KR100864538B1

KR100864538B1 - Method of transferring and receiving multimedia data on demand

Info

Publication number: KR100864538B1
Application number: KR1020070085196A
Authority: KR
Inventors: 박승권; 최희철
Original assignee: 한양대학교 산학협력단
Priority date: 2007-08-23
Filing date: 2007-08-23
Publication date: 2008-10-21

Abstract

A method for transceiving multimedia data on demand is provided to use only the smaller number of channels without increasing a user standby time and a buffer capacity of a subscriber device, thereby providing a better service than an existing NVoD(Near Video on Demand) technology. A method for transmitting multimedia data on demand comprises the following steps of: dividing the multimedia data into a first section corresponding to a prior portion and a second section corresponding to a later portion, and dividing the first section into plural data segments having the same length(S300,S310); dividing a bandwidth allocated to the transmission of the multimedia data into plural logic channels(S320); matching the plural data segments composing the first section and the second section to the plural logic channels(S350); and transmitting the plural data segments and the second section repeatedly according to the matching through the plural logic channels(S360).

Description

How to send and receive multimedia data {Method Of Transferring And Receiving Multimedia Data On Demand}

The present invention relates to the transmission and reception of on-demand multimedia data, and more particularly, to a non-sequential stepped transmission method in which all multimedia data is divided into a front part and a rear part and a part of the data is partly divided. The present invention relates to a method for transmitting on-demand multimedia data and a method for receiving on-demand multimedia data using a staggered method for repeated transmission at regular intervals.

Video on Demand (hereinafter referred to as "VoD") technology according to the prior art is a TVod that occupies and uses one channel by immediately granting one channel to that subscriber when there is a request to watch one subscriber video. (True VoD), and NVoD (Near VoD), which always broadcasts a specific video at regular intervals and allows multiple subscribers to watch a single video simultaneously. In comparison, NVoD can accommodate more subscribers with the same channel bandwidth than TVoD.

Recently, many studies have been conducted to improve the performance of NVoD, and these studies are largely divided into a batch method and a patch method. The layout method divides video data into various methods based on bandwidth and length, and periodically broadcasts them to different channels. In the patch method, video data is repeatedly transmitted through a static channel at regular intervals, and the channel is padded during the repetition period of the video data. Although the layout method has an advantage of excellent channel bandwidth efficiency, it has a disadvantage in that the actual implementation has many limitations due to the increased complexity of the system. On the other hand, the patch method has a disadvantage in that the channel bandwidth efficiency is inferior, the service is limited to a limited viewer, and as the number of viewers increases, the required bandwidth also increases, but the implementation of the system is simple.

As a batch NVoD method, there are Fast Broadcasting, Harmonic Broadcasting, Staircase Broadcasting, Pyramid Broadcasting, Skyscraper Broadcasting, Pagoda Broadcasting, and the like. Each technique is classified according to video data segmentation method, channel segmentation method, and segmented data transmission method. This method uses the partitioning of video data and the storage means of the subscriber device.

Staggercase Broadcasting (Staircase Broadcasting) is the most known and relatively simple structure of NVoD. This method is not an efficient transmission method in terms of the bandwidth of the VoD server because video can be received after a predetermined waiting time by transmitting the same video to each logical channel with a predetermined time difference according to the logical channel. However, there is an advantage in that the subscriber device (for example, a client terminal or a set-top box) occupies only one channel when receiving the entire video without storing data.

Pyramid Broadcasting is a method of dividing video data into several different sizes on the time axis and transmitting the divided video data through different logical channels. If the total bandwidth is B [bits per sec; In the following description, "bps"] and the number of logical channels that can be transmitted simultaneously are k, the bandwidth of each logical channel is B / k, and the number of video data that can be simultaneously transmitted is k. At this time, the size of the divided video data increases by α times. Therefore, if the size of the first divided video data is S ₁ [bit], the size of the i-th data is

Becomes Where i = 1,2,3, ..., k

to be. Video data _Si is transmitted through the i-th logical channel.

With pyramid transmission, the system complexity of video servers and subscriber devices increases, and set-top boxes of subscriber devices not only require large storage devices that can store more than 70% of the total video for smooth, continuous service, but also many Since a number of logical channels must be used, there is a problem that is not practical in some cases.

Fast broadcasting is a method in which video data is divided into N equal sizes on the time axis and distributed in each logical channel having a constant channel bandwidth of b [bps]. The 2 ^i-1 th video segments are sequentially transmitted from the first video segment among the N divided video segments through the i th logical channel in order. Here, when the number of channels that can be transmitted is n, the total number of segments N is

Dog.

Fast transmission is an evolution of pyramid transmission, which is highly efficient in terms of channel bandwidth, but the number of video data is divided too much, and the size of the buffer required by the set-top box is 50% of the total video size. There is this.

Staircase Broadcasting is a method of dividing video data into N equal sizes on a time axis and distributing it to multiple logical channels. The basic method is the same as that of fast transmission, but the bandwidth of each logical channel is increased. The difference is that the transmission is divided again. The i th logical channel is repeatedly transmitted in order from the first video segment to the 2 ^i-1 th video segment like the fast transmission method. In this case, the i-th logical channel is divided into 2 ^i-1 sub- logical channels, and if the bandwidth of the first logical channel is b, the bandwidth of each sub- logical channel of the i-th logical channel is

to be. In addition, video data transmitted through the divided i-th logical channel is also divided into 2 ^i-1 and transmitted through each divided sub- logical channel.

According to the stepped transmission method, the viewer latency is the same as that of the fast transmission method, but the buffer size of the set-top box is relatively improved as 25% of the total video size. However, the number of segmented video data segments is too large, complicated channel management is required, and video service disconnection may occur due to segmentation. In addition, there are many logical channels used at the same time and channel hopping occurs frequently, which makes it difficult to implement the system.

In the harmonic broadcasting method, video data is divided into N equal sizes on the time axis, and the i-th divided video data is divided again into i data in the i-th logical channel and repeatedly transmitted. The harmonic transmission scheme divides channel bandwidth differently instead of dividing video data into equal lengths of time. When the bandwidth used by the first data is b, the bandwidth of the i th logical channel is divided into b / i.

The harmonic transmission scheme is very efficient in terms of channel bandwidth, but there are many difficulties in the implementation and use of the actual system because video data is divided into too many numbers and the usage bandwidth is constantly changing.

As described above, the NVoD schemes according to the related arts have contributed to increasing the efficiency of channel bandwidth or reducing the waiting time of a subscriber by using data partitioning, but have a great difficulty in realizing the system by greatly increasing the complexity of the system. This is present.

The present invention solves the above problems and is proposed in accordance with recent trends and requests. The present invention divides the entire video data into a front part and a rear part, and splits the video data into a front part. On-demand multimedia data using the uninterrupted stepped transmission method and the staggered method that repeatedly transmits data to the rear part at a regular interval, greatly reducing the complexity of the system compared to the conventional NVoD technology. The purpose is to provide a transmission and reception method.

Another object of the present invention is to provide an on-demand multimedia data transmission / reception method capable of providing a continuous NVoD service by eliminating the disconnection phenomenon of the conventional stepped transmission method.

Another object of the present invention is to provide an on-demand multimedia data transmission / reception method which requires fewer channels than conventional NVoD technology.

As an aspect of the present invention for achieving the above object, the on-demand multimedia data transmission method according to the present invention, in the on-demand multimedia data transmission method executed in the multimedia data server, the multimedia data corresponding to the whole (front) A data partitioning step of dividing the first section into a second section corresponding to a first section and a rear section, and dividing the first section into a plurality of data segments each having the same length; Dividing a bandwidth allocated for transmission of the multimedia data into a plurality of logical channels; A corresponding step of mapping the plurality of data segments constituting the first interval and the second interval to the plurality of logical channels; And a transmitting step of repeatedly transmitting the plurality of data segments and the second interval through the plurality of logical channels according to the correspondence made in the corresponding step.

The plurality of logical channels divided in the channel dividing step may be characterized in that each bandwidth is the same.

The data dividing step divides at least one data segment of the plurality of data segments into a plurality of sub segments, and the channel dividing step divides at least one logical channel of the plurality of logical channels into a plurality of sub segments. The dividing into channels and the corresponding step may be characterized in that the plurality of subsegments are mapped to the plurality of subchannels.

In the transmitting step, when there are a plurality of logical channels corresponding to the second interval among the plurality of logical channels, the logical channels corresponding to the second interval may be divided into a total length of the first interval and the first interval. It may be a technical feature to have a difference in the transmission period corresponding to an integer multiple of the sum of the length of each data segment constituting.

As another aspect of the present invention for achieving the above object, the on-demand multimedia data transmission method according to the present invention, in the on-demand multimedia data transmission method executed in the multimedia data server, the multimedia data corresponding to the whole (front) Dividing into a first section and a second section corresponding to a rear section; Dividing the bandwidth allocated for transmission of the multimedia data into m logical channels for transmitting the first interval and n logical channels for transmitting the second interval; Dividing the multimedia data into N data segments such that the first interval consists of N-1 data segments each having a length d, and the second interval consists of one data segment; Repeatedly transmitting the N-1 data segments constituting the first interval through the m logical channels; And repeatedly transmitting the second interval through the n logical channels.

As another aspect of the present invention for achieving the above object, the on-demand multimedia data receiving method according to the present invention, the first section consisting of a plurality of data segments corresponding to the whole and each having the same length and; The multimedia data configured as the second section corresponding to the rear part is repeatedly transmitted through a plurality of logical channels, and at least one data segment of the plurality of data segments is divided into a plurality of subsegments. In a subscriber device networked with a multimedia data server repeatedly transmitting through at least one logical channel divided into a plurality of subchannels among logical channels, the method for receiving the multimedia data, the plurality of logical channels Obtaining channel information regarding channel information; The multimedia data is reproduced from the plurality of data segments constituting the first interval through a plurality of logical channels allocated for transmission of the first interval among the plurality of logical channels according to the obtained channel information. A first interval reception step of receiving the plurality of subsegments through the plurality of subchannels in order of receiving the data in order; And receiving the second interval through at least one logical channel allocated for transmission of the second interval among the plurality of logical channels according to the acquired channel information. It comprises a two-segment reception step.

The channel information may include a transmission schedule in which the first section and the second section including the plurality of sub segments and the plurality of data segments are transmitted through each of the plurality of logical channels.

In the receiving of the first section, at least one of the plurality of sub-segments and the plurality of data segments is received and stored in advance before the playback order of the multimedia data in order to reproduce the multimedia data in a playback order. It can be made into a technical feature.

In the receiving of the second section, when the transmission start time point of the first data segment and the transmission start time point of the second interval are the same, the first data segment is started and the first data segment is received. Starting of the reception of two sections may be a technical feature.

In the receiving of the second interval, when the transmission start time of the first data segment and the transmission start time of the second interval are not the same, the first data segment of the plurality of data segments is the same. It may be a technical feature to receive the second section from a logical channel that transmits the second section fastest after the reception of.

According to still another aspect of the present invention, there is provided a method for receiving multimedia data on demand, wherein the plurality of sub segments, the plurality of data segments, and the second interval are received in the first interval receiving step and the second interval receiving step. The method may further include a reproducing step of reproducing the multimedia data so as to conform to the reproduction order of the multimedia data.

According to the on-demand multimedia data transmission and reception method according to the present invention has the following effects.

First, according to the present invention, the system can be easily implemented on both the server side providing the on-demand multimedia and the subscriber device (client) side receiving the on-demand multimedia.

Second, according to the present invention, it is possible to provide a continuous video service to a user by eliminating the service disconnection phenomenon of the NVoD service method by the stepped transmission method according to the prior art.

Third, according to the present invention, even if only a small number of channels are used without increasing the user latency and the buffer capacity of the subscriber device, it is possible to provide better service than the conventional NVoD technology.

The above objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like numbers refer to like elements throughout. In addition, when it is determined that the detailed description of the known function or configuration related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a diagram illustrating an NVoD system according to an embodiment of the present invention. Referring to FIG. 1, an NVoD system according to an embodiment of the present invention will be described in detail.

The NVoD system according to an embodiment of the present invention includes a multimedia data server 100, a subscriber device 200, and a network 300.

The multimedia data server 100 may include a video storage 103, a transmitter 105, and a controller 107.

The video storage unit 103 stores video data. The multimedia data server 100 may store other forms of multimedia data such as audio data in addition to video data.

The transmitter 105 transmits the video data stored in the video storage 103 to the outside through the network 300. The multimedia data server 100 may transmit the video data through the transmitter 105 in various ways. For example, the video data may be transmitted to the outside in a broadcast manner or a multicast manner. The broadcast method is a method of transmitting data to an unspecified number, and the multicast method is a method of transmitting data only to a specific number, for example, specific service subscribers.

The controller 107 controls the components included in the multimedia data server 100 and manages the overall operations of the multimedia data server according to an embodiment of the present invention.

The subscriber device 200 may include an input unit 201, a storage unit 203, a display unit 205, a communication unit 207, and a control unit 209.

The input unit 201 is a device for receiving various information or commands from a user, and may be implemented as a keypad or a touch input device having various numeric keys, direction keys, and the like. As an example of the touch input device, the touch screen may simultaneously perform an input function and a display function.

The storage unit 203 stores a predetermined program for controlling the overall operation of the subscriber device 200, and is inputted and outputted when the overall operation of the subscriber device 200 is performed by the controller 209. Data and various data to be processed. In particular, the storage unit 203 stores multimedia data such as video data transmitted from the multimedia data server 100. The storage unit 203 may include a buffer for temporarily storing the multimedia data.

The display unit 205 is a display device for displaying the state or various information of the subscriber apparatus 200 by the control signal output from the control unit 209. The display unit 205 may display the multimedia data transmitted from the multimedia data server 100 by a control signal of the controller 209.

The communication unit 207 is a communication means for transmitting and receiving data with the multimedia data server 100. The subscriber device 200 may receive various multimedia data transmitted from the multimedia data server 100 through the communication unit 207.

The control unit 209 controls the components included in the subscriber device 200 and manages the overall operation of the subscriber device according to an embodiment of the present invention.

Representative examples of the subscriber device 200 include, but are not limited to, a personal computer (PC), a mobile phone, and an Internet Protocol TeleVision (IPTV). The subscriber device 200 may include any type of terminal having a communication function. The subscriber device 200 may be implemented as one set top box except for the display unit 205.

The network 300 is a communication network for transmitting and receiving data between the multimedia data server 100 and the subscriber device 200. The network 300 may be a wired or wireless communication network. In addition, the network 300, HFC (Hybrid Fiber Coaxual) network, optical communication network, wired and wireless integrated Internet network, portable Internet (WiBRO, WiMAX), 3rd generation asynchronous mobile communication standard HSDPA (High Speed Downlink Packet Access), 3rd generation The network may include a network according to various communication standards such as CDMA 1x EV-DO, which is a synchronous mobile communication standard.

According to an on-demand multimedia data transmission method according to an embodiment of the present invention, the first section is transmitted by a non-stage staircase transmission method, and the second section is staggered for repeatedly transmitting at regular intervals. Transmit by the method. This approach can simplify system implementation and increase the utilization of channel bandwidth. 2 is a diagram illustrating an example of applying a non-sequential stepped transmission scheme to video data. Referring to Figure 2 will be described a non-sequential stepped transmission method for performing the on-demand multimedia data transmission method according to an embodiment of the present invention.

The symbols used in FIG. 2 are described as follows. D [sec] represents the length of video data. b [bps] represents the video playback consumption rate. Details of the video playback consumption rate will be described later. S represents a data segment constituting video data. C represents a logical channel.

As shown in FIG. 2, a non-stage staircase transmission method is provided with N video data (if m channels are given).

Divided into the same size and distributed to each channel for transmission. The size and data of the data transmission channel are also divided and transmitted.

A first segment S ₁ of video data is transmitted to the first channel C ₁ , and S ₂ and S ₃ are periodically transmitted to the second channel C ₂ . Third channel C _i (

)

As many pieces of divided video data are repeatedly transmitted in order. At this point,

Dividing into two subchannels, and if the bandwidth of the first and second channels is b [bps],

From the third channel, the bandwidth of each subchannel

[bps]. In addition, the video data transmitted on each channel

The data is transmitted through each of the divided subchannels. Since the first subsegment transmitted through the divided subchannels is staggered for a predetermined time according to an increase in the number of subchannels, the segment is transmitted before the segment is consumed or before being displayed unlike the stepped transmission method. The storage of all subsegments of the is completed to ensure continuous video service.

In Figure 2, because there are three channels (C ₀ , C ₁ , C ₂ ), six videos (

The data is divided into three equal data segments, and one, two, and three data segments correspond to the three channels. In the third channel C ₂ , the channel and the data are divided into three again and transmitted.

3 is a flowchart of a method of transmitting multimedia data on demand according to an embodiment of the present invention. Referring to Figure 3 will be described in detail the method for transmitting multimedia data on demand according to an embodiment of the present invention. The on-demand multimedia data transmission method according to an embodiment of the present invention may be executed in the multimedia data server 100 of the NVoD system described with reference to FIG. 1. Hereinafter, the multimedia data will be limited to video data.

The multimedia data server 100 divides the video data into a first section and a second section [S300]. The first section corresponds to the front of the video data, and the second section corresponds to the rear of the video data.

The multimedia data server 100 divides the first section into a plurality of data segments each having the same length [S310].

The multimedia data server 100 divides the bandwidth allocated for transmission of the multimedia data into a plurality of logical channels [S320]. The multimedia data server 100 may set the same bandwidth of each of the plurality of logical channels.

The multimedia data server 100 divides at least one data segment of the plurality of data segments divided in step S310 into a plurality of subsegments [S330].

The multimedia data server 100 divides at least one logical channel of the plurality of logical channels divided in step S320 into a plurality of subchannels [S340].

The multimedia data server 100 divides the plurality of sub-segments, the plurality of data segments, and the second section constituting the first section into the plurality of logical channels divided in step S320 and step S340. And corresponding to the plurality of subchannels [S350]. In this case, the plurality of subsegments may correspond to the plurality of subchannels.

The multimedia data server 100 may determine the plurality of sub-segments, the plurality of data segments, and the second section of the plurality of logical channels and the plurality of blocks according to the corresponding relationship performed in operation S350. It transmits repeatedly through the subchannels [S360]. Here, when there are a plurality of logical channels corresponding to the second interval among the plurality of logical channels, the respective logical channels corresponding to the second interval constitute the total length of the first interval and the first interval. The transmission period may correspond to an integer multiple of the sum of the lengths of the data segments.

4 is a flowchart of a method of transmitting multimedia data on demand according to another embodiment of the present invention. 5 and 6 are diagrams showing examples of video data to which the on-demand multimedia data transmission method according to another embodiment of the present invention is applied. 4 to 6 will be described in detail a method for transmitting multimedia data on demand according to another embodiment of the present invention. The on-demand multimedia data transmission method according to another embodiment of the present invention may be executed in the multimedia data server 100 of the NVoD system described with reference to FIG. 1. Hereinafter, the multimedia data will be limited to video data.

Assuming that the length of each video data shown in FIGS. 5 and 6 is D [sec] and the video playback consumption rate is b [bps], the size V [bit] of the entire video is

It can be expressed as. And if the size of the total bandwidth allocated to the transmission of the video data B [bps],

Can be expressed as

to be. The playback consumption rate refers to the minimum bandwidth or data rate required for a viewer to watch a video when the multimedia data such as video is to be transmitted through a network. For example, a playback consumption rate of 10 Mbps is required to transmit HD video over a network, and a playback consumption rate of 2 Mbps is required to transmit SD video.

The multimedia data server 100 divides the video data into a first section and a second section [S400]. The first section corresponds to the front of the video data, and the second section corresponds to the rear of the video data. 5 and 6, D _f represents the first section and D _b represents the second section.

The relationship between D _f and D _b is shown in Equation 1 below.

Here, h is a video splitting coefficient for comparing D _f and D _b relatively, and d [sec] is the length of one data segment divided into the same size in D _f . The size V _f of the divided first section is

And the size V _b of the divided second section is

to be.

The multimedia data server 100 divides the total bandwidth B [bps] allocated for transmission of the video data into k logical channels, wherein the k logical channels are m logical channels for transmitting the first interval. A channel and n logical channels for transmitting the second interval [S410]. The k logical channels may all be configured to have the same bandwidth. The video partition coefficient h is a constant indicating the degree of division of the second section and may have a value equal to the number n of logical channels for transmitting the second section.

The number k of logical channels divided in step S410 may be expressed by Equation 2 below.

Denotes a maximum integer not exceeding β. For example, if the total bandwidth B = 32bps, the bandwidth b = 10bps of each channel, β = 3.2, and the number k of logical channels divided in step S410 is k = 3. Here, since the channel loss is reduced by 0.2 channel, the efficiency is lowered. Therefore, when β is set to an integer, better performance can be obtained.

Assume that m is the number of channels allocated to the first section to which the uninterrupted stepped transmission scheme is applied, and n is the number of channels allocated to the second section to which the staggered transmission scheme is applied. At this time, the relation k = m + n is established.

Hereinafter, the channel allocated to the first interval

, The channel allocated to the second interval

It is indicated by.

The mean represents the l-th channel of the part _{D i (i = f, b} ).

The multimedia data server 100 divides the video data into N segments, but sets the first section to be N-1 data segments and the second section to be one data segment [S420]. Here, when m = 1, when N = 2, when m = 2, when N = 3, and when m is 3 or more, N has a relationship as shown in Equation 3 below.

The divided N data segments are referred to as S. Where S _i represents the i th data segment. If the N data segments are displayed all the way in order, the entire video can be viewed. The lengths of S ₁ to S _N _-1 , which are the N-1 data segments constituting the first interval, may be equally set to d [sec].

The multimedia data server 100 repeatedly transmits the N-1 data segments constituting the first section through the m logical channels [S430].

Here, the multimedia data server 100 divides the N-1 data segments constituting the first section into m segment groups having the same number as m number of logical channels for transmitting the first section. The divided m segments may be matched to each of the m logical channels, and data segments included in each matched segment group may be repeatedly transmitted through the m logical channels according to the matching relationship. Hereinafter, the step S430 will be described using a formula.

Channel for transmitting the first interval

(Where i = 0, ..., m-1), when i = 0, S ₁ is a channel with bandwidth b

It is transmitted repeatedly through.

And when i = 1, S ₂ and S ₃ are channels with bandwidth b

It is transmitted repeatedly in turn.

And

Each channel

Through

Video data segments,

This is sent repeatedly. At this time

Each of the video data segments

Is divided into three subsegments. At this time

Sub-segments, all of the size can be set to be the same.

Channel

(here,

Matched above)

Video data segments

S _v of

Subsegments

Will be displayed.

Here, it is necessary to divide the channels to be transmitted due to the division of the subsegments. Channel

(here,

)so

It is divided into subchannels. Each of the subchannels may be configured to have the same bandwidth. The divided subchannels

Will be displayed. The channel bandwidth of each subchannel is

Becomes

Each sub-channel

(here,

), The subsegments,

The first subsegment transmitted repeatedly in this order and transmitted on each subchannel as u increases.

silver

Staggered as many as they are sent.

The multimedia data server 100 repeatedly transmits the second section through the n logical channels [S440].

In step S440, a channel for transmitting the second section

(here,

The video data segment S _n corresponding to the second section is periodically and repeatedly transmitted through the staggered transmission method through). In this case, the repetition period D _s of the staggered transmission method is used to match the period with the uninterrupted stepped transmission method applied to the first interval.

Should be That is, each of the n logical channels transmitting the second interval should have a difference between transmission periods corresponding to an integer multiple of the sum of the length D _f of the first interval and the length d of the video data segment.

The number of channels n allocated to the staggered transmission scheme is

It can be expressed as. Accordingly, the number of channels m allocated to the first interval, uninterrupted stepped transmission scheme is

It can be expressed as.

Hereinafter, an application example of the on-demand multimedia data transmission method according to an embodiment of the present invention will be described with reference to FIG. 6.

In FIG. 6, the length D of the video is divided into D _f and D _b by the video splitting factor h. here,

Represents the l-th channel of the D _i portion,

Denotes the i-th subchannel and the u-th subchannel of the D _f portion (the first interval).

In FIG. 6, the number m of channels allocated to transmit D _f (the first section) in the non-sequential stepped transmission scheme is 3, and transmits D _b (the second section) in the staggered transmission scheme. The number n of channels allocated for is n. The transmission period D _s of D _b to which the staggered transmission scheme is applied is D _f + d, where d is used to transmit D _f in an uninterrupted stepped transmission scheme.

The length of the segment equally divided by the length of. channel

Video data segments that are periodically sent through

from

Until.

6 shows the case where k = 6, β = 6, h = 3, m = 3, n = 3. Full length D [sec] of the video is _f D [sec] and D _b [sec] by the video division coefficient h (= 3)

Correlated with and can be divided.

Since the number of channels m = 3 allocated to the first section corresponding to the entire video, the portion D _f is divided into six video data segments, so that three channels,

Is sent periodically via As described above, the transmission scheme may be broadcast transmission or multicast transmission.

Since the number of channels n = 3 allocated to the second section corresponding to the rear part of the video is equal to three, the D _b portion is three channels in one segment.

Through the staggered transmission method. The second interval may also be broadcast transmission or multicast transmission. Here, the staggered transmission period D _s is 7d.

Video data segments S ₁ , S ₂ , S ₃ , and S ₇ are not divided. Video data segments S ₄ , S ₅ , and S ₆ are each

,

Divided into.

channel

S ₁ is transmitted periodically, and the channel

In S ₂ and S ₃ are repeatedly transmitted in order. Subchannel

Through

2, subchannel

Through

2, subchannel

Through

Each of these is repeatedly transmitted in order.

Subchannel

The first subsegment of each data segment transmitted through the STA is staggered by the increasing number of subchannels and transmitted. Subchannel

The first subsegment S ₅ _{, 1} of segment S ₅ transmitted through is subchannel d,

A first segment portion of the segment S ₆ sent through S _{6, 1} is sent as the de 2d staggered.

7 is a flowchart of a method for receiving multimedia data on demand according to an embodiment of the present invention. Referring to FIG. 7, a method of receiving multimedia data on demand according to an embodiment of the present invention will be described in detail. The on-demand multimedia data receiving method according to an embodiment of the present invention is a method of receiving on-demand multimedia data transmitted by the on-demand multimedia data transmission method described with reference to FIGS. 1 to 6. May be executed at 200. The subscriber device 200 may receive a request for viewing specific multimedia data from the user through the input unit 201. Hereinafter, a process after the subscriber device 200 receives a request for viewing specific multimedia data from a user will be described. It is assumed that the specific multimedia data requested by the user is video data.

As described above with reference to FIGS. 1 to 6, the multimedia data server 100 includes a first section and a rear section, each of which includes a plurality of data segments corresponding to the front part and each having the same length. Iteratively transmits video data composed of a second interval corresponding to the plurality of logical channels, wherein at least one data segment of the plurality of data segments is divided into a plurality of sub-segments of the plurality of logical channels It transmits repeatedly through at least one logical channel divided into a plurality of subchannels. The subscriber device 200 is connected to the multimedia data server 100 through the network 300.

The subscriber device 200 obtains channel information about the plurality of logical channels for transmitting the video data requested by the user [S700]. The channel information may include a transmission schedule in which the first section and the second section including the plurality of sub segments and the plurality of data segments are transmitted through each of the plurality of logical channels. The subscriber device 200 should receive the first section and the second section including the data segment and the sub-segment in accordance with the playback order of the video data and provide them to the user without interruption. The transmission schedule knows in advance the reception order and the reception time of the data segment, the sub-segment, the first section and the second section so that the video data can be seamlessly reproduced in the subscriber device 200. To be able.

The subscriber device 200 configures the first interval through a plurality of logical channels allocated for transmission of the first interval among the plurality of logical channels according to the channel information obtained in step S700. A plurality of data segments are received in accordance with a playback order of the video data, but the plurality of subsegments are received and reproduced through the plurality of subchannels [S710].

The subscriber device 200 according to the channel information obtained in step S700, at least one logical channel allocated for transmission of the second interval of the plurality of logical channels to match the playback order of the video data. The second section is received and played through [S720].

5 and 6, the steps S710 and S720 will be described in detail below. In performing the steps S710 and S720, the reception operation of each data may occur at the same time, and the reproduction operation of each data is made to match the reproduction order of the video data.

The subscriber device 200 is a channel based on a time point at which the user wants to watch.

While receiving the first download transfer video data segment S ₁ is in, and outputs the video data segment S ₁ so that the user can view directly through the display unit 205. The

The subscriber device 200 channels the video data segment S ₁ .

While downloading via

and

Start downloading data segments between channels as needed. The last video data segment S _N of the video transmission starts when the video data, the start point of the starting and S ₁ are the same, and have to start at the same time stored in a S _N S _1, S ₁ and if the other is the start of the S _N is It saves the fastest appearing S _N from the beginning of S ₁ so that the user can watch the video without interruption.

channel

The data segment in is called S _v , and the channel

Subchannel in the

Will be displayed. here

,

to be. If the video data segment S ₁ begins to download at t ₀ , the channel

If the data length of S ₁ in d is [sec], the subchannel

The section to be recorded and played on

from

Until.

The subscriber device 200 downloads video data segments while

In order to be able to watch without being cut off.

channel

In

When the first video data segment is received, the download stops on the channel. channel

The download stops when the last video data segment S _N is received on one channel.

<User wait time>

The user may request the subscriber device 200 to watch the video and watch the requested video after a predetermined time elapses. The amount of time a user waits to start watching a video after requesting to watch the video is called user waiting time.

Maximum user latency is channel

Is the length of the video data segment S ₁ . Because the subscriber device 200 channels the first video data segment S ₁ of the video data.

If you miss, then you have to wait for the length of S ₁ to receive and play the video data. channel

Since the repeated transmission of the video data segment S ₁ , the maximum time that the subscriber device 200 must wait for the reception / reproduction of the video data is a time corresponding to the length of S ₁ .

The length of S ₁

It can be represented as. channel

The bandwidth of is expressed in B / k at the given channel bandwidth for video transmission. Therefore, the maximum user latency d [sec] required for watching a video when transmitting video using the non-stage staircase staggered transmission scheme according to an embodiment of the present invention at a given total channel bandwidth B is given by Equation 4 below. Can be represented by

k is β when β is an integer, and Equation 4 is

It is simply expressed in the form of. Where the video full length D [sec] is

ego,

Therefore, using these relationships, the maximum user waiting time can be expressed by Equation 5 below.

For example, if the length D of the video is 6000 seconds (100 minutes), the number of total channels k allocated for video transmission is 10, and the video partition coefficient h is 4, the conditions for video transmission are given. Using the non-stage stair staggered transmission method according to the embodiment, the maximum user waiting time is about 24 seconds and the average user waiting time is about 12 seconds. However, under the same conditions, the maximum user latency of the staggered transmission method according to the prior art is 600 seconds (10 minutes). As shown in such a simple comparison, the non-stage staircase staggered transmission scheme according to the embodiment of the present invention can greatly increase the efficiency of bandwidth usage with a simple structure compared to the conventional scheme.

<Buffer Demand of Subscriber Device 200>

In order to provide a seamless screen to the user in order to receive various segments constituting the video data and to match the playback order, the subscriber apparatus 200 may receive some segments of the video data before playback and store them in the storage unit 203. Need to set. For this reason, the subscriber device 200 may include a buffer for temporarily storing data in the storage unit 203. From the standpoint of the subscriber device 200, a buffer is required even if the playback speed of the received video data is slower than the reception speed of the video data.

In the present invention, the maximum buffer request amount of the subscriber device 200 is a point at the maximum in the D _f section corresponding to the first section. Because the required amount of the buffer increases in interval D _f is reduced, but the interval D _b corresponding to the second section is due to the persistent store in the buffer upon receipt of the V _f all.

8 is a diagram illustrating an increase rate of a buffer required by a subscriber device during a D _f interval. If at t ₀ the user starts watching the video, the channel between t ₀ and t ₀ + d

From channels

All subsegments in between must be stored in a buffer.

If is a channel

The size of the subsegment of is one data segment

Is divided by.

In other words, between t ₀ and t ₀ + d, S ₁ and S ₂ are stored in a buffer and S ₁ is reproduced and consumed at the same time. Between t ₀ + d and t ₀ + 2d, S ₂ is consumed and S ₃ is then stored in a buffer for consumption.

If is a channel

The data segment in

Called the channel

Sub-channel

Will be displayed. here

,

to be. Where segment S _v is the subchannel

Through

Wow

Stored between,

Consumed in

As shown in FIG. 8, the channel

The buffer for

Is released. But at the same time the channel

The buffer for is up to. That is, the channel assigned to V _f [bit] is m (

), The buffer requirement within the D _f interval

Is the maximum at. But

Afterwards, the buffer reduction rate of the uninterrupted stepped transmission in the D _f interval is smaller than that of the staggered transmission in the D _b interval.

The buffer requirement does not maximize at. For this reason, in the non-stage stepped staggered transmission method according to the embodiment of the present invention, the increase in the buffer is such that the buffer of the D _f interval is released and the decrease rate and the increase rate of the buffer are the same.

Continue until. Therefore, in the non-stage staircase staggered transmission method according to the embodiment of the present invention, the maximum buffer requirement Z [bit] of the subscriber device 200 may be expressed as Equation 6 below.

As can be seen from Equation 6, the maximum buffer demand varies depending on the size of V _f [bit]. That is, the maximum buffer demand amount is affected by the video splitting factor h. In FIG. 6, the minimum buffer demand occurs at t ₁ , and the maximum buffer demand occurs at t ₀ . For example, in FIG. 6, d is represented as D / 27, which is the maximum user waiting time. The minimum viewer buffer requirement is when the viewer receives the video data segment from t ₁ , where the buffer for V _b (D _b part) is not needed. When the viewer buffer requirement is maximized, the video data segment is received from t _{0. In} this case, V _f [bit] must be downloaded as well as V _b [bit]. The reason is that the video can be viewed without disconnection by playing V _b immediately after playing V _f .

According to the prior art and the present invention Example Compare>

The length D of the video is 6000 seconds (100 minutes), and the video splitting coefficient h is 2 and 4, and the multimedia data transmission / reception method according to the prior art and the multimedia data transmission / reception according to the embodiment of the present invention are changed while changing the number of channels. We compared the methods (uninterrupted staircase staggered transmission method). In addition, we measured the maximum latency d and the maximum buffer demand Z according to the video partition coefficient h.

9 is a graph illustrating a relationship between the maximum waiting time d and the number of channels β required for video transmission. FIG. 10 is a graph showing a relationship between the maximum buffer demand amount Z and the number of channels β required for video transmission. FIG. 11 is a graph showing a relationship between the video splitting factor h and the maximum waiting time d when the number k of logical channels is determined and the video length D is 6000 seconds. FIG. 12 is a graph showing the relationship between the video partition coefficient h and the maximum buffer demand amount Z for a given logical channel number k. 9 to 12, data denoted by "USSB" represents data by the on-demand multimedia data transmission and reception method according to an embodiment of the present invention. Hereinafter, referring to FIG. 9 to FIG. 12, the on-demand multimedia data transmission / reception method according to the prior art and the on-demand multimedia data transmission / reception method according to an embodiment of the present invention will be described in detail.

Relationship between the maximum latency d and the number of channels β (see FIG. 9)

In FIG. 9, the length D of the video was 6000 seconds (100 minutes), and the video splitting coefficients h were 2 and 4. The result of the uninterrupted stepped transmission scheme according to the embodiment of the present invention appears from a portion where 1 is increased by more than the video splitting factor h. This is because, since the video splitting coefficient h determines the number of staggered channels, at least one channel to which the uninterrupted stepped transmission method is applied may be applied to the uninterrupted stepped staggered transmission method.

As shown in FIG. 9, the maximum user waiting time of the harmonic transmission method is the shortest in all sections. When the video splitting factor h is 2, the user maximum latency of the uninterrupted stepped staggered transmission is smaller than that of the pyramid transmission, and is almost the same as that of the fast transmission and the stepped transmission. In addition, it can be seen that as the video splitting factor h decreases, the user maximum waiting time d also decreases in the non-stage stepped staggered transmission. However, as the number of video channels increases, the difference in maximum latency almost disappears.

Relationship between the maximum buffer demand Z and the number of channels β (see FIG. 10)

In FIG. 10, the video splitting coefficients h of the uninterrupted stepped staggered transmission scheme were experimented with 2 and 4. The maximum buffer demand of the uninterrupted staggered staggered transmission scheme also appears from the attachment, which is increased by 1 more than the video partition coefficient h for the same reason as for the maximum latency.

As a result, the maximum buffer demand of the subscriber device 200 converges to 50% of the video data in the fast transmission method, 37% in the harmonic transmission method and 25% in the stepped transmission method. However, the maximum buffer requirement Z of the uninterrupted stepped staggered transmission method according to the embodiment of the present invention is 20% of the video data, which is smaller than the stepped transmission method when the video splitting factor h is 4. In the non-segmented stepped staggered transmission scheme, it can be seen that the maximum buffer requirement Z decreases as the video partition coefficient h increases.

Relationship between video splitting factor h and maximum latency d (see FIG. 11)

In FIG. 11, it can be seen that the maximum waiting time d [sec] of the user also increases as the video partition coefficient h increases within the determined number of logical channels. Also, it can be seen that the maximum latency increases quickly as the number of logical channels k is allocated and the video partition coefficient h is set large. That is, in an environment in which the uninterrupted stepped staggered transmission scheme is the same, as the number of channels allocated to the uninterrupted stepped transmission scheme increases, that is, the number of channels allocated to the first section corresponding to the entire video is increased. It can be seen that the more, the shorter the maximum waiting time of the user.

Relationship between video splitting factor h and maximum buffer demand Z (see FIG. 12)

12, it can be seen that as the video partition coefficient h increases, the maximum buffer demand decreases. As the number of logical channels k is allocated and the video partition coefficient h is set to a large value, the maximum buffer demand is reduced. Here, when the value of the video splitting factor h is small, the maximum buffer demand does not show any difference. This result indicates that the larger the number of channels allocated to the staggered transmission method, the smaller the maximum buffer requirement is for the non-stage staircase staggered transmission method.

Complexity of system implementation (see Table 1)

The complexity of the VoD system is a very important factor for system implementation. No matter how high the performance of VoD implementation, the high complexity makes it difficult to implement the system, making it less practical and increasing the price of VoD servers and set-top boxes. Important factors of complexity include the number of segments of video data, the number of management channels, the number of channels used simultaneously, and the number of hopping channels. Table 1 below shows these elements by comparing the VoD transmission method (USSB) according to the present invention and the VoD transmission method according to the prior art. Where NH is the number of channels allocated to the harmonic transmission scheme,

Can be obtained through Through Table 1, it can be seen that according to the VoD transmission method according to the present invention, since the data is transmitted by performing data division only for the short part of the entire video, the complexity is greatly reduced compared to the conventional VoD transmission method. have.

Transmission way Number of segments Number of management channels Number of concurrent channels Number of hopping channels USSB (Invention)

Pagoda broadcasting

k

1 to k k

Fast Broadcasting

k

1 to k k Staircase Broadcasting

Harmonic Broadcasting

N _H N _H N _H

The on-demand multimedia data transmission method and the on-demand multimedia data reception method according to the present invention described above may be provided by recording on a computer-readable recording medium as a program for executing on a computer.

The on-demand multimedia data transmission method and the on-demand multimedia data reception method according to the present invention can be executed through software. When implemented in software, the constituent means of the present invention are code segments that perform the necessary work. The program or code segments may be stored on a processor readable medium or transmitted by a computer data signal coupled with a carrier on a transmission medium or network.

Computer-readable recording media include all kinds of recording devices that store data that can be read by a computer system. Examples of computer-readable recording devices include ROM, RAM, CD-ROM, DVD ± ROM, DVD-RAM, magnetic tape, floppy disks, hard disks, optical data storage devices, and the like. The computer readable recording medium can also be distributed over network coupled computer devices so that the computer readable code is stored and executed in a distributed fashion.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

1 is a diagram illustrating an NVoD system according to an embodiment of the present invention.

2 is a diagram illustrating an example of applying a non-sequential stepped transmission scheme to video data.

3 is a flowchart of a method of transmitting multimedia data on demand according to an embodiment of the present invention.

4 is a flowchart of a method of transmitting multimedia data on demand according to another embodiment of the present invention.

5 and 6 are diagrams showing examples of video data to which the on-demand multimedia data transmission method according to another embodiment of the present invention is applied.

7 is a flowchart of a method for receiving multimedia data on demand according to an embodiment of the present invention.

8 is a diagram illustrating an increase rate of a buffer required by a subscriber device during a D _f interval.

9 is a graph illustrating a relationship between the maximum waiting time d and the number of channels β required for video transmission.

FIG. 10 is a graph showing a relationship between the maximum buffer demand amount Z and the number of channels β required for video transmission.

FIG. 11 is a graph showing a relationship between the video splitting factor h and the maximum waiting time d when the number k of logical channels is determined and the video length D is 6000 seconds.

FIG. 12 is a graph showing the relationship between the video partition coefficient h and the maximum buffer demand amount Z for a given logical channel number k.

100: multimedia data server 103: video storage

105: transmitter 107: controller

200: subscriber device 201: input unit

203: storage unit 205: display unit

207: communication unit 209: control unit

300: network

Claims

In the on-demand multimedia data transmission method executed in the multimedia data server,

A data partitioning step of dividing the multimedia data into a first section corresponding to all parts and a second section corresponding to a rear part, and dividing the first section into a plurality of data segments each having the same length ;

Dividing a bandwidth allocated for transmission of the multimedia data into a plurality of logical channels;

A corresponding step of mapping the plurality of data segments constituting the first interval and the second interval to the plurality of logical channels; And

A transmission step of repeatedly transmitting the plurality of data segments and the second interval through the plurality of logical channels according to a correspondence made in the corresponding step;

Custom multimedia data transmission method comprising.

The method of claim 1, wherein the plurality of logical channels divided in the channel dividing step,

On-demand multimedia data transmission method, characterized in that each bandwidth is the same.

The method of claim 2, wherein the data segmentation step,

Dividing at least one data segment of the plurality of data segments into a plurality of subsegments,

The channel division step,

Dividing at least one logical channel among the plurality of logical channels into a plurality of subchannels,

The corresponding step,

And mapping the plurality of subsegments to the plurality of subchannels.

The method of claim 3, wherein the transmitting step,

When there are a plurality of logical channels corresponding to the second interval among the plurality of logical channels, the logical channels corresponding to the second interval constitute the total length of the first interval and the respective data forming the first interval. On-demand multimedia data transmission method characterized in that the difference in the transmission period corresponding to the integral multiple of the length of the segment.

Dividing the multimedia data into a first section corresponding to the front part and a second section corresponding to the rear part;

Dividing the bandwidth allocated for transmission of the multimedia data into m logical channels for transmitting the first interval and n logical channels for transmitting the second interval;

Dividing the multimedia data into N data segments such that the first interval consists of N-1 data segments each having a length d, and the second interval consists of one data segment;

Repeatedly transmitting the N-1 data segments constituting the first interval through the m logical channels; And

Repeatedly transmitting the second interval through the n logical channels

Custom multimedia data transmission method comprising.

The method of claim 5, wherein each of the m logical channels and each of the n logical channels,

On-demand multimedia data transmission method characterized by having the same bandwidth.

The method of claim 6, wherein the number N of data segments to be divided is

2 when m is 1, 3 when m is 2, and when m is 3 or more

On-demand multimedia data transmission method characterized in that.

Here, S refers to the divided N data segments.

The method of claim 7, wherein transmitting the first interval comprises:

The N-1 data segments constituting the first section are divided into m groups to match each of the m logical channels to each of the m logical channels, and through the m logical channels according to the matching. On-demand multimedia data transmission method characterized by repeatedly transmitting the data segments included in each matched group.

The method of claim 8, wherein the transmitting of the first interval comprises:

Each of the m logical channels is called C _i (where i is an integer from 0 to m-1) and each of the N-1 data segments constituting the first interval is S _k (where k is from 1). An integer up to N-1)

Match S ₁ to C ₀ , match S ₂ and S ₃ to C ₁ , and for each C _i with _i greater than or equal to 2

And S _k (where k is an integer equal to or greater than 4).

The method of claim 9, wherein the transmitting of the first interval comprises:

Each C _i with _i equal to or greater than 2

Split each of the sub-channels S _k matched for each C _i

And dividing the data into three sub-segments, and repeatedly transmitting the divided sub-segments through the divided sub-channels.

The method of claim 10,

And wherein each subchannel has the same bandwidth and each subsegment has the same length.

The method of claim 10, wherein the transmitting of the second section comprises:

And each of the n logical channels transmitting the second interval has a difference between a length of the first interval and a transmission period corresponding to an integer multiple of the sum of d.

A computer-readable recording medium having recorded thereon a computer program capable of executing the method of any one of claims 5 to 12.

Repetitively transmitting the multimedia data consisting of a first section consisting of a plurality of data segments corresponding to the front part and each having the same length and a second section corresponding to the rear part through a plurality of logical channels, A multimedia data server that divides at least one data segment of the plurality of data segments into a plurality of subsegments and repeatedly transmits the data segment repeatedly through at least one logical channel divided into a plurality of subchannels among the plurality of logical channels. In the subscriber device connected to the network and the method, Receiving the multimedia data,

Channel information obtaining step of obtaining channel information on the plurality of logical channels;

A playback order of the multimedia data of the plurality of data segments constituting the first section through a plurality of logical channels allocated for transmission of the first section among the plurality of logical channels according to the obtained channel information. A first interval receiving step of receiving the plurality of sub-segments through the plurality of subchannels; And

A second section for receiving the second section through at least one logical channel allocated for transmission of the second section of the plurality of logical channels according to the obtained channel information according to the reproduction order of the multimedia data; Section receiving step

On-demand multimedia data receiving method comprising.

The method of claim 14, wherein the channel information,

On-demand multimedia data receiving method characterized in that it comprises a transmission schedule in which the first interval and the second interval consisting of the plurality of sub-segments and the plurality of data segments are transmitted through each of the plurality of logical channels. .

The method of claim 15, wherein the receiving of the first section comprises:

In order to reproduce the multimedia data in accordance with the playback order, at least one of the plurality of sub-segments and the plurality of data segments is received and stored in advance before the playback order of the multimedia data. Receiving method.

The method of claim 16, wherein the receiving of the second section comprises:

If the transmission start time point of the first data segment and the transmission start time point of the second interval among the plurality of data segments are the same, starting reception of the first data segment and at the same time starting reception of the second period. On-demand multimedia data receiving method characterized in that.

The method of claim 17, wherein the receiving of the second section comprises:

If the transmission start time of the first data segment of the plurality of data segments is not the same as the transmission start time of the second interval, the second after the reception start of the first data segment of the plurality of logical channels And receiving the second section from a logical channel that transmits the section fastest.

The method of claim 18,

A reproduction step of reproducing the plurality of sub-segments, the plurality of data segments, and the second section received in the first section receiving step and the second section receiving step in accordance with a playback order of the multimedia data;

Custom multimedia data receiving method further comprising.

20. A computer readable recording medium having recorded thereon a computer program capable of executing the method of any one of claims 14-19.