WO2007123283A1

WO2007123283A1 - Method for the delivery of multimedia file compressed by differential pulse code modulation through p2p data exchange

Info

Publication number: WO2007123283A1
Application number: PCT/KR2006/001561
Authority: WO
Inventors: Gyung Sueng Yang
Original assignee: Celrun Co., Ltd.
Priority date: 2006-04-25
Filing date: 2006-04-25
Publication date: 2007-11-01

Abstract

There is provided a method for the delivery of a multimedia file compressed by differential pulse code modulation (DPCM) comprised of a header, I frames consisting of I1, I2, I 3,..., I n, P frames consisting of P1, P2, P3,..., Pm and B frames consisting of B1, B2, B3,..., Bk, through P2P data exchange in response to the user's request. In accordance with the present invention, prior to the delivery of the multimedia file to the user terminal, a reference file in which start point, end point and size of the frames included in the multimedia file are specified is delivered to the user terminal and the transport units of the multimedia file are set up referring to the reference file. This prevents the split of a single frame into two transport units and ensures that the multimedia file is delivered in frame units. Further, the method in accordance with the present invention enables actively cope with the trick mode such as fast forward or fast reverse. In addition, the present invention enables quick playback of the multimedia file and significantly reduces the waiting time for the playback of the multimedia file.

Description

METHOD FOR THE DELIVERY OF MULTIMEDIA FILE

COMPRESSED BY DIFFERENTIAL PULSE CODE

MODULATION THROUGH P2P DATA EXCHANGE

Technical Field

[1] The present invention relates to a method for the delivery of multimedia file compressed by differential pulse code modulation (DPCM) to user terminal through P2P (peer to peer) data exchange. Background Art

[2] Typical examples of data transfer are server-to-client file transfer and P2P file transfer. In a P2P (peer to peer) network, the peers are computer systems which are connected to each other via the network. Files can be shared directly between systems on the network without the need of a central server. In other words, each computer on a P2P network becomes a file server as well as a client. With aid of common P2P software, the computers on a P2P network can search for files on other peers and download them. While P2P networking has a disadvantage supporting illegal music downloads, it makes file sharing easy and convenient. Especially, differently from the server-to-client file transfer model, P2P file sharing can disperse the load on the central server to the peers. Further, through distributed file transfer, P2P file sharing can increase the speed of file download. For these reasons, file transfer based on P2P is expected to become more and more important. With regard to the conventional techniques of file transfer through P2P data exchange, please refer to US Patent Nos. 5,761,421, 5,764,982, 5,806,075 and 6,094,676.

[3] Fig. 1 illustrates a typical example of the conventional P2P file transfer. In the conventional P2P file transfer, the file to be delivered is cut into transport units. The peers or central server, each of which ensuring the best condition of the delivery of the transport units, delivers the allocated units to the user terminal, and the user terminal reassemble the transport units to form a file and provides the file to the user. Generally, Split of the multimedia file into the transport units is performed randomly with a predetermined size (e.g., 1024 byte). For example, a multimedia file compressed by differential pulse code modulation (DPCM) comprises a header, multiple I frames (intraframes) consisting of I , I , I , ... , I , multiple P frames (predicted frames)

1 2 3 n consisting of P , P , P , ..., P and multiple B frames (bi-directional frames) consisting

1 2 3 m of B , B , B , ..., B . In the conventional file transfer, each of the transport units are set up with a given length and requests for the transport units are delivered to the peers. Thus, a single frame may be split into two transport units. Specifically, as illustrated in Fig. 1, the I frame may be split into the transport unit 3 (TU ) and the transport unit 4 (TU ), the user terminal receives the transport unit 3 from the peer 3 and the transport unit 4 from the peer 4, respectively. In this situation, the user terminal should wait for the reception of the transport unit 4 to display I frame on the user screen, even if the delivery of the transport unit 3 has been completed. Consequently, the processing of the I frame is delayed until the transport unit 4 is received. Further, in the conventional P2P file transfer, requests for the transport units of the multimedia file are processed in order. Specifically, the requests for the transport unit 1 (TU ), transport unit 2 (TU ), transport unit 3 (TU ), ..., transport unit N (TU ) are processed in order. Sometimes, such a sequential processing does not actively cope with a trick mode such as fast forward. Disclosure of Invention Technical Problem

[4] An object of the present invention is to attain an efficient delivery of multimedia file through P2P file transfer based on the structure of the multimedia file. Specifically, according to the present invention, there is provided a method for the delivery of multimedia file compressed by differential pulse code modulation (DPCM) through P2P data exchange to the user terminal.

[5] Another object of the present invention is to provide a method for the delivery of multimedia file through P2P file transfer, which allows quick playback of the multimedia file and reduced waiting time.

[6] Still another object of the present invention is to provide a method for the delivery of multimedia file through P2P file transfer, which allows trick mode play (fast forward) of the multimedia file even when all the transport units of the multimedia file have not been downloaded. Technical Solution

[7] In accordance with a preferred embodiment of the present invention, there is provided a method for the delivery of multimedia file compressed by differential pulse code modulation comprised of a header, I frames consisting of I , I , I , ..., I , P frames consisting of P , P , P , ..., P and B frames consisting of B , B , B , ..., B , through

1 2 3 m 1 2 3 k

P2P data exchange in response to a request from a user, comprising delivering to a user terminal a reference file in which a start point, an end point and a size of each of the frames are specified, prior to the delivery of the multimedia file, and setting up transport units of the multimedia file based on the reference file. The multimedia file is set up into the multiple transport units such that a single frame is not split into two transport units. This reduces the waiting time resulted from the split of a single frame into two transport units. [8] In accordance with a preferred embodiment of the present invention, there is provided a method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange, wherein the transport unit for the header is set up independently of the transport units for the I, P and B frames, and the transport units for the I frame are set up independently of the transport units for the P and B frames. Independent requests for the header and I frames make it possible rapid reception of the header and the I frames that take up a small portion of the entire multimedia. Rapid reception of the header and the I frames enables to actively cope with the user's trick mode request, even without downloading of P and B frames.

[9] In accordance with a specific embodiment of the present invention, there is provided a method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange, comprising the steps of: a) at a user terminal, in response to the user's request for a multimedia file compressed by differential pulse code modulation (DPCM), which comprises a header, I frames consisting of I , I , I , ..., I , P frames consisting of P , P , P , ..., P and B frames

1 2 3 n 1 2 3 m consisting of B , B , B , ..., B , delivering the request from to a P2P server or peers; b)

1 2 3 k at the P2P server or peers, prior to the delivery of the multimedia file, delivering a reference file into which the start point, the end point and the size of each of the frames that constituting the multimedia file are specified; c) at the user terminal, setting up the transport units of the multimedia file referring to the reference file; d) at the user terminal, requesting the delivery of the transport units to the P2P server or peers; e) at the P2P server or peers, delivering the allocated transport units to the user terminal in response to the request; and f) at the user terminal, receiving the transport units and displaying the multimedia file based on the transport units.

[10] In accordance with still more preferred embodiment of the present invention, there is provided a method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange, wherein in the step c), the transport unit for the header is set up independently of the transport units for the I, P and B frames, and the transport units for the I frame are set up independently of the transport units for the P and B frames.

[11] In accordance with still more preferred embodiment of the present invention, there is provided a method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange, wherein in the step c), the transport units are set up such that a single frame is not split into two transport units.

[12] In accordance with still more preferred embodiment of the present invention, there is provided a method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange, wherein in the step d), a request for the transport unit for the header is processed preferentially over those of the transport units for the I, P and B frames.

[13] In accordance with still more preferred embodiment of the present invention, there is provided a method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange, wherein in the step d), following the processing of the request for the transport unit for the header, requests for the transport units for the I frames are processed faster than those of the transport units for the P frames and B frames.

[14] In accordance with still more preferred embodiment of the present invention, there is provided a method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange, wherein requests for the transport units for the I frames consisting of I , I , I , ..., I are processed in the order of I → I

° 1 2 3 n ^r 1 2

→ I → ... → I and, processing of requests for the transport units for the P frames

3 n consisting of P , P , P , ... , P are determined such that when the current playback

1 2 3 m point of the multimedia file is I (g is an integer from 1 to n) frame, requests for the g transport units for the P frames following the I frame are processed faster than those g of the P and B frames skipped without being displayed by a fast forward mode and, processing of requests for the transport units for the B frames consisting of B , B , B , ..., B , is determined such that the transport units for the B frames following the I k g frame are processed faster than the B frame that have been skipped by the fast forward mode without being displayed.

[15] In accordance with still more preferred embodiment of the present invention, there is provided a method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange, wherein in the step f), the I frames consisting of I , I , I , ..., I are sequentially displayed on a screen, when fast forward

1 2 3 n or fast reverse of the multimedia file is requested from the user.

[16] In accordance with still more preferred embodiment of the present invention, there is provided a method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange, comprising the steps of: receiving a user's request for a multimedia file compressed by differential pulse code modulation (DPCM), which comprises a header, I frames consisting of I , I , I , ..., I , P frames

1 2 3 n consisting of P , P , P , ..., P and B frames consisting of B , B , B , ..., B , by ma-

1 2 3 m 1 2 3 k nipulation of an input device though an IR receiving unit; delivering the received request to a control processor; delivering from the control processor to a P2P module a control signal that requests downloading of the multimedia file through P2P data exchange; delivering the request to a P2P server or peers through an interactive interface unit through which data are exchanged under the control of the P2P module; prior to the delivery of the multimedia file, delivering from the P2P server or peers to the user terminal a reference file in which a start point, an end point and a size of the frames that constitutes the multimedia file are specified through the interactive interface unit; setting up transport units by analyzing the reference file under the control of the control processor; processing requests for the transport units by the P2P module an delivering the requests for the transport units to the P2P server or peers through the interactive interface unit; receiving the transport units from the P2P server or peers through the interactive interface unit; storing the received transport units into storage with aid of the P2P module; delivering the transport units to a decoder based on a playback point of the multimedia file under the control of the control processor; and displaying the decoded multimedia file on a user screen. The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange in accordance with the present invention is particularly suitable to the delivery of the multimedia file to a set-top box that processes interactive digital broadcasting signals and displayed a television screen. The data exchange between the set-top box and the P2P server or peers is performed through the interactive broadcasting network.

Advantageous Effects

[17] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange in accordance with the present invention provides the following advantages.

[18] (1) In accordance with the present invention, a reference file in which a start point, an end point and a size of each of the frames are specified is delivered to the user terminal prior to the delivery of the multimedia file and the transport units of the multimedia file are set up referring to the reference file. This allows set up of transport units in view of the structure of the file. Consequently, this prevents the split of a single frame into two transport units, which reduces the waiting time.

[19] (2) In accordance with the present invention, requests for the header and I frames are preferentially processed. This allows an independent playback of the multimedia file and enables quick playback of the multimedia file in the trick mode.

[20] (3) The processing order of the requests for the transport units for P and B frames is determined depending on the playback point of the multimedia file. The P and B frames that have been skipped by the trick mode without being displayed are not urgently requested data. The requests for these data are processed later than that for the urgently needed frames (P and B frames following the currently displayed I frame, g and, more urgently, the P or B frames preceding the I frame referenced by the P g frames following the I frame). Accordingly, an efficient data processing is attained g based on the playback point of the multimedia file.

Brief Description of the Drawings [21] Fig. 1 is a drawing illustrating a typical example of the set up of transport units of multimedia file for file transfer through P2P data exchange, in accordance with the prior art.

[22] Fig. 2 is drawing illustrating a preferred embodiment of a reference file used in the method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange, in accordance with the present invention.

[23] Fig. 3 is a drawing illustrating a preferred embodiment of the set up of transport units of multimedia file requested from the user based on the reference file illustrated in Fig. 2.

[24] Fig. 4 is a flowchart illustrating a preferred embodiment of the method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange, in accordance with the present invention.

[25] Fig. 5 is a block diagram illustrating a preferred embodiment of the method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange, in accordance with the present invention. Mode for the Invention

[26] Differential pulse code modulation (DPCM) is a modulation technique in which an analog signal is sampled and the difference between the actual value of each sample and its predicted value, which is derived from the previous sample or samples, is quantized and converted, by encoding, to a digital signal. In differential pulse code modulation, the differences between input sample signals are minimal. Differential pulse code modulation is designed to calculate this difference and then transmit this small difference signal instead of the entire input sample signal. Since the difference between input samples is less than an entire input sample, the multimedia file can be effectively compressed.

[27] A multimedia file compressed by differential pulse code modulation comprises multiple I frames (intraframes), multiple P frames (predicted frames) and multiple B frames (bi-directional frames). For example, a particular multimedia file may be represented as IBBPBBPIBB...BBP.

[28] I frames are entire frames requiring no reference to other frames. Accordingly, I frames include all the information contained in each of the scenes and can be played independently even without other frames.

[29] P frames include only the difference information with reference to the I frames. For example, in news program, some scenes following the first scene (I frame) will not be quite different from the first scene (I frame). Thus, these scenes are represented as P frames by differential pulse code modulation. The playback of P frames requires prior decoding of the I frames (or previous P frames) referenced by the P frames. P frames have smaller size than I frames.

[30] B frames are encoded with reference to two frames (previous frame and next frame). The B frames have smaller size than the P frames and is played referring to the two frames.

[31] According to the method of the present invention, the transfer of a multimedia file compressed by differential pulse code modulation is performed based on the structural characteristics of the multimedia file. To attain this, a reference file in which a start point, an end point and a size of each of the frames included into the multimedia file are specified is delivered to user terminal prior to the delivery of the multimedia file, which is one of the distinguishing features of the present invention. Fig. 2 illustrates a preferred embodiment of the reference file used in the present invention. As shown in Fig. 2, the reference file (100) includes the information on the start point, the end point and the size of each of the frames including a header that constitute the multimedia file. For example, the multimedia file may be comprised of a header, I frames consisting of I , I , I , ..., I , P frames consisting of P , P , P , ..., P and B frames

1 2 3 n 1 2 3 m consisting of B , B , B , ..., B , As specified in the reference file (100), the I frame is from 376 to 56775, the I frame from 84225 to 127164 and the I frame is from 464163

2 n to 481287. The I , I and I frames have sizes of 56400, 43240 and 47125 bytes, re-

1 2 n spectively. And, the P frame is from 58281 to 66364, the P frame is from 69184 to 84224 and the P frame is from 483363 to 500000. The P , P and P frames have sizes m 1 2 m of 8084, 15041 and 16638 bytes, respectively. Similarly, the B frame is from 56776 to 57340, the B frame is from 57341 to 58280, the B frame is from 66365 to 68244, the

2 3

B frame is from 68245 to 69183, the B frame is from 127165 to 128780, the B frame

4 5 6 is from 128781 to 129532 and the B frame is from 482416 to 483362. The B , B , B , k 1 2 3

B , B , B and B frames have sizes of 565, 940, 1880, 939, 1316, 752 and 947 bytes,

4 5 6 k respectively. If necessary, the reference file (100) may further include the information about the I frames referenced by the P frames. For example, if the P frame is encoded with reference to the I frame, such information may be included in the reference file (100). Typically, the reference file (100) is first created by a P2P (peer to peer) server. Peers connected to the P2P network receives the reference file (100) from the P2P server prior to the delivery of the multimedia file and stores it into the storage. Then, in response to the request for the reference file (100) from other user terminal (peer) connected to the P2P network, the reference file (100) is delivered through P2P data exchange.

[32] Fig. 3 illustrates a preferred embodiment of the determination of transport units of a multimedia file. As shown in Fig. 3, another important feature of the present invention is that the transport units of the multimedia file are set up referring to the reference file (100). With referring to the information of the frames included in the multimedia file, the split of one frame into two transport units can be prevented when setting up the transport units. This reduces the waiting time caused by the split of a single frame into two transport units. In accordance with more preferred embodiment of the present invention, the transport unit for the header is set up independently of the transport units for the I, P and B frames, and the transport units for the I frames are independent of the transport units for the P and B frames at the set up of the transport units. As shown in Fig. 3, the transport unit 1 (TU ) for the header is independent of the other I, P and B frames. And, the transport unit 2 (TU ) for the I frame, the transport unit 9 (TU ) for the I frame and the transport unit N-3 (TU ) for the I frame are also independent of the other P and B frames. Herein, each of the I frames can be played even without downloading of other frames. Usually, the header and the I frames take up a small portion of the entire multimedia. Accordingly, they can be delivered in a short time. Further, the multimedia file can be played independently if the header and the I frames are received, even when the P frames and B frames have not been delivered. Rapid reception of the header and the I frames enables to actively cope with the trick mode such as fast forward. More detailed description will be given later.

[33] Most preferably, as illustrated in Fig. 3, the transport units for the B and P frames are also determined independently each other. As shown in Fig. 3, each of the B frame, B frame, P frame, B frame, B frame, P frame, and so forth has an independent transport unit TU , TU , TU , TU , TU , TU , etc., respectively. ^{r Γ} 3 4 5 6 7 8 ^{r J}

[34] The user terminal determines the transport units referring to the reference file (100) and delivers requests for the transport units to the P2P server or peers. At the user terminal, the request for the transport unit for the header is processed preferentially over those of the I, P and B frames. And, following the processing of the request for the transport unit for the header, requests for the transport units for the I frames are processed faster than those of the transport units for the P frames and B frames. Specifically, as shown in Fig. 3, the request for the transport unit 1 (TU ) for the header is processed preferentially over those of other remaining transport units. Then, the requests for the transport units 2 (TU ), 9 (TU ) and N-3 (TU ) for the I frames are processed faster than those of the transport units (TU to TU , TU , TU , TU to ^{r C} 3 8 10 11 N-2

TU ) for the P frames and B frame.

N

[35] The reason why the requests for the transport units (TU , TU and TU ) for the I frames are preferentially processed at the user terminal rather than in the order of TU → TU → TU → TU → ... → TU → TU is because the header and the I frames (I

2 3 4 N-I N

, I , ..., I ) need to be transferred faster than the transport units (TU to TU , TU , TU

I 2 n 3 8 10

, TU , ... , TU ) for the B and P frames. When the transport unit 1 (TU ) for the

I I N-2 N ^r 1 header and the following transport units for the I frames (TU , TU , ..., TU ) are received, the user terminal can perform playback of the multimedia file independently based on the header and I frames. In most cases, the I frame emerges once in scores of seconds, although slightly different depending on the kind of the multimedia file and the encoding option. When the user inputs the action of fast forward or fast reverse of the multimedia file, the I frames are displayed on the screen in sequence. Consequently, the trick mode requested by the user can be attained effectively by processing the requests for the transport units for the I frames (TU , TU , ..., TU )

2 9 N-3 faster than the transport units (TU to TU , TU , TU , TU , ..., TU ) for the B and P

3 8 10 11 N-2 N frames.

[36] In accordance with more preferred embodiment of the present invention, requests for the transport units for the I frames I , I , ..., I are processed in the order of I → I

1 2 n 1 2

→ ... → I . Specifically, requests for the transport units for the I frames are processed n in the order of TU → TU → ... → TU . In contrast, the priority of the P and B

2 9 N 3 frames is determined based on the currently displayed I frame. Suppose that the user has requested for fast forward and the current playback point of the multimedia file is I

(g is an integer from 1 to n) frame. In this situation, the P frames and B frames g following the I frame are preferentially required over the P frames and B frames g preceding the I frame. Accordingly, at the user terminal, the requests for the transport g units for the P frames and B frames following the I frame are processed faster than g those of the P and B frames skipped by the fast forward mode. Sometimes, the P frames may refer to the P frames preceding the I frame. The number of the frame that g can be referred by the P frames is determined by the encoding option of the multimedia file. Specifically, in a multimedia file encoded by MPEG- 1 or MPEG-2, one P frame can refer the P frame located just before, while in MPEG-4 or H.264, it can refer the frame positioned up to preceding 5th frame. Accordingly, when the current playback point of the multimedia file is the I frame (g is an integer from 1 to n), the requests for g the transport units for the P and B frames is preferably processed in the following order: the P frame which precedes the I frame and is referred by the P frames g following the I frame, the P and B frames following the I frame, and then the P and B g g frames preceding the I frame, which have been skipped by the fast forward mode g without being displayed. In this way, the entire multimedia file is delivered to the user terminal, and the reference file (100) and the multimedia file are stored into the storage. Thereafter, the user terminal can act as another peer that delivers the multimedia file to other peers. [37] Fig. 4 is a flowchart illustrating a preferred embodiment of the method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange according to the present invention. In response to the user's request for a multimedia file compressed by differential pulse code modulation (DPCM), which comprises a header, I frames consisting of I , I , I , ..., I , P frames consisting of

1 2 3 n P , P , P , ..., P and B frames consisting of B , B , B , ..., B , the user terminal

1 2 3 m 1 2 3 k delivers a request for the multimedia file to a P2P server or peers connected to the P2P network (SlOO). In response to the request from the user terminal, the P2P server or peers delivers to the user terminal, prior to the transfer of the multimedia file, a reference file in which the start point, the end point and the size of each of the frames that constitute the multimedia file are specified (S200). Specifically, at the user terminal, P2P software is installed to connect the user terminal to the P2P network and to assist search for files stored in the peers on the network. Therefore, in response to the user's request, the request for the multimedia file is transmitted from the user terminal to the P2P server or peers with the aid of the P2P software. In response to such a request, the server or peers on the P2P network delivers the reference file to the user terminal. The user terminal set up the transport units of the multimedia file referring to the reference file (S300). As described earlier, the transport units are set up such that a single frame is not split into two transport units. Further, preferably, the transport unit for the header is independent of the transport units for the I, P and B frames and the transport units for the I frames are independent of the transport units for the P and B frames. Following the set up of the transport units referring to the reference file, the user terminal delivers requests for the transport units to the P2P server or peers (S400). At the user terminal, the request for the transport unit for the header is processed preferentially over those of the I, P and B frames and, following the processing of the transport unit for the header information, requests for the transport units for the I frames are processed faster than those of the transport units for the P frames and B frames. Requests for the transport units for the I frames are processed in order. In contrast, requests for the transport units for the P and B frames are processed not in order but depending on the current playback point of the multimedia file, as illustrated in the above. [38] In response to the request, the P2P server or peers deliver the transport units allocated to them to the user terminal (S500). Then, the user terminal receives the delivered transport units and displays the multimedia file on the screen (S600). The order of the delivery of the frames to the user terminal is not necessarily dependent upon the processing order of the requests at the user terminal. For example, depending on the network situation, the P frame in Fig. 3 may be transferred to the user terminal earlier than the I frame. However, it is preferable that the transport unit for the I

3 3 frame is processed faster than the transport unit at the P frame so that the I frames are preferentially ready for the display over the P and B frames. This allows an independent playback of the multimedia file. Further, this provides a base to actively cope with the request for the trick mode from the user. [39] Fig. 5 is a block diagram for a preferred embodiment of the method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange according to the present invention. As illustrated in Fig. 5, the user terminal (300) comprises an IR receiving unit (301), a control processor (302), a P2P module (303), an interactive interface unit (304), a storage (305) and an A/V decoder (306). Although not shown in Fig. 5, P2P software is installed in the user terminal (300) as part of middleware or application. The P2P software provides the connection to the P2P network and the search for multimedia files stored in the server or peers connected to the P2P network.

[40] The user may select a particular multimedia file using an input device (500) such as remote control, wireless keyboard, etc. For example, the multimedia file may be one of various multimedia contents including video on demands (VOD), news program files, soccer game video files, and so forth. If the multimedia file selected by the user is a file compressed by differential pulse code modulation (DPCM), it comprises a header, I frames consisting of I , I , I , ..., I , P frames consisting of P , P , P , ..., P and B

1 2 3 n 1 2 3 m frames consisting of B , B , B , ..., B .

° 1 2 3 k

[41] The request for the multimedia file compressed by differential pulse code modulation (DPCM) by the manipulation of the input device (500) is delivered to the IR receiving unit (301) of the user terminal (300). Upon reception of the request signal from the IR receiving unit (301), the control processor (302) generates a control signal that requests downloading of the multimedia file and delivers it to the P2P module (303) that manages P2P data exchange under the control of the control processor (302).

[42] The P2P module (303) delivers the request for the multimedia file to the P2P server

(401) or peers (402a to 402n, collectively "402") with aid of the P2P software (not shown) installed in the user terminal (300). Prior to the delivery of the multimedia file, P2P systems that ensures best condition for the delivery of the reference file corresponding to the multimedia file is selected. Referring to Fig. 5, the peer A (402a) can transfer the reference file to the user terminal (300) most quickly. The peer A (402a) delivers through the interactive interface unit (304) to the user terminal (300) the reference file, into which the start point, the end point and the size of each of the frames that constitute the multimedia file are specified, and the user terminal (300) stores the reference file into the storage (305). Subsequently, at the user terminal (300), the transport units of the multimedia file are set up by analyzing the reference file under the control of the control processor (302). For details on the set up of the transport units, please refer to Fig. 2 and the explanation thereof. The requests for the transport units for the frames are processed by the P2P module (303). Request for the transport unit for the header is processed preferentially. Then, requests for the transport units for the I frames are processed, and thereafter requests for the transport units for the P and B frames are processed. The requests for the transport units for the I frames are processed in the order of I → I → I → ... → I . In contrast, the processing order

1 2 3 n of the P and B frames is determined depending on the currently displayed I frame. Then, each of the requests for the transport units is delivered through the interactive interface unit (304) with aid of the P2P software. Referring to Fig. 3, requests for the transport unit TU for the header and the transport unit TU for the I frame are delivered to the peer B (402b) and the request for the transport unit TU for the I frame is delivered to the peer C (402c). Similarly, requests for the remaining transport units may be delivered to the P2P server (401) or peers (402) that retain the transport units. The P2P server (401) or peers (402) deliver the transport units allocated to them to the user terminal (300) through the interactive interface unit (304). The delivered transport units are stored in the storage (305) by the P2P module (303) and the data stored in the storage (305) are processed and delivered to the A/V decoder (306) based on the playback point of the multimedia file under the control of the control processor (302). The decoded multimedia file is displayed on the user screen. When a request for fast forward or fast reverse is received from the user to the IR receiving unit (301) during the playback of the multimedia file, the I frames consisting of I , I , I , ..., I are

1 2 3 n displayed in order on the screen in response to the request. At the same time, the proc essing order of the transport units for the P and B frames, which have not been processed by the P2P module (303), is determined again depending on the point of the presently displayed I frame. [43] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange in accordance with the present invention is particularly suitable to the delivery of the multimedia file to a set-top box that processes interactive digital broadcasting signals. In this case, the multimedia file is displayed on the television screen and the data exchange between the set-top box and the P2P server or peers is performed through the interactive broadcasting network.

Claims

[1] A method for the delivery of multimedia file compressed by differential pulse code modulation (DPCM) comprised of a header, I frames consisting of I , I , I , ..., I , P frames consisting of P , P , P , ..., P and B frames consisting of B , B , n ^σ 1 2 3 m ° 1 2

B , ... , B , through P2P data exchange in response to a request from a user,

3 k comprising delivering to a user terminal a reference file in which a start point, an end point and a size of each of the frames are specified, prior to the delivery of the multimedia file, and setting up transport units of the multimedia file referring to the reference file.

[2] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 1 , wherein the transport units are set up such that a single frame is not split into two transport units.

[3] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 2, wherein the transport unit for the header is set up independently of the transport units for the I, P and B frames, and the transport units for the I frame are set up independently of the transport units for the P and B frames.

[4] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 3, wherein the request for the transport unit for the header is processed preferentially over those of the transport units for the I, P and B frames.

[5] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 4, wherein, following the processing of the request for transport unit for the header, requests for the transport units for the I frames are processed faster than those of the transport units for the P and B frames.

[6] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 5, wherein requests for the transport units for the I frames consisting of I , I , I , ..., I are

1 2 3 n processed in the order of I → I — > I → ... → I and, processing of requests for the transport units for the P frames consisting of P , P , P , ..., P are determined

1 2 3 m such that when the current playback point of the multimedia file is I (g is an g integer from 1 to n) frame, requests for the transport units for the P frames following the I frame are processed faster than those of the P and B frames g skipped without being displayed by a fast forward mode and, processing of requests for the transport units for the B frames consisting of B , B , B , ... , B , is determined such that the transport units for the B frames following the I frame g are processed faster than the B frame that have been skipped by the fast forward mode without being displayed.

[7] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 6, wherein the I frames consisting of I , I , I , ..., I are sequentially displayed on a screen, when

1 2 3 n fast forward or fast reverse of the multimedia file is requested from the user.

[8] A method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange comprising the steps of: a) at a user terminal, in response to the user's request for a multimedia file compressed by differential pulse code modulation (DPCM), which comprises a header, I frames consisting of I , I , I , ..., I , P frames consisting of P , P , P , ...,

1 2 3 n 1 2 3

P and B frames consisting of B , B , B , ... , B , delivering the request from to a m 1 2 3 k

P2P server or peers; b) at the P2P server or peers, prior to the delivery of the multimedia file, delivering a reference file into which the start point, the end point and the size of each of the frames that constituting the multimedia file are specified; c) at the user terminal, setting up the transport units of the multimedia file referring to the reference file; d) at the user terminal, requesting the delivery of the transport units to the P2P server or peers; e) at the P2P server or peers, delivering the allocated transport units to the user terminal in response to the request; and f) at the user terminal, receiving the transport units and displaying the multimedia file based on the transport units.

[9] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 8, wherein in the step c), the transport unit for the header is set up independently of the transport units for the I, P and B frames, and the transport units for the I frame are set up independently of the transport units for the P and B frames.

[10] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 9, wherein in the step c), the transport units are set up such that a single frame is not split into two transport units.

[11] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 8, wherein in the step d), a request for the transport unit for the header is processed preferentially over those of the transport units for the I, P and B frames.

[12] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 11 , wherein in the step d), following the processing of the request for the transport unit for the header, requests for the transport units for the I frames are processed faster than those of the transport units for the P frames and B frames.

[13] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 8, wherein requests for the transport units for the I frames consisting of I , I , I , ..., I are

1 2 3 n processed in the order of I → I → I → ... → I and, processing of requests for

1 2 3 n the transport units for the P frames consisting of P , P , P , ..., P are determined

1 2 3 m such that when the current playback point of the multimedia file is I (g is an g integer from 1 to n) frame, requests for the transport units for the P frames following the I frame are processed faster than those of the P and B frames skipped without being displayed by a fast forward mode and, processing of requests for the transport units for the B frames consisting of B , B , B , ... , B , is determined such that the transport units for the B frames following the I frame g are processed faster than the B frame that have been skipped by the fast forward mode without being displayed.

[14] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 8, wherein in the step f), the I frames consisting of I , I , I , ..., I are sequentially displayed on

1 2 3 n a screen, when fast forward or fast reverse of the multimedia file is requested from the user.

[15] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 8, wherein the user terminal is a set-top box that processes digital broadcasting signals and the screen is a television screen.

[16] A method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange comprising the steps of: receiving a user's request for a multimedia file compressed by differential pulse code modulation (DPCM), which comprises a header, I frames consisting of I , I , I , ..., I , P frames consisting of P , P , P , ..., P and B frames consisting of B ,

3 n ° 1 2 3 m ° 1

B , B , ... , B , by manipulation of an input device though an IR receiving unit;

2 3 k delivering the received request to a control processor; delivering from the control processor to a P2P module a control signal that requests downloading of the multimedia file through P2P data exchange; delivering the request to a P2P server or peers through an interactive interface unit through which data are exchanged under the control of the P2P module; prior to the delivery of the multimedia file, delivering from the P2P server or peers to the user terminal a reference file in which a start point, an end point and a size of the frames that constitutes the multimedia file are specified through the interactive interface unit; setting up transport units by analyzing the reference file under the control of the control processor; processing requests for the transport units by the P2P module an delivering the requests for the transport units to the P2P server or peers through the interactive interface unit; receiving the transport units from the P2P server or peers through the interactive interface unit; storing the received transport units into storage with aid of the P2P module; delivering the transport units to a decoder based on a playback point of the multimedia file under the control of the control processor; and displaying the decoded multimedia file on a user screen.

[17] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 16, wherein a request for the transport unit for the header is processed preferentially over those of the transport units for the I, P and B frames, and following the processing of the request for transport unit for the header, requests for the transport units for the I frames are processed faster than those of the transport units for the P and B frames.

[18] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 16, wherein the I frames consisting of I , I , I , ... , I are sequentially displayed on a screen, when

[19] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 16, wherein requests for the transport units for the I frames consisting of I , I , I , ..., I are

1 2 3 m such that when the current playback point of the multimedia file is I (g is an g integer from 1 to n) frame, requests for the transport units for the P frames following the I frame are processed faster than those of the P and B frames g skipped without being displayed by a fast forward mode and, processing of requests for the transport units for the B frames consisting of B , B , B , ..., B , is determined such that the transport units for the B frames following the I frame g are processed faster than the B frame that have been skipped by the fast forward mode without being displayed.

[20] The method for the delivery of multimedia file compressed by differential pulse code modulation through P2P data exchange as set forth in claim 16, wherein the user terminal is a set-top box that processes digital broadcasting signals and the screen is a television screen and data exchange between the set-top box and the P2P server or peers is performed through an interactive broadcasting network.