KR101839500B1 - Method for payload formatting and deformatting for burst loss recovery - Google Patents

Abstract

A payload formatting method according to the present invention is a payload formatting method performed in a transmitter, which is a payload formatting method performed in a transmitter, in which one of enhancement layer packets of a group of pictures (GoP) including a base layer packet and at least one enhancement layer packet Generating an XOR operation packet by performing an exclusive OR (XOR) operation based on the base layer packet, and adding the XOR operation packet to the GoP.

Description

[0001] METHOD FOR FORDING FORMATTING AND DEFORMATING FOR BURST LOSS RECOVERY FOR BURST DATA LOSS RECOVERY [

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to data loss recovery in a communication system, and more particularly, to a payload formatting method and a formatting method for recovering errors and losses occurring in transmission of multimedia data.

Due to the characteristics of the mobile communication service environment, the terminal does not receive data when it passes behind a building or a shadow area such as a tunnel. Therefore, there is a case where a burst loss is incurred. In this case, there is a method for constructing a forward error correction (FEC) packet in the payload as a method used for loss recovery.

A forward error correction technique is a technique used to protect data from corruption, and is a technique for recovering errors on the side receiving the data. In many communication systems, the transmission type uses a unidirectional channel and there is no reverse channel in many cases. Therefore, retransmission can not be requested. Even if retransmission is possible, there is a delay time. Therefore, if an error occurs, the FEC Lt; / RTI >

However, if the channel condition is good, the payload format using the forward error correction method having a function for recovering the existing burst loss will only increase the transmission bandwidth, and if a collective error occurs in a group of data such as a burst error There is a problem that can not completely recover the loss.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a payload formatting method capable of effectively recovering burst loss without retransmission.

It is another object of the present invention to provide a payload de formatting method capable of effectively recovering a burst loss without retransmission.

According to an aspect of the present invention, there is provided a payload formatting method performed in a transmitter, the method comprising: receiving a enhancement layer packet of a group of pictures (GoP) including a base layer packet and at least one enhancement layer packet, Generating an XOR operation packet by performing an exclusive or (XOR) operation based on any one of the packet and the base layer packet, and adding the XOR operation packet to the GoP .

Here, the payload formatting method may further include removing the base layer packet from the GoP.

Herein, the base layer packet is related to the most important frame in the GoP, and the enhancement layer packet used for the XOR operation is related to the second most important frame in the GoP.

Here, the payload formatting method may include generating a forward error correction (FEC) packet for the GoP, adding a base layer packet of a forward or a backward GoP separated by a predetermined time interval from the GoP to generate a forward error correction encoding of the GoP to generate the FEC packet of the GoP, and adding the generated FEC packet to the GoP.

Here, the payload formatting method may include generating a forward error correction (FEC) packet for the GoP, adding a base layer packet of forward and backward GoPs separated by a predetermined time interval from the GoP, correction encoding of the GoP and generating the FEC packet of the GoP and adding the generated FEC packet to the GoP.

According to another aspect of the present invention, there is provided a payload formatting method performed by a receiver, the method comprising: receiving an XOR packet generated by performing an XOR operation on a base layer and a first enhancement layer packet; Comprising: receiving packets of a GoP including at least one enhancement layer packet and an FEC packet including a packet; confirming whether loss of packets of the GoP is lost; And restoring the base layer packet of the GoP by performing an XOR operation based on the XOR packet and the first enhancement layer packet when it is determined that the packet and the packet other than the XOR packet are lost, Thereby providing a method of deforming the road.

Here, the FEC packet of the GoP is a packet generated by performing FEC (forward error correction) encoding by adding a base layer packet of a forward or backward GoP separated by a predetermined time interval from the GoP.

The method may further include receiving packets of the GoP and storing the packets in the buffer, wherein all the packets of the forward or backward GoP within a predetermined time interval from the GoP are stored in the buffer.

Here, the payload de formatting method may further include a step of performing FEC decoding on the basis of the packets of the forward GoP that are separated from the GoP by a predefined time interval when it is determined that the first enhancement layer packet or the XOR packet is lost, And restoring the base layer packet of the GoP by performing the second step.

Here, the second step of restoring the base layer packet of the GoP uses packets of the forward GoP that are separated by the predetermined time interval stored in the buffer.

Here, the payload de formatting method may further include a step of, when it is determined that the first enhancement layer packet or the XOR packet is lost, And restoring the base layer packet of the GoP by performing decoding on the base layer packet.

In the case of using the payload formatting and de-formatting method for recovering burst data loss according to the present invention as described above, it is expected to improve the performance as much as the XOR coding gain by performing FEC coding (Forward Error Correction Coding) using XOR (Exclusive OR) . In addition, the method according to the present invention provides an Unequal Error Protection (UEP) function for XOR-coding significant data such as base layer data or first enhancement layer data to make the loss robust.

Also, even if all packets in a specific GoP section are lost, the most important data part of the GoP is added to the FEC calculation of the forward or backward GoP section, so that even if all data in the GoP section is lost, So that it is possible to provide a continuous service.

1 is a flowchart illustrating a payload formatting process for burst loss recovery according to an embodiment of the present invention.
2 is a block diagram illustrating the structure of scalable video data and the payload structure reconstructed according to an XOR operation in accordance with one embodiment of the present invention.
FIG. 3 is a block diagram illustrating packets of a GoP configured according to a payload structure according to an embodiment of the present invention, in time intervals.
4 is a block diagram illustrating a FEC encoding and payload formatting method for burst loss recovery according to an embodiment of the present invention.
FIG. 5 is a flowchart illustrating payload formatting for burst loss recovery according to an embodiment of the present invention. Referring to FIG.
6 is a block diagram illustrating a FEC decoding and payload formatting method for burst loss recovery according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, A, B, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the present invention, the same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

A payload formatting and de-formatting method for burst loss recovery according to the present invention will now be described. The present invention provides a method for recovering a lost packet without retransmission and recovering even only the data of a base layer packet having the most important data, even if all packets are lost, to provide an uninterrupted service. This makes it possible to achieve coding gain and loss compensation with high efficiency by combining the error correction technique and the payload formatting technique.

1 is a flowchart illustrating a payload formatting process for burst loss recovery according to an embodiment of the present invention.

Referring to FIG. 1, a payload formatting process for burst loss recovery according to an exemplary embodiment of the present invention may be performed at a data transmitter side. The XOR operation packet generation step S110, the XOR operation packet addition step S120, A base layer packet removal step (S130), an FEC packet generation step (S140), and an FEC packet addition step (S150).

Referring to FIG. 1, each step of the payload formatting process for burst loss recovery according to an embodiment of the present invention can be described as follows.

The XOR operation packet generation step S110 is a step for generating a XOR operation packet for a group of pictures (GoP) including a base layer packet and at least one enhancement layer packet, And generating an XOR operation packet as a result of performing an XOR (Exclusive OR) operation based on the XOR operation packet.

Meanwhile, the XOR operation packet generated in the XOR operation packet generation step S110 may be added to the GoP (S130), the base layer packet may be removed from the GoP (S130), and the GoP packets may be transmitted.

An example of the XOR operation packet configuration described above in the scalable video data structure will be described with reference to the drawings.

2 is a block diagram illustrating the structure of scalable video data and the payload structure reconstructed according to an XOR operation in accordance with one embodiment of the present invention.

2, the scalable video data includes a base layer packet (Base_n, 0) 211, a first enhancement layer packet (Enh_n, 1) 212, a second enhancement layer packet (Enh_n, 2 (213).

Referring to FIG. 2, in the base layer packet (Base_n, 0) 211, n is a time index indicating an nth picture group (Group of Pictures), and 0 is an index indicating the highest importance have. Thus, the base layer packet may refer to the most significant packet or the most significant frame in the actual video coding data group.

For example, in the case of H.264 / AVC, there may be one IDR (Instantaneous Decoding Refresh) frame (I frame) and several P and B frames which are most important in one GoP. In this case, the base layer (Base_n, 0) 211 may mean an IDR frame. In case of H.264 / SVC, there can be a base layer and at least one enhancement layer in one GoP, and I, P and B frames exist in each layer. In this case, base layer packets Base_n, 0 ) 211 denotes an entire data group of the base layer, or may refer to only I frames among I, P and B frames constituting the base layer. Also, in the first enhancement layer packet (Enh_n, 1) 212, n may represent a time index and 1 may have a significance following 0.

Referring to FIG. 2B, the structure of the payload reconstructed according to the XOR operation of the embodiment of the present invention is shown. In the GoP, an XOR operation packet (X_n, 0) 221, (Enh_n, 1) 222, and a second enhancement layer packet (Enh_n, 2) 223.

At this time, the XOR operation packet (X_n, 0) 221 includes the base layer packet (Base_n, 0) 211 and the first enhancement layer packet (Enh_n, 1) (Exclusive OR) operation on the packet 212, and can be expressed by the following equation.

[ Equation  One]

{X_3,0} = {Base_3,0} XOR {Enh_3,1}

Here, {} denotes a bit-wise operation.

Therefore, if the result value X_3,0 of Equation (1) is used, if either Base_3,0 or Enh_3,1 is present without loss, there is an advantage that the remaining one can be recovered.

FIG. 3 is a block diagram illustrating packets of a GoP configured according to a payload structure according to an embodiment of the present invention, in time intervals.

Referring to FIG. 3, XOR packets 311, 321, and 331 generated by performing an XOR operation based on a base layer packet and an enhancement layer packet in an interval-based GoP according to an embodiment of the present invention are transmitted to each GoP 310, 320, and 330, in which case the base layer packets in the GoP may be removed and transmitted.

The FEC packet generation step S140 generates a forward error correction (FEC) packet for the GoP, adds a base layer packet of the forward or backward GoP separated by a predetermined time interval from the GoP to the FEC source block, And performing FEC (forward error correction) encoding based on the FEC source block to generate the FEC packet of the GoP. At this time, the FEC encoding can use an XOR operation.

The generated FEC packet may be added to the GoP (S150) and transmitted. In addition, when packets of GoP are transmitted, the base layer packet of the forward or backward GoP added in the FEC encoding can be removed and transmitted.

Hereinafter, the configuration of the FEC packet and the payload format will be described by way of example with reference to the drawings.

4 is a block diagram illustrating a FEC encoding and payload formatting method for burst loss recovery according to an embodiment of the present invention.

4, video data per GoP is composed of base layer packets 411, 431 and 451, first enhancement layer packets 412, 432 and 452 and second enhancement layer packets 413, 433 and 453 . Also, an FEC source block may be generated for each GoP period, but is not limited to this example. Also, the maximum guard interval L for burst loss recovery is set to 2 GoP, but this can be changed according to the design.

In order to protect low-speed data such as the SVC base layer, it is possible to retrieve data that is separated by a distance L, add redundancy to the current source block, and generate FEC data.

For example, the base layer packet (Base3,0) 431 and the first enhancement layer packet (Enh3,1) 432 in the GoP-3 430 are XORed to generate a new XOR packet X3,0 ( 434).

Meanwhile, the base layer packet (Base 3, 0) 431 is inserted into the FEC block-1 416 in front of the GoP-1 410 and is calculated as shown in the following Equation 2 to generate the FEC- have.

[ Equation  2]

FEC-1 = f {Base_3,0, X_1,0, Enh_1,1, Enh_1,2},

Here, f {} is defined as an encoding function for generating a parity of the FEC for recovering an erased bit when a data packet indicated by an internal parameter is partially lost at a receiving end during transmission and reception .

For example, in the case of a Systematic Reed-Solomon Code or a Systematic Raptor code, the information bits are the packet data group referred to by the internal parameters of the f {} function And the encoding process becomes a function of the function f {}, and a packet composed of the resultant redundancy parity can be the FEC-1 415. [

In addition, the FEC corresponding to the rear FEC block-5 (456) can be calculated by the following Equation (3) to generate the FEC-3 (455).

[ Equation  3]

FEC-3 = f {Base_3,0, X_5,0, Enh_5,1, Enh_5,2},

In a similar way, these two methods can be used together to protect the burst loss of 2L if necessary. Here, base layer packets (Base 3, 0) 417 and 458 added as duplicates are used only for FEC calculation and can be removed and transmitted when video frames (packets) and FEC data are transmitted. Therefore, the method according to the present invention does not increase the transmission data rate. The FEC coding rate (= k / n) may be slightly increased due to the inserted base layer packet, but is sufficiently compensated for with XOR coding and burst loss recovery rates.

FIG. 5 is a flowchart illustrating payload formatting for burst loss recovery according to an embodiment of the present invention. Referring to FIG.

5, the payload formatting for burst loss recovery according to an embodiment of the present invention includes a packet reception step S510, a packet loss check step S520, a base layer packet restoration step using an XOR packet (S530), and a base layer packet recovery step using FEC decoding (S540).

Referring to FIG. 5, each step of the payload decomposing process for burst loss recovery according to an embodiment of the present invention can be described as follows.

The packet reception step S510 may be a step of receiving packets constituting one GoP of the multimedia data. For example, GoPs constructed according to the payload formatting method of the present invention, that is, GoP packets including an XOR packet generated based on a base layer and a first enhancement layer packet, at least one enhancement layer packet, and an FEC packet .

In the packet loss checking step (S520), it is possible to confirm whether all or a part of the packets of the packets in the received GoP are not lost during transmission. At this time, if the packet is lost, the formatting method may be changed depending on which packet is lost.

For example, if there is no lost packet as a result of checking, the base layer packet may be restored (S530) by performing an XOR operation based on the XOR packet included in the GoP and the first enhancement layer packet. Therefore, it is possible to reproduce data using all the data packets constituting the original GoP, together with the restored base layer packet.

If the first enhancement layer packet or the XOR packet is not lost even if the packet is lost, for example, if the second enhancement layer packet is lost, an XOR operation is performed based on the XOR packet and the first enhancement layer packet, To restore the base layer packet (S530). In this case, even if there is no second enhancement layer packet, it is possible to reproduce data using both the base layer packet and the first enhancement layer packet, which are at least the most important data.

On the other hand, when the first enhancement layer packet or the XOR packet is lost, the base layer packet of the GoP can be restored by performing FEC decoding on the packets of the forward or backward GoP separated by a predetermined time interval from the GoP (S540). Whether to use the forward GoP packet or the backward GoP packet for FEC decoding can be determined according to the FEC encoding method performed by the transmitter. For example, if FEC encoding is performed by adding a base packet of 2L forward GoP in FEC encoding by a receiver, the transmitter may be required to perform FEC decoding using a packet of 2L backward GoP to recover a base packet.

The payload formatting method according to the present invention will be described in more detail with reference to the drawings, for example.

6 is a block diagram illustrating a FEC decoding and payload formatting method for burst loss recovery according to an embodiment of the present invention.

Referring to FIG. 6, there is shown a restoration procedure when a burst loss occurs in the GoP-3 section 630. In this case, it is assumed that the buffer storage period of the video frame is at least L duration. However, if both front and rear are used, 2L should be able to be stored.

1) There is no lost packet.

(X3,0) 634 of the FEC block-3 636 and the first enhancement layer packet (Enh_3,1) of the FEC block-3 636 as shown in Equation (4) below if there is no lost packet in the GoP- Base_3,0, that is, the base layer packet, can be obtained by XORing the base layer packet 637 with the bitwise operation.

[ Equation  4]

{Base_3,0} = {X_3,0} XOR {Enh_3,1},

Here, {} denotes a bitwise operation.

The first enhancement layer packet (Enh_3,1) 637 and the second enhancement layer packet (Enh_3,2) 638 together with the base layer packet obtained through the above-described Equation (4), and the corresponding GoP is displayed Can

2) If the second enhancement layer packet is lost

If the second enhancement layer packet (Enh3,2) 633 in the GoP-3 section 630 is lost, the XOR packet (X3,0) 634 of the FEC block-3 (636) ) And the first enhancement layer packet (Enh_3,1) 637 are XOR'd by bitwise operation to obtain Base_3,0, that is, base layer packet.

Meanwhile, the first enhancement layer packet (Enh_3,1) 637 and the second enhancement layer packet (Enh_3,2) 638 are not provided and the corresponding GoP is displayed together with the base layer packet obtained through Equation (4) Can

3) When the first enhancement layer packet is lost

When the first enhancement layer packet (Enh3,1) 632 in the GoP-3 section 630 is lost, the base layer packet can not be obtained from the XOR packet (X3,0) 634. Accordingly, the FEC packet (FEC-1) 615 of the encoded GoP-1 section 610 including the base layer packet of the GoP-3 section 630 can be used.

That is, an FEC block-1 616 may be generated from the buffer. Since this also includes a packet of Base 3 and 0, this is obtained by using the following equation (5).

[ Equation  5]

Base_3,0 = {X_1, 0, Enh_1, 1, Enh_1, 2, FEC-1}

Where the inverse of {f} is the data packets referred to by the parameters in {}, eg XOR packet (X1,0) 614 in FEC block-1 616, first enhancement layer packet (Ehn1, 1) 617, a second enhancement layer packet (Ehnl, 2) 618, and an FEC packet (FEC-1) 615 to recover the resultant data bit strings of the function.

Accordingly, the first enhancement layer packets (Enh_3,1) 632 (Enh_3,1) lost as shown in Equation (6) using the base layer packet (Base_3,0) 619 and the XOR packet 634 obtained through Equation ) Can be obtained.

[ Equation  6]

{Enh_3,1} = {X_3,0} XOR {Base_3,0},

In the case of using the backward GoP section 650, the same operation as described above can be performed after waiting until the FEC Block-5 656 can be generated.

In addition to the base layer packet Base_3,0 619 obtained through Equation 5 and the first enhancement layer packets Enh_3,1 637 obtained through Equation 6, the second enhancement layer packets Enh_3, 2) 638 to display the corresponding GoP.

4) When the XOR packet is lost

When the XOR packet (Enh3,1) 634 in the GoP-3 section 630 is lost, as in the case where the first enhancement layer packet is lost as described above, the GoP- (FEC-1) 615 of the FEC packet 610 can be used.

That is, the first enhancement layer packet (Enh_3,1) 637 and the second enhancement layer packet (Enh_3,2) 637, which are not lost, together with the base layer packet Base_3,0 619 obtained using Equation (5) ) 638 may be displayed.

4) If all packets are lost

When all the packets in the GoP-3 section 630 are lost, an FEC block-1 616 is generated from the buffer, and the base layer packet Base_3,0 619 is generated using Equation (5) Can be obtained.

The thus obtained base layer packet can be displayed.

As described above, even if all packets are lost, the most important base layer packet can be restored.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims It can be understood that

Claims (15)

As a payload formatting method performed at a transmitter,
(Exclusive or) operation based on any one of the enhancement layer packets of a group of pictures (GoP) including a base layer packet and at least one enhancement layer packet and a base layer packet, ;
Adding the XOR operation packet to the GoP;
Removing the base layer packet from the GoP;
Generating a FEC packet of the GoP by performing a forward error correction (FEC) encoding by adding a base layer packet of a GoP separated by a predetermined time interval from the GoP; And
And adding the FEC packet to the GoP. delete The method according to claim 1,
The base layer packet includes:
Related to the most important frame in the GoP,
The enhancement layer packet used for the XOR operation is,
Lt; RTI ID = 0.0 > GoP. ≪ / RTI > The method according to claim 1,
The step of generating the FEC packet of the GoP includes:
Generating a FEC packet of the GoP by performing FEC encoding by adding a base layer packet of a forward or a backward GoP separated by a predefined time interval from the GoP. The method according to claim 1,
The step of generating the FEC packet of the GoP includes:
And generating FEC packets of the GoP by performing FEC encoding by adding base layer packets of forward and backward GoPs separated by a predefined time interval from the GoP. The method according to claim 4 or 5,
Removing the base layer packet of the forward or backward GoP added in the FEC encoding when transmitting the packets of the GoP. The method according to claim 4 or 5,
The FEC encoding,
Using the XOR operation. A payload de-formatting method performed at a receiver,
A base layer and an XOR packet generated by XOR (exclusive or) operation based on the first enhancement layer packet, at least one enhancement layer packet including the first enhancement layer packet, and a picture including a forward error correction Receiving packets of a group of pictures (GoP);
Checking whether packets of the GoP are lost; And
If it is determined that there is no lost packet or a packet other than the first enhancement layer packet and the XOR packet is lost, an XOR operation is performed based on the XOR packet and the first enhancement layer packet, And a first step of restoring the hierarchical packet
The FEC packet includes:
And performing FEC encoding by adding a base layer packet of GoP a predetermined time interval away from the GoP. 9. The method of claim 8,
The FEC packet includes:
And performing FEC encoding by adding a base layer packet of a forward or a backward GoP separated by a predefined time interval from the GoP. 9. The method of claim 8,
Receiving packets of the GoP and storing them in a buffer,
Wherein the buffer stores packets of all forward or backward GoPs within a predefined time interval from the GoP. 10. The method of claim 9,
If it is determined that the first enhancement layer packet or the XOR packet is lost,
Further comprising: a second step of restoring the base layer packet of the GoP by performing FEC decoding based on packets of a forward GoP a predetermined time interval from the GoP. 12. The method of claim 11,
The second step of restoring the base layer packet of the GoP includes:
Using the packets of the forward GoP that are separated by the predefined time interval stored in the buffer. 10. The method of claim 9,
If it is determined that the first enhancement layer packet or the XOR packet is lost,
Further comprising: a third step of restoring the base layer packet of the GoP by performing FEC decoding on packets of a backward GoP a predetermined time interval from the GoP. 14. The method of claim 13,
The third step of restoring the base layer packet of the GoP includes:
And after receiving the packets of the backward GoP that are separated by the predefined time interval. 10. The method according to claim 8 or 9,
The base layer packet includes:
Related to the most important frame in the GoP,
Wherein the first enhancement layer packet comprises:
Lt; RTI ID = 0.0 > GoP. ≪ / RTI >

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