KR102160567B1 - Method for transmitting transport characteristics of multimedia data in broadcast system - Google Patents

Abstract

The present invention relates to a method of transmitting media data in a multimedia system, comprising a process of transmitting a transport packet generated based on a media data unit (MPU), wherein the transport packet is an asset including at least one MPU ( asset), and the transmission characteristic information includes bitstream information for transmission of the asset and quality of service (QoS) information of the asset, and the quality of service information is a packet of the asset A first field indicating loss-related characteristics and a second field classifying a service class of the asset, wherein the bitstream information includes a first field indicating a minimum bit rate of the MPU and transmission of the media data of the asset. And a second field indicating a maximum buffer size for, and the transport packet further includes a flag indicating that transmission characteristic information of the asset exists.

Description

Transmission method of transmission characteristic information of multimedia data in broadcasting system {METHOD FOR TRANSMITTING TRANSPORT CHARACTERISTICS OF MULTIMEDIA DATA IN BROADCAST SYSTEM}

The present invention relates to a method and apparatus for transmitting a multimedia data packet in a broadcasting system, and more particularly, in a broadcasting system supporting a multimedia service based on an Internet protocol, composed of one or more Media Processing Units (MPUs). The present invention relates to a method of transmitting multimedia data transmission characteristic information in MPU units for QoS (Quality Of Service) control when serving multimedia contents in a network environment that dynamically changes over time.

In IEEE802.16 (WIMAX), IEEE802.11e (WiFi TXOP), 3GPP UMTS (3rd Generation Partnership Project Universal Mobile Telecommunication System), and 3GPP Long Term Evolution (LTE), a resource is reserved and the reserved resource is guaranteed (guarantee). There is this. In real-time multimedia services, such a resource reservation protocol can be used to guarantee the quality of service. Representatively, the Internet Engineering Task Force (IETF) defines parameters necessary for network resource reservation between a user's terminal and a content server in the resource reservation protocol RSVP (Resource reservation Protocol).

1 is a schematic diagram of a process of expressing data of a variable bit rate with a double leaky bucket parameter.

Variable BitRate (VBR) traffic is expressed as a double leaky bucket using four parameters (Rg, Rp, Bp, B) included in the traffic specification (Tspec). Rg is an average given bit rate, and even if it exceeds this bit rate momentarily, overflow does not occur when stored in the buffer. The required buffer size is promised by B in advance. Similarly, reserve the peak bitrate. Assuming that the peak bit rate is maintained within the period of sending one packet, the buffer size Bp for the peak bit rate Rp can be set as the maximum size of the SDU (Service Data Unit). This value can usually be expressed in MTU (Maximum Transfer Unit).

Table 1 shows that the four parameters of the double leaky bucket are used in various protocols.

IETF RSVP,
IEEE802.11e
'tspec' IEEE802.16 (WIMAX) 3GPP UMTS & LTE MPEG-4 OD ATM Rp p Min. reserved traffic rate Maximum bitrate (4B) avgBitrate PCR Bp M SDU size Maximum SDU size MAX_AU_SIZE CDVT Rg r Max. sustained traffic rate Guaranteed bitrate (4B) AverageBitRate SCR Bg b Maximum Latency k*Maximum SDU bufferSizeDB BT

Therefore, generating multimedia transport characteristics using a double leaky bucket parameter is advantageous in terms of compatibility with other protocols. In general, such a resource reservation protocol is performed in the process of establishing a service session to provide multimedia services, and while the service continues, that is, end-to-end on a network that transmits data for the entire multimedia content. Is assumed to be established. However, reserving resources between end-to-end services is impossible in a general open Internet environment. In addition, in the case of a core network, while stable and broadband transmission is possible, a problem occurs due to resource sharing among multiple users as it approaches the end. In particular, in the case of wireless and mobile communication networks, the network resource environment dynamically changes due to various reasons such as movement of users and interference of radio waves.

2 shows SINR results measured for 10 minutes in an IEEE 802.16 network environment.

In such a dynamic network environment in which the SINR changes in real time, if resources are reserved at the start of a service session using an existing RSVP, it is difficult to guarantee the reserved resources. In addition, a new resource reservation process is required because the base station changes when the user moves due to the nature of the mobile environment. In the case of reserving resources to guarantee QoS of multimedia services in such a dynamic network environment, resource reservation in units shorter than overall resource reservation of contents is effective. Therefore, a method of inserting MPU Delivery Characteristics information, which is auxiliary information for controlling QoS for an MPU, in a Media Processing Unit (MPU) unit, which is a detailed unit constituting media content, should be provided.

The problem to be solved by the present invention is to provide a method and apparatus for more effectively guaranteeing QoS of a multimedia service by providing characteristic information on temporally distinguishable media data in a dynamic network environment.

A method of transmitting media data in a multimedia system according to an embodiment of the present invention includes a process of transmitting a transport packet generated based on a media data unit (MPU), wherein the transport packet includes at least one MPU. It includes transmission characteristic information for transmission of an asset, and the transmission characteristic information includes bitstream information for transmission of the asset and quality of service (QoS) information of the asset, and the quality of service information is the asset A first field indicating a characteristic of a packet loss of the asset and a second field for classifying a service class of the asset, wherein the bitstream information includes a first field indicating a minimum bit rate of the MPU and the media data of the asset. And a second field indicating a maximum buffer size for transmission, and the transport packet further includes a flag indicating that transmission characteristic information of the asset exists.

According to the present invention, by utilizing characteristic information for transmission for each media data unit of a small time unit, more effective QoS control is possible in a situation where a transmission environment is dynamically changed, such as a mobile network.

1 is a diagram illustrating a process of expressing data of a variable bit rate with a double leaky bucket parameter
2 is a diagram showing SINR results measured for 10 minutes in an IEEE 802.16 network environment
3 is a diagram showing the structure of an MMT encapsulator header according to an embodiment of the present invention
4 is a diagram illustrating an example of utilizing characteristic information for transmission of media data between an MMT server and a client according to an embodiment of the present invention

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The terms used are terms selected in consideration of functions in the embodiment, and the meaning of the terms may vary according to the intentions or precedents of users or operators. Therefore, the meaning of the terms used in the embodiments to be described later follows the definition when it is specifically defined in the present specification, and when there is no specific definition, it should be interpreted as the meaning generally recognized by those skilled in the art.

The characteristic information on the media data in the MPU unit proposed by the present invention may be generated during a content generation (capture, grab) process and a pre-encapsulated process of media data. The method of using the generated feature information in the transmission process is as follows. In an embodiment of the present invention, for convenience of description, the description is based on the MPEG Media Transport (MMT), which is currently being standardized by the Moving Picture Experts Group (MPEG), but the present invention is not limited thereto. The MMT system internally divides it into an encapsulation layer, a delivery layer, and a control (signaling) layer according to its function. Therefore, the method of using feature information according to each layer is described below. Describe separately.

MMT encapsulation layer

The MMT encapsulation layer performs a function of generating feature information for media data in units of MPU proposed in the present invention.

3 shows a header structure of an MMT encapsulation layer.

Since an MMT asset composed of one or more MPUs refers to individual components (for example, video components or audio components) constituting media content, characteristic information of media data exists for each MMT asset. The characteristic information of the unit of the MMT asset may be utilized for overall QoS control and resource reservation of a service in the process of establishing a session of a corresponding MMT asset using the aforementioned RSVP or the like. The feature information for each MPU proposed in the present invention is added as information for transmission and QoS control using a flag for one or more MPUs, that is, MPU groups constituting an MMT asset.

MMT control layer

The MMT control layer is responsible for exchanging service discovery information, quality of experience (QoE) management information, and digital rights management (DRM) information between the server and the client. In the process of exchanging service discovery information, a network resource reservation process for establishing a session can be performed, so QoS control such as resource reservation is performed using media characteristic information included in the MMT asset. As described above, since QoS control in units of assets is performed in units of overall content, QoS control in units of smaller units of MPU groups is required in a dynamic environment.

MMT delivery layer

The MMT transport layer is responsible for the function of transmitting the encapsulated media data packet from the server to the client and the function of inter-layer information exchange (eg, cross-layer interface) within the terminal. To this end, the MMT transport layer generates a transport packet. The MMT transport layer obtains QoS-related information that should be included for each transport packet from feature information in order to guarantee the QoS of the transport packet.

4 illustrates an embodiment in which transport characteristics of media data generated in an MMT encapsulation layer are utilized in a media transmission service process.

The MPU delivery characteristic of media data in units of MPU groups proposed in the present invention is generated in the MMT server 601 side encapsulation layer 603 and inserted in the form of a flag. Media characteristic information in units of MPU groups proposed in the present invention is included in information necessary for resource reservation (e.g., double leaky bucket parameter; bitstream_descriptor) and information indicating a relative priority for each packet (QoS_descriptor) It is divided into The bitstream_descriptor is delivered 606 to the control layer (C layer 605) and is delivered to the C layer 609 of the client 602 through signaling protocols such as RTSP (Real-Time Stream Protocol) and SIP (Session Initiation Protocol). . In the case of the QoS_descriptor, the information parsed by the C layer 605 is transmitted to the delivery layer 604 (607), inserted into each delivery packet, and then a data channel is established. It can be delivered to the client 602 and an intermediate network device (not shown). Alternatively, it is possible to obtain information and transmit it by directly accessing the encapsulation header of data transmitted through path 608 and parsing the corresponding field. Since such a series of processes are performed in units of MPU, they may be performed in units of time shorter than units of assets.

Next, syntax and semantics for media feature information in units of MPU groups according to an embodiment of the present invention will be described in detail.

Table 2 shows syntax and semantics for each field for auxiliary information for transmission and QoS control in an MPU group unit (or a media data unit of a time unit smaller than an asset such as GOP) proposed by the present invention. In Table 2, the names, sizes, and types of variables representing each field are selected in consideration of functions in the embodiment as described above, and thus may vary according to the intentions or precedents of users and operators. However, the meaning of each field should follow the definition provided in this specification.

Syntax No. Of bits Mnemonic MPU_Header(){
mpu_length;
header_length;
mpu_sequence_number;
number_of_au;
for(int i=0; i<number_of_au; i++){
au_length;
}
private_header_flag;
if(private_header_flag == 1)(
private_header_length
private_header
}
MPU_delivery_characteristic_header_flag;
if(MPU_delivery_characteristic_header_flag == 1){
QoS_descriptor(){
loss_priority;
delay_priority;
class_of_service;
hybrid_sync_indicator;
}
Bitstream_descriptor(){
sustainable_rate;
buffer_size;
peak_rate;
max_MFU_size;
MFU_perid;
}
}
}
MPU_Payload()

Element or Attribute Name Use Description mpu_sequence_number specifies sequence number of MPU in a single MMT Asset. It is incremented by 1 and will be unique within in an MMT Asset. number_of_au specifies the number of AUs in this MPU. au_length specifies length of each AU in this MPU private_header_flag indicates that there is private_header private_header_length specifies the length of private_header MPU_delivery_characteristic_header_flag MDC Flag indicating presence or absence. If 1, MDC information follows. loss_priority It represents the characteristics of MPU transmission packet loss.
11: loss priority 0 (Lossless)
10: loss priority 1 ( Lossy , High priority)
01: loss priority 2 ( Lossy , Medium priority)
00: loss priority 3 ( Lossy , Low priority) delay_priority It shows the characteristics of the delay sensitivity of the MPU.
11: high sensitivity: end-to-end delay << 1sec (e.g., VoIP, video-conference)
10: medium sensitivity: end-to-end delay approx . 1 sec (e.g., live-streaming)
01: low sensitivity: end-to-end delay <5~10 sec (e.g., VoD)
00: don’t care (e.g., FTP, file download) class_of_service Characteristics of MPU data Bitstream It is represented by classifying it by characteristics.
111: The Constant Bit Rate ( CBR ) service class shall guarantee peak bitrate at any time to be dedicated for transmission of the MPU. This class is appropriate for realtime services which require fixed bitrate such as VoIP without silence suppression.
110: The Real-Time Variable Bit Rate (rt- VBR ) service class shall guarantee sustainable bitrate and allow peak bitrate for the MPU with delay constraints over shared channel. This class is appropriate for most realtime services such as video telephony, videoconferencing, streaming service, etc.
101: The Non-Real-Time Variable Bit Rate ( nrt - VBR ) service class shall guarantee sustainable birate and allow peak bitrate for the MPU without delay constraint over shared channel such as file downloading.
100: The Available Bit Rate ( ABR ) class shall not guarantee any bitrate, but may report available bitrate for feedback control. This class is appropriate for applications which can be adaptive to time-varying bitrate such as video streaming with RTCP feedback.
011: The Unspecified Bit Rate (UBR) class shall not guarantee any bitrate and shall not indicate congestion. This class is appropriate for interactive applications such as Web browsing. UBR service is equivalent to the common term “best effort service”. hybrid_sync_indicator Flag for synchronization of transfers. If it is 1, it is not necessary to consider transmission synchronization with other MPUs, and if it is 0, it is necessary to consider transmission synchronization.
1: no dependency.
0: dependent on other MPU for synchronization in hybrid delivery. sustainable_rate The sustainable_rate defines the minimum bitrate that shall be guaranteed for continuous delivery of the MPU. The sustainable_rate corresponds to drain rate in token bucket model. The sustainable_rate is expressed in kilobits of MFU (or MPU) per second. buffer_size The buffer_size defines the maximum buffer size for delivery of the MPU. The buffer absorbs excess instantaneous bitrate higher than the sustainable_rate and the buffer_size shall be large enough to avoid overflow. The buffer_size corresponds to bucket depth in token bucket model. Buffer_size of a CBR (constant bit rate) MPU shall be zero. The buffer_size is expressed in kilobits peak_rate The peak_rate defines peak bitrate during continuous delivery of the MPU. The peak_rate is the highest average bit rate during every MFU period . The peak_rate is expressed in kilobits of MFU (or MPU) per second. MFU_period The MFU period defines minimum period of MFU during continuous delivery of the MPU. The MFU period is expressed in millisecond. max_MFU_size The max_ MFU _size is the maximum size of MFU , which is MFU_period*peak_rate. The max_MFU_size is expressed in kilobits.

That is, as shown in Table 3, sustainable_rate represents the minimum bit rate guaranteed for MPU data transmission, buffer_size represents the maximum buffer size for MPU data transmission, peak_rate represents the peak bit rate during MPU data transmission, and MFU_period represents the MFU Represents the minimum period of (Media Fragment Unit), and max_MFU_size represents the maximum size of MFU.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (4)

In a method for transmitting media data in a multimedia system,
It includes a process of transmitting a transport packet generated based on a media data unit (MPU),
The transport packet includes transmission characteristic information for transmission of an asset including at least one MPU,
The transmission characteristic information includes bitstream information for transmission of the asset and quality of service (QoS) information of the asset,
The quality of service information includes a first field indicating a characteristic of a packet loss of the asset and a second field for classifying a service class of the asset,
The bitstream information includes a first field indicating a minimum bit rate of the MPU and a second field indicating a maximum buffer size for transmission of the media data of the asset,
The transport packet further includes a flag indicating that transmission characteristic information of the asset exists. The method of claim 1,
The bitstream information includes a third field indicating a peak bit rate for transmission of the asset, a fourth field indicating a period of a subunit of the MPU for transmission of the asset, and a fifth field indicating the maximum size of the subunit. The method further includes at least one of the fields. The method of claim 1,
The quality of service information further includes a third field indicating a characteristic of the delay sensitivity of the asset. The method of claim 1,
The service class is a method of classifying a type of bitstream indicating a fixed bit rate or a variable bit rate.

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