CN1129322C - Variable block matching motion estimation apparatus - Google Patents

Abstract

The present invention relates to a device for detecting a motion vector between the current frame and a previous frame in a video signal according to a block matching motion estimation method, which comprises a variable block forming part and a motion estimating part, wherein the variable block forming part is used for defining a variable search block from the current frame, the variable search block is expanded from a selected search block of a smooth picture in the current frame, and the smooth picture does not have a target edge line; the motion estimating part is used for estimating the motion of the variable search block relative to all candidate blocks contained in the previous frame to provide a plurality of motion vectors and a plurality of error functions, and the motion vectors and the error functions are corresponding to the variable search block. The motion vectors represent the displacement of pixels between the search block and one candidate block obtaining one minimum-error function.

Description

Variable block matching motion estimation apparatus

Technical field

The present invention relates to be used in a kind of motion estimation apparatus in the image signal encoding system; More specifically, relate to a kind of motion estimation apparatus that detects the motion vector of a variable-block according to a kind of block matching algorithm.

Background technology

When representing with digital form to comprise picture intelligence of a sequence image " frame ", the data that generate considerable amount need transmission, especially in the situation of high-definition television system.Yet,,, to compress or reduce data quantity transmitted inevitably in order to send the numerical data of these considerable amount by this limited frequency bandwidth because the available frequency bandwidth of a traditional transmission channel is limited.In various video compression technologies, the motion compensation interframe coding techniques that a kind of time redundancy with the vision signal between the frame of video of two adjacency is used for Signal Compression is one of known effective compress technique.

In the motion compensation interframe encoding scheme, current frame data is to predict from the frame data of front according to a kind of estimation of the motion between current and previous frame.The two-dimensional motion vector of the displacement of the pixel between the motion of this estimation available expression front and the present frame is described.

One of motion vector estimation scheme that proposed in the present technique is a block matching algorithm.According to block matching algorithm, a present frame is divided into a plurality of equal-sized search block.The size of a search block is usually in the scope between 8 * 8 and 32 * 32 pixels.In order to determine displacement, carry out similitude calculating between each in the search block of present frame and a bigger usually field of search that is included in the former frame in a plurality of equal-sized candidate blocks from one of present frame given search block.In carrying out similitude mensuration, there are many error functions can supply to utilize, such as MSE (mean square error) or MAE (mean absolute error).

According to definition, motion vector is represented search block and is drawn displacement between the candidate blocks of a smallest error function value.In receiver, utilize then this motion vector from former frame on the basis of block-by-block picture of reconstruct.

In the motion estimation on this block-by-block basis, it is desirable or easily utilizing equal-sized search block.Sometimes, has one on the some adjacent piece in present frame without any the level and smooth image mode of a target in sideline or wherein have only slight sideline.In last situation, block matching motion estimation may draw different motion vector mutually for each piece; And in the situation of back, may generate an identical motion vector of a motion vector with the smooth picture pattern that does not have the sideline.

Summary of the invention

Therefore, a main purpose of the present invention is for providing a kind of by utilizing a kind of variable piece can accurately detect the improved motion estimation apparatus of a motion vector.

According to the present invention, the present frame that utilizes a kind of block matching motion estimation method to detect vision signal and a kind of device of the motion vector between the former frame are provided, present frame wherein is divided into some equal-sized search block, former frame then is the field of search that is divided into corresponding number, each field of search has the candidate blocks of a plurality of described equal sizes, this device comprises: a variable-block forms part, be used for from variable search piece of current block definition, described variable search piece is not have the search block of the choosing expansion of a smooth picture piece in target sideline to form from present frame; And motion estimation part, the motion that is used for estimating this variable search piece with respect to each candidate blocks to be providing a corresponding with it motion vector and error function, and described motion vector is represented this search block and drawn the displacement of the pixel between the candidate blocks of smallest error function value.

Description of drawings

From the description of the preferred embodiment that provides below in conjunction with accompanying drawing, above-mentioned and other purpose of the present invention and feature will be conspicuous, in the accompanying drawing:

Fig. 1 illustrates the schematic block diagram that is used for according to the variable-block motion vector determinator of a kind of movement evaluation system of the present invention;

Fig. 2 illustrates the more detailed block diagram that the variable-block shown in Fig. 1 forms part; And

Fig. 3 A and 3B represent to illustrate the exemplary diagram of a variable-block of expansion on the pixel basis.

Embodiment

Referring to Fig. 1, wherein show a preferred embodiment that is included in a kind of variable-block motion vector determinator in a kind of motion estimation scheme, this scheme utilization frame in succession, promptly to be adjacent frame be former frame to present frame, between redundancy realize tangible data compression.This is to say, may exist the difference by the displacement or the motion initiation of a target between present frame and former frame; Yet this difference can be confined in the interior relatively little zone of a frame.Therefore, there is no need whole pictorial data of present frame are sent to a receiver (not shown).Otherwise, be that motion vector is just enough as long as send displacement information.Then, in the former frame the frame memory of receiver in its pictorial data is stored in this receiver, utilize these motion vector reconstruct present frames.Current frame signal offers variable-block by a circuit 12 and forms part 100.Variable-block forms part 100 and is used for present frame is divided into some equal-sized search block of carrying out the piece coupling a sequence that are ready to use in.In Fig. 3 A, the present frame of describing as a reference number 200 is depicted as and has the search block S1 to S20 that separates such as 20 generally, and each piece comprises H * V pixel.In order to illustrate, the H of each the piece pixel in the present frame 200 is the number 16 that equates with the V both.Moreover, variable-block forms the search block that part 100 sequentially selects not comprise in the expression present frame a level and smooth picture block in target sideline, and on the basis of pixel one by one the selected search block of expansion till the border of search block comprises a sideline.From Fig. 3 B as seen, when selective sequential during such as S7 and these two search block of S14, just search block S7 and S14 are expanded to respectively till the sideline portion boundary E7 and E14 that comprises target 202 and 204.

The pixel block of each expansion is sequentially offered some compatible portion 41 to 49.According to the present invention, the piece that can be expansion calculates a variance (variance) and detects whether comprise a sideline, and this point will further describe with reference to Fig. 2 below.

Fig. 2 illustrates the more detailed block diagram that variable-block forms part 100.In order to select the search block of an expression smooth picture, variable-block forms part 100 and by a series of formation stages (wherein only exemplarily showing three 111,112 and 119 in them) present frame on the circuit 12 is divided into some search block, as shown in Fig. 3 A.Form in the stage 111,112 and 119 at each piece, pixel ground of per step increases progressively expansion to a search block from step 0 to n on its level and vertical direction.More specifically, the search block of H * V pixel mode of first formation stage 111 generation; Second formation stage 112 is extended to this search block the pattern of (H+1) * (V+1) individual pixel; And last piece forms the search block that the stage 119 generates (H+N) * (V+N) individual pixel mode.Form stages 111 to 119 generation by piece and be fed to a variable-block selector 160 and a series of variance detector 121 to 129 with the search block of expanding, whether the variance that they calculate these search block respectively wherein exists the sideline to detect.Each variance that variance detector 121 to 129 is calculated is defined as follows: $\mathrm{var}=\frac{1}{\mathrm{EH}\×\mathrm{EV}}\underset{i=1}{\overset{\mathrm{EH}}{\mathrm{\Σ}}}\underset{j=1}{\overset{\mathrm{EV}}{\mathrm{\Σ}}}(I(i,j)-\mathrm{mean}{)}^2$ Wherein var represents the variance of the search block of an expansion; EH * EV is the size of an extension blocks; (i j) is (i, j) intensity level of the pixel on of coordinate in the extension blocks to I; Mean then represents the average level of the pixel in the extension blocks.

Average level is defined as follows: $\mathrm{mean}=\frac{1}{\mathrm{EH}\×\mathrm{EV}}\underset{i=1}{\overset{\mathrm{EH}}{\mathrm{\Σ}}}\underset{j=1}{\overset{\mathrm{EV}}{\mathrm{\Σ}}}I(i,j)$

The whole variances that calculate of the search block of the expansion of auto-variance detector 121 to 129 act on the variance selector 150 in the future.Variance selector 150 compares variance and a predetermined threshold value of the search block of these expansions.According to the present invention, this predetermined threshold value be chosen to be have greater than and approach to represent the value of variance of the search block of smooth picture most.Thereby variance selector 150 is selected a variance that satisfies this threshold value, and the selection signal of variance that generates this selection of indication is to variable-block selector 160.This variance can be selected so that the variance of selecting is minimum greater than the size of the search block of this threshold value and corresponding expansion in the search block that has greater than the expansion of the variance of this threshold value.Have variable-block selector 160 these selection signals of response of a traditional multiplexer, select the search block corresponding with selected variance.As shown in Figure 1, the search block of the expansion of selection and size thereof are offered piece compatible portion 41 to 49 and are offered the field of search by circuit L120 by circuit L110 respectively and formed part 10 and candidate blocks formation part 21 to 29 from variable-block selector 160.

Referring to Fig. 1, at this moment, will be stored in a former frame in the memory (not shown) by a circuit 13 and present to a field of search formation part 10.In response to the size of the search block of the expansion of selecting, this field of search forms the common bigger field of search in former frame of part 10 definition, searches for whereby or comparison.

Determined the field of search in field of search formation part 10 after, the candidate blocks that also field of search data is acted on corresponding number forms on the part, only exemplarily shows wherein three 21,22 and 29 among Fig. 1.Form in the part in each candidate blocks, size in response to the search block of the expansion of selecting, when a pixel location is flatly moved in the field of search of the certainly top-left position of search block at every turn, move a scan line by the field of search vertically downward then at every turn, in this field of search of final arrival, till the position, bottom right the time, just from this field of search, generated candidate's pixel.In this field of search of determining, just formed all possible candidate blocks of the search block size of expansion with selection.Extrapolate relative displacement then, and offer a multiplexer 60 by circuit 31 to 39 as a motion vector of this candidate blocks subsequently corresponding to each candidate blocks of the position that forms the search block that part 100 provides by variable-block.

Also the pixel data of each candidate blocks is formed part 21 to 29 from this candidate blocks respectively and offer each piece compatible portion 41 to 49.In this piece compatible portion 41 to 49 respectively, calculate the search block that forms part 100 from variable-block with from the error function between the candidate blocks of this candidate blocks formation part 21 to 29 respectively.Traditionally, carry out the intensity level between the corresponding pixel of search block and candidate blocks or the comparison of luminous intensity, to draw the error function of this candidate blocks.This error function is represented the similarity degree between the candidate blocks of search block and selection.

To act on from all error functions of piece compatible portion 41 to 49 on the minimal error detector 50.This minimal error detector 50 is these error functions relatively, therefrom select an error function with minimal error.

The selection signal of the piece that indication of minimal error detector 50 outputs is corresponding with this smallest error function is to motion vector selector 60.Motion vector selector 60 with a traditional multiplexer is selected the displacement vector of the candidate blocks corresponding with smallest error function.As mentioned above, if candidate blocks has minimum error function, this candidate blocks is similar in appearance to search block; As a result, just select the displacement vector of this candidate blocks as motion vector.

In this connection, the motion compensation that will carry out in a transmitter and receiver reaches with respect to this search block rather than extension blocks, and the latter's main purpose is a moving displacement that is used for accurately measuring between a search block and the candidate blocks.

Though the present invention shows with reference to certain embodiments and describe, person skilled in the art person will be understood that, can make many changes and correction under the condition that does not break away from defined spirit of the present invention and scope in the appended claims.

Claims (6)

1, a kind of in vision signal present frame and former frame between adopt the block matching motion estimation method, detect a search block (S7 of this present frame; The device of motion vector S14), wherein this present frame is divided into the search block (S7 of a plurality of H * V pixel size; S14), and former frame is divided into the field of search of corresponding number, and each field of search has a plurality of candidate blocks, it is characterized in that this device comprises:

(a) if be used for search block (S7; S14) be the interior smooth picture piece that does not have the target sideline of present frame, detect this search block (S7; Search block (the E7 of expansion S14); E14) device (100), the wherein search block (E7 that should expand; E14) by expanded search piece (S7; Therefore S14) sideline of border in it comprises it is and detected and be (H+i) * (V+i) pixel, and I is a nonnegative integer;

(b) be used to generate search block (E7 corresponding to this expansion; The device (10) of a field of search E14);

(c) be used for providing the device (21-29) of the candidate blocks of (H+i) * (V+i) pixel from this field of search;

(d) be used for candidate blocks, search block (E7 that motion estimation should expansion with respect to these (H+i) * (V+i) pixels; E14) so that the search block (S7 that treats the passive movement compensation to be provided; The device of motion vector S14) (41-49,50,60), this motion vector is illustrated in the search block (E7 of this expansion; E14) and the displacement that draws the pixel between the candidate blocks of smallest error function in this block matching algorithm.

2, the device of claim 1, the wherein said search block (E7 that is used to detect expansion; E14) dress (100) comprising:

(a1) be used on the basis of pixel one by one expanded search piece (S7 on level and vertical direction; S14), thus produce N+1 search block (E7 that expands; E14) device (111-119), the search block (E7 of this expansion; E14) have the size of scope from H * V pixel to (H+N) * (V+N) individual pixel, N is a positive integer;

(a2) be used to calculate the respectively search block (E7 of expansion; The device of variance E14) (121-129); And

(a3) be used for according to one the expansion search block (E7; E14) variance determines whether include this sideline in it, thereby selects the search block (E7 of the expansion of (H+i) * (V+i) pixel; E14) as a search block (E7 who expands with this sideline; E14).

3, the device of claim 1, should determine wherein that device (150,160) comprising:

(a31) be used for each variance and a predetermined threshold value are compared the search block (E7 that indicates the expansion of being somebody's turn to do (H+i) * (V+i) pixel to generate; The device (150) of a selection signal E14); And

(a32) be used for being somebody's turn to do the search block (E7 of the expansion of (H+i) * (V+i) pixel in the search block selection of N+1 expansion; E14) device (160).

4, the device of claim 3 wherein is somebody's turn to do the search block (E7 of the expansion of (H+i) * (V+i) pixel; E14) corresponding to the search block that has greater than the expansion of the minimum in the search block of the expansion of the variance of this predetermined threshold.

5, arbitrary device among the claim 2-4, variance wherein is defined as follows: $\mathrm{var}(i,j)=\frac{1}{\mathrm{EH}\×\mathrm{EV}}$ $\underset{i=1}{\overset{\mathrm{EH}}{\mathrm{\Σ}}}\underset{j=1}{\overset{\mathrm{EV}}{\mathrm{\Σ}}}(I(i,j)-\mathrm{mean}{)}^2$ Wherein Var represents the search block (E7 of an expansion; E14) variance; EH * EV is the search block (E7 of this expansion; E14) size; (i j) is the search block (E7 of this expansion to I; E14) in coordinate (i, j) intensity level of the pixel on; I and j are respectively the positive integers of indication one level and a vertical coordinate; Mean then represents the search block (E7 of this expansion; E14) average level.

6, the device of claim 5, wherein the average level of the search block of this expansion is defined as follows: $\mathrm{mean}=\frac{1}{\mathrm{EH}\×\mathrm{EV}}\underset{i=1}{\overset{\mathrm{EH}}{\mathrm{\Σ}}}\underset{j=1}{\overset{\mathrm{EV}}{\mathrm{\Σ}}}I(i,j)$

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