CN101184225A - Spatial resolution transformation based video switch encoding method - Google Patents

Abstract

The invention discloses a video switch encoding method based on the spatial resolution transformation, which can re-estimate the motion vector the video flow after the code conversion by utilizing the motion information of the video flow before the code conversion and the DCT direct current coefficient of discrete cosine transform; the method is implemented in a pixel field; when in space field sampling, an average mode of N<2> pixel value is selected; a greater DCT direct current coefficient is selected as a judgment flag of macroblock activity; each macroblock of the video flow after the code conversion is corresponding to the N<2> macroblock of the video flow before the code conversion; the motion vector of the corresponding macroblock in the video flow after the code conversion is calculated by utilizing the motion vector Vi of the N<2> macroblock and the motion vector Vnj of the 4(N+1) adjacent macroblock, wherein N is a natural number with N is more than or equal to 2. The invention can reduce the calculated amount in the process of video switching coding greatly and improve the speed of coding. Furthermore, the invention can obtain a reconstructive video image quality from a matching method of full search block.

Description

Video transformation coding method based on spatial resolution transformation

Technical field

The present invention relates to field of video compression, relate in particular to a kind of video transformation coding method based on spatial resolution transformation.

Background technology

Video transformation coding can be understood as the conversion from a kind of video compression format to another kind of video compression format, here said form comprises the sentence structure of code stream and the relevant parameter in the code stream, as encoder bit rate, video image spatial resolution, temporal resolution, to adaptive capacity of the network bandwidth etc., its essence is exactly for the different bandwidth situation that adapts to transmission network or according to the decoding capability of client, a kind of video flowing of compressed format is converted to the video flowing of of the same race or another kind of compressed format.

Scalable video coding be another kind of with multilayer the mode compressed video and according to the coding method of wherein suitable which floor of the situation of change transmission of the network bandwidth.It is compressed into a basic layer and several enhancement layers with original video data, and basic layer must guarantee all transmission, and bandwidth is wide more, the enhancing number of plies that can transmit is just many more, reconstruction video picture quality is good more, and enhancement layer depends on basic layer, does not have basic layer to have many again enhancement layers also of no use.The scalable video coding method mainly contains the spatial domain layering, the time domain layering, SNR (Signal toNoise Ratio, signal to noise ratio) layering, FGS (Fine Granularity Scalability, meticulous layering) but method such as, it is by once encoding, just can generate the code stream of one road suitable multiple channel circumstance, thereby its flexibility is higher than video transformation coding method, but extending video requires decoder to support the multilayer decoding, this complex decoding function is not easy to be supported on the handheld terminal of the coming years, its Rate Control mode is more complex than video transformation coding far away in addition, cause the computational complexity of streaming media server end to improve, and because layering causes header to increase, it is poor that the reconstruction video picture quality that this coded system obtains is compared with the reconstruction video picture quality that video transformation coding under identical bandwidth condition obtains.Multiple description coded is a kind of original video to be encoded into multi-path video stream, the broadcast of all can decoding separately of wherein any one road video flowing, merging by the multipath decoding video flowing obtains better reconstructed image quality and strengthens the adaptability of video flowing to network, but its implementation complexity is very high, and the fluctuation of reconstruction video picture quality is bigger usually.Therefore, the scalable video coding method is compared with video transformation coding method, and the computational complexity height is of limited application.

Continuous development along with mobile communication, the wireless access bandwidth is more and more higher, watch video more and more noticeable by the less handheld terminal of screen, the continuous development of multimedia retrieval simultaneously also requires the enough narrower bandwidth of energy, the less space of a whole page to browse partial video information, therefore need do deep research to the spatial resolution switch technology of encoded video streams.

The spatial resolution down conversion method of traditional encoded video streams is to video flowing to be converted decoding earlier, carry out to down-sampling in pixel domain then, encode at last, yet because the amount of calculation of estimation is very big, therefore make that this transform coding amount of calculation is very big, the quick revaluation method of macroblock motion vector behind the down conversion of many acquisitions spatial domain occurs.In the inter-frame encoding frame of video flowing to be converted, if each macro block becomes the piece of a 8*8 size, the motion vector of simultaneously original macro block after down-sampled by 1/4th spatial domains Divided by 2 motion vectors that just become this 8*8 piece, then obtain macroblock motion vector in the conversion rear video stream inter-frame encoding frame

The simplest method is exactly that the motion vector of four 8*8 pieces that constitute this macro block is asked on average (MEAN), sees formula (1-1).If it is identical to constitute the value of the horizontal component of motion vector of four 8*8 pieces of this macro block and vertical component, it is fully suitable adopting this method so, but when the motion vector of four 8*8 pieces that constitute this macro block was incomplete same, this method can produce very big error.Based on this, document " Adaptive motion-vector resampling for compressed video downscaling " adopts adaptive motion vector method for resampling (AMVR), promptly obtains the motion vector of down-sampled back, spatial domain macro block with weighted-average method The weight of each motion vector

Equal before the conversion of its correspondence in the video flowing 4 8*8 pieces in the macro block through the number A of the non-zero ac coefficient behind the dct transforms _i(value after the normalization) sees formula (1-2).Document " Motion vector re-estimation for fast video transcoding fromMPEG-2to MPEG-4 " has proposed the another kind of method of obtaining macroblock motion vector behind the down-sampling of spatial domain, be called median method (MEDIAN), from the motion vector of four down-sampled preceding macro blocks in spatial domains

In choose with other three motion vectors apart from that motion vector of minimum divided by 2 motion vectors as down-sampled back gained macro block See formula (1-3).Document " Modified predictive motion estimation forreduced-resolution video from high-resolution compressed video " proposes the motion vector with four down-sampled preceding macro blocks in spatial domains

And average carries out estimation, if the sad value that obtains by certain motion vector is zero, then with this motion vector as final motion vector Otherwise obtain a new motion vector by formula (1-4)

The sad value that this vector is obtained compares with five sad values that obtain before then, and that motion vector of selecting the sad value minimum is as final motion vector

${\stackrel{\&RightArrow;}{v}}_s=\left(\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}{\stackrel{\&RightArrow;}{v}}_i\right)/8---(1-1)$

${\stackrel{\&RightArrow;}{v}}_s=(\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}{A}_i\&times;{\stackrel{\&RightArrow;}{v}}_i)/2---(1-2)$

$d_i=\underset{\underset{j\&NotEqual;i}{j=1}}{\overset{4}{\mathrm{\&Sigma;}}}|{\stackrel{\&RightArrow;}{v}}_i-{\stackrel{\&RightArrow;}{v}}_j|---(1-3)$

${\stackrel{\&RightArrow;}{v}}_{\mathrm{ni}}=\left(\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}\frac{1}{\mathrm{SA}{D}_i}{\stackrel{\&RightArrow;}{v}}_i\right)/\left(\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}\frac{1}{{\mathrm{SAD}}_i}\right)---(1-4)$

Above-mentioned literature research the revaluation method of rapid movement vector and the replacement criteria of motion vector in the video resolution transform coding process of relevant space, but the reconstruction video picture quality that their obtain and not fully up to expectations.

In addition, in another piece Chinese patent (applying date: 2005-12-22 that the inventor has applied for; Application number: 200510122589.3), the method (hereinafter to be referred as LLA) that a kind of movable information that utilizes adjacent eight macro blocks carries out the space video transformation coding is proposed, though this method can obtain reconstruction video quality preferably, its video conversion effect when video motion is violent is relatively poor.

Summary of the invention

For overcoming the deficiencies in the prior art, the object of the present invention is to provide a kind of video transformation coding method based on spatial resolution transformation, it can greatly reduce the amount of calculation in the video transformation coding process, improve coding rate, and obtain to approach the reconstruction video picture quality of full search block matching process.

To achieve these goals, the invention provides a kind of video transformation coding method based on spatial resolution transformation, by utilizing the DCT DC coefficient of the movable information in the video flowing and discrete cosine transform before the transform coding to reappraise the motion vector of transform coding rear video stream, described method is carried out in pixel domain, selects N when the spatial domain is down-sampled for use ²The mode that is averaged of some pixel value is selected the judgement symbol of big DCT DC coefficient as the macro block activity, each macro block that the transform coding rear video flows corresponding to transform coding before the N of video flowing ²Individual macro block utilizes described N ²The motion vector of individual macro block And the motion vector of the individual adjacent macroblocks of 4 (N+1) Calculate the motion vector of respective macroblock in the transform coding rear video stream Wherein N is a natural number, and N 〉=2.

N before the method according to this invention, the transform coding of the macro block correspondence behind the described transform coding ²In the individual macro block, if there is any one macro block to adopt intraframe coding method, then the macro block behind the transform coding adopts intraframe coding method, and the macroblock encoding process behind the transform coding finishes.

N before the method according to this invention, the transform coding of the macro block correspondence behind the described transform coding ²In the individual macro block, if adopt intraframe coding method without any a macro block, then the macro block behind this transform coding is adopted inter-frame encoding, the motion vector of the macro block behind the described transform coding is calculated by following formula (a) and obtains:

${\stackrel{\&RightArrow;}{v}}_s=(r\&times;{\stackrel{\&RightArrow;}{v}}_i+(1-r)\underset{j=1}{\overset{12}{\mathrm{\&Sigma;}}}{w}_{\mathrm{nj}}\&times;{\stackrel{\&RightArrow;}{v}}_{\mathrm{nj}})/2---\left(a\right)$

In the described formula (a), r,

w _NjValue mode as follows:

If described N ²Individual macro block

All equate, so choose N ²Arbitrary in the individual macro block

In following formula

Value, r=1;

If described N ²Individual macro block

All unequal, choose N ²The macro block of residual error DCT DC coefficient maximum in the individual macro block

In following formula

Value, and r=0.75, at this moment, if having the motion vector of n macro block to obtain in the individual adjacent macroblocks of 4 (N+1), w then _Nj=1/ (4N+4-n), if the motion vector of the individual adjacent macroblocks of 4 (N+1) all can't obtain, w then _Nj=0;

If above-mentioned situation all is false, choose N ²The macro block of residual error DCT DC coefficient minimum in the individual macro block In following formula

Value, make its overall movement trend that approaches object, and r=1.The method according to this invention further comprises according to the N before the transform coding of the macro block correspondence behind the transform coding ²The motion vector of individual macro block

Situation, select suitable search window right Upgrade:

If described N ²Individual macro block All equate, show the N that the macro block behind the transform coding comprises ²Individual 8*8 piece has identical movement tendency, and it is right not need

Upgrade;

If described N ²Individual macro block

All unequal, search box size is chosen for ± and 2;

If above-mentioned situation all is false, to choose less relatively search window it is upgraded, search box size is chosen for ± and 1.

The present invention by transform coding before the DC coefficient that obtains of movable information in the video flowing and dct transform reappraise the motion vector of transform coding rear video stream, adopt the motion vector formula of macro block of inter-frame encoding coding and right behind the transform coding

Upgrade, thereby can greatly reduce amount of calculation in the video transformation coding process, improve coding rate, and acquisition approaches the reconstruction video picture quality of full search block matching process, and can reduce network bandwidth variation effectively to rebuilding the influence of video image quality, improve utilization of network bandwidth, guarantee the extensibility and the interactivity of video flowing simultaneously, splendid visual experience is provided.

Description of drawings

Fig. 1 is the schematic diagram of the estimation of motion vectors in the spatial resolution video transformation coding of the present invention.

Fig. 2 is the schematic diagram of DC DC coefficient correspondence position of the present invention.

Fig. 3 be video sequence of the present invention when using different spatial domains transformation coding method PSNR change schematic diagram.

Embodiment

In order to make purpose of the present invention, technical scheme and advantage clearer,, the present invention is further elaborated below in conjunction with drawings and Examples.Should be appreciated that specific embodiment described herein only in order to explanation the present invention, and be not used in qualification the present invention.

The present invention proposes a kind of video transformation coding method based on spatial resolution transformation (Spatial FastMotion Vector Reestimate, SFMVRE), this method reappraises the motion vector of transform coding rear video stream by utilizing the movable information in the video flowing and dct transform obtain before the transform coding DC coefficient, can reduce the amount of calculation in the video transformation coding process, improve coding rate, and obtain to approach the reconstruction video picture quality of full search block matching process.It may be noted that, this method is handled and is all carried out in pixel domain, the main cause of carrying out at frequency domain is not that the frequency domain video transform coding is based upon the linearisation of movement compensation process, the truncation funcation before the considered frame buffer memory not, DCT/IDCT (Inverse Discrete CosineTransformation, inverse discrete cosine transform) conversion has in encoding-decoding process behind consistent arithmetic precision and the transform coding under corresponding to four assumed conditions of coding mode before each macroblock encoding pattern and conversion, but generally these four kinds hypothesis be difficult to be set up, and therefore can produce drift error and reduce the quality of reconstruction video image.

The spatial domain desampling fir filter is selected N for use ²The mode that is averaged of some pixel value, each macro block of transform coding rear video stream corresponding to transform coding before the N of video flowing ²Individual macro block, described N are natural number, and N 〉=2.Consider factors such as complexity that transcriber is realized and speed in the present embodiment, mode or other method that the spatial domain desampling fir filter selects for use the simplest 4 pixel values (being N=2) to be averaged realize that the spatial resolution of supposing conversion back encoded video streams is 1/4th of the preceding encoded video streams of conversion.

In the video coding international standard, inter prediction encoding can adopt frame prediction and field prediction dual mode, so the number of each macroblock motion vector of forward predicted frame may be one or two.If use the macro block of inter-frame encoding coding to adopt the frame prediction mode before the spatial resolution transform coding in the input coding video flowing, the motion vector of gained is exactly the motion vector of this macro block so.If employing field prediction, each macro block is divided into two pieces of 16*8 odd even, then the motion vector of this macro block is the motion vector that has the 16*8 piece correspondence of big DC coefficient sum behind the dct transform, the reason of doing like this is that block matching method sets up in the macro block all pixels and all be under the translation state and have under this assumed condition of identical movement tendency, but usually at the object edge place, this condition is difficult to satisfy, so there is big this trend of predicated error that produces in block matching method at the object edge place, the pixel value of the residual error macro block that process motion compensation simultaneously obtains is obeyed laplacian distribution, this means and quantize the non-vanishing possibility of back DC coefficient greater than ac coefficient, and the activity that experimental results show that macro block is relevant with the energy of DCT coefficient, so select the judgement symbol of big DC coefficient as the macro block activity.

Each macro block of the encoded video streams that obtains behind the spatial resolution transform coding is corresponding to the N of the preceding encoded video streams of conversion ²Individual macro block (N 〉=2) can utilize described N ²The motion vector of individual macro block

And the motion vector of the individual adjacent macroblocks of 4 (N+1)

Calculate the motion vector of respective macroblock in the transform coding rear video stream.Present embodiment is the simplest N=2 situation, so each macro block of transform coding rear video stream corresponding to transform coding before four macro blocks of video flowing, in order to accelerate motion vector revaluation process, can utilize the motion vector of these four macro blocks and 12 adjacent macroblocks thereof to calculate the motion vector of respective macroblock in the transform coding rear video stream.As shown in Figure 1,

Be the motion vector that adopts the macro block of inter-frame encoding coding in the transform coding rear video stream,

(i=1 ... 4) being the motion vector that constitutes the preceding corresponding macro block of four transform codings of this macro block correspondence, is to reduce the interblock effect to rebuilding the influence of video quality, and method is also utilized the motion vector of ten two macro blocks adjacent with them

(i=1 ... 12) the motion vector revaluation process that participates in the part macro block is come the smooth motion field, thereby improves reconstruction video picture quality, and Fig. 2 has represented the position of residual error DC DC coefficient.

If the N behind the transform coding before the transform coding of macro block correspondence ²Any one macro block adopts intraframe coding method in the individual macro block, and then the macro block behind the transform coding also adopts intraframe coding method, and the macroblock encoding process behind the transform coding finishes; If the N behind the transform coding before the transform coding of macro block correspondence ²Adopt intraframe coding method without any a macro block in the individual macro block, then the macro block behind the transform coding adopts inter-frame encoding, and reason is can improve the quality of reconstruction video image by an amount of introducing inter-coded macroblocks.Adopt the motion vector of the macro block of interframe encode to calculate acquisition behind the described transform coding by following formula (1-5):

${\stackrel{\&RightArrow;}{v}}_s=(r\&times;{\stackrel{\&RightArrow;}{v}}_i+(1-r)\underset{j=1}{\overset{12}{\mathrm{\&Sigma;}}}{w}_{\mathrm{nj}}\&times;{\stackrel{\&RightArrow;}{v}}_{\mathrm{nj}})/2---(1-5)$

In the described formula (1-5), r,

w _NjValue mode as follows:

If described N ²Individual macro block

All equate, so choose N ²Arbitrary in the individual macro block

In following formula Value, r=1;

If described N ²Individual macro block

All unequal, choose N ²The macro block of residual error DCT DC coefficient maximum in the individual macro block

In following formula

Value, r=0.75, at this moment, if n is arranged (n≤4N+4) motion vector of individual macro block can't obtain, then w in the individual adjacent macroblocks of 4 (N+1) _Nj=1/ (4N+4-n), if the motion vector of the individual adjacent macroblocks of 4 (N+1) all can't obtain, w then _Nj=0;

If above-mentioned situation all is false, choose N ²The macro block of residual error DCT DC coefficient minimum in the individual macro block

In following formula Value, make its overall movement trend that approaches object, r=1.

In order to make

Precision more need be according to the N before the transform coding of the macro block correspondence behind the transform coding ²The motion vector of individual macro block

Situation, select suitable search window right

Upgrade (hereinafter to be referred as SFMVRE+R), comprising:

If described N ²Individual macro block

All equate, show the N that the macro block behind the transform coding comprises ²Individual 8*8 piece has identical movement tendency, and it is right not need

Upgrade;

If described N ²Individual macro block

All unequal, search box size is chosen for ± and 2;

If above-mentioned situation all is false, to choose less relatively search window it is upgraded, search box size is chosen for ± and 1.

N=2 described in the present embodiment, so four macro blocks before the transform coding of macro block correspondence behind the transform coding, then these four macro blocks have 12 adjacent macroblocks.

In the experiment of spatial resolution transform coding, to seven different motion complexities, code rate is that the CIF format video sequence of 384kbit/s is tested, each sequence 100 frames of all encoding, default search box size is ± 7, GOP (Group Of Picture, group of picture) adopt the such structure of IPPPPPPPPP (being that sequence is that I frame back connects 9 P frames continuously), down-sampled back, spatial domain code rate is 96kbit/s.

The different sequences of table 1 are used various spatial domain transformation coding method gained PSNR (Peak Signal toNoise Ratio, Y-PSNR) (unit: dB) (with respect to FS, full search method)

Compared MEAN, AMVR, MEDIAN, PME, SFMVRE, SFMVRE+R (Refinement) method PSNR situation of change in the table 1 with respect to the FS method.As can be seen, the reconstruction video picture quality of MEAN method is the poorest, and reason is that this method is just done the motion vector of four macro blocks simply and on average and not considers any texture information; The AMVR method is taken second place, reason is the weight of its number of passing through the non-zero ac coefficient as four motion vectors, so motion vector can obtain to a certain degree differentiation by this weight when video sequence motion is mild relatively, thereby the reconstruction video quality that slightly is better than the MEAN method, as video sequence Akiyo, Garden, but when video sequence moves when violent, each macro block all may comprise more non-zero ac coefficient, the weight that obtains by the non-zero ac coefficient has just lost meaning so, this moment, the AMVR method was similar to the MEAN method, even at the violent video sequence Football of motion, the reconstruction video quality of AMVR method is lower than the MEAN method among the Mobile; The MEDIAN method is by choosing in four motion vectors and the motion vector of the minimum motion vector of other three distances as current macro, when video motion is mild relatively, this method tends to choose the little motion vector of prediction residual, so reconstruction video picture quality is better, but when motion is violent, because the motion change of each macro block is very big, the motion vector of selecting by this method lacks representativeness, so reconstruction video is second-rate; The PME method is by carrying out series of steps acquisition motion vectors such as piece matching operation to four motion vectors and average thereof, when video motion is mild, the motion vector that this method obtains is more accurate, and when video motion is violent, this method with the piece matching operation after the inverse of sad value as the weight of each motion vector, owing to utilized the actual sad value of current coding macro block in reference frame, the final motion vector that obtains slightly is better than above-mentioned other method; DC coefficient was carried out the motion vector renewal after the LLA algorithm utilized the movable information of adjacent eight macro blocks and uses discrete cosine transform, obtained reconstruction video quality preferably, but when video transformation is violent, still had bigger room for improvement; SFMVRE method of the present invention is by carrying out smoothly the violent zone of motion in the video sequence, simultaneously the mild relatively zone of motion is selected to make it more approach the method for regional area overall movement trend, improved reconstruction video picture quality well, particularly move when violent when video sequence, as Football, Mobile; The SFMVRE+R method is upgraded by the motion vector that the SFMVRE method is obtained, can obtain to approach the reconstruction video picture quality of FS method, especially for the Football video sequence, the reconstruction video picture quality that the reconstruction video picture quality that this method obtains is calculated a little more than FS, reason is that this sequence motion is very violent, so the motion vector that some images obtains near or be positioned at the edge of search window, further upgrade this moment again, may find the motion vector that more meets object of which movement trend, cause the reconstruction video picture quality can be a little more than the FS method.

With reference to shown in Figure 3, PSNR is with respect to the situation of change of FS method when adopting different spatial domains transformation coding method by the mild video sequence Akiyo of comparing motion with the violent video sequence Football of motion, SFMVRE method of the present invention as can be seen is little to the reconstruction video quality improvement of the mild video sequence that moves, but the violent video sequence that moves is compared other method reconstruction video picture quality and had more significantly and to improve.

Certainly; the present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; those of ordinary skill in the art work as can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection range of the appended claim of the present invention.

Claims (4)

1. video transformation coding method based on spatial resolution transformation, by utilizing the DCT DC coefficient of the movable information in the video flowing and discrete cosine transform before the transform coding to reappraise the motion vector of transform coding rear video stream, it is characterized in that, described method is carried out in pixel domain, selects N when the spatial domain is down-sampled for use ²The mode that is averaged of some pixel value is selected the judgement symbol of big DCT DC coefficient as the macro block activity, each macro block that the transform coding rear video flows corresponding to transform coding before the N of video flowing ²Individual macro block utilizes described N ²The motion vector of individual macro block

And the motion vector of the individual adjacent macroblocks of 4 (N+1)

Calculate the motion vector of respective macroblock in the transform coding rear video stream Wherein N is a natural number, and N 〉=2.

2. the video transformation coding method based on spatial resolution transformation according to claim 1 is characterized in that, the N before the transform coding of the macro block correspondence behind the described transform coding ²In the individual macro block, if there is any one macro block to adopt intraframe coding method, then the macro block behind the transform coding adopts intraframe coding method, and the macroblock encoding process behind the transform coding finishes.

3. the video transformation coding method based on spatial resolution transformation according to claim 1 and 2 is characterized in that, the N before the transform coding of the macro block correspondence behind the described transform coding ²In the individual macro block, if adopt intraframe coding method without any a macro block, then the macro block behind this transform coding is adopted inter-frame encoding, the motion vector of the macro block behind the described transform coding is calculated by following formula (a) and obtains:

${\stackrel{\&RightArrow;}{v}}_s=(r\&times;{\stackrel{\&RightArrow;}{v}}_i+(1+r)\underset{j=1}{\overset{12}{\mathrm{\&Sigma;}}}{w}_{\mathrm{nj}}\&times;{\stackrel{\&RightArrow;}{v}}_{\mathrm{nj}})/2---\left(a\right)$

In the described formula (a), r,

w _NjValue mode as follows:

If described N ²Individual macro block

All equate, so choose N ²Arbitrary in the individual macro block

In following formula

Value, r=1;

If described N ²Individual macro block

All unequal, choose N ²The macro block of residual error DCT DC coefficient maximum in the individual macro block

In following formula

Value, and r=0.75, at this moment, if having the motion vector of n macro block to obtain in the individual adjacent macroblocks of 4 (N+1), w then _Nj=1/ (4N+4-n), if the motion vector of the individual adjacent macroblocks of 4 (N+1) all can't obtain, w then _Nj=0;

If above-mentioned situation all is false, choose N ²The macro block of residual error DCT DC coefficient minimum in the individual macro block

In following formula Value, make its overall movement trend that approaches object, and r=1.

4. the video transformation coding method based on spatial resolution transformation according to claim 3 is characterized in that, further comprises according to the N before the transform coding of the macro block correspondence behind the transform coding ²The motion vector of individual macro block

Situation, select suitable search window right Upgrade:

If described N ²Individual macro block All equate, show the N that the macro block behind the transform coding comprises ²Individual 8*8 piece has identical movement tendency, and it is right not need

Upgrade;

If described N ²Individual macro block

All unequal, search box size is chosen for ± and 2;

If above-mentioned situation all is false, to choose less relatively search window it is upgraded, search box size is chosen for ± and 1.

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