail with reference to FIG. 6 and Table 1 and Table 2.

FIG. 6 shows the structure of the MMT payload header described in the technical document prior to IS (International Standard) approval of MMT technology.

Referring to FIG. 6, the MMT payload header includes an FT (MPU Fragment Type) field 610 indicating an MPU fragment type mapped to a payload. The existing values are as shown in Table 1 below .

However, in the present invention, in addition to the FT values shown in Table 1, in addition to mapping movie fragment metadata with MPU metadata (case 1), when movie fragment metadata is mapped with MFU (case 2) It is necessary to include the values indicating the case where the metadata is mapped together with the MFU as well as the MPU metadata (case 3).

For this, an embodiment of the meaning and corresponding values of the MPU Fragment Type according to the present invention is shown in Table 2 below.

Referring to Table 2, when the MPU metadata + movie fragment metadata is payloaded to one payload (case 1), ?? 3 ?? is assigned as the FT value, and movie fragment metadata + MFU is payload 4 is assigned as the FT value for case 2, and 5 is assigned as the FT value for case 3 of payload of MPU metadata + movie fragment metadata + MFU. Accordingly, the header generating unit 540 sets the FT value of the header according to the configuration of the payload generated by the payload generating unit 530 as shown in Table 2 below.

7 is a flowchart illustrating an MMT overhead reduction type payloading method according to an embodiment of the present invention.

Referring to FIG. 7, in step S720, the MMT overhead reduction type payload device (hereinafter referred to as a 'device') determines the type of the MPU fragment according to the MPU fragment input (S710). That is, as described above, the types of the three MPU fragments include MPU metadata including the ftyp, mmpu, and moov boxes of the MPU file, Movie fragment metadata including the rest of the media except for the media data of the moof box and the mdat box, And an MFU (media fragment unit) composed of an mdat box including the MBs.

If it is determined in step S720 that the MPU fragment type is MPU metadata, the apparatus determines whether the size of the unified packet exceeds the MTU size in case of CASE 1 that integrates movie fragment metadata with MPU metadata (S730).

As a result of the determination in S730, if the packet size exceeds the MTU size, the device separates the movie fragment metadata from the MPU metadata to configure the MMT packet (S740). On the other hand, if the size of the unified packet does not exceed the MTU size in Case 1 of S730, in case of CASE 3 which integrates movie fragment metadata together with MFU metadata as well as MFU, (S750).

If the size of the packet exceeds the MTU size in case of S750, the device forms a payload with CASE 1 that integrates movie fragment metadata with MPU metadata (S760). On the other hand, if it is determined in S750 that the size of the packet does not exceed the MTU size in CASE 3, the device configures a payload with CASE 3 that integrates movie fragment metadata together with MPU metadata together with MFU (S770).

If it is determined in step S720 that the MPU fragment type is movie fragment metadata, the apparatus determines whether the size of the unified packet exceeds the MTU size in case of CASE 2 that integrates movie fragment metadata with the MFU (S780). If it is determined in S780 that the size of the packet does not exceed the MTU size, the device constructs a payload with CASE 2 that integrates movie fragment metadata with the MFU (S790). On the other hand, if it is determined in step S780 that the packet size exceeds the MTU size, the device separates the movie fragment metadata and the MFU to form a payload (S800).

On the other hand, if it is determined in step S720 that the MPU fragment type is an MFU, the device configures a payload with the MFU (S810).

Claims

A type classification unit for classifying input media processing unit (MPU) fragment types;
A size comparing unit for comparing the size of the unified packet and the size of a maximum transmission unit (MTU) when integrating the MPU fragment with another MPU fragment of the different type from the classified MPU fragment type;
A payload generating unit for generating an MMT payload by combining two or more different types of MPU fragments according to the size comparison result;
And a header generator for adding a header to the generated payload.

The method of claim 1, wherein the MPU fragments
Wherein the MPU fragment type is one of MPU fragment types including MPU metadata, Movie fragment metadata, and Media Fragment Unit (MFU).

3. The apparatus of claim 2, wherein the payload generator
If movie fragment metadata is integrated with MPU metadata within the MTU size range, movie fragment metadata is integrated with MFU, and movie fragment metadata is mapped with MFU metadata as well as MPU metadata, thereby constituting a payload Wherein the MMT overhead reduction type payloading apparatus comprises:

4. The apparatus of claim 3, wherein the header generating unit
And sets the value of the MPU Fragment Type (FT) field included in the header to indicate that the packet is a unified packet.

5. The apparatus of claim 4, wherein the header generating unit
When the MPU metadata and the movie fragment metadata are integrated, the FT value is allocated to 3. When the movie fragment metadata and the MFU are integrated, the FT value is allocated to 4. When the MPU metadata, the movie fragment metadata and the MFU are integrated, And the FT value is assigned to 5.

An MMT overhead reduction type payloading method in a transfer function layer of an MMT system,
Classifying an input media processing unit (MPU) fragment type;
Comparing the size of the unified packet and the size of the maximum transmission unit (MTU) when integrating the MPU fragment with another MPU fragment of the different type from the classified MPU fragment type;
Generating an MMT payload by combining two or more different types of MPU fragments according to the size comparison result;
And adding a header to the generated payload. &Lt; RTI ID = 0.0 > 11. < / RTI >

7. The method of claim 6, wherein the MPU fragments
Wherein the MPU fragment type is one of MPU fragment types including MPU metadata, Movie fragment metadata, and Media Fragment Unit (MFU).

8. The method of claim 7, wherein generating the payload comprises:
If movie fragment metadata is integrated with MPU metadata within the MTU size range, movie fragment metadata is integrated with MFU, and movie fragment metadata is mapped with MFU metadata as well as MPU metadata, thereby constituting a payload Wherein the MMT overhead reduction type payload method comprises:

9. The method of claim 8, wherein adding the header further comprises:
And setting the value of the MPU Fragment Type field included in the header to indicate that the packet is a unified packet.

10. The method of claim 9, wherein adding the header further comprises:
When the MPU metadata and the movie fragment metadata are integrated, the FT value is allocated to 3. When the movie fragment metadata and the MFU are integrated, the FT value is allocated to 4. When the MPU metadata, the movie fragment metadata and the MFU are integrated, And the FT value is assigned to 5.