KR100482282B1 - Flexible (Enhanced) coding Enhancement Layer coding method - Google Patents

Abstract

1 The technical field to which the invention described in the claims belongs

Image coding method

2. The technical problem to be solved by the invention

In the conventional scan interleaving method, since the enhancement layer is encoded using a lossless coded base layer, when the base layer is loss coded, the enhancement layer is encoded. To solve an impossible problem.

3, the summary of the solution of the invention

In the flexible encoding method of a binary mask for encoding a higher layer by using a base layer, when the base layer is lossy or losslessly encoded, the higher layer is selectively lost or losslessly encoded. It is characterized by.

4. Important uses of the invention

It is applied to the coding of the higher layer in the flexible coding method.

Description

Enhancement Layer Encoding Method for Flexible (Scalable) Encoding

According to the present invention, in the flexible coding method, regardless of whether the base layer is loss coded or lossless coded, the present invention provides a flexible type such that an enhancement layer may be encoded using the encoded base layer. An object of the present invention is to provide an enhancement layer encoding method in scalable coding.

The present invention relates to flexible coding among the functions supported by MPEG-4, which is currently being standardized.

In general, the MPEG-4, which has developed and decided on international standards on video and audio encoding technology and system construction, has been adopted by the MPEG Group as an international standard. International Standard (MPEG-4) is being researched and developed. The development of MPEG-4 began with the need to support the next generation of video and audio applications that cannot be supported by existing known standards. MPEG-4 provides new methods for communicating and accessing and manipulating video and audio data, such as object-oriented interactive functionality and access over networks of differing characteristics.

In addition, it provides a characteristic that operates usefully in a communication environment where errors are easily generated and a low transmission rate communication environment. Moreover, the integration of computer graphics technology provides the ability to encode and manipulate natural and artificial images and sounds together. In summary, MPEG-4 provides all the features required and expected in many applications. In summary, MPEG-4 must support all the features required and expected in many applications. As a result, the expansion and openness of multimedia information can be extended to support the functions required for all possible low-cost, high-performance applications that are newly developed or will be developed. Among them are transmission and storage functions and improved compression efficiency required for cost reduction. Applications currently expected to apply MPEG-4 technology include Internet Multimedia (IMM), Interactive Video Games (IVG), video conferencing and video telephony. Networked Database Service (NDB) using Interpersonal Communications, Interactive Storage Media (ISM), Multimedia Mailing (MMM), Wireless Multimedia (WMM), and ATM networks ), Remote Emergency Systems (RES), and Remote Video Surveillance (RVS).

In order to support existing applications or applications expected in the future, an image encoding technology that can be edited so that users can communicate only with the desired objects in the image, can be found and read, and can be cut and pasted can be edited. MPEG-4, a new video and audio encoding technology that is currently under global standardization, is designed to meet this need.

FIG. 1 is a block diagram of a MPEG-4 VOP video encoder first determined by the present International Standards Organization. This has a structure different from that of the H.261, H.263, MPEG-1, and MPEG-2 video encoders. In particular, the introduction of the concepts of Shape Coder and VOP (Video Object Planes) shows the most significant difference. A VOP refers to an object at a point in time on an arbitrary shape of a content that can be accessed and edited by a user. The VOP must be encoded for each VOP to support content-based functionality.

When the VOP coder inputs a VOP for each object image formed by the VOP forming unit 20 to the MOTION ESTIMATION 31, the motion estimating unit 31 performs a macroblock unit from the applied VOP. The motion is estimated.

In addition, the motion information estimated by the motion estimator 31 is input to a motion compensation unit 32 to compensate for the motion. The VOP whose motion is compensated by the motion compensator 32 is input to the subtractor 33 together with the VOP formed by the VOP forming unit 11 to detect a difference value, and the difference value detected by the subtractor 33 is The internal information of the object is encoded by the object internal encoding unit 34 in units of subblocks of the macroblock.

For example, after the X and Y axes of the macroblock are subdivided into 8 × 8 subblocks having 8 pixels each with M / 2 × N / 2, the object internal information is encoded.

On the other hand, the VOP whose motion is compensated by the motion compensator 32 and the internal information of the object encoded by the object internal encoder 34 are input to the adder 35 and added, and the output signal of the adder 35 is transferred. The previous VOP that is input to the VEV detector 36 (PREVIOUS RECONSTRUCTED VOP) 36 and is the VOP of the image immediately before the current image is detected.

In addition, the previous VOP detected by the previous VOP detector 36 is input to the motion estimator 31 and the motion compensator 32 and used for motion estimation and motion compensation.

The VOP formed by the VOP forming unit 11 is input to a shape coding unit 37 to encode shape information.

Here, the output signal of the shape information encoder 37 varies depending on the field to which the VOP encoder is applied, and as shown by the dotted line, the output signal of the shape information encoder 37 moves the output signal of the shape information encoder 37. ), And may be input to the motion compensator 32 and the object internal encoder 34 to be used for encoding motion estimation, motion compensation, and internal information of the object.

In addition, motion information estimated by the motion estimation unit 31, object internal information encoded by the object internal encoder 34, and shape information encoded by the shape information encoder 37 are applied to the multiplexer 38 to multiplex. Although not shown in the figure, the bitstream is transmitted to a multiplexer which multiplexes and outputs the outputs of the plurality of encoders.

One of the biggest features of this concept of Moving Picture Expert Group-4 (MPEG-4) is that it is based on objects. In other words, one image can be divided into several objects, and each object can be individually encoded and processed.

So you need to know the shape information to make an object. The shape information referred to here is commonly referred to as a mask. In the image, the object part is represented by '1' and the outside part of the object (background part) is represented by '0'. This shape information can be used to obtain an object from the image. Since the decoder side decodes the object part using the shape information, the shape information should be encoded and transmitted to the decoder side.

CAE is currently used to encode shape information in MPEG-4. CAE obtains the context number as shown in Equation 1 by using the context template as shown in FIG. 2 in 16 × 16 BAB (Binary Alpha Block) unit, and generates '0' when the context occurs using the obtained context number. The probability and the probability of occurrence of '1' are obtained, and the obtained probability is encoded using an arithmetic coding method.

In order to perform lossy coding, the size of BAB is reduced by CR before arithmetic coding, and when the reduced BAB is restored to its original size, it is reduced if the absolute value of the difference between the original BAB and the restored BAB is less than or equal to the threshold. If it is larger than the threshold, it is encoded by CAE using original BAB.

The conversion ratio (CR) is a variable that changes the size of BAB, and MxM BAB is reduced to (MxCR) x (MxCR). Therefore, when CR = 1/2, the number of pixels to be encoded is reduced to 1/4. Accordingly, when the size of the BAB is reduced using CR and the absolute value of the difference between the original BAB and the value of the original BAB is restored, CAE is performed using the reduced BAB when the error is less than or equal to the threshold.

Among the functions supported by MPEG-4, scalable encoding has a function of transmitting and decoding a plurality of layers (base layer, enhancement layer) having different resolutions. A lot of information must be transmitted after each piece of information having a plurality of different resolutions. Therefore, in order to reduce the amount of information to be transmitted, a method of estimating a high-resolution enhancement layer using a low resolution base layer as shown in FIG. 4 is applied.

As a method of encoding an enhancement layer using a base layer, as shown in FIG. 5, two neighboring pixel values as shown in FIG. 5 are used. If two neighboring pixel values are the same, the pixel value of the current position is also likely to have a value. Therefore, when the two out pixel values are the same and the pixel value at the current position is the same as the two neighboring pixel values, encoding is not necessary. If the two neighboring pixel values are different, the pixel value of the current position should be encoded. This case is called a transitional sample. In addition, encoding should be performed when two neighboring pixel values are the same but the pixel values of the current position are different. This diesel is called an exceptional sample.

Therefore, two types of data (TSD: Transitional Sample Data, ESD: Exceptional Sample Data) need to be transmitted in order to encode an enhancement layer. In addition, the horizontal and vertical search must be performed respectively. When TSD occurs CAE is performed using the context template as shown in FIG. 6 at the location where TSD occurs.

The current algorithm uses a method of encoding an enhancement layer by using a base layer. In this case, since the base layer is used as a reference layer, an enhancement layer is used. In order to perform lossless coding, the base layer must also be lossless encoded. Otherwise, errors will occur in the enhancement layer because the exact location of TSD and ESD will not be known during scan interleaving.

However, in the current scan interleaving method, since the enhancement layer is encoded using the lossless encoded base layer, the encoding of the enhancement layer is performed because the base layer is loss encoded. There was an impossible problem.

Accordingly, the present invention has been proposed to solve the above-mentioned problems of the prior art, and the present invention provides the encoded information regardless of whether the base layer is loss coded or lossless coded in the flexible coding method. An object of the present invention is to provide an enhancement layer encoding method in a flexible (scalable) encoding that enables encoding of an enhancement layer by using a base layer.

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

The video encoding system to which the present invention is applied is the same as the configuration of the MPEG-4 VOP video encoder first determined by the present International Standards Organization shown in FIG. A method of encoding an enhancement layer during (scalable) encoding will be described with reference to FIGS. 7 and 8 as follows.

First, when a base layer is loss coded or lossless coded in a flexible coding, a method of loss coding or lossless coding of an enhancement layer is proposed.

If three layers are included in the flexible encoding, the conditions under which each layer is encoded are shown in Table 1 below.

Meanwhile, a method of encoding an enhancement layer using the base layer of FIG. 7A is as follows. As shown in FIG. 7, an image having the same size as an enhancement layer (hereinafter, the inferred image, FIG. 6B) is made by interpolation of a base layer or some other existing method. . Lossy coding or lossless coding is performed on the transmission side such that Table 1 above satisfies a desired condition. If the base layer is losslessly encoded, a pixel having a base layer value in the speculative image has a correct value without being encoded. However, if the base layer has been subjected to lossy coding, it must be encoded again at the position of the base layer.

As a method of encoding in the process of making FIG. 6C, there is a method of encoding by a CAE method using a context using a pixel value of a position to be encoded as shown in FIG. 8.

The encoding method may be different for each of the following cases.

(1) If the base layer is lossless coding and lossless coding of the enhancement layer, in this case, since the base layer is lossless coding, it is not necessary to perform coding. Therefore, lossless coding is performed using the CAE method only in the interpolated part (a position represented by white) in FIG. 7. At this time, the arithmetic encoding uses the context as shown in FIG.

(2) When the base layer is lossless coding and loss coding the enhancement layer, the encoding is not performed at the position of the base layer as in the case of (1) above. In the position of, lossy coding is performed by varying the CR, as in the case of lossy coding when no elastic coding is performed.

(3) When the base layer is lossy coding and lossless coding of the enhancement layer, in this case, lossless coding is performed for the entire region of the speculative image by the CAE method. In this case, the arithmetic encoding uses the context as shown in FIG.

(4) When the base layer is lossy coding and lossy coding the enhancement layer, in this case, CR is changed as if lossy coding is performed when the entire coding region is not stretched. To perform lossy coding.

In other words, the encoding method varies depending on whether the base layer is loss coded or lossless coded. Therefore, syntax should be added to the VOL class as to whether or not the base layer is loss-coded and to what degree it is loss-coded.

In addition, syntax is added to the VOL class as to whether to encode a higher layer (enhancement layer) or not and how much error loss coding to allow for loss coding.

As described above, the present invention has the effect of lossy coding or lossless coding of the enhancement layer in all cases where the base layer is loss coded or lossless coded in the flexible coding method. There is.

1 is a configuration diagram of a MPEG-4 VOP video encoder primarily determined by the present International Standardization Organization;

FIG. 2 is a diagram illustrating a CONTEXT template in flexible encoding supported by MPEG-4 of FIG. 1.

(a) is the INTRA context template,

(b) is the INTER context template.

3 is a binary alpha block size conversion diagram using CR in flexible encoding supported by MPEG-4;

4 is a conceptual diagram of spatial scalability encoding in flexible encoding supported by MPEG-4 of FIG. 1;

5 is an example of scan interleaving for flexible coding;

6 is a configuration diagram of context information for a conventional horizontal and vertical directions;

7 is an exemplary diagram illustrating a high layer encoding method using a base layer according to the present invention;

8 is a configuration diagram of context information using pixel values to be encoded in the present invention.

<Explanation of symbols for main parts of drawing>

20: VOP forming unit 31: Motion estimation unit

32: motion compensation unit 33: subtractor

34: object internal encoding unit 36: old VOP detection unit

37: Shape information encoder 38: Multiplexer

Claims (7)

In the flexible encoding method of a binary mask for encoding a higher layer by using a base layer, Enhancement layer encoding in the scalable (scalable) encoding, characterized in that if the base layer is lossy coding or lossless coding, the enhancement layer is selectively lost or losslessly encoded. Way. The method of claim 1, A high-level (scalable) encoding is performed by interpolation of the base layer, and an image (guessed image) having the same size as that of the higher layer is generated, and only the interpolation portion is lossless encoded using a CAE method. Enhancement layer coding method. The method of claim 2, The enhancement layer encoding method of the flexible (scalable) encoding, characterized in that for encoding the speculative image is encoded by the CAE method using the context information using the pixel value of the current position. The method of claim 1, When the base layer is lossless coding and loss coding the enhancement layer, CR is lost when the base layer is coded when no coding is performed at a location of the base layer and no elastic coding is performed at other positions. An enhancement layer encoding method in a flexible (scalable) encoding, characterized by lossy coding by changing. The method of claim 1, When the base layer is loss coding and loss coding the higher layer, the flexible layer is loss-coded by changing the CR such that loss coding is performed when the entire coding region is not stretched. Enhancement layer encoding method in scalable coding. The method of claim 1, In case of lossy coding of the base layer, a flexible (scalable) coding method is added to a VOL (Video ObjectLayer) class to add a syntax for whether lossy coding is performed on the base layer and to what extent the lossy coding is allowed. Enhancement layer coding method. The method of claim 1, In case of loss coding of the higher layer, a flexible (scalable) encoding is added to a VOL class to add a syntax on whether to encode the higher layer and how much loss is to be encoded. Enhancement layer coding method.

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