KR100874094B1 - IPTV service provision server and method - Google Patents

Abstract

Providing an IPTV service according to an embodiment of the present invention can reduce channel change delay time while increasing network efficiency by adjusting the type of each channel and the number of additional intra frames to be inserted into video data to be transmitted through each channel. The method includes determining a channel type of each channel to be provided to a user and the number of additional intra frames to be inserted into image data provided through the channels; Encoding the image data by inserting the determined number of additional intra frames into the image data; And transmitting the encoded image data to the first router or the second router prior to a user's request for the channel according to each determined channel type.

Description

IPTV service providing server and method {Server and Method for Providing Internet Protocol Television Service}

The present invention relates to an IPTV service providing server and a method thereof, and more particularly, to an IPTV service providing server and a method capable of reducing a channel change delay time while increasing network efficiency when providing an IPTV service.

Advances in telecommunications and Internet technologies have resulted in the introduction of the Triple Play Service (TPS), which allows simultaneous transmission of broadcast, telephone, and data on a single subscriber line. The demand is soaring in that it can be provided to the service provider, and so are these service providers.

One of such TPS services is IPTV (Internet Protocol Television) service. IPTV service provides a broadcasting service through the existing Internet communication network and is efficient in terms of the use of network resources as compared with the existing broadcasting service (cable, satellite, or terrestrial broadcasting). In detail, as shown in FIG. 1A, the conventional broadcast service requires a waste of bandwidth because all channels must be transmitted to the user regardless of the user's request. By adopting the cast technology, it is possible to efficiently use network resources because only the channel required by the user is transmitted, and it can solve the bandwidth problem of the insufficient subscriber line.

However, in the case of such an IPTV service, when a channel request by a user occurs, the corresponding channel is transmitted to the user. Therefore, when a user requests a new channel, a delay until the selected channel is output to the user terminal (hereinafter, 'channel change' Delay ').

This channel change delay consists of instruction processing delay, network delay, set-top box jitter buffer delay, and decoding delay. The command processing delay is the delay from when the user selects the channel through the remote controller to change the channel, until the set-top box sends the channel request message over the network. The network delay is used to receive the first packet of the requested channel. The delay to, the set-top box jitter buffer delay refers to the initial buffering delay for removing the added jitter on the network, the decoding delay refers to the delay incurred in the decoding process of the compressed video data. The decoding delay is caused by the fact that video data cannot be decoded without an intra frame.

This delay in channel change prevents the user from immediately receiving the desired video data at the desired time. Therefore, the delay in channel change is an important problem that hinders the efficiency of IPTV service provision.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and the channel change delay time can be reduced while increasing network efficiency by adjusting the type of each channel and the number of additional intra frames to be inserted into the image data to be transmitted through each channel. The technical problem is to provide an IPTV service providing server and method.

In another aspect, the present invention is to provide an IPTV service providing server and method that can reflect the user's preference for the channel in determining the type of each channel and the number of additional intra frames.

Another object of the present invention is to provide an IPTV service providing system and method capable of reducing computational complexity in determining the type of each channel and the number of additional intra frames.

In accordance with an aspect of the present invention, an IPTV service providing method includes determining a channel type of each channel to be provided to a user and the number of additional intra frames to be inserted into image data provided through the channels. ; Encoding the image data by inserting the determined number of additional intra frames into the image data; And transmitting the encoded image data to the first router or the second router before the user request for the channel according to each channel type.

Here, the channel type is classified into a first type for transmitting the image data transmitted through the channel to a first router and a second type for transmitting the image data to a second router, wherein the first router is a user terminal. The router is adjacent to the second router, characterized in that the router adjacent to the IPTV service providing server for providing the video data.

In this case, the channel type and the number of additional intra frames may be determined such that the total bandwidth of the channels required for providing the image data is minimized while the channel change delay time is less than or equal to a predetermined threshold.

In an embodiment, the determining of the number of channel types and the number of intra frames may include setting a first state by setting the channel type and the number of intra frames as a set value and calculating a channel change delay time in the first state. Doing; Determining the channel type and the number of additional intra frames based on an initial set value of the first state when the channel change delay time in the first state is less than or equal to the threshold; Calculating a channel change delay time for the changed setting values while changing the initial setting value of the first state when the channel change delay time in the first state exceeds the threshold; And if there is a setting value for causing the channel change delay time for the changed setting value to be less than or equal to the threshold value among the changed setting values, based on the setting value for minimizing the bandwidth of the channel among the setting values. Determining a channel type and the number of intra frames, and if not, updating the first state to a second state; Including, but repeating the channel change delay time calculation step and the state update step for the changed setting values until a state having a setting value for causing the channel change delay time to be the threshold value is found. .

At this time, the update from the first state to the second state is performed by determining a setting value that maximizes the cost incurred due to the change of the setting value in the first state as the initial setting value of the second state. Here, the cost is calculated as the ratio of the change amount of the difference between the channel change delay time and the threshold value with respect to the set value in the first state and the change amount of the bandwidth of the channel.

In accordance with another aspect of the present invention, an IPTV provision server includes: an operation unit configured to determine a channel type of each channel to be provided to a user and the number of additional intra frames to be inserted into image data provided through the channels; An encoder which encodes the image data by inserting the additional intra frames as many as the number determined by the calculating unit into the image data; And a data transmitter configured to transmit the encoded image data according to each channel type determined by the calculator to a first router adjacent to a user terminal or a second router adjacent to an IPTV providing server before a user request for the channel. It is characterized by including.

According to the present invention, the network efficiency can be increased and the channel change delay time can be reduced by adjusting the type of each channel and the number of additional intra frames to be inserted into the image data to be transmitted through each channel.

In addition, according to the present invention, in determining the type of each channel and the number of additional intra frame insertions, the channel having high user preference is transmitted to the router adjacent to the user terminal in advance by reflecting the user's preference for the channel. By inserting the channel change delay can be minimized.

In addition, the present invention has an effect that the computational complexity can be reduced by applying a new algorithm in determining the type of each channel and the number of additional intra frames.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, prior to the detailed description of the present invention, a general network configuration of an IPTV service providing system and a channel changing process under such an IPTV service providing system will be described.

2 is a schematic configuration diagram of a general IPTV service providing system. As shown, the IPTV service providing system 10 includes an IPTV service providing server 18 connected to a home network 12, an access network 13, a core network 14, and an end of the core network 14. Include.

The home network 12 includes a gateway 16, a user terminal 19, and a set-top box 20. The gateway 16 serves as a relay between the home network 12 and the access network 13, and performs a function of managing a channel of the home network 12. The set-top box is connected to the user terminal 19 and the gateway 16 to provide an IPTV service to the user terminal 19, and the user terminal 19 performs a function of displaying an IPTV.

The access network 13 is a network that mediates the home network 12 and the core network 14, and includes an LHR (Last Hoop Router) 22 and various switching elements (not shown). Here, the LHR 22 means a router located closest to the user terminal 19.

The core network 14 is a network that intervenes the LHR 22 and the first Hoop Router (FHR) 23. The core network 14 includes a plurality of multi-channels for transmitting a broadcast service transmitted from the IPTV service providing server 18 to the user terminal 19. It consists of cast routers (not shown). Here, the FHR 23 means a router located closest to the IPTV service providing server 18.

The IPTV service providing server 18 receives all channels from an external provider as a head-end, and transmits a broadcast channel to a user by using IP multicast technology to increase network efficiency.

A channel change process in the IPTV providing system shown in FIG. 2 will be described in detail with reference to FIG. 3.

First, when a user receiving channel 1 requests a channel change to channel 2 by using a remote controller, the set-top box 20 corresponds to IGMP (Internet for channel 1) in response to the channel change request of the user. Group Management Protocol) leave message to the gateway 16, and the gateway 16 delivers an IGMP leave message to the LHR 22. Here, IGMP defines that a router is a multicast group whose hosts are interested in a subnet consisting of one router and several hosts. After that, the LHR 22 receiving the IGMP exit message transmits an IGMP Group-Specific Query message to all gateways (not shown) managed by the LGMP 22. If no response is received for a certain time, the PIM Prune is sent to the upper router. Perform group withdrawal on channel 1 while linking messages.

Meanwhile, when the set-top box 20 transmits an IGMP join message for channel 2 to the gateway 16 to subscribe to channel 2, the gateway 16 sends an IGMP subscription message to the LHR 22. To). When receiving the IGMP subscription message, the LHR 22 transmits channel 2 to the corresponding gateway 16 if the channel 2 is already received. Otherwise, the LHR 22 associates the PIM Join message to the upper router and channel 2 Attempt to join the group. Through this process, the requested channel is received by the user according to the channel change request of the user, and the corresponding channel is displayed to the user through the decoding process of the received channel.

As described above, a network delay occurs due to the withdrawal from the group of the previous channel and the subscription to the new channel group until the new channel is received by the user in the channel change process, and the compressed video data after receiving the channel. Since the decoding delay occurs during the decoding process of the present invention, an object of the present invention is to provide an IPTV service providing server and a method for minimizing such a channel change delay. Hereinafter, a description will be given based on providing an IPTV service including M channels to N users.

4 is a schematic block diagram of an IPTV service providing server capable of providing an IPTV service according to an embodiment of the present invention. As shown, the IPTV service providing server 18 includes an operation unit 24, an encoder 26, and a data transmission unit 28.

The calculator 24 determines the channel type of each channel and the number of additional intra frames to be inserted into the image data provided through the channels so that the channel can minimize the bandwidth and the channel change delay. Here, the channel type determined by the calculator 24 is a channel type (hereinafter referred to as a 'static channel') to be transmitted to a router adjacent to the user terminal 19 before the user's request, or an IPTV service. It means whether the channel type (hereinafter referred to as "dynamic channel") that should be transmitted only to the router adjacent to the providing server 18.

The reason why the operation unit 24 determines the channel type for each channel is that if the predetermined channel is determined as a static channel, the network delay is relatively reduced, but if no user is watching the channel, it may cause a waste of network bandwidth. If the predetermined channel is determined to be a dynamic channel, the network bandwidth can be efficiently used, but when the user requests the channel, the network delay increases, so that the bandwidth and channel delay of the channel are most efficiently adjusted.

In addition, the reason why the operation unit 24 determines the number of additional intra frames to be inserted into the image data is to efficiently adjust the channel bandwidth and the channel delay, and specifically, to efficiently control the decoding delay for each channel. will be. In this case, the additional intra frame is inserted into the image data because decoding can be performed using the additional intra frame without having to wait for the intra frame of the image data during decoding, thereby reducing the decoding delay. If the number of additional infrastructure frames is increased in order to reduce the number of frames, the bandwidth of the channel is increased, so that the operation unit 24 determines the number of appropriate intra frames to adjust this.

Specifically, the calculator 24 determines the type of each channel and the number of additional intra frames so that the channel change delay time is equal to or less than a predetermined threshold while the overall bandwidth of channels required for providing image data is minimized. The type of the channel and the number of additional intra frames are determined. For this purpose, the calculation unit 24 includes the channel preference calculator 30, the delay time calculator 32, and the bandwidth calculator 34 as illustrated in FIG. 4. And a channel characteristic determiner 36.

로 표기될 수 있고, i번째 사용자의 각 채널에 대한 선호도는

로 표기될 수 있으며, M개의 채널에 대한 N명의 사용자 사이에서는 다음의 수학식 1과 같은 관계가 성립한다.The channel preference calculator 30 calculates the channel preference of each user, which is to reflect the channel preference of each user in determining the type of the channel and the number of additional intra frame insertions. This means that the channel with high user preference is determined as a static channel, the channel with low user preference is determined as a dynamic channel, and the higher the channel of the user preference, the higher the number of additional intra frames. Because it can be effective in reducing the At this time, the channel preference of the i th user is

Where the i th user's preference for each channel is

The relationship as shown in Equation 1 below is established among N users of M channels.

In one embodiment, such a user's channel preference may be calculated using statistics on the viewing status of each user's channel. Specifically, each user's channel preference is viewed by a user for a predetermined time interval. It can be estimated using one hour. This is expressed as an equation.

는 j번째 채널에 대한 i번째 사용자의 선호도를 의미하고,

는 i번째 사용자가 j번째 채널을 시청한 시간을 의미하며,

는 소정 시간 간격을 의미하고, N은 전체 사용자의 수를 의미한다.here,

Is the i th user's preference for the j th channel,

Means the time that the i th user watched the j th channel,

Means a predetermined time interval, and N means the total number of users.

The delay time calculation unit 32 calculates a channel change delay time. Specifically, the channel change delay time is a network delay time for each channel (time required for receiving each channel) and image data provided through each channel. It is calculated by multiplying the user's preference for each channel by the sum of the time taken to decode. This expansion of all channels is expressed as an equation as follows.

는 채널에 대한 네트워크 지연 시간을 나타내는 벡터로서

로 표현되고,

는 부가적인 인트라 프레임이 삽입된 영상 데이터의 디코딩 지연시간을 나타내는 벡터로서,

로 표현된다. 따라서, 수학식 3은 채널의 네트워크 지연벡터와 디코딩 지연 벡터의 합과 사용자들 각각의 채널 선호도 값

의 내적을 취함으로써 각 사용자에 대한 전체 채널의 지연시간을 산출하게 된다.here,

Is a vector representing the network latency for the channel.

Represented by

Is a vector representing a decoding delay time of image data in which an additional intra frame is inserted.

It is expressed as Therefore, Equation 3 is the sum of the network delay vector and the decoding delay vector of the channel and the channel preference value of each user.

By taking the dot product, we calculate the delay of the entire channel for each user.

와 디코딩 지연시간인

는 다음의 수학식 4 및 5와 같이 정의된다.At this time, the network delay time for the j th channel

And the decoding delay time

Is defined as in Equations 4 and 5 below.

과

은 각각 인터넷 상에서 정적 채널과 동적 채널에 대한 평균 네트워크 지연 시간을 의미하며,

은

에 비해 상대적으로 매우 길다.here,

and

Are the average network latency for static and dynamic channels on the Internet, respectively.

silver

Relatively long compared to.

는 j 번째 채널을 통해 전송되는 영상 데이터에 포함된 하나의 GOP 구간에 삽입되는 부가적인 인트라 프레임의 개수를 나타내는 것으로서, 각각의 채널을 통해 제공되는 영상 데이터에 삽입될 부가적인 인트라 프레임의 개수를 벡터로 표현하면

으로 표현할 수 있다. 한편,

는 하나의 GOP 구간내에 삽입될 수 있는 부가적 인트라 프레임의 최대 개수를 나타내며,

는 하나의 GOP의 크기를 나타낸다.here,

Denotes the number of additional intra frames to be inserted into one GOP section included in the image data transmitted through the j-th channel. The vector indicates the number of additional intra frames to be inserted into the image data provided through each channel. In terms of

It can be expressed as Meanwhile,

Represents the maximum number of additional intra frames that can be inserted in one GOP interval,

Represents the size of one GOP.

The bandwidth calculator 34 calculates the total bandwidth of channels required for providing image data, and obtains a product of a predetermined value indicating a channel type of each channel and a bandwidth required for transmitting image data through the corresponding channel. The bandwidth of each channel is calculated. If this is expanded for all channels, the following equation (6) is obtained.

는 영상 데이터의 전송시 요구되는 채널의 대역폭을 나타내는 벡터로서

로 표기되고,

는 부가적인 인트라 프레임의 전송시 요구되는 채널의 대역폭을 나타내는 벡터로서

로 표기되며,

는 각 채널의 채널 타입을 나타내는 벡터로서

로 표기된다. 수학식 6에 의하면, 부가적인 인트라 프레임이 삽입된 영상 데이터를 전송하기 위한 각 채널들의 대역폭 벡터와 각 채널들의 타입을 나타내는 벡터의 내적을 취함으로써 영상 데이터의 전송에 요구되는 전체 채널의 대역폭을 산출하게 된다. 이때,

와

는 다음의 수학식 7 및 8에 의해 정의된다.here,

Is a vector representing the bandwidth of the channel required to transmit the image data.

Denoted by,

Is a vector representing the bandwidth of the channel required for the transmission of additional intra frames.

Denoted by

Is a vector representing the channel type of each channel.

It is indicated by. According to Equation 6, the bandwidth of the entire channel required for the transmission of the image data is calculated by taking the inner product of the bandwidth vector of each channel for transmitting the image data into which the additional intra frame is inserted and the vector representing the type of each channel. Done. At this time,

Wow

Is defined by the following equations (7) and (8).

는 부가적인 인트라 프레임의 고정 비트 레이트를 의미한다.here,

Denotes a fixed bit rate of an additional intra frame.

That is, the channel type value for the corresponding channel is determined as 1 if the jth channel is a static channel, and if the jth channel is a dynamic channel, the sum of the preferences of each user for the jth channel. Is determined by the type value of the channel.

)이하가 되도록 하면서, 수학식 6에서 산출된 채널의 전체 대역폭의 값을 최소화하는

와

를 구함으로써 모 든 채널들에 대한 채널 타입 및 부가적인 인트라 프레임의 개수를 결정하게 된다.The channel characteristic determiner 36 determines the channel type of each channel and the number of additional intra frames by using the values calculated by the delay time calculator 32 and the bandwidth calculator 34 described above. In detail, the channel characteristic determiner 36 may determine that the channel change delay time calculated by using Equation 3 as described in Equation 9 below has a predetermined threshold (

While minimizing the value of the overall bandwidth of the channel

Wow

By determining the number of channels and the number of additional intra frames for all channels.

와

을 구할 수 있다. 이를 도 5에 도시된 트렐리스(Trellis)를 참조하여 구체적으로 설명한다.In one embodiment, the channel characteristic determiner 36 satisfies Equation 9 by using the Viterbi algorithm and minimizes Equation 6.

Wow

Can be obtained. This will be described in detail with reference to Trellis shown in FIG. 5.

개의 상태로 구성되어 있다. 도메인 내의 각각의 상태는 각 채널의 타입과 부가적인 인트라 프레임의 개수를 나타내며, 각 도메인 상의 상태 조합에 있어 가능한 조합의 수는

개이다. m-1번째 도메인까지의 누적 상태 조합이 수학식 10과 같이 표현되고, 도메인 상에서 선택된 상태가

일 때, m번째 도메인 상의 누적 상태 조합은 수학식 11과 같이 된다.As shown in FIG. 5, each channel constitutes one domain, and each domain

It consists of two states. Each state in the domain represents the type of each channel and the number of additional intra frames, and the number of possible combinations of state combinations on each domain is

Dog. The cumulative state combination up to the m-1 th domain is expressed as in Equation 10, and the state selected on the domain is

When the cumulative state combination on the m-th domain is as shown in equation (11).

In one embodiment, a pruning technique is applied on the trellis shown in FIG. 5 to narrow the search to find the optimal solution. That is, in determining the optimal transition from the m-1 th domain to the m th domain, it is determined whether the equation (9) is satisfied for the state selected in the m th domain, and the transition that does not satisfy this is deleted. In FIG. 5, a portion indicated by a dotted line indicates a transition to be deleted as not satisfying Equation 9 in the state of the domain.

와

을 구할 수 있다.In another embodiment, the channel characteristic determiner 36 minimizes Equation 6 while satisfying Equation 9 using another algorithm to reduce the complexity of the calculation.

Wow

Can be obtained.

를 산출한다. 여기서,

는 다음의 수학식 12에 의해 산출된다.In detail, first, the channel characteristic determiner 36 sets the channel type of all channels to a dynamic channel as an initial state, and sets the number of additional intra frames to be inserted into the image data to zero. That is, the initial state is set to a state in which the bandwidth for transmitting image data is minimized. In this state, the channel characteristic determiner 36 indicates the degree to which the channel change delay time calculated by Equation 3 exceeds the threshold value.

Calculate here,

Is calculated by the following equation (12).

값은 0 이 되고, 그렇지 않은 경우 양수의 값이 되는 것이다.That is, according to Equation 12, when the delay time is less than or equal to the threshold

The value is 0, otherwise it is a positive value.

값이 0인 경우 이러한 초기 상태의 설정값을 기준으로 채널의 타입 및 부가적인 인트라 프레임의 개수를 결정한다.The channel characteristic determiner 36 is calculated in the initial state.

If the value is 0, the channel type and the number of additional intra frames are determined based on the setting value of the initial state.

값이 0이 아닌 경우 초기상태에서 각 채널의 채널 타입 및 부가적인 인트라 프레임의 개수를 변경해 가면 서,

값을 계산하고, 계산된

값을 0으로 만드는 설정값이 존재하는 지를 판단한다.If calculated at initial state

If the value is not 0, the channel type of each channel and the number of additional intra frames are changed in the initial state.

Calculate the value,

Determine if there is a setting to make the value zero.

값을 0으로 만드는 설정값이 존재하는 경우, 그 중 채널의 대역폭이 최소가 되게 하는 설정값을 기준으로 채널의 타입 및 부가적인 인트라 프레임의 개수를 결정하고,

값을 0으로 만드는 상태가 설정값이 존재하지 않는 경우, 최초 설정값의 변경으로 인해 발생하는 코스트(Cost)를 산출한 후, 산출된 코스트 값을 이용하여 초기상태를 갱신하여 다음상태를 결정한다. 이때, 코스트는 다음의 수학식 13에 의해 산출할 수 있으며, 초기상태를 갱신함에 있어서는 산출된 코스트 값이 최대인 상태의 설정값을 이용하여 초기상태를 갱신한다.

If there is a setting value that makes the value zero, the channel type and the number of additional intra frames are determined based on the setting value of which the bandwidth of the channel is minimized.

If the state that makes the value 0 does not exist, the cost generated by the change of the initial setting value is calculated, and then the initial state is updated by using the calculated cost value to determine the next state. . At this time, the cost can be calculated by the following equation (13), and in updating the initial state, the initial state is updated using the set value of the state in which the calculated cost value is maximum.

값이 0 이 되는 상태가 발견될 때까지 상술한 과정을 반복함으로써 채널의 타입 및 부가적인 인트라 프레임의 개수를 결정하게 되는 것이다. The channel characteristic determiner 36

By repeating the above process until a state where the value becomes 0 is found, the type of the channel and the number of additional intra frames are determined.

는 상태 변화로 인해 발생하는

값의 감소량을 의미하고,

는 상태 변화로 인해 발생 되는 대역폭의 증가량을 의미한다.here,

Is caused by a change in state

Means a decrease in value,

Means the increase of bandwidth caused by the change of state.

Referring again to FIG. 4, the encoder 26 inserts an additional number of additional intra frames determined by the calculator 24 into the image data to encode the image data. In one embodiment, the image data is encoded in the structure of IBBPBBPBBPBB at 30 frames per second (fps).

When the type of the predetermined channel is determined as the static channel, the data transmitter 28 transmits the image data encoded by the encoder 26 to a router adjacent to the user terminal 19 prior to the user's request. When determined as this dynamic channel, the video data encoded by the encoder 26 is transmitted to a router adjacent to the IPTV broadcast server 18 before the user's request.

A method of providing an IPTV service using the above-described IPTV service providing server will be described with reference to FIG. 6.

First, the channel type of each channel to be provided to the user and the number of additional intra frames to be inserted into the image data provided through the respective channels are determined (step 100). In this case, the channel type is a static channel for transmitting video data to a first router adjacent to the user terminal 19 and a dynamic channel for transmitting video data to a second router adjacent to the IPTV service providing server 18 before the user requests a channel. Classified as In one embodiment, in determining the type of the channel and the number of additional intra frames to be inserted into each channel, it is preferable to determine the type of each channel by reflecting the channel preference of the user.

Here, the channel type of each channel and the number of additional intra frames are determined so that the total bandwidth of channels required for providing image data is minimized while the channel change delay time is less than or equal to a predetermined threshold. In this case, the channel change delay time is calculated by Equation 3, and the bandwidths of the channels are calculated by Equation 6. Detailed description thereof has been described in detail in the description of the equation, and thus detailed description thereof will be omitted.

In one embodiment, a Viterbi algorithm is used to determine the type of channel and the number of additional intra frames using the channel change delay time calculated by Equation 3 and the bandwidth of the channel calculated by Equation 6. Can be. This Viterbi algorithm uses the trellis shown in Figure 5 to determine the optimal channel type and the number of additional intra frames by deleting transitions from the previous state to the current state that do not satisfy Equation (9). Done.

값을 계산한다(제210단계). 계산된

값이 0인지 여부를 판단하여(제220단계),

값이 0인 경우, 초기 상태의 설정값을 기준으로 채널의 타입 및 부가적인 인트라 프레임의 개수를 결정한다(제230단계).In another embodiment, the optimal channel type and the number of additional intra frames may be calculated using the algorithm shown in FIG. 7. Referring to FIG. 7, first, each channel is set to an initial state (step 200). Here, the initial state is a type of the channel is a dynamic channel, the number of additional intra frames is 0, after which the type of the channel and the number of additional intra frames are defined as the setting value of the state. Next, using the equation (12) in the initial state

The value is calculated (step 210). Calculated

Determine whether the value is 0 (step 220),

If the value is 0, the type of the channel and the number of additional intra frames are determined based on the set value of the initial state (operation 230).

값이 0이 아닌 경우, 초기상태에서 설정값을 변경시켜 가면서

값을 계산한 후(제235단계), 계산된

값을 0으로 만드는 설정값이 존재하는지를 판단한다(제240단계).

값을 0으로 만드는 설정값이 존재하는 경우, 그 중 채널의 대역폭이 최소가 되게 하는 설정값을 기준으로 채널의 타입 및 부가적인 인트라 프레임의 개수를 결정한다(제250단계). 제240단계에서

값을 0으로 만드는 설정값이 존재하지 않는 경우, 최초 설정값의 변경으로 인해 발생하는 코스트(Cost)를 산출하고(제260단계), 초기상태를 산출된 코스트가 최대가 되게 하는 상태의 설정값으로 갱신함으로써 다음 상태를 설정한다(제270단계). 이때, 코스트는 상술한 수학식 13에 의해 산출된다. 코스트의 산출과정에 대한 설명은 수학식 13의 설명 부분에서 기재하였으므로 상세한 설명은 생략하기로 한다.In step 220,

If the value is not 0, change the set value at initial state.

After calculating the value (step 235),

In operation 240, it is determined whether there is a set value that makes the value zero.

If there is a setting value that makes the value 0, the type of the channel and the number of additional intra frames are determined based on the setting value that minimizes the bandwidth of the channel (operation 250). In step 240

If there is no set value that makes the value zero, the cost (Cost) generated by the change of the initial set value is calculated (step 260), and the set value of the state that makes the initial state maximum The next state is set by updating to (step 270). At this time, the cost is calculated by the above equation (13). Since the description of the cost calculation process is described in the description of Equation 13, a detailed description thereof will be omitted.

값이 0 이 되는 설정값을 가지는 상태가 발견될 때까지 제235단계 및 제270단계를 반복함으로써 채널의 타입 및 부가적인 인트라 프레임의 개수를 결정하게 된다. after

By repeating steps 235 and 270 until a state having a set value of 0 is found, the type of the channel and the number of additional intra frames are determined.

Referring back to FIG. 6, after encoding the image data by inserting the additional intra frames of the number determined in operation 100 into the image data (operation 110), the channel type is determined as the static channel in operation 100. In case of transmitting the encoded video data before the user's channel request to the router closest to the user terminal 19, and if it is determined as the dynamic channel of the channel type, the encoded video data before the user's channel request is provided to the IPTV service providing server. In step 120, it transmits to the nearest router (18).

 8A and 8B illustrate the performance of each algorithm analyzed through an experiment of calculating the channel type and the number of additional intra frames using the two algorithms described above. First, the preconditions of the experiment are briefly described. The experimental environment was implemented using OPNET, and latency caused by channel change and bandwidth usage on the core network were used as a measure to compare the performance of the two algorithms. The link bandwidths of the core network and the access network were set to 1 Gbps and 100 Mbps, respectively, and the one-way latency on the IP network was 0.6 sec, and the number of users in the access network was set to 20 users. Image data was encoded at 30 fps (Frames Per Second), and the encoding structure is IBBPBBPBBPBB.

Channels are classified into SDTV channel group and HDTV channel group, and the bandwidth of the channel is 4.12 Mbps and 12.06 Mbps, respectively. The size of the additional intra frame to be inserted into the image data is 25000 bytes, and the maximum number of additional intra frames to be inserted into one GOP is set to three. The time interval between channel requests of each user follows the Poisson distribution, and λ (Request Rate) is set to 1/30 (Number of Requests Per Second). Channel preference of each user follows uniform or zip distribution, and in case of jeep distribution, θ (Skew Facotr) is set to 1.0. Also, in general, the preference of the HDTV channel is set slightly higher than that of the SDTV channel, and the channel number may be slightly different even if each user shows the same channel preference trend.

In the Viterbi algorithm, the computational complexity increases exponentially as the number of channels increases. For simplicity, the channel preference of the user follows the uniform distribution, and the experiment is conducted with a relatively small number of channels. In the experiment, channel 1 is an HDTV channel, and channels 2 to 5 are SDTV channels.

As can be seen from the results shown in Figs. 8A and 8B, both algorithms can be seen that as the threshold decreases, the number of static channels and the number of additional intra frames increases to satisfy Equation (9). When the thresholds are 0.4, 1.4, and 1.5, although the differences are somewhat different, the performances of the two algorithms are generally similar, but the CPU time of the algorithm shown in FIG. 7 is 0.062 sec, which is less than the 0.109 sec CPU time of the Viterbi algorithm. It can be seen that the algorithm shown in Figure 1 shows the improved performance in terms of computational complexity.

9A to 9C are diagrams showing the performance of the algorithm shown in FIG. To test the performance of the proposed algorithm, channels 1, 5, 10, 20, and 30 were set as HDTV channels and the remaining channels as SDTV channels. The channel preference of the user follows the uniform or jeep distribution, and the threshold is set to 1.0 sec.

First, when the channel preference of the user follows the uniform distribution, as shown in Figs. 9A and 9B, when all the channels are dynamic channels, the network efficiency is the best, but the user knows that there is a user whose channel change delay exceeds the threshold. If all channels are static channels, the channel change delay shows the best performance, but the network efficiency is reduced. On the other hand, in the algorithm shown in Fig. 7, the channel type is determined based on each user's channel preference, and an additional intra frame is inserted into the image data to be transmitted through each channel, thereby improving the efficiency of the network. It can be seen that the channel change delay can be made below the threshold.

On the other hand, even if the channel preference of the user follows the jeep distribution, the results are similar to the above. By using the algorithm shown in FIG. 7 as shown in FIG. 9C, the channel change delay can be reduced and the network efficiency can be improved. It can be seen that there was.

Those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features.

Therefore, it is to be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. do.

1 is a diagram showing a broadcasting service providing mechanism and an IPTV service providing mechanism;

2 is a network diagram of a general IPTV service providing system.

3 is a view showing a channel change process in the IPTV providing system shown in FIG.

4 is a schematic block diagram of an IPTV service providing server according to an embodiment of the present invention.

5 shows a trellis of the Viterbi algorithm.

6 is a flowchart showing a method of providing an IPTV service using the IPTV service providing server shown in FIG. 4.

7 is a flowchart for an algorithm for determining the type of channel and the number of additional intra frames.

8 shows a comparison of the performance of algorithms used to determine the type of channel and the number of additional intra frames.

9 shows the performance of the algorithm shown in FIG.

<Description of the symbols for the main parts of the drawings>

10: IPTV service providing system 12: home network

13: access network 14: core network

16: Gateway 18: IPTV Serving Server

19: user terminal 20: set-top box

22: LHR2 23: FHR

24: calculator 26: encoder

28: data transmission unit 30: channel preference calculator

32: delay time calculator 34: bandwidth calculator

36: channel characteristic determination unit

Claims (23)

Determining a channel type of each channel to be provided to a user and the number of additional intra frames to be inserted into image data provided through the channels; Encoding the image data by inserting the determined number of additional intra frames into the image data; And Transmitting the encoded image data to a first router or a second router prior to a user's request for the respective channels according to the determined channel type of each channel; IPTV service providing method comprising a. The channel type of claim 1, wherein the channel type of each channel is a first type for transmitting the image data transmitted through the respective channels to the first router and a second type for transmitting the image data to the second router. Classified, wherein the first router is a router adjacent to a user terminal, and the second router is a router adjacent to an IPTV service providing server. The method of claim 2, wherein the determining of the channel type of each of the channels and the number of additional intra frames includes: The channel type of each of the channels and the additional channel among the total bandwidths of the channels calculated for each channel type and the number of additional intra frames such that a channel change delay time is less than or equal to a threshold; And determining the number of intra frames by the channel type of each channel to be provided to the user and the number of additional intra frames to be inserted into the image data. 4. The method of claim 3, wherein the channel type of each channel and the number of additional intra frames are determined by reflecting a user's preference for each of the channels. 5. The method of claim 4, wherein the user's preference for each of the channels is estimated using the time the user watched the channel for a predetermined time interval. 5. The method of claim 4, wherein the channel change delay time is a product of a sum of a time taken for each of the channels to be received, a decoding delay time of the image data provided through the respective channels, and a user's preference for each of the channels. IPTV service providing method, characterized in that calculated using. The method of claim 4, wherein the total bandwidth of the channels is calculated using a product of a predetermined value representing a channel type of each of the channels and a bandwidth of each of the channels required for providing the image data. . The method of claim 7, wherein the predetermined value representing the channel type of each channel, If the predetermined channel is of the first type, the IPTV service providing method is determined as a first value, and if the second type is determined by the sum of the preferences of each user for the predetermined channel. The method of claim 3, wherein the determining of the channel type of each channel and the number of additional intra frames comprises: The channel type of each of the channels and the number of the additional intra frame is determined using a Viterbi algorithm. The method of claim 3, wherein the determining of the channel type of each channel and the number of additional intra frames is performed. Setting a first state by setting a channel type of each channel and the number of additional intra frames as a set value and calculating a channel change delay time in the first state; Determining a channel type of each of the channels and the number of additional intra frames based on an initial setting value of the first state when the channel change delay time in the first state is less than or equal to the threshold value; Calculating a channel change delay time for the changed setting values obtained by repeatedly changing the initial setting value of the first state when the channel change delay time in the first state exceeds the threshold; And If there are setting values that cause the channel change delay time for the changed setting values among the changed setting values to be less than or equal to the threshold value, the channels calculated for each of the setting values that cause the channel change delay time to be less than or equal to the threshold value. Determining a channel type of each of the channels and the number of the additional intra frames based on a set value of the minimum bandwidth of the channels, and if not, updating the first state to a second state; Including but not limited to: And repeating the channel change delay time calculation step and the state update step for the changed setting values until a state having a setting value for causing the channel change delay time to be the threshold is found. . The method of claim 10, wherein in the updating from the first state to the second state, The updating from the first state to the second state may include setting a setting value having a maximum cost due to a change from an initial setting value of the first state among the changed setting values in the first state. IPTV service providing method characterized in that performed by determining the initial set value of the state. 12. The method of claim 11, wherein the cost is calculated as a ratio of a change amount of a difference between a channel change delay time and the threshold value for each of the changed set values in the first state and a change amount of the total bandwidth of the channels. IPTV service providing method. 11. The method of claim 10, wherein the initial setting value of the first state is that the channel types of the respective channels are all second types and the number of additional intra frames is zero. A computer-readable recording medium having recorded thereon a program for performing the method according to any one of claims 1 to 13. A calculator configured to determine a channel type of each channel to be provided to a user and the number of additional intra frames to be inserted into image data provided through the channels; An encoder which encodes the image data by inserting the additional intra frames as many as the number determined by the calculating unit into the image data; And Data for transmitting the encoded video data to a first router adjacent to a user terminal or a second router adjacent to an IPTV providing server before a user's request for the respective channels according to the channel type of each channel determined by the calculator. A transmission unit; IPTV service providing server comprising a. The channel type of each of the channels determined by the calculator is a first type through which the image data is transmitted to the first router through the channels, and the image data is transmitted through the channels. IPTV service providing server, characterized in that the classification into the second type transmitted to the second router. The bandwidth of claim 16, wherein the calculator is configured to have a minimum bandwidth among channels among the total bandwidths of the channels calculated for each channel type and the number of additional intra frames, such that the channel change delay time is equal to or less than a threshold. And determining the channel type of each channel and the number of additional intra frames as the channel type of each channel to be provided to the user and the number of additional intra frames to be inserted into the image data. The method of claim 17, wherein the operation unit, A channel preference calculator configured to calculate a user's preference for each of the channels; The channel change delay time is calculated using a product of the sum of the time taken for receiving the respective channels, the decoding delay time of the image data provided through the respective channels, and the channel preference of the user for the respective channels. A delay time calculating unit; A bandwidth calculator configured to calculate an overall bandwidth of the channels using a product of a channel type of each channel and a bandwidth of each channel required for transmitting the image data; And The bandwidth of the channels among the total bandwidths of the channels calculated for each channel type of the channels and the number of additional intra frames to allow the channel change delay time calculated by the delay time calculator to be equal to or less than a threshold is the minimum. A channel characteristic determiner configured to determine the channel type of each channel and the number of additional intra frames as the channel type of each channel to be provided to the user and the number of additional intra frames to be inserted into the image data; IPTV service providing server comprising a. 18. The apparatus of claim 17, wherein the operation unit sets a first state by setting a channel type of each of the channels and the number of additional intra frames as a set value, and sets a set value such that the channel change delay time is equal to or less than the threshold. The first state is repeatedly updated while changing the set value until a state is found, and the channel change delay time is less than or equal to the threshold value when the state having the set values with the channel change delay time is less than or equal to the threshold value. And determining the channel type to be provided to the user and the number of additional intra frames to be inserted into the video data, based on a setting value of which the bandwidths of the channels are minimized among the setting values. 20. The method of claim 19, wherein the iterative update of the first state is performed when no setting value is found to cause the channel change delay time to be below the threshold among the changed setting values in the first state. IPTV service provider server. 21. The method of claim 20, wherein the iterative update of the first state uses a set value at which a cost incurred due to a change from the initial set value of the first state of the changed set values in the first state is maximum. IPTV service providing server, characterized in that for updating the first state to a second state. 22. The IPTV service providing server of claim 21, wherein the cost is calculated as a ratio of a change amount of a difference between a channel change delay time and the threshold value for each of the changed set values and a change amount of the total bandwidth of the channels. . 20. The IPTV service providing server of claim 19, wherein the initial setting value of the first state is that the channel types of the respective channels are all second types and the number of additional intra frames is zero.

Images