KR20130021318A - Method for payload formatting and deformatting for burst loss recovery - Google Patents

Abstract

PURPOSE: A payload formatting and de-formatting method for the recovery of burst data loss are provided to improve performance as much as an XOR(eXclusive OR) coding gain, to offer a UEP(Unequal Error Protection) function providing resistance to loss, and to offer a seamless service by providing a method capable of recovering the most important data even when all the data in the GoP(Group of Picture) section are lost. CONSTITUTION: A payload formatting method implemented at a transmitter includes the following steps: a step of generating an XOR operation packet(S110), by executing XOR operations based on a base layer packet and one of the enhanced layer packets of a GoP containing the base layer packet and the enhanced layer packets; a step of adding the generated XOR operation packet to the GoP(S120); a step of removing the base layer packet from the GoP(S130); a step of generating an FEC(Forward Error Correction) packet of the GoP(S140), by adding base layer packets of the front and rear GoPs separated by a predefined time interval from the GoP, and executing FEC encoding; and a step of adding the generated FEC packet(S150). [Reference numerals] (AA) Start; (BB) End; (S110) Generating an XOR operation packet by using a base layer packet in a GoP and a first enhanced layer packet; (S120) Adding the XOR operation packet generated on the GoP; (S130) Removing the base layer packet from the GoP; (S140) Generating an FEC packet for the GoP by using base layer packet of the front or rear GoP; (S150) Adding the set FEC packet to the GoP

Description

Payload formatting and deformatting method for burst data loss recovery {METHOD FOR PAYLOAD FORMATTING AND DEFORMATTING FOR BURST LOSS RECOVERY}

The present invention relates to data loss recovery of a communication system, and more particularly, to a payload formatting method and a deformatting method for recovering errors and losses in multimedia data transmission.

Due to the nature of the mobile communication service environment, the terminal does not receive data when it passes a shadow area such as a building or a tunnel. As a result, burst loss is inevitable. In this case, there is a method of configuring a Forward Error Correction (FEC) packet in the payload as a method used for loss recovery.

The forward error correction technique is used to protect data from corruption, and is a technique for recovering errors at the receiving side of the data. In many communication systems, the transmission type uses a unidirectional channel and there is no reverse channel, so retransmission cannot be requested, and even if retransmission is possible, there is a delay time. Use

However, payload format using the forward error correction method that has the function to recover the conventional burst loss only increases the transmission bandwidth when the channel condition is good, and when a group error occurs in a group of data such as burst error. There is a problem that cannot fully recover the loss.

An object of the present invention for solving the above problems is to provide a payload formatting method that can effectively recover burst loss without retransmission.

Another object of the present invention for solving the above problems is to provide a payload deformatting method that can effectively recover burst loss without retransmission.

An embodiment of the present invention for achieving the above object is a payload formatting method performed in a transmitter, an enhancement layer packet of a group of picture (GoP) including a base layer packet and at least one enhancement layer packet. Providing 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. .

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

Here, the base layer packet is associated with the most important frame in the GoP, and the enhancement layer packet used for the XOR operation is characterized in that associated with the second most important frame in the GoP.

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

In addition, the payload formatting method may generate a forward error correction (FEC) packet for the GoP, but adds base layer packets of forward and backward GoPs separated by a predetermined time interval from the GoP to forward error. generating an FEC packet of the GoP by adding an encoding, and adding the generated FEC packet to the GoP.

One embodiment of the present invention for achieving the above another object is a payload deformatting method performed in a receiver, an XOR packet generated by XOR operation based on a base layer and a first enhancement layer packet, the first enhancement layer Receiving packets of a GoP including at least one enhancement layer packet including a packet and a FEC packet, checking whether the packets of the GoP are lost or not and if there is no lost packet or the first enhancement layer If it is determined that a packet other than the packet and the XOR packet is lost, a first step of recovering the base layer packet of the GoP by performing an XOR operation based on the XOR packet and the first enhancement layer packet. Provides a load deformatting method.

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

The method may further include receiving and storing packets of the GoP in a buffer, wherein the buffer stores all the packets of the front or rear GoP within a predetermined time interval from the GoP.

In addition, the payload deformatting method may further include FEC decoding based on packets of a forward GoP separated by a predetermined time interval from the GoP when it is determined that the first enhancement layer packet or the XOR packet is lost. And performing a second step of restoring the base layer packet of the GoP.

In this case, the second step of restoring the base layer packet of the GoP is characterized by using the packets of the forward GoP separated by the predetermined time interval stored in a buffer.

Also, in the payload deformatting method, when it is determined that the first enhancement layer packet or the XOR packet is lost as a result of the checking, the payload deformatting method may perform FEC on packets of a rear GoP that are separated by a predetermined time interval from the GoP. The method may further include recovering the base layer packet of the GoP by performing decoding.

In case of using the payload formatting and deformatting method for burst data loss recovery according to the present invention as described above, FEC coding using XOR (Exclusive OR) operation is performed, and thus performance is expected to be improved by XOR coding gain. Can be. In addition, the method according to the present invention provides a UEP (Unequal Error Protection) function that is robust to loss by XOR coding mainly important data such as base layer data or first enhancement layer data.

In addition, the present invention adds the most important data portion of the corresponding GoP to the FEC calculation of the forward or backward GoP interval even if all the packets in the specific GoP interval are lost, so that the most important data can be recovered even if all the data in the GoP interval is lost. There is an advantage to enable the continuous service provision by providing a.

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 a structure of scalable video data and a payload structure reconstructed according to an XOR operation according to an embodiment of the present invention.
3 is a block diagram showing packets of a GoP configured according to a payload structure according to an embodiment of the present invention for each time interval.
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.
5 is a flowchart illustrating a payload deformatting process for burst loss recovery according to an embodiment of the present invention.
6 is a block diagram illustrating a method of FEC decoding and payload deformatting 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.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. 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 herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination 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, exemplary 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.

Hereinafter, a method of payload formatting and deformatting for burst loss recovery according to the present invention is disclosed. The present invention provides a method for recovering a lost packet without retransmission, and providing a service without interruption by recovering only the data of the base layer packet having the most important data even if all the packets are lost. This is a combination of error correction technique and payload formatting technique to achieve loss of coding gain and high efficiency.

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 embodiment of the present invention may be performed at a data transmitter, and may include an XOR operation packet generation step (S110), an XOR operation packet addition step (S120), It may include a base layer packet removal step (S130), FEC packet generation step (S140) and FEC packet addition step (S150).

In addition, referring to Figure 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.

XOR operation packet generation step (S110) is for the group of pictures (GoP) including a base layer packet and at least one enhancement layer packet, the most important enhancement layer packet and base layer packet of the enhancement layer packet of the GoP. It may be a step of generating an XOR operation packet as a result of performing an exclusive OR (XOR) operation based on the.

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

Hereinafter, 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 a structure of scalable video data and a payload structure reconstructed according to an XOR operation according to an embodiment of the present invention.

Referring to (a) of FIG. 2, the scalable video data includes a base layer packet (Base_n, 0) 211, a first enhancement layer packet (Enh_n, 1) 212, and a second enhancement layer packet (Enh_n, 2). (213) can be configured to include.

Also, referring to FIG. 2, in the base layer packet (Base_n, 0) 211, n is a time index indicating an n-th group of pictures (GoP), and 0 is an index indicating the highest importance. have. As such, the base layer packet may refer to the most important packet or the most important frame in the actual video coding data group.

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

On the other hand, referring to Figure 2 (b), shows a structure of the payload reconstructed according to the XOR operation of an embodiment of the present invention, the XOR operation packet (X_n, 0) 221, a first enhancement layer in a GoP Packet (Enh_n, 1) 222 and a second enhancement layer packet (Enh_n, 2) 223.

In this case, the XOR operation packet (X_n, 0) 221 is a bit by bit, and the base layer packet (Base_n, 0) 211 and the first enhancement layer packet (Enh_n, 1) of FIG. A new packet generated by performing an exclusive OR (XOR) operation 212 may be represented by the following equation.

[ Equation  One]

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

Where {} represents a bit-wise operation.

Therefore, using the resultant value X_3,0 of Equation 1, if only one of Base_3,0 or Enh_3,1 is lost, there is an advantage that the other one can be recovered.

3 is a block diagram showing packets of a GoP configured according to a payload structure according to an embodiment of the present invention for each time interval.

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 a section-specific GoP according to an embodiment of the present invention are each GoP 310, 320 and 330 may be added and transmitted. In this case, the base layer packet in the corresponding GoP may be removed and transmitted.

The FEC packet generation step (S140) generates a forward error correction (FEC) packet for the GoP, but adds a base layer packet of a forward or backward GoP separated by a predetermined time interval from the GoP to the FEC source block. It may be a step of generating an FEC packet of the GoP by performing forward error correction (FEC) encoding based on an FEC source block. In this case, FEC encoding may use an XOR operation.

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

Hereinafter, the configuration and payload format of the above-described FEC packet will be described 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.

Referring to FIG. 4, video data per GoP includes a base layer packet 411, 431, and 451, a first enhancement layer packet 412, 432, and 452, and a second enhancement layer packet 413, 433, and 453. Can be assumed. In addition, an FEC source block may be generated for each GoP period, but is not limited to this example. Also, the maximum protection interval L for burst loss recovery is set to 2 GoP, but this can be changed according to design.

In order to protect low-speed data such as the SVC base layer, data that is separated by an L distance may be loaded and added to the current source block as redundancy, and then FEC data may be generated.

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

Meanwhile, the base layer packet (Base3, 0) 431 may be inserted into the FEC block-1 416 in front of the GoP-1 410 and calculated as shown in Equation 2 to generate the FEC-1 415. have.

[ Equation  2]

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

Here, f {} may be defined as an encoding function for generating parity of FEC for recovering erased bits when data packets indicated by internal parameters are partially lost at the receiving end during transmission and reception. Can be.

For example, in the case of the Systematic Reed-Solomon Code or the Systematic Raptor Code, the information bits may be a packet data group referred to by an internal parameter of the f {} function. The encoding process becomes a function of the function f {} so that the packet consisting of the resulting redundancy parity may be the FEC-1 415.

In addition, the FEC corresponding to the back FEC block-5 456 may be calculated as in 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},

Similarly, these two methods can be used together to protect the 2L burst loss if necessary. Here, base layer packets (Base3, 0) 417 and 458 added as duplicates are used only for FEC calculation, and may be removed and transmitted when video frames (packets) and FEC data are transmitted. Thus the method according to the invention does not increase the transmission data rate. The FEC coding rate (= k / n) may increase slightly because of the base layer packet that was inserted, but is sufficiently compensated by the XOR coding and burst loss recovery rate.

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

Referring to FIG. 5, the payload deformatting process for burst loss recovery according to an embodiment of the present invention includes a packet receiving step (S510), a packet loss checking step (S520), and a base layer packet recovery step using an XOR packet. (S530), it may be configured to include a base layer packet reconstruction step (S540) using FEC decoding.

5, each step of the payload deformatting process for burst loss recovery according to an embodiment of the present invention may be described as follows.

The packet receiving step S510 may be a step of receiving packets constituting a GoP of multimedia data. For example, GoPs configured according to the payload formatting method of the present invention, that is, packets of a GoP 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, may be used. Can be received.

In the step of checking whether the packet is lost (S520), it is possible to check whether all or part of data of the packet has not been lost during transmission with respect to the packets in the received GoP. In this case, when a packet is lost, the deformatting method may vary depending on which packet is lost.

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

Also, even if the packet is lost, if the first enhancement layer packet or the XOR packet is not lost, for example, if the second enhancement layer packet is lost, the XOR operation is performed based on the XOR packet and the first enhancement layer packet as above. In operation S530, the base layer packet may be restored. In this case, even if there is no second enhancement layer packet, data can be reproduced using at least both the base layer packet and the first enhancement layer packet which are the most important data.

Meanwhile, when the first enhancement layer packet or the XOR packet is lost, the base layer packet of the GoP may be restored by performing FEC decoding on the packets of the forward or backward GoP separated by a predetermined time interval from the GoP. There is (S540). Whether the packet of the front GoP or the packet of the rear GoP is used for FEC decoding may be determined according to the FEC encoding method performed by the transmitter. For example, if the receiver performs FEC encoding by adding 2L forward GoP base packets during FEC encoding, the transmitter may need to perform FEC decoding using packets of 2L backward GoP to recover the base packet.

The payload deformatting method according to the present invention will be described in more detail with reference to the drawings below.

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

6 shows a recovery process when a burst loss occurs in the GoP-3 section 630. It is assumed that the buffer storage period of the video frame has at least L sections. However, if you use both front and rear, you should be able to store 2L.

1) If no packets are lost

If there is no lost packet in the GoP-3 section 630, the XOR packet (X3,0) 634 and the first enhancement layer packet (Enh_3,1) of the FEC block-3 (636) as shown in Equation 4 below. XOR operation 637 may be performed using a bitwise operation to obtain Base_3,0, that is, a base layer packet.

[ Equation  4]

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

Where {} indicates a bitwise operation.

Along with the base layer packet obtained through Equation 4 above, the GoP is displayed by including both the first enhancement layer packet (Enh_3,1) 637 and the second enhancement layer packet (Enh_3,2) 638. Can

2) when the second enhancement layer packet is lost

If the second enhancement layer packet (Enh3,2) 633 in the GoP-3 interval 630 is lost, the XOR packet (X3,0) 634 of the FEC block-3 636 is equal to Equation 4 above. ) And the first enhancement layer packet (Enh_3,1) 637 may be obtained by performing an XOR operation on the bitwise operation to obtain Base_3,0, that is, the base layer packet.

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

3) when the first enhancement layer packet is lost

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

That is, the FEC block-1 616 may be generated from the buffer. Since the packet includes Base3,0 packets, it is obtained by using Equation 5 below.

[ Equation  5]

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

Here, the inverse function {} of f denotes data packets indicated by parameters within {}, for example, XOR packets (X1,0) 614 in FEC block-1 616, first enhancement layer packet Ehn1, 1) 617, the second enhancement layer packet (Ehn1, 2) 618, and the FEC packet (FEC-1) 615 may be an FEC decoding process for reconstructing the result data bit strings of the function.

Therefore, using the base layer packets (Base_3, 0) 619 and the XOR packet 634 obtained through Equation 5, the first enhancement layer packets Enh_3, 1 632 lost as shown in Equation 6 below. ) Can be obtained.

[ Equation  6]

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

In addition, when using the rear GoP section 650, the same operation as described above may be performed after waiting until the FEC Block-5 656 can be generated.

In addition to the base layer packets (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 can be provided so that the corresponding GoP can be displayed.

4) XOR packet is lost

If the XOR packets (Enh3,1) 634 in the GoP-3 section 630 are lost, as in the case where the first enhancement layer packet is lost as described above, the GoP-1 section is used to obtain the base layer packet. The FEC packet (FEC-1) 615 of 610 may be used.

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

4) All packets lost

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

The base layer packet thus obtained may be displayed.

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

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)

A payload formatting method performed at the transmitter,
XOR operation packet by performing an exclusive or (XOR) operation based on any one packet of a enhancement layer packet of a group of picture (GoP) and a base layer packet including a base layer packet and at least one enhancement layer packet. Generating a; And
Adding the XOR operation packet to the GoP. The method of claim 1, wherein the payload formatting method comprises:
And removing the base layer packet from the GoP. 3. The method according to claim 1 or 2,
Wherein the base layer packet is associated with the most significant frame in the GoP, and the enhancement layer packet used for the XOR operation is associated with the second most important frame in the GoP. The method of claim 1, wherein the payload formatting method comprises:
Generates a forward error correction (FEC) packet for the GoP, but performs forward error correction (FEC) encoding by adding a base layer packet of a forward or backward GoP separated by a predetermined time interval from the GoP to perform FEC of the GoP. Generating a packet; And
The method further comprises adding the generated FEC packet to the GoP. The method of claim 1, wherein the payload formatting method comprises:
Generates a forward error correction (FEC) packet for the GoP, but performs forward error correction (FEC) encoding by adding base layer packets of forward and backward GoPs separated by a predetermined time interval from the GoP to perform FEC of the GoP. Generating a packet; And
The method further comprises adding the generated FEC packet to the GoP. The method according to claim 4 or 5,
When transmitting the packets of the GoP, payload formatting method characterized in that the base layer packets of the forward or backward GoP added during the FEC encoding is removed and transmitted. The method according to claim 4 or 5,
And the FEC encoding uses an XOR operation. A payload deformatting method performed at the receiver.
Receiving packets of a GoP including an XOR packet generated by XOR operation based on a base layer and a first enhancement layer packet, at least one enhancement layer packet including the first enhancement layer packet, and an FEC packet;
Confirming whether or not the packets of the GoP are lost; And
If it is determined that there is no loss packet or that packets other than the first enhancement layer packet and the XOR packet are lost, the base of the GoP is performed by performing an XOR operation based on the XOR packet and the first enhancement layer packet. A payload deformatting method comprising the first step of recovering a layer packet. The method of claim 8,
The FEC packet of the GoP is a payload deformatting method characterized in that the packet is generated by performing forward error correction (FEC) encoding by adding a base layer packet of a forward or backward GoP separated by a predetermined time interval from the GoP. . The method of claim 8, wherein the payload deformatting method comprises:
Receiving the packets of the GoP and storing them in a buffer;
And the buffer stores all forward or backward GoP packets within a predetermined time interval from the GoP. The method of claim 8, wherein the payload deformatting method comprises:
If it is determined that the first enhancement layer packet or the XOR packet is lost,
And reconstructing the base layer packet of the GoP by performing FEC decoding based on packets of the forward GoP separated by a predefined time interval from the GoP. 12. The method of claim 11,
And recovering the base layer packet of the GoP comprises using packets of a forward GoP separated by the predetermined time interval stored in a buffer. The method of claim 8, wherein the payload deformatting method comprises:
If it is determined that the first enhancement layer packet or the XOR packet is lost,
And reconstructing the base layer packet of the GoP by performing FEC decoding on packets of the rear GoP separated by a predefined time interval from the GoP. The method of claim 13,
And a third step of recovering the base layer packet of the GoP is performed after receiving the packets of the backward GoP separated by the predetermined time interval. The method of claim 8,
The base layer packet is associated with the most important frame in the GoP,
And wherein the first enhancement layer packet is associated with a second most important frame in the GoP.

Images