JP4572209B2 - Luminance information decoding device - Google Patents

Description

  The present invention relates to an encoding apparatus and an encoding method for converting video data in a frame into variable-length encoded data and transmitting it.

  In recent years, H.264 has provided videophones and video conferencing using an ISDN network (Integrated Service Digital Network). H.261 and H.264 for videophone services using the public switched telephone network (PSTN). H.263 has been proposed as a technical standard for global standardization of image compression technology.

  H. provides an ultra-low speed video compression technology like a videophone. 261 and H.H. In H.263, it is known that the quality of an image is lowered, and an improvement for upgrading the image quality is required. On the other hand, motion picture-related compression technologies are MPEG1 (Motion Picture Expert Group) for DSM (Digital Storage Media), DSM, HDTV (High Density Television), MPEG2 for ATV (Advanced Television) is standardized.

  These H.C. 261, H.M. The compression techniques of H.263, MPEG1, and MPEG2 employ block-based encoding methods. However, when these encoding methods are applied to ultra-low speed transmission, the image quality is noticeably degraded. For this reason, a completely new system that is differentiated from the existing system is proposed as MPEG4, and standardization is proceeding to block-based coding in which the object concept is introduced.

Among these, the object-oriented coding method (Object Oriented Coding) is based on an object (Object) in a region that moves between two images without using a block as a basis. In this method, coding is performed by dividing into a covered region (Uncovered Region), a region where motion compensation is possible (MC-Region), and a region where motion compensation is impossible (MF-Region).
Here, a motion-compensable object (MC-object) refers to an object that moves with a certain rule such as horizontal movement, rotational movement, linear deformation, etc. by converting an object in a three-dimensional space into a two-dimensional object. An impossible object (MF-object) refers to an object to which this certain rule is not applied.

  FIG. 7 is a diagram showing the relationship between one unit macroblock 33 in one frame grid 31. One frame grid 31 is divided into an array in the X-axis and Y-axis directions, and each divided frame becomes a unit macroblock 33. FIG. 7A shows a frame grid whose grid start position points are X-0 and Y-0, and FIG. 7B shows an enlarged view of one unit macroblock. A state where the X-axis is divided into 8 and the Y-axis is divided into 8 is shown. Here, the divided elements are referred to as pixels (pixels) 34. The unit macroblock 33 is called an N × M macroblock depending on the number of pixels. Accordingly, the unit macroblock in FIG. 7B is an 8 × 8 macroblock.

A conventional shape adaptive technique used as a technique for encoding an object divided in this way will be considered with reference to FIG.
Here, the frame grid has an 8 × 8 macroblock, and when all the objects that cannot be compensated for movement are filled in this macroblock, the same as two-dimensional DCT (Discrete Cosine Transform) It becomes efficiency. When not all of the motion compensation-incapable objects are filled in the block, the one-dimensional DCT is performed on the X-axis and the Y-axis is further performed on the shape part of the corresponding motion-compensation-free object.

Hereinafter, the conventional shape adaptive technique will be described in more detail.
FIG. 8A shows a state in which an object that cannot be compensated for movement (the hatched portion) exists in an 8 × 8 macroblock.
In order to encode the motion uncompensated object by the shape adaptive DCT, first, as shown in FIG. 8B, the upper boundary of the block is filled with the motion uncompensated object in the vertical direction, that is, the Y direction. In addition, encoding is performed by one-dimensional DCT.

  The black circles in FIG. 8C represent discrete cosine transform (DC) values in the vertical one-dimensional DCT. In this state, Y direction one-dimensional DCT is performed. When the one-dimensional DCT in the Y direction is performed in this way and the state of FIG. 8D is obtained, the one-dimensional in the horizontal direction (X direction) is filled again with the left boundary of the block as shown in FIG. 8E. DCT encoding is performed. When the X direction one-dimensional DCT is completed, the one-dimensional shape adaptive DCT in the X direction and the Y direction is finally completed as shown in FIG.

A zigzag scan (ZIGZAG SCAN) is performed with the final configuration shown in FIG. 8F, and a moving object is scanned diagonally from the uppermost block on the left side.
MPEG-1, MPEG-2, JPEG, H.264 using the block center coding described above. 261, H.M. In an existing standard such as H.263, a macro block MB having a form as shown in FIG. 3 is used. In this case, there are four blocks Y1, Y2, Y3, Y4 in one macroblock as shown in FIG. When four blocks existing in the macro block MB are encoded, there are cases where data exists and does not exist in each of the blocks Y1, Y2, Y3, Y4. In the existing standard, a code block pattern is used to display whether or not data exists in the block.

  FIG. 2 shows a variable length code table for a code block pattern used in the H.263 standard. The variable-length code table includes an index field indicating 16 states, a CBPY (intra mode) field indicating a code block pattern (CBPY) in the intra (INTRA) mode, and a code block pattern (CBPY) in the inter (INTER) mode. ) CBPY (intermode) column, a bit number column indicating the bit length of variable-length encoded data, and a variable-length encoded data column indicating variable-length encoded data.

  Also, (1, 2, 3, 4) in the CBPY column corresponds to the four unit blocks Y1, Y2, Y3, Y4 in which data exists, where 1 is Y1, 2 is Y2, 3 is Y3, 4 corresponds to Y4. Therefore, for example, in the index 1, the value of CBPY (intra mode) is represented by (0, 0, 0, 1). There is no data in the blocks Y1, Y2, and Y3, and the block Y4 has no data. Indicates that data exists. In this case, the variable length coded data is 5 bits and is represented as 00101. By using the variable length code table in this way, it is possible to effectively display whether or not data exists in each macro block, and to transmit using the variable length coded data obtained by the conversion. The amount of data can be reduced, i.e. data compression can be realized.

  However, in such a conventional data compression method using block-centered video signal encoding, a code block pattern is used to indicate whether or not data exists in a macroblock. At this time, a variable for the code block pattern is used. Since the long code table is fixed to one, there is a problem that the data reduction efficiency of transmitted data is lowered.

In other words, the number of objects in one macroblock is different from each other and distributed (for example, a small object exists only in a part of the macroblock or an object exists in the entire macroblock). Therefore, the data reduction efficiency is reduced.
An object of the present invention is to provide a data compression method for increasing the reduction efficiency of transmitted data, in order to solve the problem of lowering the coding efficiency that occurs during the conventional object-center coding.

Luminance information decoding apparatus of the present invention, there is provided an apparatus for decoding a luminance information encoded in block format by applying different variable length code table according to the number of unit blocks an object exists within the macro block The unit block in which the object exists is a block having shape information in the unit block, the shape information in the macroblock is decoded from the received bitstream, and the macroblock is decoded from the decoded shape information. The number of unit blocks in which an object is present is calculated, and the macroblock indicating which of the plurality of luminance blocks in the macroblock has encoded luminance information from the received bitstream . The luminance component code block pattern (CBPY) is taken in and the calculated number Ri select a variable length decoding table for the CBPY, characterized in that it comprises a Lud code da turn into decoding the luminance information by decoding the CBPY using the selected variable length decoding table.

  As described above, according to the present invention, different variable length code tables having the highest coding gain are applied in accordance with the presence / absence of an object in a unit block obtained by dividing each macroblock, so that transmission is performed. There is an advantage that the data reduction rate can be increased and the coding gain can also be increased.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The system to which the present invention is applied is a general video encoding system shown in FIG. 5, and receives a video signal and divides the video of one frame into video according to objects. Surface) forming unit 10, an encoding unit 20 that encodes shape information of each object obtained from the VOP forming unit 10, and encoders 21, 22, 23,... In the encoding unit 20. It comprises a multiplexing unit 30 that multiplexes the obtained encoded video signals. The video information of one frame input from the video signal input means is divided by object in the VOP forming unit 10 and the shape information for each object is obtained by the respective encoders 21, 22, 23,. Encode.

  Here, one encoder 21 in the encoder 20 is configured as shown in FIG. A switch 21a for selecting object shape information, a shape information encoding unit 21c that encodes the shape information selected by the switch 21a, shape information encoded by the shape information encoding unit 21c, and arbitrary shape information A selection switch 21d for selecting the motion information, a motion estimation unit 21e for estimating the motion of the shape information selected by the switch 21a based on the reproduced previous shape information or information on an arbitrary shape, and the motion estimation unit 21e A motion compensation unit 21f that compensates the motion of the shape information according to the amount of motion performed, a subtractor 21g that subtracts the video compensated by the motion compensation unit 21f from the video obtained by the VOP forming unit 10, and a subtractor 21g The video signal encoding unit 21h that encodes the obtained video signal and the video information obtained from the video signal encoding unit 21h and the motion compensation unit 21f An adder 21i that adds the compensated video signal, a VOP reproduction unit 21j that reproduces a VOP using the video signal obtained from the adder 21i, and different blocks according to the number of blocks in which an object exists in the macroblock And a memory 21b in which a variable length code table for the pattern is stored.

  The encoder 21 configured as described above selects the object shape information obtained from the VOP forming unit 10 by the switch 21a, and the selected shape information is encoded as the shape information of the corresponding object by the shape information encoding unit 21c. It becomes. Then, the selection switch 21d selectively transmits the encoded shape information and the VOP of arbitrary shape information to the multiplexing unit 21k, and the motion estimation unit 21e performs motion from the shape information obtained by the VOP formation unit 10. Then, the motion compensation unit 21f compensates the motion according to the estimated amount of motion of the object.

The motion compensated video is subtracted by the subtractor 21g from the object shape information obtained from the VOP forming unit 10, and then the video signal is encoded by the video signal encoding 21h to the multiplexing unit 21k as signal information. Communicated.
At this time, the video signal encoding unit 21h selectively applies the variable length code table for different block patterns stored in the memory 21b according to the number of blocks in which the object in the macroblock exists, Generate a pattern.

  The video signal encoded by the video signal encoding unit 21h is added to the video signal compensated for motion by the adder 21i, and then reproduced as a previous VOP by the VOP reproduction unit 21j. The motion estimation unit 21e estimates the motion of the object shape information obtained from the VOP formation unit 10, and transmits the motion information estimated based on the result to the multiplexing unit 21k.

Thereafter, the multiplexing unit 21k multiplexes and outputs the encoded shape information, motion information, and signal information that are respectively input, and the multiplexed signal is transmitted as a bit stream to a decoder (not shown) via the buffer unit 21m. Is transmitted.
Here, the core of the present invention is to selectively apply a large number of variable length code tables stored in the memory 21b in accordance with the number of objects present in each unit block in the macroblock.

Next, an embodiment of the present invention for this purpose will be described.
That is, as shown in FIG. 1, since the object P does not necessarily form a square, when divided in units of macroblocks MB, blocks in which the object P is included and blocks that are not included in the divided macroblock MB You can.

As shown in FIG. 1A, an object P represented as video information data in one frame divided into a large number of macroblocks MB is a portion that exists as data in each divided macroblock and a portion that does not exist There is.
FIG. 1B is an enlarged view of a region Q surrounded by a dotted line in FIG. The hatched portion in the figure indicates the object P. In FIG. 1B, four macroblocks MB1, MB2, MB3, and MB4 are shown, and each macroblock is composed of four unit blocks Y1, Y2, Y3, and Y4.
Therefore, it can be seen that there are a unit block in which the object P is included in the macroblock MB and a unit block in which the object P is not included. This is shown in FIG.

  That is, the macroblock 1 (MB1) shown in FIG. 2A has all the objects in the other unit blocks Y2, Y3, Y4 except the first unit block Y1, and the macro of (B). Block 2 (MB2) has all objects in all unit blocks Y1, Y2, Y3, Y4, and macroblock 3 (MB3) in (C) has objects only in the second unit block Y2. Macroblock 4 (MB4) in (D) has an object only in the first unit block Y1 and the second unit block Y2.

  As described above, since an object is selectively present in each unit block in the macroblock, a different variable length code table is applied to each case to increase the coding gain and increase the data reduction efficiency.

  That is, since an object exists only in the three unit blocks Y2, Y3, and Y4 in the macroblock 1 (MB1), applying a variable length code table as shown in Table 1 enables data reduction and encoding. Gain can be increased.

  Since all objects exist in the four unit blocks Y1, Y2, Y3, and Y4 in the macroblock 2 (MB2), in this case, the existing variable length code table shown in FIG. Since an object exists only in one unit block Y2 in MB3), a variable length code table as shown in Table 3 is applied, and an object exists only in two unit blocks Y1 and Y2 in macroblock 4 (MB4). Therefore, the variable length code table as shown in Table 2 is applied.

In the above-described embodiment, a case has been described in which different variable-length code tables are applied when each macroblock is divided into four square unit blocks. However, the number of divisions is not limited to this, When the number of divisions is adopted, different variable length code tables having the highest coding gain can be obtained in the same manner by experiments in accordance with the presence / absence of an object in each unit block.
In this way, by applying different variable length code tables (variable length code tables having the best coding gain) according to the presence / absence of an object in each unit block in the macroblock, the data reduction rate and coding gain can be reduced. Can be increased.

Here, the different variable-length code tables shown in Tables 1, 2, and 3 are new variable-length code tables obtained by experiments. Here, the terms “INTRA” and “INTER” are as follows. Defined in
The characteristics of the object on the time axis are the object that did not appear in the previous frame but appeared in the current frame (object type I), and the case of an extremely small object (object within 10 pixels; object type II). In the case of relatively large objects (objects of 10 pixels or more; object type III), there are cases where objects that were not present in the previous frame but appeared in the current frame are The encoding type is determined to be the INTRA mode (non-prediction mode) in the case of an extremely small object having a size of less than 10 pixels, and the INTER mode (prediction mode) is determined in the case of an object not having the above characteristics. .

The example figure which divided | segmented the arbitrary objects per macroblock. The figure which displayed the unit block in which an object exists in a macroblock. MPEG-1, MPEG-2, H.264. 261, H.M. The figure which shows macroblock MB containing four unit blocks Y1, Y2, Y3, Y4 used by the existing standards, such as H.263. H. A variable length coding table for code block patterns used in the H.263 standard. 1 is a block configuration diagram of an object video encoding system to which the present invention is applied. FIG. 6 is a detailed configuration diagram of one encoder 21 in FIG. 5. Explanatory drawing of a general frame grid and a macroblock. Explanatory drawing of general shape adaptive DCT conversion.

Explanation of symbols

10 VOP forming unit 20 Coding unit 30 Multiplexing unit MB1 to MB4 Macroblock Y1 to Y4 Unit block

Claims (3)

An apparatus for decoding a luminance information encoded in block format by applying different variable length code table according to the number of unit blocks is an object of the macro block is present,
The unit block in which the object exists is a block having shape information in the unit block,
Decoding the shape information in the macroblock from the received bitstream , calculating the number of unit blocks in which the object in the macroblock exists from the decoded shape information, and
Capturing a luminance component code block pattern (CBPY) of the macroblock indicating which of the plurality of luminance blocks in the macroblock has encoded luminance information from the received bitstream ;
Select a variable length decoding table for the CBPY according to the calculated number,
Luminance information decoding apparatus comprising: a Lud code da turn into decoding the luminance information by decoding the CBPY using a variable length decoding table said selected. The variable length decoding table is
A first variable length decoding table used when there is one object in the macroblock;
The first variable length decoding table is:

The luminance information decoding apparatus according to claim 1 , wherein: The variable length decoding table is
A third variable length decoding table used when there are three objects in the macroblock;
The third variable length decoding table is:

The luminance information decoding apparatus according to claim 1, wherein:

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