Method and device for delivering multimedia data using IETF QoS protocols

0001The present invention relates to a multimedia data transmission device and method using an Internet Engineering Task Force (IETF) Quality of Service (QoS) protocol.

0002Circuit switching networks were used in the 1990s to transmit digital video information. Due to the fixed bandwidth of such circuit switching networks QoS was guaranteed. In the late 1990s the use of packet switching networks became universal due to the popularity of the Internet. When using such packet exchange networks, various bandwidths can be used. However QoS is not guaranteed because packet exchange networks use a best effort protocol which does not differentiate packets and shares the network resources among all users on the Internet.

0003The advantages of both circuit switching and packet switching should be used when transmitting video. That is, various bandwidths should be used and QoS should be partially (or completely) guaranteed. The IETF has defined various QoS protocols to meet such needs. Most companies have already started manufacturing routers that support the IETF QoS protocols. IETF QoS protocols are also used in WINDOWS XP, more advanced versions of the WINDOWS series OS, and LINUX. In addition, since IPv6, the next generation Internet protocol that will be widely used before 2010, was standardized in the 1990s when real-time multimedia services started to gain recognition as an important service among the Internet services, the IPv6 is largely different from the existing Internet protocol (IPv4) in that it is easy for IPv6 to use such IETF QoS protocols. The next generation Internet is currently in trial operation and will be commercially adopted and used in wireless networks. The next generation wireless network standard, UMTS (Universal Mobile Telecommunication Systems) is compatible with the QoS control protocol. If the UMTS is realized through AII-IP, IPv6 and the QoS protocol will be widely used.

0004Meanwhile, in the wireless Internet, fees are charged on a per packet basis and the packet transmission price varies depending on the service and time of use. In addition, demand for services that simultaneously use wired Internet and wireless Internet is increasing. When charging on a per packet basis, issues such as reducing the number of transmitted packets and whether quality can be maintained while reducing the number of high priority packets become very important.

0005It is an undoubted fact that there will be an increase in the use of the movie picture experts group (MPEG) standard and the Internet, and currently MPEG and the Internet are both used in the communication devices carried by individuals. In the MPEG standard, various standards for multimedia compression and processing are established, while the IETF standards are established for ways of transmitting various information using the Internet. When using these standards set by the two organizations, multimedia transmission is very effective. However since a minimum amount of interfacing is provided between the standards set by the two organizations, many protocols are yet to be effectively used. In particular, years ago the IETF established QoS protocols such as RSVP, diffServ, and intServ, and had them control QoS when transmitting multimedia. However, the MPEG standard does not consider using these methods. That is, the MPEG standard assumes the use of only the packet exchange network, which uses a best effort protocol, and does not define any interface with network layers. Thus, interfacing the packet network with a router on the Internet is impossible. Therefore, when the network is congested the quality of the service (QoS) may deteriorate.

0006A mechanism that guarantees that loss and delay remain within a predetermined range is needed for multimedia service to be carried out effectively. To realize such a mechanism, functions such as granting priority to packets and resource reservation are used. Routers and operating systems with such functions are already being manufactured. However, since the MPEG standard does not assume the use of such a mechanism, such functions cannot be used. Therefore, an agreement between the MPEG and IETF on the values that quantitatively define the correlation between the network resources and quality of multimedia should be made to use such functions effectively.

0007Therefore, for the MPEG standard and IETF QoS protocol to be effectively compatible, the type and definition of information exchanged should be coordinated and standardized. In addition, a standard for exchanging information and a procedure of exchanging information should be prepared. Information that should be exchanged are classified with traffic descriptor information and QoS information. In the MPEG standard, traffic related descriptors include DecoderConfigDescriptor and QoS_Descriptor in the ISO/IEC 14496-1 MPEG-4 system, and QoS_metrics in the ISO/IEC 14496-6 MPEG-4 DMIF system (however, complete compatibility between these two does not exist), and such traffic related descriptors should be coordinated to be identical to parameters of Sender_Tspec of the RSVP protocol, which is an IETF standard, and identical to factors in the FlowSpec.

0008In addition, for the current Internet QoS protocol to be widely used among the traffic descriptors, qualitative elements among the definitions of the traffic descriptors should be changed into quantitative definitions. For example, the packet priority on the Internet has eight levels defining the characteristic of the traffic known as a flow label. However, the methods to use the packet priority and flow label and what levels reserve how much resources are not completely standardized.

0009Meanwhile, while fees are currently charged monthly by most wired Internet providers, fees are likely to be charged on a per packet basis in the future. Per-packet payment policies have already been implemented for wireless Internet. Therefore, a way of maintaining media quality while minimizing the number of packets and priority of delivery should be sought.

0010MPEG started out as a standard for compressing and storing multimedia, however real-time transmission through the Internet has become the most important service provided these days. Therefore, all feasible means in the Internet protocol should be used to search for a way to receive differentiated service when transmitting MPEG media.

0011<patcit id="pcit0001" dnum="US20030056014A"><text>US 2003/0056014</text></patcit> discloses a transmission system comprising a gateway for interconnecting first and second networks. The gateway comprises first and second quality of service translation means and interconnection means for interconnecting the first and second quality of service translation means. The first quality of service translation means are arranged for receiving input data having an associated input quality of service from the first network and for translating the input data into interconnection data having an associated interconnection quality of service. The second quality of service translation means are arranged for receiving the interconnection data from the interconnection means and for translating the interconnection data into output data having an associated output quality of service. The gateway is characterised in that the interconnection data further comprises information representative of the input quality of service and in that the second quality of service translation means are arranged for translating the interconnection data into output data dependent on the information.

0012<patcit id="pcit0002" dnum="US20020097798A"><text>US2002/0097798</text></patcit> discloses a method and system for integrating voice, video and data. The method encodes a signal including at least one of a plurality of quality of service measurements. Further, the method compresses the signal to produce a packet flow. In addition, the method varies compression based on at least one of the plurality of quality of service measurements, wherein an amount of information transferred by the packet flow varies to maintain a predetermined quality of service associated with the packet flow between the source of the packet flow and the destination of the packet flow.

0013Dell' Uomo, L., Fraccalvieri, F., Teloni, U. "RQDMA: a MAC Protocol supporting QoS in an IP-based Broadband Wireless Local Loop" discloses an IP-based wireless local loop system supporting different services such as fast Internet access, data, voice and video conferencing.

0014According to the present invention there is provided an apparatus and method as set forth in the appended claims. Preferred features of the invention will be apparent from the dependent claims, and the description which follows.

0015In accordance with an aspect of the present invention, a device to effectively transmit MPEG media data by partially modifying a MPEG standard so that a Quality of Service (QoS) protocol of an Internet Engineering Task Force (IETF) can be used within the MPEG standard, modifying quantitative factors so that the MPEG standard and a network class level are compatible within the IETF standard, and mapping traffic of the MPEG, a QoS descriptor, and QoS control procedure onto the IETF QoS protocol and a method thereof are provided.

0016Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

0017In an aspect of the present invention, a device for effectively transmitting MPEG media data by reserving a bandwidth and buffer at a router, which exists on a pathway so that QoS is guaranteed even when a network is congested, and a method thereof are provided.

0018In an aspect of the present invention, a device for effectively transmitting MPEG media data by allowing configuration of priority and an amount of resource (bandwidth, buffer size, etc.) that should be reserved when making a reservation so that a user can decide on the service quality beforehand and a method thereof are provided.

0019According to an aspect of the present invention, there is provided a multi media data transmission device, comprising: a mapping unit arranged to analyse data traffic including a QoS factor and to represent the QoS factor as a second QoS factor; a packet transmitter/receiver unit arranged to transmit packets through a network according to the second QoS factor; characterised by: a media processing unit arranged to create multi media traffic including a compressed media resource; a call control unit arranged to manage call set-up and call control with another multi media data transmission device, to receive QoS change requests from the other multi media data transmission device, users or to receive QoS change requests according to changes in a network environment, and to transmit the received QoS change requests to a media packet transmitter/receiver through the mapping unit; wherein the mapping unit is arranged to analyze the multi media traffic including the compressed media resource, traffic factors, and QoS factors and to represent the multi media traffic by layer factors used in a network layer; and the media packet transmitter/receiver unit is arranged to transmit the multi media data in real time through the network by a double leaky bucket condition according to the represented layer factors, to receive the QoS change requests from the call control unit and to transmit a control signal to the media processing unit; and the media processing unit is arranged to change the production of multi media traffic according to the control signal from the media packet transmitter/receiver unit.

0020According to another aspect of the present invention, there is provided a multi media data transmission method, the method comprising: reading a QoS factor of data traffic; mapping the read QoS factor onto a second QoS factor; transmitting the data traffic on through a network according the second QoS factor; characterised by: generating multi media traffic including a compressed media resource; performing call set-up and management with a multi media data transmission device; reading the multi media traffic including the compressed media resource, traffic factors, and quality of service (QoS) factors; mapping the read multi media traffic onto network factors used in a network layer; transmitting multimedia data through the network by a double leaky bucket condition according to the mapped network factors; and receiving QoS change requests and changing the production of multi media data according to the QoS change request.

0021These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: <ul id="ul0001" list-style="none"><li><figref idref="f0001">Figure 1</figref> is a block diagram of a MPEG terminal according to an embodiment of the present invention;</li><li><figref idref="f0002">Figure 2</figref> illustrates the structure of the MPEG terminal and routers which recognize QoS protocols;</li><li><figref idref="f0003">Figure 3</figref> illustrates the leaky bucket algorithm of an embodiment of the present invention;</li><li><figref idref="f0003">Figure 4</figref> illustrates an MPEG-21 file format and the packet format of a QoS change command;</li><li><figref idref="f0004">Figure 5</figref> is a table comparing candidate factors of the MPEG standard with the factors of other protocols; and</li><li><figref idref="f0005">Figure 6</figref> is a graph illustrating the relationship between the bit rate of the encoding media traffic and buffer size.</li></ul>

0022Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.

0023In an exemplary embodiment of the present invention MPEG media data is transmitted using the RSVP/diffServ protocols, which record reservation states only in the routers connected to an MPEG terminal 102.

0024<figref idref="f0001">Figure 1</figref> is a block diagram of a MPEG terminal according to an embodiment the present invention.

0025Referring to <figref idref="f0001">Figure 1</figref>, the MPEG terminal 102 includes a network control unit 112, a call control unit 114, a QoS factor mapping unit 116, a media packet transmitter/receiver 118, and an MPEG media processing unit 110, and can be connected to the MPEG terminal of an opposite party 106 through either a network 104 or an end-to-end communication 134.

0026The call control unit 114 manages call set-up and call control between the MPEG terminals 102 and 106. Through call set-up and call controlling signals which are control signals exchanged with the MPEG terminal of the opposite party, an Internet address and port number of both parties, a service option, capability exchange parameter of the terminal, and end-to-end QoS specific factors using a real time transmission control protocol (RTCP) are exchanged, and users' demands are relayed. In this case, the set-up and call controlling signals are end-to-end signals and do not need to be read in the network. Meanwhile, network information 128 needed for the network control unit 112 among information included in the set-up and call controlling signals is relayed to the network control unit 112 from the call control unit 114 and is used in a network control signal 136. For example, a portion of the contents of an object descriptor (OD) in a MPEG-4 file can be used as the network information that defines traffic information in the network.

0027The QoS factor mapping unit 116 reads MPEG compressed media resources, traffic factors, and QoS factors and performs mapping according to the traffic and QoS factors and a priority number used in a network layer. In addition, among the factors used in the MPEG standard to reserve network resources, factors (e.g., a number of media streams, amount of resources required by a media stream) and signals 124 are exchanged with the call control unit 114.

0028Referring to <figref idref="f0002">Figure 2</figref>, the network control unit 112 handles call set-up and call control between an MPEG terminal 202 and an edge router 204, and call set-up and call control are performed according to a resource reservation protocol (RSVP) which is an IETF standard. The network control unit 112 reserves resources with the network 104 and exchanges the network control signals 136 containing information on the change of resources in the middle of the process of RSVP. The MPEG-4 DMIF (14496-6) standard includes, an operation to perform call set-up and call control according to the RSVP protocol. Furthermore when performing call set-up in MPEG-21 a process of capability exchange between terminals is expanded to capability exchange between the terminals and the network. In this case, a PATH packet of RSVP and RESV packets are used for call set-up and call control. The PATH packet is used for a path set up between a server and a client. In other words, if the PATH packet moves to a client from a server and confirms the amount of traffic that can be supported in each visit to routers on the way to the client, the confirmed results about the routers will be recorded on a PATH, the client's ability will be transmitted to the RESV packet, and the server decides whether to start the call set-up service by confirming the RESV packet. The specific mapping method of the traffic factor is described in detail below. In addition, the network control unit 112 exchanges the signal mapping the factor used in MPEG onto a factor conforming to the Internet protocol and the signal indicating whether reservations are made with the QoS factor mapping unit 116.

0029Meanwhile, the priority when transmitting and receiving MPEG video using the IETF protocol is decided by the importance of the data. For example, in MPEG videos, intra frames or intracoded macro blocks are more important than those of uni-directional prediction coding and uni-directional prediction coding is more important than bidirectional prediction encoding. In addition, in intracoding, a DC value is more important than a discrete cosine transform (DCT) coefficient and in prediction coding, motion vector data is more important than the DCT coefficient. In scalable videos, lower layer data is more important than higher layer data. Depending on the importance of the data, the DSCP (Differentiated Services Code Point) value of an Internet IP header is set differently. When indicating the DSCP value using three bits, the importance is expressed with eight different levels. The value of a priority field value of the MPEG-21 traffic descriptor is likely to be the same as the DSCP value in the future. In the future of the Internet, the price of packet transmission is likely to be changed according to priority. For reference, 3GPP expresses priority using six levels, and the priority levels used in MPEG and IETF should be equivalent to the priority levels used in 3GPP. In other words, a priority of 1 is the most important and as the number increases priority goes down. The higher the priority the earlier it is processed in the router, and packets with low priority are the first to be discarded when the router buffer is full. Priorities can be categorized into suspended priority and loss priority. For example, when eight levels, represented by three bits, are used to indicate priority, 1, 2, and 3 can be used as loss priority levels while 4, 5, and 6 can be used as delay priority levels, and the remaining two levels are reserved.

0030The media packet transmitter/receiver 118 plays the role of transmitting and receiving media packets 138 in real time. A predetermined stream identifier is inserted into the media packet header, of each media packet 138 transmitted. For example, in the next generation Internet protocol (IPv6), a stream identifier is inserted in a traffic class and flow label field. Furthermore, in the media packet transmitter/receiver 118, interleaving takes place with forward error correction (FEC), which is a QoS control method of the transport layer.

0031In addition, the media packet transmitter/receiver 118 measures a network packet loss rate and round trip time (RTT) using real-time transmission protocol (RTP)/real-time transmission control protocol (RTCP), and transmits signals 122, 124, and 126 to the call control unit 114 through the network control unit 112. The call control unit 114 takes certain measures to change the QoS by using the QoS function of MPEG-21 according to changes of the network QoS. Meanwhile, when the user from either the transmitting party or receiving party requests a QoS change, the call control unit 114 transmits necessary measures for the request process of a QoS change to the media packet transmitter/receiver 118 using signals 122, 124, and 126.

0032For example, in real-time services such as baseball broadcasting, a control signal 132 is sent to the MPEG media-processing unit 110. Such control signals 132 read the characteristics of the media stream and request changes in traffic volume, and the MPEG media processing unit 110 creates compressed media traffic 130 out of these signals according to leaky bucket conditions. In a service that streams encoded media, a file server is used instead of the MPEG media processing unit 110, and control signals 132 are used to select a medium and perform traffic shaping.

0033<figref idref="f0002">Figure 2</figref> illustrates an example of routers that identify the MPEG terminal and QoS protocol according to the embodiments of present invention. As shown in <figref idref="f0002">Figure 2</figref>, an edge router 204 is connected to the MPEG terminal 202 and functions as the entrance to the QoS control network 210. Overall QoS is controlled on the basis of an RSVP/diffServ protocol. Therefore an edge router 204 reads the RSVP packet that the MPEG terminal 202 transmits and forwards it to an internal core router 206. If a bandwidth broker 208 exists in the network 210, call allowance can be confirmed. The bandwidth broker 208 adds up a degree of network occupation by traffic class and notifies the edge router 204 of the amount of usable resources when requested. If the amount of resources that are requested by the edge router 204 exceed the usable amount, call allowance is refused. The bandwidth broker 208 identifies real-time service and non-real-time service, and the priority levels of the service classes are classified in the real-time service. In this case, the edge router 204 should be notified about the amount of usable resources so that the edge router 204 may modify its request. Call admission is performed according to service or to media streams within a service. If call set-up is performed, the MPEG terminal 202 transmits the media packet 138, and the edge router 204 reads and identifies the information written in the header of the media packet 138, which has arrived from the MPEG terminal 202, and after identification, writes the traffic class concerning diffServ in the media packet header and performs forwarding. When using multi protocol label switching (MPLS) an adequate label should be used.

0034Meanwhile, the bandwidth broker 208 determines whether allocated resources are being used by bitstreams and computes a charge by bitstream. Factors such as the number of packets transmitted/received, the priority of the packets, the current congestion rate of the network, the size of the packets, and the security and protection level are used to calculate the amount to charge a user. When computing the amount to charge, credit is accumulated for resources that are not used due to conservation of allocated resources. Results of the charge computation are constantly relayed through the MPEG terminal during service, and after service is finished the final total amount a user will be charged is indicated. In the wireless Internet, edge routers 204 are categorized as either home agents or access points. A home agent indicates the very first edge router that has performed call set-up and an access point indicates an edge router that exists in a base station of a calling cell to which the mobile terminal belongs when in motion. An access point takes over service from the home agent and continuously provides call control so that service may be provided without interruption and the home agent supports call control until the provided service ends. In this case, when a hand off takes place, paths and resources should be secured so that a call is not dropped.

0035<figref idref="f0003">Figure 3</figref> illustrates a double leaky bucket algorithm according to an embodiment of the present invention. As shown in <figref idref="f0003">Figure 3</figref>, the double leaky bucket is defined by four factors: maximum bit rate (p) 304; first buffer size (bp) 306; guaranteed bit rate (r) 308; and second buffer size (b) 310. A bit rate for variable bit rate traffic 302 is defined by a maximum permissible average bit rate over a certain period of time and by the minimum buffer size that can be used without the data overflowing when storing data that will exceed a permissible amount in the buffer. A first leaky bucket bit rate refers to the maximum average bit rate 304 when taking an average of the bits over short periods of time, usually within approximately a ms. Transmission is carried out with this average bit rate and if this bit rate is exceeded, the minimum buffer size in which the data does not overflow when storing the data in the buffer and transmitting, is set to the first buffer size 306. Reference numbers 304 and 306 each refer to p and bp in <figref idref="f0005">Figure 6</figref>, respectively. The bit rate of the second leaky bucket refers to the guaranteed average bit rate 308 when averaging over long periods of time, usually 100-200ms. In cases where the bit rate is exceeded, the second buffer size 310 is set to the minimum buffer size that can be used without the data overflowing when storing the data. Reference numbers 308 and 310 each refer to r and b in <figref idref="f0005">Figure 6</figref>, respectively.

0036The MPEG terminal gives out a call admission when performing call set-up or call control on the condition that the sum of p values of all real time traffic does not exceed the maximum bandwidth of a link. A bandwidth equal to p-r, which is the value obtained by subtracting r from the real time traffic p, can be used for non-real-time service.

0037For compression and transcoding of the MPEG media, the double leaky bucket based control used in the QoS protocol is carried out instead of the existing fixed bit rate control. However, the current MPEG traffic descriptor is not compatible with the double leaky bucket algorithm, and therefore the MPEG traffic descriptors have to be changed to be compatible with (p, bp) and (r, b). A more detailed description of such change will be provided below.

0038<figref idref="f0003">Figure 4</figref> is a modified MPEG -21 file format and a QoS modified order packet format according to an embodiment of the present invention. An MPEG media data decoding program and a transcoding program can be transmitted separately or with the compressed media data. The MPEG-21 file format shown in <figref idref="f0003">Figure 4</figref> illustrates a structure which includes a decoding program 401 and a transcoding program 402. The decoding program 401 and the transcoding program 402 can be transmitted with a QoS signal. It is preferable that such programs be transmitted through credible protocols, for example, a TCP protocol. In addition, when a program is written in JAVA language, the program can be inserted into an execution file regardless of the type of computer on which the program is run. The algorithm used in these programs may also be an algorithm that does not follow a standard and is made arbitrarily by a user to suit the features of the relevant media. However, a descriptor identifying that the algorithm is arbitrary should be included in the MPEG data.

0039<figref idref="f0004">Figure 5</figref> is a table, in which candidate factors that can be changed in the MPEG standard are compared with factors related to different protocols. For example, in the asynchronous transmission mode (ATM), (p, bp) = (PCR, CDVT) corresponds to (r, b) = (SCR, BT+CDVT) and in the UMTS standard (European IMT-2000 standard) of the 3GPP, (p, bp) = (maximum bitrate, maximumSDUsize) corresponds to (r, b) = (guaranteed bitrate, k * maximumSDUsize). In Sender_Tspec of the RSVP standard, (p, bp) = (peak rate, maxPacketSize) corresponds to (r, b) = (tokenBucketrate, tokenBucketSize).

0040Meanwhile, candidate factors related to the MPEG-4 system (ISO/IEC 14496-1) that are changeable include DecodeConfigDescrTag and QoS_Descriptor. DecodeConfigDescrTag includes bufferSizeDB, maxBitrate, and avgBitrate and while maxBitrate corresponds to a maximum bit rate (p), the remaining three factors bp, r, and b cannot be inferred from bufferSizeDB and avgBitrate. MAX_AU_SIZE, AVG_AU_SIZE, and MAX_AU_RATE are the candidate factors most closely related to the QoS_Descriptor, however, to guarantee compatibility with p, bp, r, and b, the definition of the factors should be modified. In addition, QoS_metrics of MPEG-4 DMIF (ISO/IEC 14496-6) also include PRIORITY, MAX_AU_SIZE, AVG_BITRATE, MAX_BITRATE which are also not compatible with p, bp, r, and b. Therefore, the DecoderConfigDescrTag of the current MPEG-4 standard, the QoS_Descriptor, and the QoS_metric factors should be represented with the factors that have the same meaning as p, bp, r, and b without modification. Meanwhile, a NetworkCondition descriptor of MPEG-21 Digital Item Adaptation (DIA) should include factors such as AvailableBandwidth, minimum, maximum, average, and interval, however, these descriptors should also be represented with factors that are equivalent to p, bp, r, and b. The DIA generally specifies natural environment description tools used to adapt digital contents to the network conditions in MPEG-21, such as, for example, location, time and audiovisual environment. Representing the DIA descriptors with factors equivalent to p, bp, r and b, entails changes to the MPEG standard and mapping of RSVP factors to the MPEG descriptors, which will be mentioned in the following embodiment.

0041Meanwhile, when the traffic descriptors of MPEG, IETF and 3GPP are all equivalent to p, bp, r, and b, the call control unit 114 illustrated in <figref idref="f0001">Figure 1</figref> can be directly connected to the network control unit 112 without going through the QoS factor mapping unit 116.

0042Also in the case of priority the definition of factors and the meaning of the values of the factors are standardized. One way to coordinate them is to coordinate the six levels of priority used in the 3GPP UMTS standard. The six levels can be divided into three levels of delay priority and three levels of loss priority. In cases of video transmission the loss priority of DC value, motion vector value, intraframe, and base layer data should be increased to guarantee transmission during network congestion. The suspended priority of services such as video conferencing, screen telephones, and live broadcasting is increased to minimize delay.

0043P, bp, r, and b factors can be calculated for traffic descriptor mapping. In fixed bit rate traffic, p = r = average bit rate and bp = b = 0. In encoded variable bit rate media traffic, using the leaky bucket algorithm, the correlation of the bit rate and buffer size is calculated as a ratio of 1:1. This correlation can be expressed in a graph in which the Y-axis is the buffer size and the X-axis is the bit rate. Although such a graph differs for each media stream, it is always in the form of a uniformly decreasing graph. Therefore, p, bp, r, and b values can be adequately chosen and used according to circumstances by saving the buffer size graph, which is drawn within the range of being larger than the average bit rate and smaller than the maximum bit rate, in the bit stream header or the OD of the MPEG-4 file format. The guaranteed bit rate r is a value between p and the average bit rate. Meanwhile, instead of the double leaky bucket a single leaky bucket could be used by setting p equal to r and bp equal to b.

0044Meanwhile, in the case of a live service, which is a real time service such as sports or new broadcasting, real-time encoding and transcoding should be performed to satisfy the double leaky bucket limitations that are set. However, an encoding algorithm and a transcoding algorithm are not elements standardized in the MPEG standard. In video data, the maximum size of the encoded frame is set and p is the maximum size of the encoded frame divided by frame duration (e.g., 20 frames during 1 second is 50ms). The buffer size bp should be equal to approximately 5% of r multiplied by group of pictures (GOP) hours. Since GOPs are consecutive, for the accumulated buffer size to not exceed b, either the quantization value should be controlled, the macro block skipped, or the frame skip method should be used. When the video sequence is simple and the average bit rate is r, if a quantization index, that is a Q value becomes small the Q value should not fall under a predetermined value, for example Q ≤ 4. Thus, the bit rate is much lower than the average bit rate and packet transmission expenses are saved.

0045Embodiments of the present invention transmit MPEG media data using IETF QoS protocol so that the MPEG media data is effectively transmitted according to network circumstances.

0046Furthermore, according to embodiments of the present invention, transmitting MPEG media data through the Internet by packet differential transmission according to priority is possible, which enables effective multimedia service and charging.

0047Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

0048All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

0049Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

0050The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.