JP7361838B2 - Video encoding device, video decoding device, and these programs - Google Patents

Description

The present invention relates to a video encoding device, a video decoding device, and programs thereof in a video encoding method using motion compensation prediction.

In general, in video encoding methods that use motion compensation prediction, it is considered that there is no point in compression encoding the positive and negative signs (+, -) of motion vectors and difference vectors because their appearance frequency is not biased. (Reversible compression) is not performed.

For example, in the MPEG-H HEVC/H.265 system, a motion vector is expressed as the sum of a predicted vector (PMV) and a difference vector (MVD) (see, for example, Non-Patent Document 1).

The difference vector is expressed differently depending on whether the absolute value of the vector is 0 or other than 0. This is represented by abs_mvd_greater0_flag, and when abs_mvd_greater0_flag is 0, the difference vector is 0. On the other hand, when abs_mvd_greater0_flag is 1, the difference vector is expressed by a combination of the absolute value of the difference vector and the sign of the difference vector called mvd_sign_flag. Since the positive and negative signs (+ and -) generally have no bias in their frequency of appearance, mvd_sign_flag uses bypass mode that does not perform reversible compression and expresses the positive and negative signs (+/-) as 1/0 bits without performing reversible compression. It is arithmetic encoded and transmitted in association with the absolute value of the difference vector. That is, in the MPEG-H HEVC/H.265 system, the positive and negative signs of the difference vector are not compressed at all.

ITU-T Recommendation H.265 (2013), High efficiency video coding; ISO/IEC 23008-2:2013, Information technology High efficiency coding and media delivery in heterogeneous environments Part 2: High efficiency video coding, 2003, 〈https:/ /www.iso.org/standard/35424.html〉

As mentioned above, in general video encoding methods such as MPEG-H HEVC/H.265, there is no bias in the appearance frequency of the positive and negative signs of the difference vector, so there is no point in performing compression encoding. and does not perform compression (reversible compression).

However, depending on the position of the block of interest within the frame, there may be a bias in the probability of occurrence of the positive or negative sign (+, -) of the difference vector, so compression may be possible using context-adaptive reversible compression. be. Therefore, a technique is desired that enables compression (reversible compression) of the positive and negative signs (+, -) of the difference vector and further improves the compression efficiency related to video encoding.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a video encoding device configured to improve the compression efficiency related to the positive and negative signs (+, -) of a difference vector in a video encoding method using motion compensation prediction. , a video decoding device, and programs thereof.

The video encoding device of the present invention is a video encoding device in a video encoding method using motion compensation prediction, and includes difference vector generation means for generating a difference vector based on motion compensation prediction for a predetermined block within a frame. , the estimated sign of the difference vector is estimated by estimating the sign of the difference vector according to a predetermined rule based on information regarding the predetermined block, the absolute value of the difference vector, and a predicted vector related to the difference vector. A difference vector sign estimating means that determines the sign of the difference vector obtained from the difference vector generating means and an estimated sign of the difference vector obtained from the difference vector sign estimating means are compared, and it is determined that the signs of the difference vector are equal. correct/incorrect flag generating means for generating a correct/incorrect flag indicating true if the case is true and false if different; and a reversible method that adapts the correct/incorrect flag generated by the correct/incorrect flag generating means to a context according to the position of the predetermined block. comprising a context-adaptive reversible compression means that performs compression processing, and a stream generation means that generates a stream for transmitting the correct/incorrect flag, which has undergone the reversible compression processing, in association with the absolute value of the difference vector. It is characterized by

Further, in the video encoding device of the present invention, the difference vector code estimating means calculates positive side and negative side candidate vectors using information regarding the predetermined block, the absolute value of the difference vector, and the prediction vector. According to the positional relationship between the position of the block corresponding to each candidate vector and the screen edge of the frame, or the coordinates and size of the predetermined block, the positive side and negative side candidate vectors, and the The present invention is characterized in that the sign of the difference vector is estimated based on a predetermined rule that is divided into cases according to the positional relationship of the screen width of the frame.

Further, in the video encoding device of the present invention, the frame is divided into an area at the center of the screen and an area within a predetermined range at the edge of the screen, and the predetermined block is contained in at least an area within the predetermined range at the edge of the screen. In this case, the present invention is characterized in that it further comprises a control means for controlling the operation of the correct/incorrect flag generating means.

Further, in the video encoding device of the present invention, the control means may control the difference vector based on which region of the plurality of divided regions within a predetermined range of the edge of the screen the predetermined block fits. The present invention is characterized by comprising means for controlling to switch the component for which the correct/incorrect flag is used for each of the horizontal component and the vertical component.

In the video encoding device of the present invention, if the predetermined block is closer to the left and right sides of the screen of the frame than to the top and bottom sides, the control means controls the difference vector code estimating means to detect the horizontal component of the difference vector. If the predetermined block is closer to the top and bottom sides of the screen of the frame than to the left and right sides of the screen, the difference vector sign estimating means first determines the sign of the vertical component of the difference vector. and when the predetermined block is equidistant from the left and right sides and the top and bottom sides of the screen of the frame, the difference vector sign estimating means calculates the positive and negative signs of the horizontal and vertical components of the difference vector in a predetermined order. It is characterized by having means for controlling the determination.

Furthermore, the video decoding device of the present invention inputs and reads the stream transmitted by the video encoding device of the present invention, and calculates the absolute value of the difference vector and the lossless compression process for a predetermined block in the frame to be decoded. a stream reading means for extracting correct/incorrect flags, and a sign of the difference vector according to a predetermined rule based on information regarding the predetermined block, the absolute value of the difference vector, and a predicted vector related to the difference vector. difference vector sign estimating means that determines the estimated sign of the difference vector by estimating; a context-adaptive reversible decoding means that generates a decoded correct/incorrect flag by performing a decoding process; and when the decoded correct/incorrect flag indicates true, the estimated code of the difference vector is converted to a difference vector sign determining means for determining a sign obtained by inverting the estimated sign of the difference vector as the sign of the difference vector when the sign is positive or negative; difference vector restoring means for restoring the difference vector of the predetermined block in the frame to be decoded using the absolute value of the difference vector determined by the difference vector and the sign of the difference vector determined by the difference vector sign determination means; It is characterized by having the following.

Further, in the video decoding device of the present invention, the context adaptive reversible decoding means refers to a block at a predetermined position as a block to be referred to as a context according to the position of the predetermined block in the screen, The present invention is characterized in that the reversible decoding process is performed on the correctness flag that has been subjected to the reversible compression process.

Further, in the video decoding device of the present invention, the context adaptive reversible decoding means may be configured to determine that the predetermined block is closer to the screen than the top and bottom sides of the screen as a block to be referred to as a context according to the position of the predetermined block in the screen. If it is close to the left and right sides, refer to the block directly above the predetermined block, and if the predetermined block is closer to the top and bottom sides of the screen than to the left and right sides of the screen, refer to the block immediately to the left of the predetermined block, and refer to the block directly above the predetermined block. If the block is equidistant from the top and bottom sides of the screen than from the left and right sides of the screen, the reversible block is The present invention is characterized in that the reversible decoding process is performed on the correctness flag that has been subjected to the compression process.

Furthermore, the program of the present invention is configured as a program for causing a computer to function as the video encoding device of the present invention.

Furthermore, the program of the present invention is configured as a program for causing a computer to function as the video decoding device of the present invention.

According to the present invention, it is possible to reversibly compress the positive and negative signs (+, -) of a difference vector in a video encoding method using motion compensated prediction, and at least focus on prediction targets located at the screen edges of frames constituting a video. Compression efficiency related to the positive and negative signs (+, -) of the difference vector in the block can be improved.

1 is a block diagram showing a schematic configuration of a video encoding device according to an embodiment of the present invention. 1 is a block diagram showing a schematic configuration of a video decoding device according to an embodiment of the present invention. 2 is a flowchart illustrating processing for estimating the sign of a difference vector in Example 1 in a video encoding device and a video decoding device according to an embodiment of the present invention. (a) and (b) are explanatory diagrams of processing related to estimating the sign of a difference vector in Example 1 in a video encoding device and a video decoding device according to an embodiment of the present invention. (a), (b), and (c) respectively correspond to a target block, a candidate vector, and a candidate vector related to the process of estimating the sign of a difference vector in Example 1 in a video decoding device according to an embodiment of the present invention. FIG. FIG. 3 is an explanatory diagram during a panning operation related to estimating the sign of a difference vector in Example 1 in a video encoding device and a video decoding device according to an embodiment of the present invention. The video encoding device and video decoding device according to an embodiment of the present invention include a frame that has an area that uses the correct/incorrect flag and an area that uses +/- of the plus/minus sign as a bit representation of 1/0 as in the conventional technique. It is an explanatory diagram. 7 is a flowchart illustrating a process of determining the positive and negative signs of a difference vector in an example in a video decoding apparatus according to an embodiment of the present invention. (a), (b), and (c) are explanatory diagrams of blocks referred to as contexts related to context-adaptive reversible compression/decoding processing in a video encoding device and a video decoding device according to an embodiment of the present invention. . 7 is a flowchart illustrating processing for estimating the sign of a difference vector in Example 2 in a video encoding device and a video decoding device according to an embodiment of the present invention. 12 is a flowchart showing a process for estimating the sign of a difference vector in Example 3 in a video encoding device and a video decoding device according to an embodiment of the present invention.

(Definition of terms)
First, regarding motion vectors, there are cases where the motion vector itself is transmitted as in the MPEG-2/H.262 system, and cases where it is transmitted as the sum of a predicted vector and a difference vector as in the MPEG-H HEVC/H.265 system. There is. Therefore, in order to generalize the motion vectors used in the video encoding device 1 and video decoding device 2 according to the present invention, the motion vectors will be described assuming that they satisfy equation (1).

Motion vector = predicted vector + difference vector (1)

The "predicted vector" in Equation (1) means data that does not transmit the vector itself, but rather transmits a predetermined number or the like, and calculates a vector from the number or the like according to a predetermined rule. Furthermore, the "difference vector" in equation (1) means data that transmits the vector itself.

Since the present invention is not directly related to the predicted vector in equation (1), but directly related to the sign of the difference vector, an image of an embodiment according to the present invention, which will be described later with reference to FIGS. 1 and 2. In the encoding device 1 and the video decoding device 2, only the main components related to the transmission of the positive and negative signs of the difference vector will be illustrated and explained.

In the case of the MPEG-H HEVC/H.265 method, the predicted vector of equation (1) is the predicted vector (PMV) of the MPEG-H HEVC/H.265 method, and the difference vector of equation (1) is the MPEG-H HEVC The video encoding device 1 and the video decoding device 2 according to the present invention can be applied to the video encoding device 1 and the video decoding device 2, which directly correspond to the vector difference (MVD) of the /H.265 system.

In addition, in the case of a video encoding method that does not use a predictive vector, the predictive vector in equation (1) can be treated as 0, and the difference vector in equation (1) can be treated as the motion vector of the method, without loss of generality. The video encoding device 1 and video decoding device 2 according to the present invention are applicable.

In addition, in recent years, in order to calculate a motion vector, a video encoding method that adds a third vector related to calculating the predicted vector in addition to the predicted vector and the difference vector has been considered. The predicted vector of (1) can be set as the predicted vector of the method + the third vector of the method, and the difference vector of equation (1) can be treated as the difference vector of the method. The video encoding device 1 and video decoding device 2 according to the invention can be applied.

Hereinafter, a video encoding device 1 and a video decoding device 2 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

(Video encoding device)
FIG. 1 is a block diagram showing a schematic configuration of a video encoding device 1 according to an embodiment of the present invention. The video encoding device 1 includes an image encoding unit 10, a difference vector code estimating unit 13, a correctness flag generating unit 14, a context adaptive reversible compression unit 15, a positive/negative binarization unit 16, a switching unit 17, a setting control unit 18, and a stream generation unit 19. The image encoding unit 10 includes a motion compensation prediction unit 11 and a difference vector generation unit 12.

The image encoding unit 10 is a functional unit that inputs a frame image of a video to be encoded, divides it into blocks, and performs intra prediction and inter prediction on a block-by-block basis. The present invention relates to compression/decoding of the positive/negative sign of a difference vector based on motion compensated prediction related to inter prediction. Therefore, in FIG. 1, only the motion compensation prediction unit 11 and the difference vector generation unit 12 are illustrated, assuming that the image encoding unit 10 has a function of generating a difference vector based on motion compensation prediction for the block of interest, and the prediction Illustrations and explanations of other processes including vector transmission processing and local decoding processing are omitted.

Note that the motion compensation prediction unit 11 performs motion compensation prediction based on motion detection using the target block of the input image and the locally decoded reference block, generates a predicted image block, and outputs it to the difference vector generation unit 12. do.

Further, the difference vector generation unit 12 approximates the motion vector generated by the motion estimation with a predetermined number such as an index, as shown in equation (1), with respect to the motion vector indicating the position of the block of the predicted image. Generate a difference vector to be added to the predicted vector.

Here, the image encoding unit 10 separates and outputs the difference vector generated by the difference vector generation unit 12 into the absolute value of the difference vector and the sign of the difference vector.

The difference vector code estimating unit 13 receives, from the image encoding unit 10, the target block information regarding the target block (including the position and size of the target block, and the size of the frame image), the predicted vector, and the absolute value of the difference vector. Then, the sign of the difference vector is estimated based on a predetermined rule (i.e., the "process for estimating the sign of the difference vector" described later), and the estimated sign of the difference vector indicating the estimated sign is set as a right/wrong flag. It is output to the generation unit 14.

The correctness/incorrect flag generation unit 14 compares the difference vector estimation code obtained from the difference vector code estimation unit 13 and the sign of the difference vector obtained from the image encoding unit 10, and if the two are equal, it determines “true”; If they are different, a correct/incorrect flag indicating "false" is generated and output to the context adaptive reversible compression unit 15.

The context adaptive reversible compression unit 15 inputs the target block information from the image encoding unit 10 and the correct/incorrect flag from the correct/incorrect flag generating unit 14, specifies a context model based on the target block information, and By performing context-adaptive reversible compression encoding processing on the correct/incorrect flag, a reversibly compressed correct/incorrect flag is generated and output to the switching unit 17 . Note that the context adaptive reversible compression encoding processing is, for example, CABAC (Context-based Adaptive Binary Arithmetic Coding) when using a video encoding method based on the MPEG-H HEVC/H.265 method, and AVC/H.264. In the case of using a video encoding method according to the CABAC or CAVLC (Context-based Adaptive Variable Length Coding). That is, the context adaptive reversible compression unit 15 performs adaptive binarization encoding according to the surrounding situation (context) at the position of the block of interest according to the context model.

However, in the video encoding device 1 according to the present embodiment, as a context model related to reversible compression of correct/incorrect flags, which block around the block of interest is referred to as a context, which will be described in detail later with reference to FIG. There are good examples.

Similar to the conventional technique, the positive/negative binarization unit 16 performs a binarization process in which +/− of the positive/negative sign is expressed as a 1/0 bit representation, and outputs the result to the switching unit 17 .

Under the control of the setting control unit 18 , the switching unit 17 transmits the positive/negative sign of the difference vector of the target block by using the positive/incorrect flag reversibly compressed by the context adaptive reversible compression unit 15 or by the positive/negative binarization unit 16 . This is a functional unit that switches whether to transmit using simply binarized plus/minus signs and outputs the result to the stream generation unit 19.

The setting control unit 18 selects an area for specifying a context model related to "the process of estimating the sign of a difference vector" according to the position of the block of interest in the frame image, and a region for specifying a context model for "estimating the sign of the difference vector" according to the position of the block of interest in the frame image. It has setting information that predetermines an area in which +/- is expressed as a bit of 1/0, and controls switching in the switching unit 17 based on the setting information. In this example, an example will be explained in which the setting control unit 18 outputs the setting information to the stream generation unit 19, but when the setting information is determined in advance between the video encoding device 1 and the video decoding device 2, the video code It is not necessary to transmit the data from the encoding device 1 to the video decoding device 2.

Note that in FIG. 1, a configuration example is shown in which the setting control unit 18 controls switching in the switching unit 17 and switches the outputs of the context adaptive reversible compression unit 15 and the positive/negative binarization unit 16. The operation of the sign estimating section 13, the correct/incorrect flag generating section 14, and the context adaptive reversible compression section 15 and the operation of the positive/negative binarizing section 16 may be switched.

The stream generation unit 19 converts the absolute value of the difference vector corresponding to the block of interest obtained from the image encoding unit 10 into the correct/incorrect flag after the reversible compression obtained from the switching unit 17 or the simply binarized positive/negative value. Generates a stream for transmission by associating codes and outputs it to the outside. In this example, the setting information obtained from the setting control unit 18 includes the block of interest information (including the position and size of the block of interest, and the size of the frame image) as well as the header (slice or tile header, picture header and sequence header). Note that the stream also includes information necessary for decoding, such as predicted vectors. Any method based on conventional techniques can be used for transmitting signals other than the positive and negative signs of the difference vector, so a description thereof will be omitted.

In this way, the video encoding device 1 generates a difference vector based on motion compensation prediction for the target block, and uses the target block information, the absolute value of the difference vector, and the predicted vector related to the difference vector for the positive and negative signs of the difference vector. The sign of the difference vector is estimated according to a predetermined rule based on (that is, "process for estimating the sign of the difference vector" to be described later). Then, the video encoding device 1 sets the correctness flag to be true if the plus/minus sign estimated for the difference vector (difference vector estimation sign) is equal to the plus/minus sign of the difference vector obtained when generating the difference vector, and to make it false if different. is generated, subjected to context-adaptive lossless compression processing, and transmitted.

As a result, in the case of a block of interest in a frame image where the probability of occurrence is biased, the positive and negative signs (+, -) of the difference vector are expressed as true/false flags, and compression (reversible compression) becomes possible, which improves video encoding. It becomes possible to improve the compression efficiency related to

(Video decoding device)
FIG. 2 is a block diagram showing a schematic configuration of a video decoding device 2 according to an embodiment of the present invention. The video decoding device 2 includes a stream reading unit 20, an image decoding unit 21, a setting control unit 24, a switching unit 25, a context adaptive reversible decoding unit 26, a difference vector code estimation unit 27, a difference vector code determination unit 28, and a sign determination unit 28. A section 29 is provided. The image decoding unit 21 includes a difference vector restoring unit 22 and a motion compensation prediction unit 23.

The stream reading unit 20 reads the stream transmitted from the video encoding device 1, outputs a signal related to the absolute value of the difference vector in the block of interest to the image decoding unit 21 and the difference vector code estimation unit 27, and outputs the signal regarding the absolute value of the difference vector in the block of interest to the image decoding unit 21 and the difference vector code estimation unit 27. The correctness flag after the reversible compression or the simply binarized plus/minus sign, which is transmitted in association with the absolute value, is output to the switching unit 25.

The image decoding unit 21 is a functional unit that performs intra prediction and inter prediction on a block-by-block basis and performs decoding. The present invention relates to compression/decoding of the positive/negative sign of a difference vector based on motion compensated prediction related to inter prediction. Therefore, in FIG. 2, briefly, the image decoding unit 21 performs motion compensation prediction using the restored difference vector, prediction vector, and decoded reference block for the block of interest, and restores the transmitted image. However, only the difference vector restoring unit 22 and the motion compensation prediction unit 23 are illustrated, and illustrations and explanations of other processes including the prediction vector decoding process are omitted.

Note that the difference vector restoring unit 22 uses the absolute value of the difference vector inputted from the stream reading unit 20 and the correct/incorrect flag after the reversible compression, which is transmitted in association with the absolute value of the difference vector, or the simply The difference vector is restored using the binarized positive and negative signs.

Further, the motion compensation prediction unit 23 performs motion compensation prediction using the difference vector restored by the difference vector restoration unit 22, the transmitted prediction vector, and the decoded reference block, and restores the image of the block of interest.

The setting control unit 24 selects a region for specifying a context model related to "the process of estimating the sign of a difference vector" according to the position of the target block in the frame image, and a region for specifying a context model for "estimating the sign of the difference vector" according to the position of the block of interest in the frame image. Switching in the switching unit 25 is controlled based on setting information that predetermines a region in which +/- is represented by bits of 1/0. In this example, the configuration information is embedded in a header (including one or more of a slice or tile header, a picture header, and a sequence header) in the stream. Therefore, the setting control unit 24 extracts the setting information and controls switching in the switching unit 25 based on the extracted setting information. Note that when the setting information is determined in advance between the video encoding device 1 and the video decoding device 2, there is no need to transmit it from the video encoding device 1 to the video decoding device 2, and it is necessary to embed the setting information in the header. Nor.

Under the control of the setting control unit 24, the switching unit 25 switches the sign of the reversibly compressed true/false flag and the simply binarized difference vector, and outputs them to the context adaptive reversible decoding unit 26 and the sign determining unit 29, respectively. It is a functional part.

In this example, FIG. 2 shows a configuration example in which the setting control unit 24 controls switching in the switching unit 25 and switches inputs to the context adaptive reversible decoding unit 16 and the sign determining unit 29, respectively, which will be described later. However, the configuration may be such that the operations of the context adaptive reversible decoding unit 26, the difference vector code estimation unit 27, and the difference vector code determination unit 28, which will be described later, and the operation of the sign determination unit 29 are switched.

The context adaptive reversible decoding unit 26 inputs the target block information from the stream reading unit 20 and the correctness flag that has been reversibly compressed on the video encoding device 1 side via the switching unit 25, and decodes the target block based on the target block information. By specifying a context model and performing context-adaptive reversible decoding processing on the correct/incorrect flag, a decoded correct/incorrect flag is generated and output to the difference vector code determination unit 28 . For context-adaptive reversible decoding processing, for example, CABAC can be used when the video encoding method is based on the MPEG-H HEVC/H.265 method, while CABAC can be used when the video encoding method is based on the AVC/H.264 method. When using a method, CABAC or CAVLC can be used. That is, the context adaptive reversible decoding unit 26 performs binarization decoding adaptively according to the surrounding situation (context) at the position of the block of interest according to the context model. In addition, the target block information (including the position and size of the target block, and the size of the frame image) is based on one or more of the headers (slice or tile header, picture header, and sequence header) in the stream. (including).

However, in the video decoding device 2 according to the present embodiment, as a context model related to reversible compression of correct/incorrect flags, details will be described later with reference to FIG. There is an example.

The difference vector code estimation unit 27 performs the same processing as the difference vector code estimation unit 13 on the video encoding device 1 side. The difference vector code estimating unit 27 inputs the target block information and the absolute value of the difference vector from the stream reading unit 20, inputs the predicted vector from the image decoding unit 21, and uses the predetermined rule (i.e., the “difference vector” described later). The positive/negative sign of the difference vector is estimated based on the process of estimating the positive/negative sign of the vector), and a difference vector estimated code indicating the estimated positive/negative sign is output to the difference vector sign determination unit 28.

When the correctness flag obtained from the context adaptive reversible decoding section 26 indicates "true", the difference vector code determination section 28 directly uses the difference vector estimated code obtained from the difference vector code estimation section 27 as the plus/minus sign of the difference vector. It is determined and output to the image decoding unit 21, and when the correct/incorrect flag indicates “false”, a code obtained by inverting the difference vector estimation code is determined as the plus/minus sign of the difference vector, and is output to the image decoding unit 21.

In response to the 0/1 bit representation of the sign of the simply binarized difference vector obtained via the switching unit 25, the sign determining unit 29 determines the sign of the difference vector as in the conventional technique. +/- is determined and output to the image decoding section 21.

As a result, the difference vector restoring unit 22 in the image decoding unit 21 receives the absolute value of the difference vector input from the stream reading unit 20 and the reversibly compressed The difference vector is restored using the correctness flag or the simply binarized plus/minus sign.

In this way, the video decoding device 2 calculates the sign of the difference vector regarding the block of interest read from the stream based on the predetermined rule (i.e., "process for estimating the sign of the difference vector" described later). The sign of the vector is estimated, and the correct/incorrect flag read from the stream and subjected to context-adaptive reversible compression is reversibly decoded. Then, when the correctness flag indicates true, the video decoding device 2 uses the estimated plus/minus sign (difference vector estimation code) as the plus/minus sign of the difference vector, and when it indicates false, the video decoding device 2 sets the estimated plus/minus sign (difference vector estimation code) as the plus/minus sign of the difference vector. The sign obtained by inverting the vector estimation sign) is determined as the plus/minus sign of the difference vector.

As a result, in the case of a block of interest in a frame image where the probability of occurrence is biased, it becomes possible to decode (reversible decoding) the correct/incorrect flag compressed (reversible compression) for the positive/negative sign (+, -) of the difference vector. It becomes possible to further improve the compression efficiency related to video encoding.

(Example 1: Estimating the sign of the difference vector)
FIG. 3 shows estimation of the positive and negative signs of the difference vector in Example 1 in the video encoding device 1 (difference vector code estimating unit 13) and the video decoding device 2 (difference vector code estimating unit 27) according to an embodiment of the present invention. 3 is a flowchart showing processing.

First, the difference vector sign estimation units 13 and 27 input (read) the absolute value of the difference vector for the block of interest (step S11), and determine whether the absolute value of the difference vector = 0 (step S12). .

As for the method of reading the absolute value of the difference vector from the bit stream, a method similar to the conventional technique may be used. For example, reading the absolute value of a Golomb-encoded difference vector from a bitstream, a flag indicating that the absolute value of the difference vector is greater than 0, or a flag indicating that it is greater than 1, as in the HEVC/H.265 system. , the absolute value of the Golomb-encoded difference vector, etc. may be read in combination.

When the absolute value of the difference vector is 0 (step S12: Y), the difference vector sign estimating unit 13, 27 ends the estimation process by determining that the difference vector has no sign (step S13). If the absolute value of the read difference vector is 0, there is no need to determine the sign, so no further processing is performed, the difference vector becomes 0, and the estimation process ends with the difference vector having no sign.

On the other hand, when the absolute value of the difference vector≠0 (step S12: N), the difference vector sign estimating units 13 and 27 first calculate the positive side and negative side candidate vectors V _A and V _B for the block of interest. (Step S14).
Candidate vector V _A = Predicted vector + absolute value of difference vector Candidate vector V _B = Predicted vector - absolute value of difference vector

Note that the predicted vector can be obtained using a conventional method such as the HEVC/H.265 method. The predicted vector may be obtained before the absolute value of the difference vector or the correct/incorrect flag.

Subsequently, _{the difference vector sign estimating units 13 and 27 calculate a block BKA and a block BK B obtained} by moving the block of interest BKn to the candidate vector V _A and the candidate vector V _B , respectively (step S15).

Subsequently, the difference vector sign estimation units 13 and 27 determine whether both blocks BK _A and BK _B are completely within the screen (step S16).

When both blocks BK _A and BK _B are completely within the screen (step S16: Y), the difference vector sign estimation units 13 and 27 estimate the positive and negative signs of the difference vector as default values, and the difference vector estimated sign= It is determined as a default value (step S17). In this example, "positive" is used as the default value, but "negative" may be used as the default value.

In addition, in this example, the default value of the difference vector estimation code related to step S17 is set to the header in the stream (including any one or more of a slice or tile header, a picture header, and a sequence header) as setting information. embedded in. However, if the default value is determined in advance between the video encoding device 1 and the video decoding device 2, there is no need to transmit it from the video encoding device 1 to the video decoding device 2, and it is necessary to embed the setting information in the header. Nor.

When both blocks BK _A and BK _B are not completely within the screen (step S16: N), the difference vector sign estimation units 13 and 27 then determine whether both blocks BK _A and BK _B are both completely outside the screen. is determined (step S18).

When both blocks BK _A and BK _B are completely outside the screen (step S18: Y), the difference vector sign estimating units 13 and 27 determine the distance between block BK _A and its nearest screen edge, and The "distance between block _BKB and its nearest screen edge" is compared (step S19).

When the distance between block BK _A and its nearest screen edge is greater than the distance between block BK _B and its nearest screen edge (step S19: Y), the difference vector sign estimation units 13 and 27 calculate the difference vector The estimated sign is determined to be negative (step S21).

Further, when the distance between block BK _A and its nearest screen edge is smaller than the distance between block BK _B and its nearest screen edge (step S19: N), the difference vector sign estimating units 13 and 27: The difference vector estimation sign is determined to be positive (step S20).

For example, as shown in FIG. 4A, assuming that the positive sign of the difference vector indicates the right direction and the negative sign of the difference vector indicates the left direction, the block BK _A corresponding to the candidate vector V _A corresponds to the candidate vector V _B. An example in which both blocks BKB _{and B} are outside the screen will be explained. When the distance D _{A between block BK A and its nearest screen edge is smaller than the distance D B between} block BK _B corresponding to candidate vector V _B and its nearest screen edge, the difference vector estimation sign is assumed to be positive. By making this determination, it is determined that block BK _A has higher prediction accuracy than block BK _B.

Further, when the distance between block BK _A and its nearest screen edge is equal to the distance between block _BKB and its nearest screen edge, the difference vector sign estimating units 13 and 27 determine that the difference vector estimated sign is positive. or a negative prespecified one (in step S19 shown in FIG. 3, the difference vector estimation sign=positive) is determined.

In addition, in the comparison related to step S19, when determining the difference vector estimation sign as the prespecified positive or negative one, setting information indicated as the second default value (or as a commonly used default value) is set in the stream. It may also be transmitted by being embedded in a header (including any one or more of a slice or tile header, a picture header, and a sequence header). However, when the second default value is determined in advance between the video encoding device 1 and the video decoding device 2, there is no need to transmit the second default value from the video encoding device 1 to the video decoding device 2, and the setting information is sent to the header. There is no need to embed it in.

On the other hand, when both blocks BK _A and BK _B are neither completely within the screen nor completely outside the screen (step S18: N), that is, when at least one of the blocks BK _A and BK _B is partially outside the screen, The difference vector sign estimation units 13 and 27 calculate the area of the off-screen area of the blocks BK _A and BK _B (step S22).
Area S _A = Area of block BK _A that protrudes from the screen Area S _B = Area of block BK _B that protrudes from the screen

Subsequently, the difference vector sign estimation units 13 and 27 compare the area _SA and the area _SB (step S23).

When the area S _A is larger than the area S _B (step S23: Y), the difference vector sign estimation units 13 and 27 determine that the difference vector estimation sign is negative (step S25).

When the area _SA is smaller than the area S _B (step S23: N), the difference vector sign estimating unit 13, 27 determines that the difference vector estimation sign is positive (step S24).

For example, as shown in FIG. 4(b), assuming that the positive sign of the difference vector indicates the right direction and the negative sign of the difference vector indicates the left direction, the block BK _A corresponding to the candidate vector V _A corresponds to the candidate vector V _B. An example in which a portion of both blocks BK and _B is outside the screen will be described. When the area S _B is larger than the area S _A , the difference vector estimation sign is determined to be positive, thereby determining that the prediction accuracy of the block BK _A is higher than that of the block BK _B.

When the area S _A is equal to the area S _B , the difference vector sign estimating units 13 and 27 determine the difference vector estimation sign = positive or negative, whichever is specified in advance (in step S23 shown in FIG. 3, the difference vector estimation sign = positive). ).

In addition, in the comparison related to step S23, when determining the difference vector estimation sign as the prespecified positive or negative one, setting information indicated as the third default value (or as a commonly used default value) is set in the stream. It may also be transmitted by being embedded in a header (including any one or more of a slice or tile header, a picture header, and a sequence header). However, when the third default value is determined in advance between the video encoding device 1 and the video decoding device 2, there is no need to transmit the third default value from the video encoding device 1 to the video decoding device 2, and the configuration information is sent to the header. There is no need to embed it in.

The difference vector estimation code determined through steps S17, S20, S21, S24, and S25 is sent to the correctness flag 14 on the video encoding device 1 side shown in FIG. 1, and the difference vector code is determined on the video decoding device 2 side shown in FIG. It is output to the section 28 (step S26).

In this way, the difference vector sign estimating units 13 and 27 use the target block information, the absolute value of the difference vector, and the predicted vector to calculate the positive side and negative side candidate vectors V _A and V _B , The sign of the difference vector is estimated based on a predetermined rule that is divided into cases according to the positional relationship between the positions of the blocks BK _A and BK _B corresponding to the candidate vectors V _A and V _B and the edge of the screen, and the difference Determine the vector estimate sign.

Then, on the video encoding device 1 side, the correctness flag generation unit 14 compares the difference vector estimation code obtained from the difference vector code estimation unit 13 and the sign of the difference vector obtained from the image coding unit 10. , a correct/incorrect flag is generated that indicates "true" if the two are equal, and "false" if they are different.

Furthermore, on the video decoding device 2 side, the difference vector code determining unit 28 determines the difference vector estimation code as it is as the plus/minus sign of the difference vector when the correctness flag indicates "true", and when it indicates "false" , the sign obtained by inverting the estimated sign of the difference vector is determined as the sign of the difference vector.

(Principle of the present invention)
Here, the principle related to the process of estimating the sign of the difference vector in the first embodiment will be explained. FIGS. 5(a), (b), and (c) show a block of interest BKn and candidate vectors V _A , FIG. 3 is an explanatory diagram regarding blocks BK _A and BK _B corresponding to V _B and candidate vectors V _A and V _B , respectively.

In order to simplify the explanation of the principle of the present invention with reference to FIG. 5, the predicted vector is set to 0, and further, focusing only on the sign of the horizontal component of the difference vector, the video decoding device 2 calculates the positive and negative signs of the difference vector. The decoding operation and the effects of the present invention will be explained. In the explanation shown in FIG. 5, it is assumed that the positive sign of the difference vector indicates the right direction, and the negative sign of the difference vector indicates the left direction.

As shown in FIG. 5A, it is assumed that the block of interest BKn exists at the edge of the screen. Assume that the absolute value of a difference vector having a predetermined length is input (read) to this block of interest BKn.

As shown in FIG. 5B, first, the difference vector sign estimating units 13 and 27 calculate positive and negative candidate vectors V _A and V _B for the block of interest BKn (FIG. 3: Step S14). .

As shown in FIG. 5(c), next, the difference vector sign estimating units 13 and 27 calculate blocks BK _A and BK _B obtained by moving the block of interest BKn to the candidate vector V _A and the candidate vector V _B , respectively. (FIG. 3: Step S15).

In the example shown in FIG. 5(c), the block BK _A is located within the screen and the block BK _B is located outside the screen, so the difference vector sign estimating units 13 and 27 detect the outside of the screen BK _A and BK _B. The areas S _A and S _B of the regions are calculated (FIG. 3: Step S22).

Then, the difference vector sign estimation units 13 and 27 compare the area _SA and the area _SB (FIG. 3: step S23). In the example shown in FIG. 5(c), the area S _B of block BK _B that protrudes outside the screen (=area of block BK _B ) is larger than the area S _A that protrudes outside the screen of block BK _A (=0), The difference vector estimation sign of this block of interest BKn becomes "positive" (FIG. 3: Step S24).

On the video encoding device 1 side, if the estimated difference vector code obtained by the estimation process by the difference vector code estimator 13 is equal to the sign of the actual difference vector, it is determined to be true, and if it is different, it is determined to be false. A flag is generated, context-adaptive lossless compression processing is performed, and the flag is transmitted. For example, the video encoding device 1 transmits a correctness flag indicating true to the video decoding device 2.

On the video decoding device 2 side, when the correctness flag indicates true, the estimated difference vector sign is used as the sign of the difference vector, and when it indicates false, the sign obtained by inverting the estimated sign is used as the sign of the difference vector. Determine as a sign. For example, if the video encoding device 1 has transmitted a true/false flag indicating true to the video decoding device 2, the video decoding device 2 uses the difference vector estimation code as the plus/minus sign of the difference vector. Therefore, in the present example with reference to FIG. 5, the video decoding device 2 finally determines that the sign of the difference vector of this block of interest BKn is positive.

In this way, in the video encoding device 1 and the video decoding device 2 according to the present invention, the positive and negative signs of the difference vector are expressed by the correct/incorrect flag, and for the following two reasons, the video encoding device 1 and the video decoding device 2 perform compression using context adaptive reversible compression. is possible.

The first reason is that, in general, when a block indicated by a candidate vector protrudes outside the screen, the effect of motion compensation prediction decreases if the area of the block that protrudes outside the screen is large. For this reason, many motion vectors often do not point outside the screen. Therefore, in the "estimation process of the sign of the difference vector" according to the present invention, in the case where it is assumed that the sign of the difference vector of the block of interest BKn is "positive" (candidate vector V _A , block BK _A ), and when it is assumed that the sign is "negative" (candidate vector V _B , block BK _B ), and the code with the smaller area protruding outside the screen of each block BK _A , BK _B is set as the estimated code. Therefore, the probability that the correct/incorrect flag representing the correctness of the estimated code becomes "true" becomes high, and compression (reversible compression) becomes possible.

The second reason is that compression (reversible compression) is possible even in scenes where the assumption in the first reason above that "many motion vectors often do not point outside the screen" does not hold. An example is shown in FIG.

FIG. 6 is an example of an image obtained by panning the camera, and shows how the frame of interest F _N of the object is shifted to the left as a whole relative to the previous frame F _N-1 . For the target block BKn located at the edge of the screen in the target frame _FN , for example, as shown in the figure, the appropriate block as a reference destination for motion compensation prediction of this target block BKn is the block _BKA in the previous frame _FN-1. be. That is, the motion vector of the block of interest BKn points outside the screen. To simplify the explanation, if all predicted vectors are assumed to be 0, the sign of the difference vector will be positive.

In the "estimation process for the sign of the difference vector" according to the present invention, the difference vector sign estimating units 13 and 27 calculate candidate vectors V _A and V _B on the positive side and the negative side (FIG. 3: Step S14), A block BK A and a block BK _{B are calculated by moving the block of interest BKn to the candidate vector V A and the candidate vector V B , respectively (} FIG. 3: Step S15).

At this time, block BK _A has an area that protrudes outside the screen, whereas block BK _B remains within the screen. The areas S _{A and S B of} the areas outside the screen of A and BKB are calculated (FIG. 3: Step S22).

Subsequently, the difference vector sign estimation units 13 and 27 compare the area _SA and the area _SB (FIG. 3: step S23). In the example shown in FIG. 6, the area S _B of block BK _B that protrudes outside the screen is smaller than the area S _A that protrudes outside the screen of block BK _A , so the difference vector estimation sign of this block of interest BKn is "negative" (candidate vector V _B , block _BKB ) (FIG. 3: Step S25).

Therefore, on the video encoding device 1 side, since the estimated difference vector code obtained by the estimation process by the difference vector code estimator 13 is different from the sign of the actual difference vector, it is determined that the difference vector is false. A flag is generated, context-adaptive lossless compression processing is performed, and the data is transmitted.

Then, on the video decoding device 2 side, since the correctness flag indicates "false", the similarly estimated difference vector estimation sign indicating "negative" is inverted, and finally the sign of the difference vector of this block of interest BKn is determined to be positive or negative. The sign is determined to be "positive" (candidate vector V _A , block BK _A ).

In this way, for the block of interest BKn in the frame of interest _FN , while ultimately determining the correct "positive" (candidate vector V _A , block BK _A ) as the sign of the difference vector, the estimated sign of the difference vector is determined. As such, "negative" (candidate vector V _B , block _BKB ), which is the code with the smaller area protruding from the screen of each block BK _A and BK _B , is set as the estimated code, and the correct/incorrect flag is set as "false".

Similarly, when the blocks BKn(1), BKn(2), BKn(3), and BKn(4) located above the block of interest BKn located at the edge of the screen in the frame of interest _FN are set as blocks of interest, Each motion vector points outside the screen, and the correct/incorrect flag for each is "false".

Then, the video encoding device 1 and the video decoding device 2 perform context-adaptive reversible compression/decoding processing on the correctness flag related to the sign of the difference vector regarding the block of interest BKn. In the context-based reversible compression/decoding process, the compression/decoding processing is performed adaptively according to the values (i.e., the values of the correct/incorrect flags) of the surroundings of the block of interest BKn (for example, blocks directly above, upper right, upper left, etc., according to a predetermined context model). Reversible compression encoding/decoding is performed by determining the bit value. In the example shown in FIG. 6, many blocks with true/false flags that are "false" are lined up in the periphery, so when the true/false flags are "false", the compression effect increases and compression (reversible compression) becomes possible. In particular, on the video decoding device 2 side, it is possible to restore that the correct/incorrect flag is "false" for the block of interest BKn through context-adaptive reversible decoding processing, and finally the correct "correct" (candidate vector V _A , The block BK _A ) can be determined.

Therefore, according to the video encoding device 1 and the video decoding device 2 according to the present invention, the probability that the correct/incorrect flag becomes “true” increases, so that reversible compression of the correct/incorrect flag becomes possible, or a large number of “false” ” appears, there is a tendency for “false” blocks to gather around the block, so it is possible to compress the true/false flag using context-adaptive reversible compression.

In particular, in the process of estimating the sign of the difference vector in Example 1 shown in FIG. Since this corresponds to using a comparison of S _A and S _B ), it is effective from the viewpoint of compression effect if it is applied only to blocks located around the edge of the screen.

(Area where correct/incorrect flags are used in the frame image)
As an example of the video encoding device 1 and video decoding device 2 of the present embodiment, the setting control unit 18 in the video encoding device 1 and the setting control unit 24 in the video decoding device 2 control the block of interest in the frame image. Based on predetermined setting information, it is possible to control, depending on the position, an area in which the correct/incorrect flag is used and an area in which the plus/minus sign +/- is represented by 1/0 bits as in the conventional technique.

As described above, in the video encoding device 1 and the video decoding device 2 of the present embodiment, it is possible to switch the correct/incorrect flag after the lossless compression or the simply binarized positive/negative code based on the setting information. can.

More specifically, as an example below, the setting control unit 18 in the video encoding device 1 and the setting control unit 24 in the video decoding device 2 control the target block BKn from the area AR1 to the screen edge according to the setting information. The operation of switching the correct/incorrect flag or the simply binarized positive/negative sign for expressing the positive/negative sign of the difference vector based on whether or not it falls within AR8 will be described.

FIG. 7 shows areas in which correct/incorrect flags are used in the video encoding device 1 and video decoding device 2 according to an embodiment of the present invention, and the positive/negative sign +/- is expressed as 1/0 bits as in the conventional technique. FIG. 3 is an explanatory diagram of a frame image having a region where

As shown in FIG. 7, the frame _FN constituting the frame image can be separated into an area AR0 at the center of the screen and areas AR1 to AR8 within a predetermined range at the edge of the screen. The area AR0 is an area in which the plus/minus sign +/- is represented by bits of 1/0 as in the conventional technique. The areas AR1 to AR8 at the edges of the screen are areas where reversible compression/decoding processing based on the context of correct/incorrect flags is performed. Furthermore, different context models are set for each of the areas AR1 to AR8 at the edge of the screen.

These areas have widths D1, D2, D3, and D4 that are variable or fixed depending on the size of the frame _FN and the size of the basic unit (block called macroblock, CTU, etc.) that performs encoding processing. It can be specified by designating the video encoding device 1 and the video decoding device 2 in advance, or if the configuration information is transmitted, it can be specified by the configuration information. Furthermore, D1, D2, D3, and D4 may each have different values, or may have the same value. The widths D1, D2, D3, and D4 are determined based on the size of the basic unit (block called macroblock, CTU, etc.) that performs encoding processing, as an area where true/false flags indicating "true" or "false" tend to gather. It is preferable that the width be 1 to 3 times as wide.

Since the difference vector is a two-dimensional vector, it is expressed by two vectors: a horizontal component and a vertical component. Therefore, the setting control unit 18 in the video encoding device 1 and the setting control unit 24 in the video decoding device 2 determine whether the block of interest BKn falls within one of the areas AR1 to AR8 at the edge of the screen, as an example of the setting information. The correct/incorrect flag after reversible compression or the simply binarized sign can be switched for each component of the difference vector based on whether the difference vector is correct or not.

For example, when the block of interest BKn is located in areas AR3 and AR4 near the left and right sides of the screen, the setting control unit 18 in the video encoding device 1 performs context-adaptive reversible compression processing using the correct/incorrect flag only for the horizontal component of the difference vector. The positive and negative signs in the vertical direction are controlled so that +/- of the positive and negative signs are represented by bits of 1/0 as in the conventional technique.

Furthermore, when the block of interest BKn is located in the areas AR1 and AR2 near the top and bottom sides of the screen, the setting control unit 18 in the video encoding device 1 only controls the vertical component of the difference vector. Context-adaptive reversible compression processing is performed using the correct/incorrect flag, and the horizontal positive/negative sign is controlled so that +/- of the positive/negative sign is represented by a bit of 1/0, as in the conventional technique.

Furthermore, when the target block BKn is in the four corner areas AR5, AR6, AR7, AR8 of the screen, the setting control unit 18 in the video encoding device 1 uses the correct/incorrect flags for both the horizontal component and the vertical component, and performs a context-adaptive Control to perform reversible compression processing.

Similarly, the setting control unit 24 in the video decoding device 2 performs the reversible compression for each component of the difference vector based on whether the target block BKn falls within one of the areas AR1 to AR8 at the edge of the screen. The subsequent correct/incorrect flag or the simply binarized positive/negative sign can be switched.

For example, with reference to FIG. 8, a process of determining the sign of the difference vector in one embodiment by the setting control unit 24 in the video decoding device 2 will be described. FIG. 8 is a flowchart illustrating a process of determining the sign of a difference vector in an example in the video decoding device 2 according to an embodiment of the present invention.

First, the setting control unit 24 determines whether the block of interest BKn falls within a predetermined range at the left and right ends of the screen (that is, within the areas AR3, AR4, AR5, AR6, AR7, and AR8 near the left and right sides of the screen shown in FIG. 7). It is determined whether there is one (step S31).

Then, when the block of interest BKn does not fall within a predetermined range (within areas AR3, AR4, AR5, AR6, AR7, AR8) at the left and right ends of the screen (step S31: N), the block BKn is simply converted into a binary value as in the conventional technique. The positive/negative sign of the horizontal component of the difference vector is determined so as to have the positive/negative sign of the difference vector (step S32).

On the other hand, when the block of interest BKn falls within a predetermined range (within areas AR3, AR4, AR5, AR6, AR7, AR8) at the left and right ends of the screen (step S31: Y), the "sign of difference vector" according to the present invention is determined. The sign of the horizontal component of the difference vector is estimated by the ``estimation process'', and the sign of the horizontal component of the difference vector is determined using the correctness flag (step S33).

Next, the setting control unit 24 determines whether the target block BKn falls within a predetermined range at the top and bottom of the screen (that is, within the areas AR1, AR2, AR5, AR6, AR7, AR8 near the left and right sides of the screen shown in FIG. 7). (Step S34).

Then, when the block of interest BKn is not within a predetermined range (within areas AR3, AR4, AR5, AR6, AR7, AR8) at the left and right ends of the screen (step S34: N), the block BKn is simply converted into a binary value as in the conventional technique. The positive/negative sign of the horizontal component of the difference vector is determined so as to have the positive/negative sign of the difference vector (step S35).

On the other hand, when the block of interest BKn falls within a predetermined range (within areas AR3, AR4, AR5, AR6, AR7, AR8) at the left and right ends of the screen (step S34: Y), the "sign of difference vector" according to the present invention is determined. The sign of the horizontal component of the difference vector is estimated by the ``estimation process'', and the sign of the horizontal component of the difference vector is determined using the correctness flag (step S36).

Therefore, in the case of a block that uses the correct/incorrect flag for only one of the horizontal and vertical components of the difference vector, one correct/incorrect flag is read from the bitstream, and in the case of a block that uses the correct/incorrect flag for both the horizontal and vertical components. reads two correct/incorrect flags.

In the example shown in FIG. 8, an example was explained in which the sign of the horizontal component of the difference vector is determined and then the sign of the vertical component of the difference vector is determined. It is also possible to adopt a configuration in which control is performed such that the sign of the horizontal component is then determined.

In this way, the component for which the correct/incorrect flag is used is switched for each of the horizontal and vertical components of the difference vector based on whether the block of interest BKn falls within one of the areas AR1 to AR8 at the edge of the screen. be able to. For each of the horizontal and vertical components of the difference vector, the components for which correct/incorrect flags are used are determined in advance between the video encoding device 1 and the video decoding device 2, or included in the configuration information, and (including any one or more of a slice or tile header, a picture header, and a sequence header) and transmit it from the video encoding device 1 to the video decoding device 2.

Note that when the block of interest BKn is within the areas AR1 to AR8 at the edge of the screen, the setting information specifies the order in which the horizontal or vertical components of the difference vector are determined depending on the position of the block of interest BKn. You can also leave it there. This is related to the switching of the true/false flag after the reversible compression or the simply binarized positive/negative sign, and it is possible to uniquely identify the component in which the true/false flag is used according to the position of the block of interest BKn, and sequentially This has the advantage that extra processing such as determining which one is being used can be omitted, resulting in faster processing operations.

For example, the setting control unit 18 in the video encoding device 1 and the setting control unit 24 in the video decoding device 2 perform the process of estimating the sign of the difference vector so that the block of interest BKn is within the areas AR1 to AR8 at the edge of the screen. If it is closer to the left and right sides of the screen than the top and bottom sides of the screen, control is performed so that the sign of the horizontal component of the difference vector is first determined, and then the sign of the vertical component is determined.

In addition, the setting control unit 18 in the video encoding device 1 and the setting control unit 24 in the video decoding device 2 perform the process of estimating the sign of the difference vector so that the block of interest BKn is within the areas AR1 to AR8 at the edge of the screen. If the target block BKn is closer to the top and bottom sides of the screen than to the left and right sides, control is performed to first determine the sign of the vertical component of the difference vector, and then determine the sign of the horizontal component.

In addition, the setting control unit 18 in the video encoding device 1 and the setting control unit 24 in the video decoding device 2 perform the process of estimating the sign of the difference vector so that the block of interest BKn is within the areas AR1 to AR8 at the edge of the screen. If the block of interest is located at the same distance from the left and right sides and the top and bottom sides of the screen, the block of interest is placed in a predetermined order (for example, first find the sign of the horizontal component, then find the sign of the vertical component. control to determine the positive and negative signs of the horizontal and vertical components of the difference vector.

In addition, as a further modification, instead of the predetermined range of the screen edge, based on whether the block of interest BKn is adjacent to the top, bottom, left, and right sides of the screen, for each component of the difference vector, the true/false flag after the reversible compression or the simple You can switch the positive and negative signs of the binarized data. In particular, if the block of interest BKn touches only the top side of the screen, AR1, if it touches only the bottom side of the screen, AR2, if it touches only the left side of the screen, AR3, and if it touches only the right side of the screen, AR4, AR5 if it touches both the top and left sides of the screen, AR6 if it touches both the top and right sides of the screen, AR7 if it touches both the bottom and left sides of the screen, and AR7 if it touches both the bottom and right sides of the screen. It is preferable to control the block as a block that falls within the area of AR8 if it is within the area of AR8, and otherwise as a block that falls within the area of AR0.

(block referenced as context)
As described above, in the video encoding device 1 and the video decoding device 2 of the present embodiment, depending on the position of the block of interest in the frame image, the area where the correct/incorrect flag is used and the +/- sign of the plus/minus sign are determined as in the conventional technique. The area in which /- is expressed as a bit of 1/0 can be controlled based on predetermined setting information. Then, context-adaptive reversible compression/decoding processing is applied to transmit the correct/incorrect flag.

That is, as described above, the context adaptive reversible compression unit 15 in the video encoding device 1 of this embodiment and the context adaptive reversible decoding unit 26 in the video decoding device 2 specify a context model based on the focused block information. Then, context-adaptive reversible compression encoding/decoding processing is performed on the correct/incorrect flag.

In the context-adaptive reversible compression encoding/decoding process, for example, when using a video encoding method according to the MPEG-H HEVC/H.265 method, CABAC is used as a video encoding method according to the AVC/H.264 method. In some cases, CABAC or CAVLC can be used.

However, in the context model related to lossless compression/decoding of the correct/incorrect flag according to the present embodiment, there is a preferable example regarding which block around the block of interest is referred to as a context.

That is, in the context model according to this embodiment, the position of a block to be referred to as a context is determined in advance according to the position of the block of interest BKn in the screen. This can be expected to further improve compression efficiency.

More specifically, if the target block BKn is closer to the left and right sides of the screen than the top and bottom sides of the screen, the block directly above the target block BKn is referred to as a block to be referred to as a context depending on the position of the target block BKn on the screen. do. For example, as shown in FIG. 9(a), if the block of interest BKn is closer to the left side of the screen (distance d1) than the bottom edge of the screen (distance d2) (d1<d2), refer to the block RBK directly above the block of interest BKn. do.

Further, as a block to be referred to as a context depending on the position of the target block BKn in the screen, if the target block BKn is closer to the top and bottom sides of the screen than to the left and right sides of the screen, the block immediately to the left of the target block BKn is referred to. For example, as shown in FIG. 9B, if the block of interest BKn is closer to the bottom edge of the screen (distance d2) than the left edge of the screen (distance d1) (d1>d2), the block RBK immediately to the left of the block of interest BKn is refer.

In addition, when the target block BKn is located at an equal distance from the top and bottom sides of the screen than from the left and right sides of the screen, the blocks to be referred to as a context depending on the position of the target block BKn on the screen are the right left, right upper left, right upper left of the target block BKn, Reference is made to one or more predetermined blocks immediately above and immediately above to the right. For example, as shown in FIG. 9(c), when the block of interest BKn is equidistant from the left side of the screen (distance d1) and the bottom side of the screen (distance d2) (d1=d2), the block immediately to the left of the block of interest BKn Reference is made to one or more predetermined blocks among RBK1, the block RBK2 immediately above the left, the block RBK3 immediately above, and the block RBK4 immediately above the right.

In this way, one or more blocks are referenced as a context related to the lossless compression/decoding process, and adaptation is performed according to the CABAC or CAVLC method according to the value of each referenced block (i.e., the value of the correct/incorrect flag). It is possible to perform lossless compression/decoding.

(Example 2: Estimating the sign of the difference vector)
In the "process _for estimating the sign of the difference vector" in _the first embodiment shown in FIG. , an example has been described in which the corresponding blocks BK _A and BK _B are calculated, and the difference vector estimation code is determined based on their positional relationship and the areas S _A and S _B that protrude outside the screen.

As a modification of this example, the sign of the difference vector can be estimated using only the coordinates of the block, thereby making the process faster and reducing the processing load. Hereinafter, referring to FIG. 10, the processing load can be reduced and the processing speed can be further increased. FIG. 10 is a flowchart showing a process for estimating the sign of the difference vector in Example 2 in the video encoding device 1 and the video decoding device 2 according to the embodiment of the present invention.

Here, a process for estimating the sign of the horizontal component of the difference vector will be described.

First, as in the first embodiment, the difference vector sign estimation units 13 and 27 according to the second embodiment input (read) the absolute value of the difference vector for the block of interest (step S11), and the absolute value of the difference vector = 0. It is determined whether or not (step S12).

When the absolute value of the difference vector is 0 (step S12: Y), the difference vector sign estimation units 13 and 27 according to the second embodiment determine that the difference vector has no sign and end the estimation process, as in the first embodiment. (Step S13).

On the other hand, when the absolute value of the difference vector≠0 (step S12: N), the difference vector sign estimation units 13 and 27 according to the second embodiment, as in the first embodiment, candidate vectors V _A and V _B are calculated (step S14).
Candidate vector V _A = Predicted vector + absolute value of difference vector Candidate vector V _B = Predicted vector - absolute value of difference vector

Subsequently, the difference vector sign estimating units 13 and 27 according to the second embodiment calculate blocks BK _A and BK _B corresponding to the positive and negative candidate vectors V _A and V _B , respectively, in the first embodiment. , the coordinate x of the upper left pixel of the block of interest BKn, the width w of the block of interest BKn, and the width (screen width) W of the frame image are set (step S15').

Subsequently, the difference vector sign estimation units 13 and 27 according to the second embodiment determine whether "x+V _A ≧0, x+w+V _A ≦W, x+V _B ≧0, and x+w+V _B ≦W" is satisfied (step S16'). This process is an alternative process corresponding to the determination of whether the blocks BK _A and BK _B are both completely within the screen in the first embodiment (FIG. 3: Step S16).

When "x+V _A ≧0, x+w+V _A ≦W, and x+V _B ≧0, and x+w+V _B ≦W" is satisfied (step S16': Y), the difference vector sign estimation units 13 and 27 according to the second embodiment, The sign of the difference vector is estimated as a default value, and the estimated sign of the difference vector is determined as the default value (step S17). In this example, "positive" is used as the default value, but "negative" may be used as the default value.

When "x+V _A ≧0, x+w+V _A ≦W, and x+V _B ≧0, and x+w+V _B ≦W" is not satisfied (step S16': N), the difference vector sign estimation units 13 and 27 according to the second embodiment Then, it is determined whether "x+w+V _A ≦0, or x+V _A ≧W, and x+w+V _B ≦0, or x+V _B ≧W" is satisfied (step S18'). This process is an alternative process corresponding to the determination of whether both blocks BK _A and BK _B are completely outside the screen in the first embodiment (FIG. 3: Step S18).

When "x+w+V _A ≦0, or x+V _A ≧W" and "x+w+V _B ≦0, or x+V _B ≧W" is satisfied (step S18': Y), the difference vector sign estimation unit 13 according to the second embodiment , 27 compares "min(abs(x+w+V _A ), abs(x+V _A -W))" and "min(abs(x+w+V _B ), abs(x+V _B -W)" (step S19') . abs() is a _function that calculates the absolute value, and min() is a function that calculates the minimum value. This is an alternative process corresponding to the comparison of "the distance between the block _BKB and its nearest screen edge" (FIG. 3: step S19).

When "min(abs(x+w+V _A ), abs(x+V _A -W))" is larger than "min(abs(x+w+V _B ), abs(x+V _B -W)" (step S19': Y), the embodiment The difference vector sign estimating units 13 and 27 according to No. 2 determine that the estimated difference vector sign is negative (step S21).

Further, when "min(abs(x+w+V _A ), abs(x+V _A -W))" is smaller than "min(abs(x+w+V _B ), abs(x+V _B -W)" (step S19': N), The difference vector sign estimation units 13 and 27 according to the second embodiment determine that the difference vector estimated sign is positive (step S20).

Further, when "min(abs(x+w+V _A ), abs(x+V _A -W))" is equal to "min(abs(x+w+V _B ), abs(x+V _B -W)"), the difference vector according to the second embodiment The sign estimating units 13 and 27 determine the difference vector estimation sign=positive or negative, whichever is specified in advance (in the example shown in FIG. 10, the difference vector estimation sign=positive).

In addition, in the comparison related to step S19', when determining the difference vector estimation sign as the prespecified positive or negative one, the setting information indicated as the second default value (or as the commonly used default value) is set in the stream. It can be transmitted by being embedded in a header (including any one or more of a slice or tile header, a picture header, and a sequence header). However, when the second default value is determined in advance between the video encoding device 1 and the video decoding device 2, there is no need to transmit the second default value from the video encoding device 1 to the video decoding device 2, and the setting information is sent to the header. There is no need to embed it in.

On the other hand, when both steps S16' and 17' are not satisfied, the difference vector sign estimating units 13 and 27 according to the second embodiment calculate "max(abs(min(0, x+V _A )), max(W, x+w+V _A )-W)" and "max(abs(min(0, x+V _B )), max(W, x+w+V _B )-W)" are compared (step S23'). max() is a function that calculates the maximum value. This process is an alternative process corresponding to the comparison of area _SA and area _SB in Example 1 (FIG. 3: step S23).

"max(abs(min(0, x+V _A )), max(W, x+w+V _A )-W)" becomes "max(abs(min(0, x+V _B )), max(W, x+w+V _B )-W )" (step S23': Y), the difference vector sign estimation units 13 and 27 according to the second embodiment determine that the difference vector estimated sign is negative (step S25).

"max(abs(min(0, x+V _A )), max(W, x+w+V _A )-W)" becomes "max(abs(min(0, x+V _B )), max(W, x+w+V _B )-W )" (step S23': N), the difference vector sign estimation units 13 and 27 according to the second embodiment determine that the difference vector estimated sign is positive (step S24).

"max(abs(min(0, x+V _A )), max(W, x+w+V _A )-W)" becomes "max(abs(min(0, x+V _B )), max(W, x+w+V _B )-W )'', the difference vector sign estimating units 13 and 27 according to the second embodiment assume that the difference vector estimation sign = positive or negative, whichever is specified in advance (in the example shown in FIG. 10, the difference vector estimation sign = positive). decide.

In addition, in the comparison related to step S23', when determining the difference vector estimation sign as the prespecified positive or negative one, the setting information indicated as the third default value (or as the commonly used default value) is set in the stream. It can be transmitted by being embedded in a header (including any one or more of a slice or tile header, a picture header, and a sequence header). However, when the third default value is determined in advance between the video encoding device 1 and the video decoding device 2, there is no need to transmit the third default value from the video encoding device 1 to the video decoding device 2, and the configuration information is sent to the header. There is no need to embed it in.

The difference vector estimation code determined through steps S17, S20, S21, S24, and S25 is sent to the correctness flag 14 on the video encoding device 1 side shown in FIG. 1, and the difference vector code is determined on the video decoding device 2 side shown in FIG. It is output to the section 28 (step S26).

In this way, the difference vector sign estimation units 13 and 27 according to the second embodiment calculate the positive side and negative side candidate vectors V _A and V _B using the absolute value of the difference vector and the predicted vector, The sign of the difference vector is estimated based on a predetermined rule that is divided into cases according to the coordinates and size of the block of interest BKn, the candidate vectors V _A , V _B , and the positional relationship of the screen width, and the estimated sign of the difference vector is calculated. decide. In addition, as compared to the first embodiment, in the second embodiment, coordinate calculation is required instead of calculating the area, so that the rule can be simplified. Note that in FIG. 10, instead of using the functions abs(), min(), and max(), classification may be performed using an if statement.

Then, on the video encoding device 1 side, the correctness flag generation unit 14 compares the difference vector estimation code obtained from the difference vector code estimation unit 13 and the sign of the difference vector obtained from the image coding unit 10. , a correct/incorrect flag is generated that indicates "true" if the two are equal, and "false" if they are different.

Furthermore, on the video decoding device 2 side, the difference vector code determining unit 28 determines the difference vector estimation code as it is as the plus/minus sign of the difference vector when the correctness flag indicates "true", and when it indicates "false" , the sign obtained by inverting the estimated sign of the difference vector is determined as the sign of the difference vector.

Therefore, the video encoding device 1 and the video decoding device 2 each including the difference vector code estimation units 13 and 27 according to the second embodiment are the video encoding device each including the difference vector code estimation units 13 and 27 according to the first embodiment. 1 and video decoding device 2 can be obtained.

(Example 3: Estimating the sign of the difference vector)
As a further modification of the second embodiment, as shown in FIG. 11, steps S16', S18', and S19' in FIG. 10 are skipped, and step S23' is executed immediately after step S15' to simplify the process. However, in many cases, the same effect can be obtained as reversible compression/decoding regarding the sign of the difference vector.

The video encoding device 1 or the video decoding device 2 in each of the above embodiments can be configured by a computer, and a program for making each processing section of the video encoding device 1 or the video decoding device 2 function is preferably used. It can be used for. Specifically, a control unit for controlling each processing unit of the video encoding device 1 or the video decoding device 2 can be configured with a central processing unit (CPU) in a computer, and each processing unit can be operated. The storage section for appropriately storing programs necessary for this can be configured with at least one memory. That is, by causing such a computer to execute the program using the CPU, the functions of each processing section of the video encoding device 1 or the video decoding device 2 can be realized. Furthermore, a program for realizing the functions of each processing section of the video encoding device 1 or the video decoding device 2 can be stored in a predetermined area of the storage section (memory) described above. Such a storage unit can be configured with a RAM or ROM inside the device, or can also be configured with an external storage device (for example, a hard disk). Moreover, such a program can be configured as a part of software (stored in ROM or external storage device) on the OS used in the computer. Furthermore, a program for causing such a computer to function as each processing section of the video encoding device 1 or the video decoding device 2 can be recorded on a computer-readable recording medium. Moreover, each processing unit of the video encoding device 1 or the video decoding device 2 can be configured as a part of hardware or software, and each can be realized by combining them.

Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and can be modified in various ways without departing from the technical idea thereof. For example, in the above-described embodiment, rules regarding differential vector sign estimation processing are explained by exemplifying a specific order and calculation method. Various modifications such as high-precision arithmetic expressions (combination of coordinates and area, etc.) are envisioned.

In addition, in the example of the embodiment described above, for the center of the screen (FIG. 7: area AR0), the conventional technique performs a binarization process in which +/- of the plus/minus sign is represented by 1/0 bits, and switching is performed. However, the center of the screen (FIG. 7: area AR0) may also be compressed and transmitted using the correct/incorrect flag according to the present invention. In other words, even if compressed transmission is performed using correct/incorrect flags in the center of the screen (Fig. 7: area AR0), it is assumed that the probability of occurrence is unlikely to be biased in many cases, so improvement in compression efficiency may not be expected. In other words, there is no significant deterioration. Instead, there are advantages such as simplification of processing (reduction of mounting capacity) because the processing is unified regarding the transmission of the positive and negative signs of the difference vector. Therefore, the video encoding device and video decoding device according to the present invention are not limited to the above-described embodiments, but are limited only by the claims.

According to the present invention, reversible compression is possible with respect to the positive and negative signs (+, -) of a difference vector in a video encoding method using motion compensation prediction, and compression efficiency is improved. Useful for device applications.

1 Video encoding device 10 Image encoding unit 11 Motion compensation prediction unit 12 Difference vector generation unit 13 Difference vector code estimation unit 14 True/false flag generation unit 15 Context adaptive reversible compression unit 16 Positive/negative binarization unit 17 Switching unit 18 Setting control Unit 19 Stream generation unit 20 Stream reading unit 21 Image decoding unit 22 Difference vector restoration unit 23 Motion compensation prediction unit 24 Setting control unit 25 Switching unit 26 Context adaptive reversible decoding unit 27 Difference vector code estimation unit 28 Difference vector code determination unit 29 Positive/negative determining section

Claims (6)

A video encoding device that encodes a video using a video encoding method using motion compensated prediction,
Difference vector generation means for generating a difference vector based on motion compensated prediction for a predetermined block within the frame of the video;
Determining the estimated sign of the difference vector by estimating the sign of the difference vector according to a predetermined rule based on the predetermined block, the absolute value of the difference vector, and a predicted vector related to the difference vector. a difference vector sign estimation means for
correct/incorrect flag generating means for comparing the positive/negative sign of the difference vector with the estimated sign of the difference vector to generate a correct/incorrect flag indicating whether the two match;
a context-adaptive reversible compression means for performing reversible compression processing on the correct/incorrect flag ;
The difference vector sign estimating means is
The area of the first block is moved according to the first candidate vector when the sign of the difference vector is positive, and the second candidate vector when the sign of the difference vector is negative. and a second block area obtained by moving the area of the predetermined block accordingly;
An estimated sign of the difference vector is determined in accordance with a result of determining whether each of the first block region and the second block region has a region that protrudes outside the frame.
A video encoding device characterized by: 2. The video encoding apparatus according to claim 1 , wherein the reversible compression process is adapted to a context depending on the position of the predetermined block. a stream reading means for inputting and reading a stream and extracting an absolute value of a difference vector and a correct/incorrect flag subjected to reversible compression processing for a predetermined block in a frame to be decoded;
Determining the estimated sign of the difference vector by estimating the sign of the difference vector according to a predetermined rule based on the predetermined block, the absolute value of the difference vector, and a predicted vector related to the difference vector. a difference vector sign estimation means for
context-adaptive reversible decoding means for generating a decoded correct/incorrect flag by performing reversible decoding processing on the correct/incorrect flag subjected to the reversible compression processing;
When the decoded correct/incorrect flag indicates a match between the positive/negative sign and the estimated code, the estimated code is used as the positive/negative sign of the difference vector of the predetermined block, and the mismatch between the positive/negative sign and the estimated code is determined. When indicated, a difference vector sign determining means for determining a sign obtained by inverting the estimated sign as the positive or negative sign of the difference vector;
In order to restore the image of the predetermined block, the difference vector of the predetermined block in the frame to be decoded is calculated using the absolute value of the extracted difference vector and the sign of the determined difference vector. A difference vector restoring means for restoring ,
The difference vector sign estimating means is
The area of the first block is moved according to the first candidate vector when the sign of the difference vector is positive, and the second candidate vector when the sign of the difference vector is negative. and a second block area obtained by moving the area of the predetermined block accordingly;
An estimated sign of the difference vector is determined in accordance with a result of determining whether each of the first block region and the second block region has a region that protrudes outside the frame.
A video decoding device characterized by: 4. The video decoding apparatus according to claim 3 , wherein the reversible decoding process is adapted to a context depending on the position of the predetermined block. A program for causing a computer to function as the video encoding device according to claim 1 or 2 . A program for causing a computer to function as the video decoding device according to claim 3 or 4 .

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