KR20060101847A - Method for scalably encoding and decoding video signal - Google Patents

Abstract

The present invention relates to a method for scalable encoding and decoding of a video signal. A frame of a base layer or an enhanced layer is selected based on encoding level information of an enhanced layer, and the macroblock is encoded according to the inter-layer prediction method based on the frame. Therefore, the inter-layer prediction method can be applied to the frame of the enhanced layer in which the frame is not simultaneously present in the base layer when the video signal is scalablely encoded, and the encoding level is determined from the bit stream of the base layer. Even when information cannot be obtained, it is possible to reasonably select and use a frame of a corresponding base layer, thereby improving coding efficiency.

MCTF, base layer, enhanced layer, inter-layer prediction, temporal decomposition level, prediction behavior

Description

Scalable method for encoding and decoding video signals {Method for scalably encoding and decoding video signal}

FIG. 1 illustrates an example of generating and encoding a prediction image for an image frame sequence by using a multi-layer structure having two layers of a base layer and an enhanced layer.

2 illustrates a configuration of a video signal encoding apparatus to which a scalable coding method of a video signal according to the present invention is applied.

3 illustrates a configuration of temporal decomposition of an image signal at any one temporal decomposition level,

4 illustrates an embodiment of a method of selecting a frame of a base layer to be used when performing a prediction operation by an inter-layer prediction method on a frame of an enhanced layer in which no frame exists simultaneously in the base layer. Is shown,

5 illustrates a configuration of an apparatus for decoding a data stream encoded by the apparatus of FIG. 2,

6 illustrates a configuration of temporally synthesizing an 'H' frame sequence of temporal decomposition level N and an 'L' frame sequence into a 'L' frame sequence of level N-1.

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

100: EL encoder 101: estimator / predictor

102: updater 105: BL decoder

110: texture encoder 120: motion coding unit

130: eat 150: BL encoder

200: Demuxer 210: Texture Decoder

220: motion decoding unit 230: EL decoder

231: reverse updater 232: reverse predictor

233: motion vector decoder 234: array

240: BL decoder

The present invention relates to a scalable encoding and decoding method of a video signal, and more particularly, to a method for scalable encoding and decoding of a video signal by applying an inter-layer prediction method.

For digital video signals transmitted and received wirelessly by mobile phones and laptops and mobile TVs and handheld PCs, which are widely used in the future, it is difficult to allocate wide bands as in TV signals. Therefore, the standard to be used for the image compression method for such a mobile portable device should be higher the compression efficiency of the video signal.

In addition, such a mobile portable device is inevitably varied in its ability to process or present. Therefore, the compressed image has to be prepared in such a variety that it is different from each other by various variables such as transmission frames per second, resolution, bits per pixel, etc. for the same image source. This means that it must be provided, which is a burden on the content provider.

For this reason, the content provider has high-speed bitrate compressed image data for one image source, decodes the compressed image when requested by the mobile device, and then fits the image capability of the requested device. This is provided by re-encoding the video data. However, this method requires a transcoding (decoding + scaling + encoding) process, and thus a time delay occurs in providing a video requested by the mobile device. Transcoding also requires complex hardware devices and algorithms as the target encoding varies.

Scalable video codec (SVC) has been proposed to solve such disadvantages. This method encodes a video signal, and encodes at the highest quality, but decodes a partial sequence of the resulting picture (frame) sequence (sequence of frames selected intermittently throughout the sequence) to some extent. It's a way to ensure that.

Motion Compensated Temporal Filter (or MCTF) is an example of an encoding scheme proposed for use with the scalable video codec. Since the MCTF scheme is likely to be applied to a transmission environment such as a bandwidth-limited mobile communication, a high compression efficiency, that is, a high coding efficiency is required to lower the number of bits transmitted per second.

As mentioned above, although only a part of the picture sequence encoded by the scalable MCTF is received and processed, the image quality is guaranteed to some extent. However, when the bit rate is lowered, the image quality deteriorates. In order to solve this problem, a separate auxiliary picture sequence for low bit rate, for example, a small picture and / or a low picture sequence per frame may be provided.

The auxiliary picture sequence is called a base layer, and the main picture sequence is called an enhanced (or enhanced) layer. Since the base layer and the enhanced layer encode the same video content at different spatial resolutions or frame rates, redundancy exists in the video signals of both layers. Therefore, in order to improve coding efficiency of the enhanced layer, the video signal of the enhanced layer is predicted and encoded using motion information and / or texture information of the base layer, and the inter-layer prediction method is performed. method).

FIG. 1 illustrates an example of generating and encoding a predictive image for an image frame sequence in a multi-layer structure having two layers of a base layer and an enhanced layer. In FIG. 1, the base layer encodes an input video signal using a hierarchical B picture, and in the enhanced layer, encodes the input video signal through a temporal decomposition process in an MCTF structure.

An inter-layer prediction method using the same base layer picture may be applied to a picture (frame) of an enhanced layer having a temporally coincident picture (frame) in the base layer. In FIG. 1, H pictures of Temporal Decomposition levels 1 and 2 of the enhanced layer correspond to this.

On the other hand, as shown in the H picture of the temporal decomposition level 0 of the enhanced layer in FIG. 1, the inter-layer prediction method may not be applied to a picture of the enhanced layer in which no pictures exist simultaneously in the base layer.

In order to apply the inter-layer prediction method to a picture of an enhanced layer having no simultaneous picture in the base layer, a corresponding picture of the base layer must be selected, but a reasonable method has not been proposed. In particular, when the base layer is encoded without encoding information such as temporal decomposition level, such as H.264, there is a problem that there is no criterion for selecting a picture corresponding to a picture of the enhanced layer from the base layer.

The present invention has been made to solve this problem, and an object of the present invention is to provide an inter-layer prediction method for a picture of an enhanced layer in which a picture is not simultaneously present in a base layer so as to improve coding efficiency. To provide a way to apply it.

A specific object of the present invention is to provide a reasonable method for selecting a base layer or a picture of an enhanced layer corresponding to a picture of an enhanced layer.

According to an aspect of the present invention, there is provided a method of encoding a video signal, the method comprising: generating a bit stream of a first layer by scalable encoding of the video signal; And generating a bit stream of a second layer by encoding the video signal in a predetermined manner, wherein the generating of the bit stream of the first layer comprises: a video block to be encoded. And selecting a frame of the second layer to be used for inter-layer prediction based on the encoding level information of the first layer, for any frame of the first layer.

In the above embodiment, the generating of the bit stream of the first layer may include generating the second layer in the header area of the image block in the arbitrary frame in which no frame exists simultaneously in the second layer. The method may further include recording information indicating that encoding is performed according to the inter-layer prediction method used.

In one embodiment, frames concurrently exist in the second layer, and among the frames of the first layer having the lowest encoding level, the frame closest to the arbitrary frame is searched for, and the retrieved first layer The frame of the second layer at the same time as the frame of may be selected.

Alternatively, in another embodiment, among the frames of the first layer having the lowest encoding level, a frame closest to the arbitrary frame is searched, and the frames of the retrieved first layer may be selected as the frames of the second layer. Can be.

The encoding level information is characterized in that the temporal decomposition level information or the order information that the frame is decoded.

In the above embodiment, when there are two or more frames of the selected first layer, the first frame among them is selected as the frame of the first layer.

According to another embodiment of the present invention, a method of decoding an encoded video bit stream includes: decoding a bit stream of a second layer that is encoded and received in a predetermined second manner; And decoding the bit stream of the first layer that is scalable and encoded using the decoded second layer, wherein the decoding of the first layer comprises: Selecting a frame of a second layer used for inter-layer prediction based on encoding level information of the first layer, for any frame of the first layer including an image block encoded according to the inter-layer prediction method using Characterized in that it comprises a step.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram of a video signal encoding apparatus to which a scalable coding method of a video signal according to the present invention is applied.

The video signal encoding apparatus of FIG. 2 is an enhanced layer (EL) encoder 100 that scalablely encodes an input video signal in macroblock units by, for example, an MCTF method and generates appropriate management information. Texture coding unit 110 for converting the data of each encoded macro block into a compressed bit string, and motion vectors of an image block obtained by the EL encoder 100 in a specified manner. The motion coding unit 120 coding the compressed bit stream by using a predetermined method, for example, MPEG 1, 2, or 4, or H.261, H.264, to encode a small picture, For example, a base layer (BL) encoder 150 that generates a sequence of pictures that are 25% of the original size, output data of the texture coding unit 110, a small picture sequence of the BL encoder 150, and the motion coding. Part 120 In the capsule (encapsulate), and then groups the specified transmission format to output a vector data group with the specified format is configured to include a meokseo 130, and outputting the cross-Muxing.

The EL encoder 100 performs a prediction operation of subtracting a reference block obtained by motion estimation with respect to a macroblock in an image frame (or picture), and further extracts an image difference between the macroblock and the reference block. An update operation is added to the reference block. Here, the update operation may be omitted as necessary.

The EL encoder 100 separates an input image frame sequence into a frame having an error value and a frame to which the error value is added, for example, an odd frame and an even frame, to predict and update the frame. The operation is performed over several encoding levels, for example, for one group of pictures (GOP) until the number of L frames (frames generated by the update operation) is one, while FIG. The configuration related to the predictive operation and the update operation is shown.

The configuration of FIG. 3 extracts encoding information such as a frame rate and a mode of a macro block for a stream of a small picture sequence encoded by the BL encoder 150, and decodes the base layer stream to decode the macro block or macro blocks. A base layer (BL) decoder 105 having a function of generating a frame consisting of a frame, and for a frame that will have residual data through motion estimation, for example, an odd frame, An estimator / predictor 101 for finding a reference block for each macro block and performing a prediction operation for calculating an image difference (difference value of each corresponding pixel) and a motion vector from the reference block, and further for the macro block. For a frame including a reference block, for example, an even frame, the image difference calculated for the macro block is normalized. and an updater 102 for performing an update operation to add to the corresponding reference block.

Here, the block with the smallest image difference is the block with the highest correlation. The size of the image difference is determined by, for example, a sum of pixel-to-pixel difference values or an average thereof, and refers to a macroblock or blocks having the smallest size among the blocks whose size is less than or equal to a predetermined threshold. ) Is called block (s).

An operation performed by the estimator / predictor 101 is called a 'P' operation, and a frame generated by the 'P' operation is called an 'H' frame. In addition, an operation performed by the updater 102 is referred to as an 'U' operation, and a frame generated by the 'U' operation is referred to as an 'L' frame.

The estimator / predictor 101 and the updater 102 of FIG. 3 may simultaneously perform parallel operations on a plurality of slices in which one frame is divided instead of a frame unit. The term 'frame' used in the following embodiments should be construed to include the meaning of 'slice' when the equivalent of technology is maintained even if it is replaced with 'slice'.

The estimator / predictor 101 divides each of the inputted image frames or odd-numbered frames of 'L' frames obtained at all levels into macro-blocks having a predetermined size, The process of finding a block having the most similar image in a before and after even frame at the same temporal decomposition level or in its own frame to create a predictive image and obtaining a motion vector.

Alternatively, the estimator / predictor 101 may find a reference block for a macro block in a base layer frame, which will be described later or in the same frame of the base layer reconstructed by the BL decoder 105. A reference block can be found within the frame of the base layer selected according to the method according to the invention (when no base layer frame at the same time exists). In this case, the estimator / predictor 101 encodes the macroblock by an inter-layer prediction method using texture information and / or motion vector information of the found reference layer of the base layer.

Further, the estimator / predictor 101 inserts information indicating that the macroblock of the due layer has been encoded using texture information and / or motion vector information of the base layer into the header area of the macroblock and informs the decoder. .

The estimator / predictor 101 performs the above process on all macroblocks in a frame to complete an 'H' frame, which is a prediction image for the frame. In addition, the estimator / predictor 101 completes an 'H' frame, which is a predictive image for each frame, for all odd frames of an input image frame or an 'L' frame obtained at all levels.

On the other hand, the updater 102, as described above, the image difference in each macro block in the 'H' frame generated by the estimator / predictor 101 'L' frame with the corresponding reference block (input An even frame of an image frame or an 'L' frame obtained at the previous level).

4 illustrates a method of selecting a base layer frame (BasePic) to be used when performing a prediction operation by an inter-layer prediction method on a current frame (CurrPic) of an enhanced layer in which no frame exists simultaneously in the base layer. It is explained with reference.

As in FIG. 1, although the prediction operation and the updating operation are performed using only the immediately neighboring frame in the enhanced layer of FIG. 4, this is for simplicity of drawing. There is no limitation on the frames used for the prediction operation and the update operation in the enhanced layer.

In addition, in the enhanced layer, except for the 'L8' frame generated at the last level, the temporal decomposition level to which the 'L' frame belongs is determined by the level to which the 'H' frame belongs to the 'L' frame. . In FIG. 4, the 'L' frame at the same time as frame 2 belongs to level 1 because it is the same time as 'H2', and the two 'L' frames that are the same time as frame 4 are the same time as 'H4' and therefore level 2 'L' frame, which is the same time as frame 6, belongs to level 1 because it is the same time as 'H6'. Also, two 'L' frames that are the same time as frame 8 belong to level 3 because they are the same time as 'L8'.

First, the frame that meets the following three conditions simultaneously (refPic) is found in the enhanced layer.

The first condition is a frame that satisfies at least one of the following three detailed conditions. i) the first reference frame in List_0 reference frames and List_1 reference frames of the current frame (CurrPic), ii) the active reference frame in List_0 and List_1, or iii) the current Group of Picture (GOP) or Decoded Frame in Picture Buffer.

Here, the reference frame refers to frames that can be used when performing a prediction operation on the current frame CurPic, and a predetermined number of reference frames may be included in List_0 and List_1, respectively. The first reference frame in List_0 and List_1 points to the first frame in each frame list. Also, among the plurality of reference frames in List_0 and List_1, the reference frame actually used in the current frame for use in the prediction operation and / or the update operation is called an active reference frame.

The second condition 2 is a frame in which simultaneous frames exist in the base layer.

The third condition is the frame with the lowest temporal decomposition level among the frames satisfying both the first condition and the second condition.

Next, if there are two or more frames in the enhanced layer that satisfy all three conditions above, refPic becomes the frame having the smallest time difference (absolute value) from the current frame (CurrPic). If there is not one frame, the frame earlier than that, that is, the frame preceding the current frame CurPic, is determined as refPic.

The frame of the base layer simultaneously with the determined refPic may be determined as the BasePic. A prediction operation on the current frame CurPic of the enhanced layer may be performed using the determined texture and / or motion vector information of BasePic.

Or, instead of predicting the current frame CurPic of the enhanced layer by using the frame BasePic of the base layer simultaneously with refPic, assuming that the determined refPic itself is the frame BasePic of the base layer simultaneously, the current of the enhanced layer The frame CurrPic can be predicted. At this time, the second condition does not need to be considered. That is, a frame in which no frame exists simultaneously in the base layer may be determined as refPic.

Here, instead of the condition related to the temporal decomposition level, the value of frame_num existing in each frame or slice may be used instead. In this case, the condition of the frame having the lowest temporal decomposition level is changed to the condition of the frame having the highest frame_num. Here, frame_num is a number assigned sequentially according to the order in which each frame is encoded (the transmission order and the decoding order are also the same). Since a frame having a high frame_num has a lower or equal temporal decomposition level than a frame having a low frame_num, It is possible to replace.

For example, assume that the detailed condition i) is applied in the first condition. A total of two frames satisfying the detailed condition i) exist in List_0 and List_1, respectively. It is determined whether the temporal decomposition level of the two frames is the same. First, when the temporal decomposition levels of the two frames are the same, a frame having a small time difference from the current frame CurPic is determined as refPic, and when the time difference is also the same, it is determined as refPic in the previous frame List_0. In contrast, when the temporal decomposition levels of the two frames are not the same, a frame having a low temporal decomposition level is determined as refPic. BasePic becomes a frame of the base layer simultaneously with the determined refPic or refPic.

A method of selecting a frame of the base layer to be used for such prediction is applied to FIG. 4 as follows.

In FIG. 4, a case where a base layer frame BasePic corresponding to the current frame CurPic H3 of the enhanced layer is selected will be considered. Frames belonging to List_0 are H2 and L0, and frames belonging to List_1 are H4, H6 and L8. Here, the frames are arranged in the order close to CurrPic H3. Therefore, the first frames of List_0 and List_1 satisfying the detailed condition i) of the first condition are H2 and H4. Since both H2 and H4 satisfy the second condition and the temporal decomposition levels are 1 and 2, respectively, H2 becomes refPic according to the third condition. Accordingly, B2 at the same time as H2 or H2 which is refPic becomes BasePic, and H3 can be encoded by an inter-layer prediction method using texture and / or motion information of H2 of the enhanced layer or B2 of the base layer.

In the same way, H2, H4, H6 or B2, B6, B6 can be selected as BasePic for H1, H5, H7 where no frame exists at the same time in the base layer.

As described above, the method may be applied even when the information on the temporal decomposition level cannot be obtained from the bit stream of the base layer because the temporal decomposition level information of the enhanced layer is used.

The data stream encoded by the method described so far is transmitted to the decoding device by wire or wirelessly or transmitted through a recording medium, and the decoding device reconstructs the original video signal according to the method described later.

5 is a block diagram of an apparatus for decoding a data stream encoded by the apparatus of FIG. The decoding apparatus of FIG. 5 includes a demux 200 for separating the compressed motion vector stream and the compressed macro block information stream from the received data stream, and texture decoding for restoring the compressed macro block information stream to the original uncompressed state. A unit 210, a motion decoding unit 220 for restoring a compressed motion vector stream to an original uncompressed state, an enhanced layer EL for inversely converting the decompressed macroblock information stream and the motion vector stream into an original video signal. Decoder 230, a base layer (BL) decoder 240 for decoding the base layer stream by a predetermined method, for example, MPEG4 or H.264. The EL decoder 230 uses frame rate, encoding information of the base layer such as the mode of the macro block, and / or a frame (or macro block) of the decoded base layer. The EL decoder 230 may inversely convert the original video signal according to, for example, the MCTF scheme.

The EL decoder 230 reconstructs an original frame sequence from an input stream. FIG. 6 illustrates a main configuration of the EL decoder 230 in detail and is an example of an MCTF scheme.

FIG. 6 is a configuration of temporal composition of an 'H' frame sequence of temporal decomposition level N and an 'L' frame sequence into a 'L' frame sequence of temporal decomposition level N-1. 6, an inverse updater 231 for selectively subtracting a difference value of a pixel of an input 'H' frame from an input 'L' frame, an 'L' frame having an image difference of the 'H' frame subtracted, and the 'H' Inverse predictor 232 which restores the 'L' frame with the original image using the frame, and decodes the input motion vector stream to invert the motion vector information of each block in the 'H' frame. Between the motion vector decoder 233 provided to the updater 231 and the reverse predictor 232, and the 'L' frame completed by the reverse predictor 232, between the output 'L' frame of the reverse updater 231. Inserter 234 into a sequence of 'L' frames in normal order. Here, if the update process is omitted in the encoding process, the reverse updater 231 may also be omitted.

The 'L' frame output by the arranger 234 becomes a 'L' frame sequence 701 of level N-1, which is accompanied by an input 'H' frame sequence 702 of N-1 level. It is restored to the 'L' frame sequence by the inverse updater and the reverse predictor of the next stage, and this process is performed by the level performed when encoding and restored to the original image frame sequence.

Reconstruction (temporal synthesis) at level N where the received 'H' frame at level N and the 'L' frame at level N generated at level N + 1 are restored to the 'L' frame at level N-1 in more detail. Explain.

First, the inverse updater 231 refers to a motion vector provided from the motion vector decoder 233 for an arbitrary 'L' frame (level N). Identify all 'H' frames (level N) whose image difference is obtained by using blocks in the original 'L' frame (level N-1) updated to level N) as reference blocks, and then macroblocks in the 'H' frame. An error value of is subtracted from the pixel value of the corresponding block in the arbitrary 'L' frame, thereby restoring the original 'L' frame.

Among the blocks in the current 'L' frame (level N), the reverse update operation is performed on the block updated by the error value of the macro block in the 'H' frame in the encoding process, thereby performing the 'L' frame at the level N-1. Restore to.

The inverse predictor 232 refers to a motion vector provided from the motion vector decoder 233 for a macro block within an arbitrary 'H' frame, by using an 'L' frame (the inverse updater 231). After recognizing the reference block in the reversely output 'L' frame, the original image is restored by adding the pixel value of the reference block to the difference value (error value) of the pixel of the macro block.

Alternatively, when the inverse predictor 232 includes information indicating that a macroblock in an arbitrary 'H' frame is encoded using texture information and / or motion vector information of the base layer, the header of the macroblock includes: The original image for the macro block is reconstructed using the header information in the stream provided from the BL decoder 240 and the frame of the decoded base layer. In this case, the inverse predictor 232 selects the frame BasePic of the base layer according to the method described above, and performs the inverse predictive operation using texture information and / or motion vector information of the reference block of the selected frame.

When all macro blocks in the current 'H' frame are restored to the original image through the above operation, and all of them are combined and restored to the 'L' frame, the 'L' frame is stored through the arranger 234. The reverse updater 231 alternately arranges the 'L' frame and outputs the next stage.

According to the method described above, the encoded data stream is recovered into a complete image frame sequence. In particular, in the case of performing the NOP for the GOP that performed the prediction operation and the updating operation in the encoding process described using the MCTF method as an example, if the reverse update operation and the reverse prediction operation are performed N times in the MCTF decoding process, the image quality of the original video signal may be obtained. If the number of times is smaller, the image quality may be lowered slightly, but the image frame sequence having a lower bit rate may be obtained. Accordingly, the decoding apparatus is designed to perform the reverse update operation and the reverse prediction operation to the extent appropriate for its performance.

The above-described decoding apparatus may be mounted in a mobile communication terminal or the like or in an apparatus for reproducing a recording medium.

As described above, preferred embodiments of the present invention have been disclosed for the purpose of illustration, and those skilled in the art can improve, change, and further various embodiments within the technical spirit and the technical scope of the present invention disclosed in the appended claims. Replacement or addition may be possible.

Therefore, the inter-layer prediction method can be applied to the frame of the enhanced layer in which the frame is not simultaneously present in the base layer when the video signal is encoded in a scalable manner. In addition, even when the information on the temporal decomposition level cannot be obtained from the bit stream of the base layer, the frame of the corresponding base layer can be rationally selected and used, thereby improving coding efficiency.

Claims (12)

Scalablely encoding the video signal to generate a bit stream of the first layer; And Generating a bit stream of a second layer by encoding the video signal in a predetermined manner; The generating of the bit stream of the first layer may include And selecting a frame of a second layer to be used for inter-layer prediction based on encoding level information of the first layer, for any frame of the first layer including an image block to be encoded. Characterized by a video signal encoding method. The method of claim 1, Generating the bit stream of the first layer, Recording information indicating that the image block is encoded according to an inter-layer prediction method using the second layer in a header region of the image block in the arbitrary frame in which no frame exists simultaneously in the second layer. The video signal encoding method, characterized in that made. The method of claim 1, Selecting a frame of the second layer, Retrieving a frame having a closest temporal distance from the arbitrary frame among the frames of the first layer having simultaneous frames in the second layer and having the lowest encoding level; And And selecting a frame of the second layer at the same time as the retrieved frame of the first layer. The method of claim 1, Selecting a frame of the second layer, Retrieving a frame closest to the temporal distance from the random frame among the frames of the first layer having the lowest encoding level; And And selecting the retrieved frame of the first layer as the frame of the second layer. The method of claim 1, And the encoding level information is temporal decomposition level information or order information in which frames are decoded. The method of claim 3, wherein And if the searched frames of the first layer have two or more frames, selecting the most advanced frame among them as the frame of the first layer. Decoding a bit stream of a second layer encoded and received in a predetermined second manner; And Decoding the bit stream of the first layer, which is scalable and encoded using the second layer, Here, the step of decoding the first layer, A second layer used for inter-layer prediction based on encoding level information of the first layer, for any frame of the first layer including an image block encoded according to the inter-layer prediction method using the second layer And selecting a frame of the encoded video bit stream. The method of claim 7, wherein Decoding the first layer, And reading information indicating that the image block has been encoded according to the inter-layer prediction method using the second layer from the header area of the image block. . The method of claim 7, wherein Selecting a frame of the second layer, Retrieving a frame having a closest temporal distance from the arbitrary frame among the frames of the first layer having simultaneous frames in the second layer and having the lowest encoding level; And Selecting a frame of a second layer at the same time as the retrieved frame of the first layer. The method of claim 7, wherein Selecting a frame of the second layer, Retrieving a frame closest to the temporal distance from the random frame among the frames of the first layer having the lowest encoding level; And Selecting the retrieved frame of the first layer as the frame of the second layer. The method of claim 7, wherein Wherein the encoding level information is temporal decomposition level information or order information in which frames are decoded. The method of claim 9, If there are two or more frames of the found first layer, selecting the most advanced frame among the frames of the first layer, wherein the encoded image bit stream is decoded.

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