JP5020829B2 - Moving picture decoding apparatus and moving picture encoding apparatus - Google Patents

Description

  The present invention relates to a moving image encoding device and a moving image decoding device that use a plurality of reference images for motion compensation.

  As a conventional technique, a moving picture decoding apparatus using the MPEG-4 AVC method (Non-patent Document 1; ISO / IEC 14496-10) will be described below with reference to the block diagram shown in FIG.

  The moving image decoding apparatus 3 includes a variable length code decoding unit 100, a motion vector decoding unit (motion vector decoding unit) 101, a prediction vector deriving unit 102, a buffer memory 103, an image decoding unit 104, a predicted image deriving unit (predicted image deriving unit). ) 105.

  The variable length code decoding unit 100 performs variable length decoding on input encoded data, and decodes encoded information such as a prediction scheme, prediction residual data, a difference vector, and time information. The motion vector decoding unit 101 decodes a motion vector from the prediction vector and the difference vector. The prediction vector deriving unit 102 derives a prediction vector using the decoded motion vector based on the prediction method. The buffer memory 103 temporarily records motion vectors, images, time information, and the like. The image decoding unit 104 decodes an image from the prediction method, the prediction residual data, and the predicted image. The predicted image deriving unit 105 derives a predicted image by motion compensation using the motion vector and the reference image.

<Outline of Decoding Procedure Using Conventional Technology>
The outline of the decoding process in the moving picture decoding apparatus using the prior art will be described below with reference to the flowchart of the decoding process procedure shown in FIG.

  First, the variable-length code decoding unit 100 performs variable-length decoding on encoded data input from the outside of the video decoding device 3 (step 10, hereinafter abbreviated as S10). The output of the variable-length code decoding unit 100 is encoded information such as a prediction method, prediction residual data, a difference vector, and time information. The prediction method is output to the prediction vector deriving unit 102 and the image decoding unit 104, the prediction residual data is output to the image decoding unit 104, the difference vector is output to the motion vector decoding unit 101, and the time information is the image The data is output to the decoding unit 104.

  Next, the prediction vector deriving unit 102 derives a prediction vector corresponding to the prediction method input from the variable length code decoding unit 100 using the motion vector recorded in the buffer memory 103 (S20). The prediction vector deriving unit 102 outputs the derived prediction vector to the motion vector decoding unit 101 and the buffer memory 103. Details of the operation of the prediction vector deriving unit 102 will be described later.

  Next, the motion vector decoding unit 101 adds the difference vector input from the variable length code decoding unit 100 to the prediction vector input from the prediction vector derivation unit 102, and outputs the result as a motion vector (S30). The output motion vector is output to the buffer memory 103 and recorded.

  Next, the predicted image deriving unit 105 reads the reference image recorded in the buffer memory 103. The predicted image derivation unit 105 performs motion compensation prediction using the motion vector input from the motion vector decoding unit 101 via the buffer memory 103 and the read reference image, derives a predicted image, and derives the predicted prediction The image is output to the image decoding unit 104 (S40).

  Next, in accordance with the prediction method input from the variable length code decoding unit 100, the image decoding unit 104 and the prediction residual input from the variable length code decoding unit 100 and the prediction residual input from the variable length code decoding unit 100 The image is decoded based on the data (S50). The decoded image and time information regarding the display timing of the image are output to the buffer memory 103 and recorded.

  Next, the image recorded in the buffer memory 103 in S50 is output to a moving image display device (not shown) at the time indicated by the time information (S60).

  As described above, in the conventional technique (MPEG-4 AVC method), decoding using motion compensation prediction is performed.

<About time direct prediction>
In the MPEG-4 AVC method, a highly efficient motion compensation prediction method called temporal direct prediction can be used as one of prediction methods.

  Next, temporal direct prediction of the MPEG-4 AVC method will be described using the conceptual diagram shown in FIG. In the following description, unless otherwise specified, it is assumed that there are two reference images, one for forward reference and one for backward reference.

As shown in FIG. 11, temporal direct prediction is a motion that uses two reference images, a forward reference image P _r0,0 and a backward reference image P _r1,0 , in deriving a predicted image of the target image P _cur. This is a compensation prediction method.

In the following, the processing target area on the target image _{P cur} (white circles in FIG. 11), referred to as a target region _{A cur.} In the conceptual diagram of FIG. 11 and the conceptual diagrams shown in FIGS. 4, 5, 6, and 14, the horizontal direction in the figure represents the display time for displaying a moving image, and the vertical bar represents each image. The vertical direction in the figure represents the position of the area in each image.

In motion compensation in temporal direct prediction of the target region _{A cur,} using the forward prediction vectors mvL0 and backward prediction vector mvL 1. The forward prediction vector mvL0 and the backward prediction vector mvL1 are motion vectors of a region B _col (double circle in FIG. 11) on the image P _col defined as a “reference image” that is spatially the same position as the target region A _cur . Calculate based on mvCol. The region B _{col is referred} to as “reference region”, and the motion vector mvCol is referred to as “reference motion vector”. _Further, it is assumed that the region _indicated by the reference motion vector mvCol is a region B _colref , and the region B _colref is on the image P _colref .

In the temporal direct prediction of the MPEG-4 AVC method, as shown in FIG. 11, the backward reference image P _r1,0 is the standard image P _col . In particular, when there are two reference images, the forward reference image _Pr0,0 becomes the image _Pcolref .

The forward prediction vector mvL0 and the backward prediction vector mvL1 are calculated by the following formula using the reference motion vector mvCol.

mvL0 = tb / tbb × mvCol (1)
mvL1 = (tb−td) / tbb × mvCol (2)

In Expressions (1) and (2), tb is the time interval of the display time between the forward reference image P _r0,0 and the target image P _cur, and td is the forward reference image P _r0,0 and the backward reference image. A time interval between P _r1,0 and tbb represents a time interval between the image P _colref and the reference image P _col . The values of the time intervals tb, td, and tbb are calculated using time information regarding the display time of each image recorded in the buffer memory 103 in the process of S50 of FIG. Time interval tb, td, and tbb a subject image _{P cur} of display time _{T cur,} the display time _{T R0,0} of the forward reference image _{P R0,0,} display time _{T R1,0} of the backward reference picture _{P R1,0,} display time _{T col} of the reference image _{P col,} and by using the display time _{T Colref} image _{P colref,} it is calculated by the following equation.

tb = T _r0,0 −T _cur (3)
_{td = T r1,0 - T r0,0 ···} (4)
tbb = T _col -T _colref (5)

In the temporal direct prediction, two objects that are images in the target area A _cur and the area B _cur shown in FIG. 11 are _changed from the area A _r0,0 to the area A _r1,0 , and from the area B _colref to the reference area B. _This is a prediction method that assumes that _col is moving at the same speed in the same direction.

In pmv (Predictor of Motion Vector) prediction, a difference vector between an estimated motion vector and a prediction vector is used. In temporal direct prediction, a motion vector is decoded without using such a difference vector. Specifically, the motion vector of forward prediction vectors mvL0 and backward prediction vector mvL1 in the target area _{A cur.}

The prediction image of the target area A _{cur includes} the area A _r0,0 on the forward reference image P _{r0,0 pointed} to by the forward prediction vector mvL0 and the area A _r1,0 on the backward reference image P _{r1,0 pointed} to by the backward prediction vector mvL1 _{. 0} is used to perform motion compensation.

<Detailed Configuration of Prediction Vector Deriving Unit 102>
A detailed configuration of the prediction vector deriving unit 102 that derives a prediction vector using temporal direct prediction is shown in the block diagram of FIG.

  The prediction vector derivation unit 102 includes a derivation method selection unit 201, a switch 202, a temporal direct prediction unit 203, a spatial direct prediction unit 204, a pmv prediction unit 205, and a zero vector output unit 206.

  The derivation method selection unit 201 selects a prediction vector derivation method according to the prediction method input from the variable-length code decoding unit 100 and the presence / absence of the reference motion vector recorded in the buffer memory 103. The switch 202 switches to the prediction vector derivation method selected by the derivation method selection unit 201. The temporal direct prediction unit 203 obtains a prediction vector by a method determined by temporal direct prediction, and outputs the prediction vector to the motion vector decoding unit 101. The spatial direct prediction unit 204 obtains a prediction vector by a method determined by spatial direct prediction, and outputs the prediction vector to the motion vector decoding unit 101. If there is a difference vector, the pmv prediction unit 205 obtains a prediction vector by pmv prediction that encodes the difference vector between the estimated motion vector and the prediction vector, and outputs the prediction vector to the motion vector decoding unit 101. The zero vector output unit 206 always outputs the zero vector as a prediction vector to the motion vector decoding unit 101 regardless of the input to the prediction vector deriving unit 102.

<Derivation procedure of prediction vector in temporal direct prediction>
Next, the procedure for deriving the forward prediction vector mvL0 and the backward prediction vector mvL1 when temporal direct prediction is used as the motion compensation prediction method will be described using the flowchart of the derivation procedure shown in FIG.

  First, the derivation method selection unit 201 requests the reference motion vector mvCol from the buffer memory 103 (S21).

Next, the derivation method selection unit 201 determines the presence / absence of the reference motion vector mvCol of the reference region B _col on the buffer memory 103 based on the notification from the buffer memory 103 (S22).

  If there is a reference motion vector mvCol, the process proceeds to the next step S23, and if there is no reference motion vector mvCol, the process proceeds to step S25.

  Next, the derivation method selection unit 201 switches the switch 202 to select the temporal direct prediction unit 203 (S23).

  Next, the temporal direct prediction unit 203 scales the reference motion vector mvCol acquired from the buffer memory 103 with time information, that is, using the expressions (1) and (2), the forward prediction vector mvL0 and the backward prediction vector mvL1. Is output to the motion vector decoding unit 101 as a prediction vector, and the process ends (S24).

In S22, when receiving a notification that the reference motion vector mvCol is not on the buffer memory 103, the derivation method selection unit 201 determines that the reference region B _col is intra-coded, and switches the switch 202, The zero vector output unit 206 is selected (S25).

  Next, the zero vector output unit 206 sets both the forward prediction vector mvL0 and the backward prediction vector mvL1 as zero vectors and outputs them as prediction vectors to the motion vector decoding unit 101, and ends the processing (S26).

  In addition to the temporal direct prediction, the MPEG-4 AVC method can perform motion compensation prediction using spatial direct prediction and pmv prediction. Regarding operations of the spatial direct prediction unit 204 and the pmv prediction unit 205 that perform these predictions. Will not be described.

As described above, in the temporal direct prediction method according to the related art, the backward reference image P _r1,0 is the reference image P _col and the reference motion vector mvCol of the reference region B _col on the reference image P _col is If available, a prediction vector that is close to the actual motion of the object in the video can be derived.

However, in the prediction vector derivation method according to the conventional technique, when the base region B _col on the backward reference image P _r1,0 is intra-coded, the base motion vector mvCol is set to a zero vector. In this case, as shown in the conceptual diagram of FIG. 14, since the calculations of Expressions (1) and (2) are performed using the zero vector, the area indicated by the forward prediction vector mvL0 is the area A _r0,0 and the backward prediction area indicated by vector becomes a region _{a r1,0,} the forward prediction vectors mvL0 and backward prediction vector mvL 1, often the difference between the actual motion of the target region _{a cur} increases. Accordingly, there is a problem that the prediction efficiency is lowered.

The present invention has been made in view of the above-described problems, and an object of the present invention is to _perform forward prediction that is not a zero vector even when the base region B _col on the backward reference image P _r1,0 is intra-coded. An object is to realize a moving picture decoding apparatus and a moving picture encoding apparatus capable of deriving a vector mvL0 and a backward prediction vector mvL1 and preventing a decrease in prediction efficiency.

  In order to solve the above-described problem, a prediction vector deriving unit that derives a prediction vector of a processing target area on a processing target image using a reference motion vector of a reference image, and using the prediction vector, Motion vector decoding means for reconstructing a motion vector, and predicted image derivation means for deriving a prediction image of the processing target region from the already decoded image after decoding processing using the motion vector, and the prediction vector derivation Means for deriving a prediction vector by temporal direct prediction, wherein the prediction vector deriving means uses at least two or more decoded images as candidate images of the reference image, and One of the candidate images based on a predetermined selection criterion that avoids a motion vector becoming a zero vector; Selected as an image, characterized by comprising a reference motion vector selecting means for selecting a motion vector of the region as a reference motion vector positioned in the processing target region and the spatially same position on the reference image.

  The processing target image is an image that is a target for reconstructing an image constituting a moving image from the state of encoded data.

  The processing target area refers to a part of the processing target image that is on the processing target image and is decoded in a unit of one decoding process.

  A prediction vector is a vector used to derive a motion vector.

  A motion vector is a vector used for deriving a prediction image when reconstructing an image constituting a moving image by a motion compensation prediction method.

  A reference image is an image having a reference motion vector for obtaining a prediction vector.

  The reference motion vector is a motion vector in the reference area of the reference image.

  The reference area is an area on the reference image that is in the same spatial position as the processing target area.

  The predicted image is an image from which the image is reconstructed from the prediction residual data included in the encoded data.

  The already-decoded image is an image constituting a moving image derived by decoding and reconstructing encoded data.

  Temporal direct prediction is based on the time interval between the display time of the processing target image, the display time of the reference image, and the display time of the decoded image indicated by the reference motion vector, and the prediction motion vector is scaled. This is a prediction method to be derived.

  The display time is time information included in the encoded data, and represents at what time each decoded image constituting the moving image should be reproduced.

  In the prior art, a prediction vector is derived using a decoded image whose display time is later than the processing target image as a reference image. When the decoded image is intra-coded, the prediction vector is a zero vector. In this configuration, the reference image is selected from a plurality of candidate images.

  According to the above configuration, even if a decoded image whose display time is later than the processing target image is intra-coded and the reference region does not have a motion vector, the reference image is selected from the plurality of decoded images included in the candidate image. Since it is possible to select an image, it is more likely that a prediction vector that reflects the motion of the object on the image will be obtained rather than a zero vector that has little correlation with the motion of the object on the image. There is an effect that it can be improved.

  In order to solve the above-described problem, a prediction vector deriving unit that derives a prediction vector of a processing target region on a processing target image using a reference motion vector of a reference image, and the processing target image and an already processed encoding process. A motion vector estimating means for estimating a motion vector using an encoded image, a motion vector encoding means for encoding the motion vector using the prediction vector, and the motion vector from the already encoded image. Prediction image deriving means for deriving a prediction image of the processing target region using the prediction vector deriving means, wherein the prediction vector deriving means derives a prediction vector by temporal direct prediction, and the prediction vector deriving means is , At least two or more of the already-encoded images are set as candidate images of the reference image, and the reference motion vector is a zero vector. And selecting one of the candidate images as the reference image based on a predetermined selection criterion, and a motion vector of a region located spatially at the same position as the processing target region on the reference image And a reference motion vector selection means for selecting as a reference motion vector.

  An already-encoded image is an image obtained by decoding and reconstructing an image from once encoded data among images constituting moving image data.

  In the prior art, a prediction vector is derived using an already-encoded image whose display time is later than the processing target image as a reference image. However, when the already-encoded image is intra-encoded, the prediction vector is a zero vector. In this configuration, the reference image is selected from a plurality of candidate images.

  According to the above configuration, even when an already-encoded image whose display time is later than that of the processing target image is intra-encoded and the reference region does not have a motion vector, among the already-encoded images included in the candidate image. Since the reference image can be selected from the above, it is highly possible to obtain a prediction vector that reflects the motion of the object on the image instead of the zero vector with little correlation with the motion of the object on the image. There is an effect that the efficiency can be improved.

It is a flowchart which shows the procedure in which the prediction vector derivation | leading-out part 112 derives | leads-out a prediction vector. It is a block diagram which shows the structure of the moving image decoding apparatus 1 in 1st Embodiment. 3 is a block diagram showing a detailed configuration of a prediction vector deriving unit 112. FIG. In the case of the forward reference picture P _R0,0 the reference image P _col, is a conceptual diagram illustrating a method of deriving a predictive motion vector by temporal direct prediction. It is a conceptual diagram explaining the derivation | leading-out method of the prediction vector by temporal direct prediction in case a some reference image is made into a reference | standard image candidate. It is a conceptual diagram explaining the derivation method of the prediction vector by temporal direct prediction in the case of including a non-reference image in a standard image candidate. It is a block diagram which shows the structure of the moving image encoder 2 in 2nd Embodiment. It is a flowchart which shows the process sequence of the moving image encoder 2 in 2nd Embodiment. It is a block diagram of the moving image decoding apparatus 3 in a prior art. It is a flowchart which shows the outline | summary of the decoding procedure of the moving image decoding apparatus 3 in a prior art. If the backward reference picture P _R1,0 is the reference image P _col, it is a conceptual diagram illustrating a method of deriving a predictive motion vector by temporal direct prediction. It is a block diagram which shows the detailed structure of the prediction vector derivation | leading-out part 102 in a prior art. In the prior art, it is a flowchart which shows the procedure in which the prediction vector derivation | leading-out part 102 derives | leads-out a prediction vector. In prior art, it is a conceptual diagram which shows a prediction vector in case the reference area _| region _Bcol is intra-predicted.

[First Embodiment]
Hereinafter, the moving picture decoding apparatus according to the first embodiment of the present invention will be described.

<Configuration of video decoding device>
2 and 3 show the configuration of the moving picture decoding apparatus according to the present embodiment. The block diagram of FIG. 2 shows the overall configuration of the video decoding device 1, and the block diagram of FIG. 3 shows the detailed configuration of the prediction vector deriving unit (predicted vector deriving means) 112 shown in FIG. is there.

  The elements shown in these drawings are the same as the block diagrams (FIGS. 9 and 12) used in the description of the prior art except for those described below, and thus the description thereof is omitted.

  In the block diagram shown in FIG. 2, the difference between the configuration of the video decoding device 1 of the present embodiment and the configuration of the video decoding device 3 according to the prior art is a prediction vector deriving unit 112. The prediction vector deriving unit 112 derives a prediction vector using the decoded motion vector based on the prediction method input from the variable length code decoding unit 100.

In the block diagram shown in FIG. 3, the difference between the configuration of the prediction vector deriving unit 112 of the present embodiment and the configuration of the prediction vector deriving unit 102 according to the prior art is that of the reference vector selection unit (reference motion vector selection unit) 210. It is presence or absence. The reference vector selection unit 210 selects an image as the reference image P _col from a plurality of reference image candidates on the buffer memory 103, and derives a reference motion vector mvCol corresponding to the selected reference image P _col. Notify

That is, in the temporal direct prediction, the video decoding device 1 according to the present embodiment determines the reference image P _col and the reference motion vector mvCol from a plurality of reference image candidates in a predetermined procedure, and determines the forward prediction vector mvL0 and the backward A prediction vector mvL1 is derived.

<Procedure for Deriving Predictive Vector in this Embodiment>
A procedure for deriving the forward prediction vector mvL0 and the backward prediction vector mvL1 in temporal direct prediction in the moving picture decoding apparatus 1 according to the present embodiment will be described with reference to the flowchart of FIG.

  First, the derivation method selection unit 201 requests the reference vector selection unit 210 for the reference motion vector mvCol (S1).

Next, after the reference vector selection unit 210 _sets the back reference image P _r1,0 as the reference image P _col in response to a request from the derivation method selection unit 201 (P _col = P _r1,0 ), the reference image A reference motion vector mvCol of P _col is requested to the buffer memory 103 (S2).

Next, the derivation method selection unit 201 determines whether or not the reference motion vector mvCol exists in the buffer memory 103 based on the response from the buffer memory 103 (S3). In this case, the reference motion vector mvCol exists in the buffer memory 103 means that the reference motion vector mvCol exists in the reference region B _col of the backward reference image P _r1,0 .

When the reference motion vector mvCol exists in the buffer memory 103 (corresponding to the conceptual diagram of FIG. 11 where the backward reference image P _r1,0 is the reference image P _col ), the process proceeds to the next step S4.

  If the reference motion vector mvCol does not exist in the buffer memory 103, the process proceeds to S6.

  When it is determined in S3 or S7 that the reference motion vector mvCol is present in the buffer memory 103, the derivation method selection unit 201 switches the switch 202 to select the temporal direct prediction unit 203 (S4).

  Next, the temporal direct prediction unit 203 uses the reference motion vector mvCol acquired from the buffer memory 103 to calculate the forward prediction vector mvL0 and the backward prediction vector mvL1 using Expression (1) and Expression (2), and the calculation result Are output to the motion vector decoding unit 101 as the forward prediction vector mvL0 and the backward prediction vector mvL1, and the process ends (S5).

If it is determined in S3 that the base motion vector mvCol does not exist in the buffer memory 103, the base vector selection unit 210 sets the forward reference image P _r0,0 as the base image P _col (P _col = P _r0,0 ), The buffer memory 103 is requested for the reference motion vector mvCol of the reference image P _col (S6).

Next, the derivation method selection unit 201 determines whether or not the reference motion vector mvCol exists in the buffer memory 103 based on the response from the buffer memory 103 (S7). In this case, the presence of the reference motion vector mvCol in the buffer memory 103 means that the reference motion vector mvCol exists in the reference region B _col of the forward reference image _Pr0,0 .

If the reference motion vector mvCol is present in the buffer memory 103 (corresponding to the conceptual diagram in FIG. 4), the process proceeds to S4. The conceptual diagram of FIG. 4 shows the relationship between the base motion vector mvCol, the forward prediction vector mvL0, and the backward prediction vector mvL1 when the forward reference image P _r0,0 is the base image P _col .

  If the reference motion vector mvCol does not exist in the buffer memory 103, the process proceeds to the next S8.

  If it is determined in S7 that the reference motion vector mvCol does not exist in the buffer memory 103, the derivation method selection unit 201 switches the switch 202 and selects the zero vector output unit 206 (S8).

Next, the zero vector output unit 206 outputs the zero vectors as the forward prediction vector mvL0 and the backward prediction vector mvL1 to the motion vector decoding unit 101, and ends the process. (S9)
According to the above procedure, if the reference motion vector mvCol is available when the backward reference image P _r1,0 is used as the reference image P _col , a prediction vector can be derived in the same manner as in the prior art. _If the reference motion vector mvCol in the backward reference image P _r1,0 is not _usable, the reference motion vector mvCol can be used with the forward reference image P _r0,0 as the reference image P _col .

Similar to the case where the backward reference image P _r1,0 is used as the base image P _col , the case where the front reference image P _r0,0 is used as the base image P _col is also used as an image in the target area A _cur shown in the conceptual diagram of FIG. each object in an image in an object and the region _{B cur,} in the region _{a R1,0} from the region _{a r0,0,} also in the area _{B R1,0} from the region _{B colref,} that in motion a constant speed in the same direction Make assumptions and make predictions.

Thus, in the conventional method, as shown in the conceptual diagram of FIG. 14, the present invention is compared with the prediction method in which the backward reference image P _{r1,0 does not} have the reference motion vector mvCol and the prediction vector is a zero vector. In the prediction method according to, since the prediction vector is derived using the standard motion vector mvCol of another reference image and used for image prediction, the actual motion of an object as an image in the region A _cur can be accurately represented. Therefore, efficient prediction is possible as compared with the prediction method according to the prior art.

<Reference image selection method when there are three or more reference image candidates>
Note that the present invention is also applicable when there are three or more reference image candidates.

For example, when there are three or more reference images, a plurality of reference images can be used as standard image candidates. As shown in the conceptual diagram of FIG. 5, there are three forward reference images P _r0,0 , P _r0,1 and P _r0,2 , and one backward reference image P _r1,0 . A case where all reference images are set as reference image candidates will be described below.

When there are three or more reference image candidates, the priorities among candidates are determined using the time interval between the display time of each reference image candidate and the display time of the target image _Pcur . For example, the backward reference images P _r1,0 are arranged in ascending order of time intervals, and then the forward reference images P _r0,0 , P _r0,1 , and P _r0,2 are arranged in ascending order of time intervals, and this order is prioritized. And According to this priority order, the priority order of each reference image candidate in FIG. 5 is that of the backward reference image P _r1,0 , the forward reference image P _r0,0 , the forward reference image P _r0,1 , and the forward reference image P _r0,2 . In order.

The reference vector selection unit 210 sets a reference image candidate having a high priority as the reference image P _col . Then, the presence or absence of the reference motion vector mvCol of the set reference image P _col is determined, and when the reference motion vector mvCol exists, the reference motion vector mvCol is selected. If it does not exist, the reference image candidate of the next priority is set as the reference image P _col , and the same processing is repeated according to the priority. If the reference motion vector mvCol is not selected after all the reference images P _col have been tried, the derivation method selection unit 201 is notified of this fact.

The conceptual diagram shown in FIG. 5 shows the relationship between the base motion vector mvCol, the forward prediction vector mvL0, and the backward prediction vector mvL1 when the reference image P _r0,1 is set as the base image P _col . Also in this case, an object as an image in the target area A _cur and an object as an image in the area B _cur are _changed from the area A _r0,0 to the area A _r1,0 , and from the area B _colref to the area B _r1,0 , respectively. Assuming constant motion in the same direction, a prediction vector can be calculated from the equations (1) and (2).

When there are three or more reference image candidates, one of the reference image candidates is set as the reference image P _col, and the reference motion vector mvCol corresponding to the reference image P _col is selected, which is shown in the conceptual diagram of FIG. Thus, compared with the case where the reference motion vector mvCol is a zero vector, there is a higher possibility that a prediction vector having a high correlation with the actual motion of an object in the image can be derived. Therefore, more efficient prediction is possible.

<Prediction method for including non-reference image in standard image candidate>
In addition to the reference image, a non-reference image that is not used for derivation of a predicted image in the related art may be included in the standard image candidate. In this case, all already decoded images can be reference image candidates. As shown in the conceptual diagram of FIG. 6, a case will be described in which a reference image candidate includes a non-reference image P _nr in addition to the two reference images of the forward reference image P _r0,0 and the backward reference image P _r1,0. To do.

Even when the reference image candidate includes the non-reference image P _nr , the operation of the reference vector selection unit 210 is the same as the operation already described. That is, the reference motion vector mvCol is selected by determining the presence or absence of the reference motion vector mvCol for each image set in the reference image P _col in order according to the priority order.

As a method of determining the priority when the reference image candidate includes the non-reference image P _nr , for example, regardless of whether it is a reference image or a non-reference image, the display time is in the order from the closest display time of the target image P _cur. There is a method of prioritizing images. In addition, images that are reference images are arranged in order of display time close to the display time of the target image P _cur , and then images that are non-reference images are arranged in order of display time close to the display time of the target image P _cur. There is also a method.

The conceptual diagram of FIG. 6 shows the relationship between the reference motion vector mvCol, the forward prediction vector mvL0, and the backward prediction vector mvL1 when the non-reference image P _nr is set to the reference image P _col (P _col = P _nr ). Yes. Also in this case, the object as the image in the target area A _cur and the object as the image in the area B _cur are respectively _changed from the area A _r0,0 to the area A _r1,0 and from the area B _colref to the reference area B _r1,0. In addition, assuming that they are moving at the same speed in the same direction, the prediction vector can be calculated from the equations (1) and (2).

By including the non-reference image in the standard image candidate, the number of standard image candidates whose display time is close to the display time of the target image P _cur is greater than when only the reference image is included in the standard image candidate. When the interval between the display time of the target image P _{cur and} the display time of the reference image P _col is narrow, the distance between the target region A _cur and the region B _cur on the target image P _cur becomes short, so these two regions It is easy to assume that is moving at the same speed in the same direction. Therefore, since there is a high possibility that a motion vector having a high correlation with the actual motion of an object in the image can be derived, more efficient prediction is possible as compared with the case where only the reference image is set as the reference image candidate.

  When a non-reference image is used as a standard image candidate, at least a motion vector corresponding to the candidate non-reference image and display time information of the non-reference image must be recorded in the buffer memory 103. There is.

<Method of using only one reference image for prediction image derivation>
In the description so far, in the temporal direct prediction, two images of the forward reference image P _r0,0 and the backward reference image P _r1,0 are used to derive the predicted image of the target area A _cur . Only one reference image may be used.

For example, as shown in the conceptual diagram of FIG. 4, when a prediction vector is derived using the forward reference image P _r0,0 as the base image P _col , a predicted image of the target area A _cur is generated only from the area A _r0,0. May be. In this case, the possibility that an object as an image in the reference area B _col moves at a constant speed from the area B _colref to the area B _{cur moves} at a constant speed from the area B _colref to the area B _{r1,0 having} a longer time interval. Higher than possible. That is, there is a high possibility that the forward prediction vector mvL0 is more accurate than the backward prediction vector mvL1. Accordingly, the prediction efficiency is improved when only the region _{Ar0, 0} is used.

Further, when the backward reference image P _r1,0 is _set as the reference image P _col and the reference motion vector mvCol indicates an image whose display time is later than the backward reference image P _r1,0 , Similar to the case of deriving the prediction vector from only the reference image P _r0,0 , the prediction efficiency is improved by using only the area A _r1,0 for deriving the prediction image.

[Second Embodiment]
Hereinafter, the moving picture coding apparatus according to the second embodiment of the present invention will be described.
<Configuration of video encoding device>
In the block diagram of FIG. 7, the structure of the moving image encoder 2 which concerns on this Embodiment is shown. The block diagram of FIG. 7 shows the overall configuration of the moving picture coding apparatus 2.

  The moving image encoding apparatus 2 includes an image encoding unit 121, a predicted image derivation unit 105, a motion vector estimation unit (motion vector estimation means) 122, a buffer memory 103, an image decoding unit 104, a prediction vector derivation unit 112, and a prediction scheme control. Unit 124, variable length encoding unit 120, and motion vector encoding unit (motion vector encoding means) 123.

  The elements shown in this figure are the same as those shown in the block diagram (FIG. 2) of the video decoding device 1 in the first embodiment, except for those described below.

  The variable length encoding unit 120 encodes the prediction residual data input from the image encoding unit 121, the difference vector input from the motion vector encoding unit 123, and the encoding information such as the prediction method input from the prediction method control unit 124. Variable length encoding and output to the outside. The image encoding unit 121 obtains prediction residual data using the moving image data input from the outside and the predicted image input from the predicted image deriving unit 105, and outputs the prediction residual data to the image decoding unit 104 and the variable length encoding unit 120. The motion vector estimation unit 122 estimates a motion vector using moving image data input from the outside and a reference image in the buffer memory 103, and obtains the obtained motion vector as a predicted image derivation unit 105, a buffer memory 103, a prediction vector derivation. Unit 112, prediction scheme control unit 124, and motion vector encoding unit 123. The motion vector encoding unit 123 obtains a difference vector using the motion vector input from the motion vector estimation unit 122, the prediction vector input from the prediction vector derivation unit 112, and the prediction method input from the prediction method control unit, and has a variable length. The data is output to the encoding unit 120. The prediction method control unit 124 sets a prediction method for deriving a prediction vector based on the motion vector input from the motion vector estimation unit 122, sets the prediction method to the prediction vector derivation unit 112, the variable length encoding unit 120, and the motion vector. The data is output to the encoding unit 123.

<About the outline of the encoding procedure in the moving image encoding device 2>
The outline of the encoding processing procedure in the moving image encoding apparatus 2 will be described below with reference to the flowchart shown in FIG.

  First, the motion vector estimation unit 122 performs motion estimation using the input moving image data and the reference image in the buffer memory 103, and obtains a motion vector of each area of the image to be encoded. The motion vector estimation unit 122 records the obtained motion vector in the buffer memory 103 and outputs the motion vector to the prediction vector derivation unit 112, the prediction method control unit 124, and the motion vector encoding unit 123 (S100).

  Next, the prediction method control unit 124 uses the motion vector input from the motion vector estimation unit 122 to determine the prediction method as one of temporal direct prediction, spatial direct prediction, or pmv prediction, and performs prediction. The data is output to the vector deriving unit 112, the variable length coding unit 120, and the motion vector coding unit 123 (S110).

  Next, based on the motion vector input from the motion vector estimation unit 122 and the prediction method input from the prediction method control unit 124, the prediction vector deriving unit 112 predicts the prediction vector described in the first embodiment. Is calculated and output to the buffer memory 103 and the motion vector encoding unit 123 (S120).

  Next, the motion vector encoding unit 123 obtains a difference vector. When the prediction method input from the prediction method control unit 124 is pmv prediction, the difference is based on the motion vector input from the motion vector estimation unit 122 and the prediction vector input from the prediction vector derivation unit 112. Calculate the vector. When the prediction method input from the prediction method control unit 124 is temporal direct prediction or spatial direct prediction, the difference vector is set as a zero vector. The motion vector encoding unit 123 outputs the obtained difference vector to the variable length encoding unit 120 (S130).

  Next, the predicted image deriving unit 105 performs motion compensation using the motion vector input from the motion vector estimating unit 122 and the reference image in the buffer memory 103 to obtain a predicted image, and the image coding unit 121 and The image is output to the image decoding unit 104 (S140).

  Next, the image encoding unit 121 calculates prediction residual data based on the moving image data input from the outside and the predicted image input from the predicted image deriving unit 105, and the image decoding unit 104 and the variable length code The data is output to the conversion unit 120 (S150).

  Next, the image decoding unit 104 reconstructs an image as an already-encoded image using the prediction residual data input from the image encoding unit 121 and the predicted image input from the predicted image derivation unit 105. (S160). The reconstructed image is recorded in the buffer memory 103. The already-encoded image is used as a reference image when a prediction vector is derived, and is also used as a reference image when a prediction image is derived.

  Next, the variable-length encoding unit 120 performs prediction residual data input from the image encoding unit 121, difference vector input from the motion vector encoding unit 123, and prediction input from the prediction scheme control unit 124. The system is variable-length encoded and output as encoded data to the outside of the moving image encoding apparatus 2 (S170).

<Supplementary items regarding the second embodiment>
As described above, the moving picture coding apparatus 2 according to the present embodiment derives a prediction vector using a plurality of reference image candidates according to the prediction vector derivation procedure described in the first embodiment. Then, since the moving image is encoded using the derived prediction vector, the moving image can be encoded with high efficiency.

  Note that in the process of S120 (derivation of a prediction vector) in the flowchart shown in FIG. 8, as described in the first embodiment, a prediction vector is derived by using three or more reference image candidates. Efficiency is improved.

  Similarly, in the process of S120, as described in the first embodiment, prediction efficiency is improved by deriving a prediction vector by including a non-reference image in a standard image candidate.

  The prediction vector derivation method in the temporal direct prediction described above can also be used for derivation of a prediction vector when pmv prediction is used as a prediction method.

<Supplementary items>
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The candidate image has a display time later than the processing target image and a display time closest to the processing target image, and a display time earlier than the processing target image and a display time closest to the processing target image. When the motion vector of a region located at the same position spatially as the processing target region exists on the candidate image whose display time is later than the processing target image, the predetermined selection criterion is: When the candidate image is selected as the reference image and the motion vector does not exist, an area located at the same spatial position as the processing target region on the candidate image whose display time is earlier than the processing target image. When there is a motion vector, it is preferable that the criterion is that the candidate image is selected as the reference image.

  Thereby, in the said structure, a reference | standard motion vector selection means judges first whether the already decoded image immediately after a process target image can be selected as a reference | standard image. If it can be selected, a predicted image is derived in the same manner as in the prior art. If it cannot be selected, it is next determined whether or not the decoded image immediately before the processing target image can be selected as the reference image. If it can be selected, a predicted image is derived using the decoded image as a reference image.

  According to the above configuration, since the decoded image having the closest display time to the processing target image is selected as the reference image, the time interval between the processing target image and the reference image is short. Therefore, the probability that the assumption that the object on the image, which is the premise of temporal direct prediction, is moving at the same speed in the same direction is increased, has the effect of improving the prediction efficiency of the predicted image.

  In addition, the predetermined selection criterion is to prioritize the decoded images that are included in the candidate image and whose display time is later than the processing target image, in order from the display time closest to the display time of the processing target image. Subsequent to the priority order, prior decoded images included in the candidate images, the display time of which is earlier than the processing target image are given priority in order of the display time closest to the display time of the processing target image. In turn, the determination on the presence or absence of a motion vector in an area located spatially at the same position as the processing target area on the candidate image is repeated until the motion vector exists. It is preferable that the criterion is that the candidate image is selected as the reference image.

  In this configuration, the reference motion vector selection unit first assigns priorities to a plurality of already decoded images, and determines whether or not the reference images can be selected in descending order of priority. This priority order is a priority order that gives priority to a decoded image having a high possibility that the prediction vector reflects the actual motion of the object.

  Thereby, according to the above configuration, by selecting any of the candidate images as a reference image and selecting a reference motion vector corresponding to the reference image, the image is compared with a case where the reference motion vector is set as a zero vector. Since there is a high possibility that a prediction vector having a high correlation with the actual motion of a certain object can be derived, there is an effect that more efficient prediction is possible.

  In addition, when the reference motion vector selection unit selects a decoded image having a display time earlier than the processing target image as the reference image, the predicted image derivation unit has a display time closest to the processing target image. It is preferable to derive the predicted image using only the reference image.

  The reference image is a decoded image having a region indicated by a motion vector.

  The forward reference image is a decoded image having a display time earlier than the processing target image among the decoded images having the area indicated by the motion vector.

  The backward reference image refers to a decoded image having a display time later than that of the processing target image among the decoded images having a region indicated by the motion vector.

  The forward prediction vector is a prediction vector indicating a forward reference image from the processing target region.

  The backward prediction vector is a prediction vector indicating a backward reference image from the processing target region.

  In this configuration, when viewed from the display time, first, there is a forward reference screen pointed to by the reference motion vector, next there is a reference image, next there is a processing target image, and then there is a backward reference image.

  Thus, according to the above configuration, when the prediction vector is derived using the forward reference image as the reference image, the prediction region of the processing target region is generated only from the region on the reference image indicated by the forward prediction vector. The possibility that an object as an image moves at a constant speed from the region on the forward reference image pointed to by the reference motion vector to the region on the processing target image is on the forward reference image pointed to by the reference motion vector having a longer time interval. The possibility of moving at a constant speed from the region to the region on the backward reference image is high.

  Furthermore, since the prediction vector is obtained using the time interval between the forward reference image and the processing target image that is shorter than the time interval between the forward reference image and the backward reference image, the object on the image that is the assumption of temporal direct prediction The possibility that the condition of moving at the same speed in the same direction is increased. Therefore, there is an effect that the prediction efficiency of the predicted image can be improved.

  Moreover, it is preferable that the already decoded image is a reference image and a non-reference image.

  A non-reference image refers to a decoded image that is not used to derive a predicted image.

  In this configuration, by including the non-reference image in the candidate image, the number of decoded images whose display time is close to the display time of the processing target image is greater than when only the reference image is included in the candidate image.

  Thus, according to the above configuration, when the interval between the display time of the processing target image and the display time of the reference image is narrow, the target region and the region on the reference image indicated by the reference motion vector are on the processing target image. Since the distance is shortened, it is easy to assume that these two regions are moving at the same speed in the same direction. Therefore, there is a high possibility that a motion vector having a high correlation with the actual motion of the object in the image can be derived, so that it is possible to improve the prediction efficiency more than in the case where only the reference image is set as the reference image candidate. .

  In addition, the candidate image has a display time later than the processing target image and the display time closest to the processing target image and a display time earlier than the processing target image and the display time of the processing target image. The closest encoded image, and the predetermined selection criterion is that there is a motion vector of an area located at the same position spatially as the processing target area on the candidate image whose display time is later than the processing target image If the candidate image is selected as the reference image, and the motion vector does not exist, the candidate image has a display time earlier than the processing target image and is spatially located at the same position as the processing target region. In the case where there is a motion vector of the located region, it is preferable that the criterion is that the candidate image is selected as the reference image.

  In this configuration, the reference motion vector selection unit first determines whether an already-encoded image immediately after the processing target image can be selected as the reference image. If it can be selected, a predicted image is derived in the same manner as in the prior art. If it cannot be selected, it is next determined whether or not the already-encoded image immediately before the processing target image can be selected as the reference image. If it can be selected, a predicted image is derived using the already encoded image as a reference image.

  Thus, according to the above configuration, since the already-encoded image having the closest display time to the processing target image is selected as the reference image, the time interval between the processing target image and the reference image is short. Therefore, the probability that the assumption that the object on the image, which is the premise of temporal direct prediction, is moving at the same speed in the same direction is increased, has the effect of improving the prediction efficiency of the predicted image.

  In addition, the predetermined selection criterion is to prioritize the already-encoded images that are included in the candidate image and whose display time is later than the processing target image, in the order that the display time is close to the display time of the processing target image, Subsequent to the priority order, the encoded images included in the candidate images and having the display time earlier than the processing target image are prioritized in the order in which the display time is close to the display time of the processing target image. When there is a motion vector, the determination of the presence / absence of a motion vector in an area spatially located at the same position as the processing target area on the candidate image is repeated in the order of rank until the motion vector exists. Is preferably a criterion for selecting the candidate image as the reference image.

  In this configuration, the reference motion vector selection unit first assigns priorities to a plurality of already-encoded images, and determines whether or not the reference images can be selected in descending order of priority. This priority order is a priority order for an already-encoded image having a high possibility that the prediction vector reflects the actual motion of the object.

  Thereby, according to the above configuration, by selecting any of the candidate images as a reference image and selecting a reference motion vector corresponding to the reference image, the image is compared with a case where the reference motion vector is set as a zero vector. Since there is a high possibility that a prediction vector having a high correlation with the actual motion of a certain object can be derived, there is an effect that more efficient prediction is possible.

  Further, when the reference motion vector selection unit selects an already-encoded image having a display time earlier than the processing target image as the reference image, the predicted image derivation unit has a display time closest to the processing target image. It is preferable to derive the predicted image using only the forward reference image.

  In this configuration, when viewed from the display time, first, there is a forward reference screen pointed to by the reference motion vector, next there is a reference image, next there is a processing target image, and then there is a backward reference image.

  Thus, according to the above configuration, when the prediction vector is derived using the forward reference image as the reference image, the prediction region of the processing target region is generated only from the region on the reference image indicated by the forward prediction vector. The forward reference pointed to by the reference motion vector has a longer time interval if the object in the image is moving at a constant speed from the region on the forward reference image pointed to by the reference motion vector to the region on the processing target image. The possibility of moving at a constant speed from the region on the image to the region on the back reference image is high.

  Furthermore, since the prediction vector is obtained using the time interval between the forward reference image and the processing target image, which is shorter than the time interval between the forward reference image and the backward reference image, it is assumed that temporal direct prediction is performed on the image. The possibility that the condition that the object moves at a constant speed in the same direction is increased. Therefore, there is an effect that the prediction efficiency of the predicted image can be improved.

  The already-encoded image is preferably a reference image and a non-reference image.

  In this configuration, including the non-reference image in the candidate image increases the number of already-encoded images whose display time is close to the display time of the processing target image, compared to the case where only the reference image is included in the candidate image.

  Thus, according to the above configuration, when the interval between the display time of the processing target image and the display time of the reference image is narrow, the target image and the region on the reference image indicated by the reference motion vector Since the distance at becomes shorter, it is easy to assume that these two regions are moving at the same speed in the same direction. Therefore, there is a high possibility that a motion vector having a high correlation with the actual motion of the object in the image can be derived, so that it is possible to improve the prediction efficiency more than in the case where only the reference image is set as the reference image candidate. .

  The moving picture decoding apparatus according to the present invention includes a prediction vector deriving unit that derives a motion vector of a processing target region on a processing target image using a motion vector of a decoded image, and a decoded image using the prediction vector. And a predicted image deriving unit for deriving a predicted image of the processing target region from the prediction vector deriving unit, wherein the predicted vector deriving unit uses at least two or more already-decoded images as reference image candidates, and a predetermined selection criterion. A reference motion vector selection means for selecting one of the candidates as a reference image based on the reference image and selecting a motion vector of an area spatially located at the same position as the processing target area on the reference image as a reference motion vector The reference motion vector may be scaled based on a display time interval between the images to derive a prediction vector. .

  In addition to the above-described configuration, the moving image decoding apparatus according to the present invention may further include a decoded image and a processing target in which the reference motion vector selection unit has a display time later than the processing target image and the display time closest to the processing target image. A decoded image whose display time is earlier than the image and whose display time is closest to the processing target image is set as the reference image candidate, and an area located at the same position as the processing target region on the reference image candidate whose display time is later than the processing target image. If a motion vector exists, the motion vector is selected as a reference motion vector. If the motion vector does not exist, an area located at the same position as the processing target area on the reference image candidate whose display time is earlier than the processing target image If there is a motion vector, the configuration may be such that the motion vector is selected as a reference motion vector.

  Furthermore, in the moving image decoding apparatus according to the present invention, in addition to the above-described configuration, the reference motion vector selection unit sets a plurality of decoded images as reference image candidates, and displays a display time from a processing target image included in the reference image candidates. The decoded images with a slower display time are arranged in the order of display time relative to the processing target image, and then the decoded images having a display time earlier than the processing target images included in the reference image candidates are arranged in the order of display time closer to the processing target image. The priority order of candidates is set, and reference image candidates are set as reference images in the order of the priority order, and if there is a motion vector of an area located at the same position as the processing target area on the reference image, the motion vector is set as a reference. The configuration may be characterized in that it is selected as a motion vector.

  In addition to the above-described configuration, the moving image decoding apparatus according to the present invention is configured such that, in the reference motion vector selection unit, a reference motion vector is selected using a decoded image whose display time is slower than the processing target image as a reference image. A prediction image is derived using a forward reference image whose display time is closest to the processing target image and a backward reference image whose display time is closest to the processing target image, and an image whose display time is earlier than the processing target image When the reference motion vector is selected, the prediction image may be derived using only the forward reference image whose display time is closest to the processing target image.

  Furthermore, the moving picture decoding apparatus according to the present invention may be configured such that, in addition to the above-described configuration, the reference motion vector selection unit uses a reference image as the already-decoded image.

  In addition to the above configuration, the moving image decoding apparatus according to the present invention may have a configuration in which the reference motion vector selection unit uses a reference image and a non-reference image as the already-decoded image.

  Furthermore, the moving image encoding apparatus according to the present invention includes a prediction vector deriving unit that derives a motion vector of a processing target region on a processing target image using a motion vector of an already encoded image that has been encoded, In the moving picture coding apparatus including a predicted image derivation unit that derives a predicted image of the processing target region from the already encoded image using the prediction vector, the prediction vector derivation unit includes at least two or more already encoded images. Is selected as a reference image candidate, one of the candidates is selected as a reference image based on a predetermined selection criterion, and a motion vector of a region located spatially at the same position as the processing target region on the reference image is selected. Reference motion vector selection means for selecting as a reference motion vector is provided, and a prediction vector is derived by scaling the reference motion vector based on a display time interval between the images. Rukoto may be configured characterized.

  In addition to the above-described configuration, the moving image encoding apparatus according to the present invention includes: the reference motion vector selection unit that includes an already-encoded image whose display time is later than the processing target image and whose display time is closest to the processing target image; An already-encoded image whose display time is earlier than the processing target image and whose display time is closest to the processing target image is set as the reference image candidate, and is located at the same position as the processing target region on the reference image candidate whose display time is later than the processing target image. If the motion vector of the region to be processed exists, the motion vector is selected as the reference motion vector. If the motion vector does not exist, the motion vector is selected at the same position as the processing target region on the reference image candidate whose display time is earlier than that of the processing target image. If there is a motion vector in a region where the position is present, the motion vector may be selected as a reference motion vector.

  Furthermore, in the moving image encoding device according to the present invention, in addition to the above-described configuration, the reference motion vector selection unit sets a plurality of already-encoded images as reference image candidates, and uses the processing target images included in the reference image candidates. Pre-coded images with a slow display time are arranged in order of display time relative to the processing target image, and then the pre-coded images with a display time earlier than the processing target images included in the reference image candidate are close to the processing target image. If a reference image candidate is set as a reference image in the order of the priority order and a motion vector of an area located at the same position as the processing target area exists on the reference image, The configuration may be characterized in that the motion vector is selected as the reference motion vector.

  In addition to the above-described configuration, the moving image encoding apparatus according to the present invention selects a reference motion vector by using the already-encoded image whose display time is slower than the processing target image as a reference image in the reference motion vector selection unit. In such a case, the prediction image is derived using the forward reference image whose display time is closest to the processing target image and the backward reference image whose display time is closest to the processing target image, and an image whose display time is earlier than that of the processing target image is obtained. When the reference motion vector is selected as the reference image, the prediction image may be derived using only the forward reference image whose display time is closest to the processing target image.

  Furthermore, the moving picture encoding apparatus according to the present invention may be configured such that, in addition to the above-described configuration, the reference motion vector selection unit uses a reference image as the already-encoded image.

  In addition to the above configuration, the moving image encoding apparatus according to the present invention may have a configuration in which the reference motion vector selection unit uses a reference image and a non-reference image as the already-encoded image.

  Finally, each block of the moving picture decoding apparatus 1 and the moving picture encoding apparatus 2, in particular, the derivation method selection unit 201, the reference vector selection unit 210, the temporal direct prediction unit 203, the spatial direct prediction unit 204, the pmv prediction unit, and zero The vector output unit 206 may be configured by hardware logic, or may be realized by software using a CPU as follows.

  That is, the moving picture decoding apparatus 1 and the moving picture encoding apparatus 2 include a CPU (central processing unit) that executes instructions of a control program that realizes each function, a ROM (read only memory) that stores the program, and the program. A RAM (random access memory) to be developed, a storage device (recording medium) such as a memory for storing the program and various data, and the like are provided. An object of the present invention is to provide a computer with program codes (execution format program, intermediate code program, source program) of control programs for the video decoding device 1 and the video encoding device 2 which are software for realizing the functions described above. The recording medium recorded in a readable manner is supplied to the moving picture decoding apparatus 1 and the moving picture encoding apparatus 2, and the computer (or CPU or MPU) reads out and executes the program code recorded on the recording medium. Is also achievable.

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  Further, the moving picture decoding apparatus 1 and the moving picture encoding apparatus 2 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Also, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  In the moving picture decoding apparatus according to the present invention, as described above, the prediction vector deriving unit determines that at least two or more of the decoded pictures are candidate images of the reference image, and the reference motion vector is a zero vector. Avoiding, selecting one of the candidate images as the reference image based on a predetermined selection criterion, and using a motion vector of a region located spatially at the same position as the processing target region on the reference image Reference motion vector selection means for selecting a motion vector is provided.

  Therefore, even when a decoded image whose display time is later than the processing target image is intra-coded and the reference region does not have a motion vector, the reference image can be selected from a plurality of decoded images included in the candidate image. Therefore, it is more possible to obtain a prediction vector that reflects the motion of the object on the image, rather than a zero vector that has little correlation with the motion of the object on the image, so the effect of improving the prediction efficiency of the predicted image Play.

  In the moving picture encoding apparatus according to the present invention, as described above, the prediction vector deriving unit uses at least two or more of the already encoded pictures as the candidate pictures of the reference picture, and the reference motion vector is a zero vector. One of the candidate images is selected as the reference image on the basis of a predetermined selection criterion, and an area located in the same position as the processing target region on the reference image is selected. Reference motion vector selection means for selecting a motion vector as a reference motion vector is provided.

  Therefore, even when an already-encoded image whose display time is later than the processing target image is intra-encoded and the reference area does not have a motion vector, a reference image is selected from a plurality of already-encoded images included in the candidate image. Since it is possible to select, it is highly possible to obtain a prediction vector that reflects the motion of the object on the image instead of a zero vector with little correlation with the motion of the object on the image, so the prediction efficiency of the predicted image can be improved. There is an effect.

Industrial applicability

  When the video decoding device 1 and the video encoding device 2 according to the present invention are used, the prediction efficiency of a prediction vector can be improved, so that a device for encoding or decoding a video, that is, a mobile terminal device, It can be suitably used for a mobile phone, a television receiver, a multimedia device and the like.

Claims (6)

Prediction vector deriving means for deriving a prediction vector of a processing target region on the processing target image using a reference motion vector of the reference image;
Motion vector decoding means for reconstructing a motion vector of the processing target region using the prediction vector;
Predicted image deriving means for deriving a predicted image of the processing target region from the already decoded image that has been decoded using the motion vector,
The prediction vector deriving means includes:
At least two or more of the already decoded images are set as candidate images of the reference image,
Selecting one of the candidate images as the reference image based on a predetermined selection criterion that avoids the reference motion vector becoming a zero vector;
A reference motion vector selection means for selecting a motion vector of a region located spatially at the same position as the processing target region on the reference image as a reference motion vector;
Further, the reference motion vector selection means includes:
When a decoded image whose display time is earlier than the processing target image is selected as the reference image,
The predicted image derivation means includes
Deriving a predicted image using only forward reference images ,
The predetermined selection criterion is:
Prioritized decoded images that are included in the candidate images and whose display time is later than the processing target image are given priority in order of display time close to the display time of the processing target image,
Following that priority,
Prior decoded images included in the candidate image, the display time of which is earlier than the processing target image, prioritize the display time closer to the display time of the processing target image,
In the order of the priority order, the determination on the presence or absence of a motion vector in an area spatially located at the same position as the processing target area on the candidate image is repeated until the motion vector exists,
A moving picture decoding apparatus according to claim 1, wherein when there is the motion vector, the candidate image is selected as the reference image . The moving image decoding apparatus according to claim 1, wherein the already decoded image is a reference image or a non-reference image . The reference motion vector selection means repeats the determination of the presence / absence of the motion vector based on the predetermined selection criterion until the motion vector exists, and when the motion vector exists, the candidate image is selected as the reference image. The moving picture decoding apparatus according to claim 1, wherein the moving picture decoding apparatus selects the moving picture decoding apparatus according to claim 1. Prediction vector deriving means for deriving a prediction vector of a processing target region on the processing target image using a reference motion vector of the reference image;
Motion vector estimation means for estimating a motion vector using the processing target image and the already-encoded image that has been subjected to the encoding process;
Motion vector encoding means for encoding the motion vector using the prediction vector;
Predicted image deriving means for deriving a predicted image of the processing target region from the already-encoded image using the motion vector;
With
The prediction vector deriving means includes:
At least two or more of the already-encoded images are set as candidate images for the reference image,
Selecting one of the candidate images as the reference image based on a predetermined selection criterion that avoids the reference motion vector becoming a zero vector;
A reference motion vector selection means for selecting a motion vector of a region located spatially at the same position as the processing target region on the reference image as a reference motion vector;
Further, the reference motion vector selection means includes:
When an already-encoded image whose display time is earlier than the processing target image is selected as the reference image,
The predicted image derivation means includes
Deriving a predicted image using only forward reference images,
The predetermined selection criterion is:
Prior coded images that are included in the candidate images and whose display time is later than the processing target image are prioritized in the order that the display time is closer to the display time of the processing target image,
Following that priority,
Prioritized images that are included in the candidate images and that are earlier in display time than the processing target image are given priority in the order in which the display time is closer to the display time of the processing target image,
In the order of the priority order, the determination on the presence or absence of a motion vector in an area spatially located at the same position as the processing target area on the candidate image is repeated until the motion vector exists,
The moving picture coding apparatus according to claim 1, wherein when there is the motion vector, the candidate image is selected as the reference image . The moving image encoding apparatus according to claim 4, wherein the already-encoded image is a reference image or a non-reference image . The reference motion vector selection means repeats the determination of the presence / absence of the motion vector based on the predetermined selection criterion until the motion vector exists, and when the motion vector exists, the candidate image is selected as the reference image. The moving picture coding apparatus according to claim 4 or 5 , wherein the moving picture coding apparatus is selected as the moving picture coding apparatus.

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