JP2004032355A - Motion picture encoding method, motion picture decoding method, and apparatus for the both method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve encoding efficiency in encoding of motion pictures, by enabling an inter-frame prediction mode of a skip macroblock to be established beside direct to utilize the fact that there exists correlation of picture contents between adjacent regions. <P>SOLUTION: The skip prediction mode judgment section 103 determines an inter-frame prediction mode in the case of defining the present region as a skip region according to a condition established in advance. A motion searching/encoding mode judgment section 102 searches motions between input pictures and reference pictures to determine prediction errors in a forward prediction modes, a backward prediction mode or a bidirectional prediction mode; then judges, by using the prediction errors, which prediction mode is to be used for encoding; and determines the motion vector to be encoded according to the judged prediction mode. Further, with regard to the prediction mode determined in the skip prediction mode judgment section 103, it is determined whether the motion vectors and the prediction errors are encoded or not. <P>COPYRIGHT: (C)2004,JPO

Description

予測モードの符号化方法は次の通りとする。まずｓｋｉｐかどうかを示すＣＯＤ情報（１ビット）があり，ｓｋｉｐの場合には１に設定し，それのみとする。ｓｋｉｐでない場合には０に設定し，続いて各ブロックの前方向予測か後方向予測か両方向予測かを示す情報（可変長４ビット）を符号化する。１の場合にはｄｉｒｅｃｔモードを示し，０１の場合には前方向予測を示し，００１の場合には後方向予測を示し，０００１の場合にはｂｉ−ｐｒｅｄｉｃｔｉｖｅモードを示すものとする。これを４ブロック分連続して符号化する。
【００７３】
このような前提で現マクロブロックは次のように符号化される。まず，Ｓｋｉｐ予測モード判定部３０３でｓｋｉｐマクロブロック内の各ブロックの予測モードを決定する。続いて再分割動き探索／符号化モード判定部３０２で各予測モードにおける評価値を求める。同時に前方向予測と後方向予測の場合には動きベクトルも求める。領域予測モード判定部３１５は，マクロブロック内の各ブロックの予測モードを決定し，さらにブロックがｓｋｉｐかどうかを決定する。決定した予測モードは，予測モード蓄積部３０４に蓄積する。
【００７４】
続いて前方向予測と判定された場合には，ＦｏｒｗａｒｄＭＣ部３０８にて予測画像を求め，後方向予測と判定された場合には，ＢａｃｋｗａｒｄＭＣ部３０９にて予測画像を求め，ｄｉｒｅｃｔモードと判定された場合には，ＤｉｒｅｃｔＭＣ部３０７にて予測画像を求め，ｂｉ−ｐｒｅｄｉｃｔｉｖｅモードと判定された場合には，Ｂｉ−ｐｒｅｄｉｃｔｉｖｅＭＣ部３１６にて予測画像を求める。ここでｓｋｉｐの場合には，式（２）で差分を０とした場合の動きベクトルを使用する。続いてｓｋｉｐではない場合には，予測誤差符号化／量子化部３１０で現画像と予測画像との間で予測誤差を求めて符号化し量子化する。
【００７５】
復号部３１１では，ｓｋｉｐではない場合には，予測誤差を逆量子化して復号し，ＦｏｒｗａｒｄＭＣ部３０８またはＢａｃｋｗａｒｄＭＣ部３０９またはＤｉｒｅｃｔＭＣ部３０７またはＢｉ−ｐｒｅｄｉｃｔｉｖｅＭＣ部３１６にて得られた予測画像を使って復号画像を求める。ｓｋｉｐの場合には，ＦｏｒｗａｒｄＭＣ部３０８またはＢａｃｋｗａｒｄＭＣ部３０９またはＤｉｒｅｃｔＭＣ部３０７またはＢｉ−ｐｒｅｄｉｃｔｉｖｅＭＣ部３１６にて得られた予測画像を復号画像とする。復号画像を参照画像メモリ３０６に蓄積する。前方向予測と後方向予測とｂｉ−ｐｒｅｄｉｃｔｉｖｅモードの場合には，動きベクトルを動きベクトル蓄積部３０５に蓄積する。
【００７６】
以上の手順をすべてのマクロブロックに対して繰り返し処理する。
【００７７】
次に復号装置の説明を行う。図７に，第２の実施の形態に係る画像復号装置の概要を示す。以下，図５に示す第２の実施の形態の画像符号化装置で得られた符号化データを復号する手順を説明する。
【００７８】
第２の実施の形態の画像復号装置は，符号化データ入力部４０１，予測モード復号部４０２，Ｓｋｉｐ予測モード判定部４０３，予測モード蓄積部４０４，動きベクトル蓄積部４０５，参照画像メモリ４０６，ＤｉｒｅｃｔＭＣ部４０７，ＦｏｒｗａｒｄＭＣ部４０８，ＢａｃｋｗａｒｄＭＣ部４０９，Ｂｉ−ｐｒｅｄｉｃｔｉｖｅＭＣ部４１６，予測誤差逆量子化／復号部４１０，スイッチ部４１２〜４１４を備える。
【００７９】
ＦｏｒｗａｒｄＭＣ部４０８では，前方向予測を行って予測画像を求め，ＢａｃｋｗａｒｄＭＣ部４０９では，後方向予測を行って予測画像を求め，ＤｉｒｅｃｔＭＣ部４０７では，ｄｉｒｅｃｔモード予測を行って予測画像を求め，Ｂｉ−ｐｒｅｄｉｃｔｉｖｅＭＣ部４１６では，ｂｉ−ｐｒｅｄｉｃｔｉｖｅモード予測を行って予測画像を求めるものとする。ＤｉｒｅｃｔＭＣ部４０７にてｄｉｒｅｃｔモードに使用する動きベクトルは，動きベクトル蓄積部４０５に蓄積されているものとする。
【００８０】
Ｓｋｉｐ予測モード判定部４０３では，予測モード蓄積部４０４に蓄積された左，左上，上，右上のマクロブロックの予測モードから，図６のフローに従ってｓｋｉｐマクロブロック内の全てのブロックの予測モードを決定する。
【００８１】
このような前提で現マクロブロックは次のように符号化される。まずＳｋｉｐ予測モード判定部４０３でｓｋｉｐマクロブロック内のブロックの予測モードを決定する。続いて予測モード復号部４０２で予測モードを復号する。まずＣＯＤ情報を復号する。１であった場合にはｓｋｉｐであり，０であった場合にはｓｋｉｐではない。ＣＯＤが０の場合に各ブロックにさらに最大４ビットの予測モード情報を復号する。１の場合にはｄｉｒｅｃｔモードであり，０１の場合には前方向予測であり，００１の場合には後方向予測であり，０００１の場合にはｂｉ−ｐｒｅｄｉｃｔｉｖｅ予測となる。ＣＯＤが１の場合には，Ｓｋｉｐ予測モード判定部４０３で決定した予測モードとなる。これを４ブロック分連続して復号する。
【００８２】
続いて予測モードが前方向予測の場合には，ＦｏｒｗａｒｄＭＣ部４０８にて予測画像を求め，後方向予測の場合には，ＢａｃｋｗａｒｄＭＣ部４０９にて予測画像を求め，ｄｉｒｅｃｔモードの場合には，ＤｉｒｅｃｔＭＣ部４０７にて予測画像を求め，ｂｉ−ｐｒｅｄｉｃｔｉｖｅモードの場合には，Ｂｉ−ｐｒｅｄｉｃｔｉｖｅＭＣ部４１６にて予測画像を求める。続いてｓｋｉｐではない場合には，予測誤差逆量子化／復号部４１０で予測誤差を逆量子化し復号し，予測誤差を使って復号画像を作成する。ｓｋｉｐの場合には，予測画像がそのまま復号画像となる。復号画像を参照画像メモリ４０６に蓄積する。前方向予測と後方向予測とｂｉ−ｐｒｅｄｉｃｔｉｖｅモードの場合には復号した動きベクトルを動きベクトル蓄積部４０５に蓄積する。復号した予測モードは予測モード蓄積部４０４に蓄積する。
【００８３】
以上の手順をすべてのマクロブロックに対して繰り返し処理する。
【００８４】
なお，以上の第１および第２の実施の形態では，Ｓｋｉｐ予測モード判定部１０３，３０３等で，図２または図６のフローに従ってｓｋｉｐ予測モードを求めたが，決定フローはこれに限るものではない。
【００８５】
さらに，画面内の位置によってＳｋｉｐ予測モード判定部１０３，３０３等の決定フローを変更してもよい。例えば，画面外周のマクロブロックまたはブロックの場合には，Ｓｋｉｐ予測モード判定部１０３，３０３等で，図２または図６のフローに従わず，ｄｉｒｅｃｔモードで予測することも好適である。
【００８６】
さらにまた，後方向予測における参照フレームの表示時刻が，現フレームよりも未来であるか過去であるかによって，Ｓｋｉｐ予測モード判定部１０３，３０３等の決定フローを変更してもよい。例えば後方向予測における参照フレームの表示時刻が現フレームよりも未来である場合には，図２または図６の決定フローに従い，後方向予測における参照フレームの表示時刻が現フレームよりも過去である場合には，常にｄｉｒｅｃｔモードにすることも好適である。
【００８７】
また，本実施の形態ではマクロブロックまたはブロック毎に予測誤差を符号化したが，複数フレーム分の画像情報をまとめて符号化しても良い。例えば，文献「石川ら，“マルチパラメータ動き補償を用いた動画像の３Ｄ／２Ｄハイブリッド符号化，”信学技報ＩＥ２００１−７６　，ｐｐ．１５−２２，２００１」のように複数フレーム分の画像情報をＤＣＴしたり，文献「Ｊ．−Ｒ．Ｏｈｍ，“Ｔｈｒｅｅ−ｄｉｍｅｎｔｉｏｎａｌ　ｓｕｂｂａｎｄ　ｃｏｄｉｎｇ　ｗｉｔｈ　ｍｏｔｉｏｎ　ｃｏｍｐｅｎｓａｔｉｏｎ　，”ＩＥＥＥ　Ｔｒａｎｓ．　，Ｉｍａｇｅ　Ｐｒｏｃｅｓｓ．，ｖｏｌ．３　，ｐｐ．５５９−５７１，１９９４」のように複数フレーム分の画像情報をＷａｖｅｌｅｔ変換しても良い。
【００８８】
このように本実施の形態によれは，Ｂピクチャのｓｋｉｐマクロブロックのフレーム間予測方法を，隣接するマクロブロックまたはブロックの予測方法から適応的に変更することができる。
【００８９】
【発明の効果】
本発明によれば，Ｂピクチャのｓｋｉｐマクロブロックのフレーム間予測方法を，隣接するマクロブロックまたはブロックの予測方法から適応的に変更することができる。これにより，従来Ｂピクチャをはさむ３フレーム間で動きが一定しない場合に，ｄｉｒｅｃｔモードによる動きベクトルでは予測誤差を低減することができない場合においても，ｓｋｉｐマクロブロックのフレーム間予測モードをｄｉｒｅｃｔ以外に設定することが可能となり，隣接領域同士で画像内容に相関があることを利用して，符号化効率を向上することができる。
【図面の簡単な説明】
【図１】第１の実施の形態の画像符号化装置の例を示す図である。
【図２】第１の実施の形態のｓｋｉｐ予測モード決定フローの例を示す図である。
【図３】第１の実施の形態の動き探索／符号化モード判定部の動作フローの例を示す図である。
【図４】第１の実施の形態の画像復号装置の例を示す図である。
【図５】第２の実施の形態の画像符号化装置の例を示す図である。
【図６】第２の実施の形態のｓｋｉｐ予測モード決定フローの例を示す図である。
【図７】第２の実施の形態の画像復号装置の例を示す図である。
【図８】予測関係の例を説明するための図である。
【図９】ｄｉｒｅｃｔモードにおける動きベクトルの関係を説明するための図である。
【符号の説明】
１０１，３０１　画像入力部
１０２　動き探索／符号化モード判定部
２０２，４０２　予測モード復号部
３０２　再分割動き探索／符号化モード判定部
１０３，２０３，３０３，４０３　Ｓｋｉｐ予測モード判定部
１０４，２０４，３０４，４０４　予測モード蓄積部
１０５，２０５，３０５，４０５　動きベクトル蓄積部
１０６，２０６，３０６，４０６　参照画像メモリ
１０７，２０７，３０７，４０７　ＤｉｒｅｃｔＭＣ部
１０８，２０８，３０８，４０８　ＦｏｒｗａｒｄＭＣ部
１０９，２０９，３０９，４０９　ＢａｃｋｗａｒｄＭＣ部
１１０，３１０　予測誤差符号化／量子化部
２１０，４１０　予測誤差逆量子化／復号部
１１１，３１１　復号部
１１２〜１１４，２１２〜２１４，３１２〜３１４，４１２〜４１４　スイッチ部
３１５　領域予測モード判定部
３１６，４１６　Ｂｉ−ｐｒｅｄｉｃｔｉｖｅＭＣ部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique relating to video coding and decoding using a bidirectional inter-frame predictive coding method. In particular, the coding efficiency is improved by adaptively changing the inter-frame predictive method of a skip macro block of a B picture. TECHNICAL FIELD The present invention relates to a moving picture coding method, a moving picture decoding method, a moving picture coding apparatus, and a moving picture decoding apparatus capable of improving video quality.
[0002]
[Prior art]
Generally, in video coding, inter-frame predictive coding is used in order to realize high coding efficiency using correlation in the time direction. In the frame encoding mode, it is possible to predict from an I frame to be encoded without using correlation between frames, a P frame to be predicted from one frame encoded in the past, and two frames to be encoded in the past. There is a B frame. In particular, the video coding method H.264. In 263, decoded images for a plurality of frames are stored in the reference image memory, and a reference image can be selected and predicted from the memory.
[0003]
The P frame is predicted from a previously encoded frame, while the B frame can be predicted from two previously encoded frames. Of the two frames used as reference frames, a method of predicting from a more recent frame is called forward prediction, and a method of predicting from a more future frame is called backward prediction. The display time of the reference frame in the backward inter-frame prediction may be later than the current frame. In this case, after displaying the current frame, a reference frame for backward frame prediction is output. When predicting from two frames in B frames (bidirectional inter-frame prediction), image information from two frames is interpolated to generate image information for one frame to generate a predicted image.
[0004]
FIG. 8A1 shows an example of a prediction relationship of a moving image when the display time of a reference frame in the backward inter-frame prediction is in the future. When the coding modes of the first frame to the seventh frame are coded in the order of IBBPBBP, there is a prediction relationship shown in FIG. 8 (A1). As shown in (1), frames are encoded in the order of (1) (4) (2) (3) (7) (5) (6).
[0005]
FIG. 8B1 shows an example of a prediction relationship of a moving image when the display time of a reference frame in backward inter-frame prediction is in the past. When the encoding modes of the first frame to the seventh frame are encoded in the order of IPBBPBB, the prediction relationship shown in FIG. 8 (B1) is established. As shown in (1), frames are encoded in the order of (1) (2) (4) (3) (5) (7) (6).
[0006]
Furthermore, these coding modes can be designated for each area into which the image is divided, for example, a macroblock. Video coding system In H.263, there are only I macroblocks to be encoded using only the intra-frame image information in the I frame. In the P frame, there is a P macro block predicted from one frame coded in the past in addition to the I macro block. It is also possible to change the image to be referred for each macro block. Within a B frame, there is a B macroblock in addition to the I and P macroblocks. In the B macroblock, there are a forward prediction mode or a backward prediction mode in which prediction is performed from one frame coded in the past similarly to the P macroblock, and a bidirectional prediction mode in which prediction is performed from two frames.
[0007]
The bidirectional prediction mode includes a bi-predictive mode for encoding a motion vector indicating a reference position in each frame and a direct mode for not encoding. In the direct mode, a forward motion vector and a backward motion vector are calculated from motion vectors of macroblocks at the same position in a future frame to be referred to.
[0008]
FIG. 9 shows a relation diagram of motion vectors in the direct mode when the display time of the reference frame in the backward inter-frame prediction is in the future. In FIG. 9, it is assumed that P1 and P2 are already encoded frames, and Pc is an encoding target frame. Equation (1) shows a motion vector calculation formula when the motion vectors of the macroblocks between Pc, P1 and P2 are MVf and MVb, respectively. MVs is a motion vector of a macroblock between P1 and P2. Generally, the time interval between frames P1 and Pc is applied to N1, the time interval between frames Pc and P2 is applied to N2, and the time interval between frames P1 and P2 is applied to D.
[0009]
MVf = MVs × N1 / D (1-1)
MVb = MVs × N2 / D (1-2)
Since the motion vector is calculated according to the equation (1), the motion vector is not encoded in the direct mode.
[0010]
When encoding a motion vector of a macroblock, there is a method of encoding a difference from a motion vector of a surrounding macroblock. For example, the video encoding system H.264. In 263, a predicted motion vector PMV is created from the motion vectors (MV1, MV2, MV3) of the left, upper, and upper right macroblocks according to equation (2), and the difference from the PMV is encoded. Note that Median (a, b, c) finds an intermediate value among the values a, b, and c.
[0011]
PMV = Median (MV1, MV2, MV3) (2)
According to this method, when the change from the motion vector of the surrounding macroblock is small, the motion vector can be encoded with higher encoding efficiency.
[0012]
Also, a macroblock without coded data is called a skip macroblock. Video coding system In H.263, the skip macroblock in the P frame has a motion vector of 0 and has no prediction error. Therefore, an image at the same position in the reference frame is defined as a decoded image.
[0013]
The skip macro block in the B frame obtains a motion vector in the same manner as in the direct mode and has no prediction error. Therefore, an image obtained by interpolating the image information of the motion vector position calculated by Expression (1) is set as a decoded image.
[0014]
Generally, information on whether or not each macroblock is a skip macroblock, whether to perform intra-coding, and coding mode information indicating an inter-frame prediction method are coded. H. In H.263, 1-bit COD coding mode information indicating whether or not it is a skip macroblock is coded. If not skip, MCBPC coding mode information indicating whether to perform intra coding or an inter-frame prediction method is coded. I do. Therefore, in the case of a skip macro block, the information indicating the inter-frame prediction method, the motion vector, and the prediction error are not encoded. Video coding system In H.264, the skip macroblock does not encode COD encoding mode information, but performs run-length encoding of the number of consecutive skip macroblocks.
[0015]
[Problems to be solved by the invention]
Since the direct mode of the B frame is obtained from the motion vector of the subsequent P frame as shown in FIG. 9, it is effective when there is a constant speed motion between three frames. That is, in the case of a moving image captured by moving the camera in parallel at a constant speed, the prediction error can be greatly reduced by the motion vector in the direct mode. If there is no prediction error, it can be encoded as a skip macroblock. Since the skip macroblock is coded with COD information or run-length coded, the coding efficiency of the entire B frame can be improved.
[0016]
However, when the motion is not constant among the three frames, the prediction error cannot be reduced by the motion vector in the direct mode. Therefore, no skip macro block is generated, and the coding efficiency cannot be reduced.
[0017]
In view of the above point, the present invention provides a skip macro block (or a specific method) even when a prediction error cannot be reduced with a motion vector in the direct mode because the motion is not constant among three frames. Block), enabling the inter-frame prediction mode of the skip macroblock to be set to other than direct, and improving the coding efficiency by utilizing the fact that the image content is correlated between adjacent regions. And
[0018]
[Means for Solving the Problems]
In order to solve the above problems, the present invention uses the following method.
[0019]
According to a first aspect of the present invention, there is provided a moving image encoding method for dividing an input image into regions and encoding image information using one of a bidirectional inter-frame predictive coding method and a forward inter-frame predictive coding method. When encoding a region as a region having no inter-frame prediction mode coded data, motion vector coded data, and prediction error coded data, an inter-frame prediction method of an adjacent region satisfies a preset condition. The method is characterized in that an inter-frame prediction method of the current area is changed.
[0020]
The second invention divides an input image into regions, and divides the current region into frames using one of a bidirectional inter-frame predictive coding system, a forward inter-frame predictive coding system, and a backward inter-frame predictive coding system. When encoding as a region having no prediction mode coded data, motion vector coded data, and prediction error coded data, the frame of the current region is determined according to whether the inter-frame prediction method of the adjacent region satisfies a preset condition. The method is characterized in that the inter prediction method is changed.
[0021]
According to the first or second aspect of the present invention, even when the inter-frame prediction mode is not coded as in the case of the skip macro block, the inter-frame prediction mode of the adjacent area is set according to the preset condition. Can be changed. For example, there are the following two types of conditions. These may be combined.
[Condition a] Of the inter-frame prediction modes of the four adjacent regions on the left, upper left, upper, and upper right, the mode with the largest number of modes is also applied to the current region.
[Condition b] If there is an area of a specific inter-frame prediction mode on the four adjacent left, upper left, upper, and upper right, the same mode is applied to the current area.
[0022]
Further, in a case where a method of encoding a difference from a motion vector of a surrounding macroblock is applied in the forward prediction, the backward prediction, and the bidirectional prediction, a motion vector of a skip macroblock is applied as a zero vector. It is also possible to apply the PMV calculated from the equation (2).
[0023]
If there is a correlation in image content between adjacent regions, coding efficiency tends to be higher in the same inter-frame prediction mode. Therefore, conventionally, when the motion is not constant among the three frames including the B picture, the inter-frame prediction mode of the skip macroblock is set to other than direct even when the prediction error cannot be reduced by the motion vector in the direct mode. And encoding efficiency can be improved.
[0024]
According to a third aspect, in the first or second aspect, a direct mode in which no motion vector is encoded and a bi-predictive mode in which forward and backward motion vectors are encoded during bidirectional inter-frame predictive encoding. And an inter-frame prediction method for the current area is determined.
[0025]
According to the third aspect, when the inter-frame prediction mode is not coded as in the skip macro block, when the inter-frame prediction mode is obtained from the inter-frame prediction mode of the adjacent area, the direct mode is used as the bidirectional prediction. And bi-predictive mode. In the case of the direct mode, the motion vector can be obtained according to the equation (1), and in the case of the bi-predictive mode, the PMV obtained according to the equation (2) or the zero vector can be applied.
[0026]
Thereby, in the case of the bidirectional prediction mode, it is possible to change the inter-frame prediction mode more finely.
[0027]
In a fourth aspect based on the first, second, or third aspect, the current area is encoded as an area having no inter-frame prediction mode encoded data, motion vector encoded data, and prediction error encoded data. Changing the inter-frame prediction method for the re-divided region of the current region according to whether or not the inter-frame prediction method for the adjacent re-divided region satisfies a preset condition for each of the sub-regions obtained by further dividing the current region. It is characterized by.
[0028]
According to the fourth aspect, when the inter-frame prediction mode, the motion vector, and the prediction error are not encoded as in the skip macro block, the inter-frame prediction mode is changed for each smaller unit such as a block. be able to. As a result, the inter-frame prediction mode can be changed in smaller units than the macroblock.
[0029]
A fifth invention is a moving picture decoding method for decoding image information using a bidirectional inter-frame predictive coding method or a forward inter-frame predictive coding method for each divided area of an image. When decoding as an area without mode encoded data, motion vector encoded data and prediction error encoded data, the inter-frame prediction of the current area is performed according to whether the inter-frame prediction method of the adjacent area satisfies a preset condition. The method is characterized by changing.
[0030]
According to a sixth aspect of the present invention, there is provided a moving image decoding apparatus for decoding image information using a bidirectional inter-frame predictive coding method, a forward inter-frame predictive coding method, or a backward inter-frame predictive coding method for each divided area of an image. In the method, when decoding the current region as a region having no inter-frame prediction mode coded data, motion vector coded data, and prediction error coded data, whether the inter-frame prediction method of an adjacent region satisfies a preset condition. The method is characterized in that the inter-frame prediction method of the current area is changed depending on whether or not the frame is predicted.
[0031]
In a seventh aspect based on the fifth or sixth aspect, the bidirectional predictive decoding includes a direct mode in which no motion vector is decoded and a bi-predictive mode in which forward and backward motion vectors are decoded. Separately, an inter-frame prediction method for the current area is determined.
[0032]
According to an eighth aspect, in the fifth, sixth, or seventh aspect, the current area is decoded as an area having no inter-frame prediction mode encoded data, motion vector encoded data, and prediction error encoded data. Changing the inter-frame prediction method of the re-divided area of the current area according to whether the inter-frame prediction method of the adjacent re-divided area satisfies a preset condition for each sub-divided area obtained by further dividing the current area. Features.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0034]
In the first embodiment, it is assumed that bidirectional prediction, forward prediction, and backward prediction are switched and coded for a B picture in macroblock units. Here, bidirectional prediction refers to the direct mode.
[0035]
First, the encoding device will be described. FIG. 1 shows an outline of an image encoding device according to the first embodiment. This image coding apparatus includes an image input unit 101, a motion search / coding mode determination unit 102, a Skip prediction mode determination unit 103, a prediction mode storage unit 104, a motion vector storage unit 105, a reference image memory 106, a DirectMC unit 107, It includes a ForwardMC unit 108, a BackwardMC unit 109, a prediction error encoding / quantization unit 110, a decoding unit 111, and switch units 112 to 114.
[0036]
The ForwardMC unit 108 performs forward prediction to obtain a predicted image, the BackwardMC unit 109 performs backward prediction to obtain a predicted image, and the DirectMC unit 107 performs bidirectional prediction to obtain a predicted image. It is assumed that the motion vector used in the direct mode by the DirectMC unit 107 is stored in the motion vector storage unit 105.
[0037]
The Skip prediction mode determination unit 103 calculates the current macroblock from the prediction modes of the left, upper left, upper, and upper right macroblocks stored in the prediction mode storage unit 104 in the motion search / coding mode determination unit 102. Determine the prediction mode for the block. FIG. 2 shows a flow of the determination.
[0038]
First, it is determined whether there is a direct macroblock at any of the left, upper left, upper, and upper right of the current macroblock (step S1). If there is a direct macroblock, the prediction mode of the skip macroblock is determined to be the direct mode (step S2).
[0039]
If there are no direct macroblocks on the left, upper left, upper, and upper right, the number Nf of forward predicted macroblocks and the number Nb of backward predicted macroblocks on the left, upper left, upper, and upper right are counted (step S3). A comparison is made between the number Nf of predicted macroblocks and the number Nb of backward predicted macroblocks (step S4).
[0040]
When the number of macroblocks Nf and Nb are equal, the prediction mode of the skip macroblock is determined to be the direct mode (step S2).
[0041]
If the number Nf of macroblocks is larger than Nb, the prediction mode of the skip macroblock is determined to be the forward prediction mode (step S5).
[0042]
If the number Nf of macroblocks is smaller than Nb, the prediction mode of the skip macroblock is determined to be the backward prediction mode (step S6).
[0043]
FIG. 3 shows an operation flow of the motion search / coding mode determination unit 102 according to the present embodiment. The motion search / coding mode determination unit 102 performs a motion search for forward prediction (step S10) and a motion search for backward prediction (step S11). In the motion search, the prediction error and the code amount of the motion vector are evaluated using Expression (3), and the position where the value becomes the smallest is determined as the motion vector in the prediction method. It is assumed that the motion vector encodes a difference obtained using Expression (2).
[0044]
Further, the evaluation value Dmb of the expression (3) relating to the direct mode, the forward prediction and the backward prediction is compared, and the case where the value is the smallest is determined as the prediction mode PM to be used (step S12). If the determined prediction mode PM is the same as the prediction mode determined to be applied to the Skip macroblock by the Skip prediction mode determination unit 103, the evaluation value obtained by Expression (3) satisfies Expression (4). It is checked whether or not it is satisfied (step S13). If the condition is satisfied, the current macroblock is skipped (step S14). If the condition is not satisfied, skip is not set (step S15).
[0045]
Note that A and B in Expression (3) are values that change depending on the quantization scale, p indicates a pixel, e [p] indicates a prediction error in the pixel p, and b (MV) indicates a motion vector. Indicates the code amount of the MV. The motion vector MV indicates a motion vector for forward prediction or a motion vector for backward prediction. THskip in equation (4) is a preset constant.
[0046]
Dmb = A * Σ | e [p] | + B * | b (MV) | (3)
(However, Σ indicates the sum of all pixels p in the macroblock.)
Dmb ≦ THskip (4)
The encoding method of the prediction mode is as follows. First, there is COD information (1 bit) indicating whether or not a skip is set. In the case of a skip, it is set to 1 and only that is set. If it is not skip, it is set to 0, and then information (2 bits) indicating forward prediction, backward prediction or bidirectional prediction is encoded. 01 indicates forward prediction, 10 indicates backward prediction, and 11 indicates bidirectional prediction.
[0047]
Under such a premise, the current macroblock is encoded as follows. First, the skip prediction mode determination unit 103 determines a prediction mode of a skip macro block. Subsequently, the motion search / coding mode determination unit 102 determines a prediction mode. At the same time, in the case of forward prediction and backward prediction, a motion vector is also obtained. If the determined prediction mode is a skip macroblock prediction mode, it is determined whether or not the macroblock is a skip. The determined prediction mode is stored in the prediction mode storage unit 104.
[0048]
Subsequently, the switch units 112 and 113 are switched, and if it is determined to be forward prediction, a predicted image is obtained by the ForwardMC unit 108, and if it is determined to be backward prediction, a predicted image is obtained by the Backward MC unit 109. If it is determined that the mode is the direct mode, the DirectMC unit 107 obtains a predicted image. Here, in the case of skip, a motion vector when the difference is set to 0 in Expression (2) is used.
[0049]
Subsequently, in the case of not skip, the prediction image is sent to the prediction error coding / quantization unit 110 through the switch unit 113, and the prediction error coding / quantization unit 110 calculates the prediction error between the current image and the prediction image. It is coded and quantized.
[0050]
In the case of not skip, the decoding unit 111 inversely quantizes and decodes the prediction error, and obtains a decoded image using the predicted image obtained by the ForwardMC unit 108, the BackwardMC unit 109, or the DirectMC unit 107. In the case of skip, a predicted image obtained by the ForwardMC unit 108, the BackwardMC unit 109, or the DirectMC unit 107 is used as a decoded image. The decoded image is stored in the reference image memory 106. In the case of forward prediction and backward prediction, a motion vector is stored in the motion vector storage unit 105.
[0051]
The above procedure is repeated for all macroblocks.
[0052]
Next, the decoding device will be described. FIG. 4 shows an outline of the image decoding apparatus according to the first embodiment. A procedure for decoding encoded data obtained by the embodiment of the image encoding device shown in FIG. 1 will be described.
[0053]
The image decoding device includes an encoded data input unit 201, a prediction mode decoding unit 202, a Skip prediction mode determination unit 203, a prediction mode storage unit 204, a motion vector storage unit 205, a reference image memory 206, a DirectMC unit 207, a ForwardMC unit 208, A Backward MC unit 209, a prediction error inverse quantization / decoding unit 210, and switch units 212 to 214 are provided.
[0054]
The ForwardMC unit 208 performs forward prediction to obtain a predicted image, the BackMC unit 209 performs backward prediction to obtain a predicted image, and the DirectMC unit 207 performs bidirectional prediction to obtain a predicted image. It is assumed that the motion vector used in the direct mode by the DirectMC unit 207 is stored in the motion vector storage unit 205.
[0055]
The Skip prediction mode determination unit 203 determines the prediction mode of the Skip macroblock from the prediction modes of the left, upper left, upper, and upper right macroblocks stored in the prediction mode storage unit 204 according to the flow of FIG.
[0056]
On this assumption, the current macroblock is decoded as follows. First, the skip prediction mode determination unit 203 determines a prediction mode of a skip macro block. Subsequently, the prediction mode decoding unit 202 decodes the prediction mode. First, the COD information is decrypted. If COD is 1, it is skip, and if it is 0, it is not skip. If COD is 0, two more bits are decoded. 01 indicates forward prediction, 10 indicates backward prediction, and 11 indicates bidirectional prediction. When COD is 1, the prediction mode determined by the Skip prediction mode determination unit 203 is used.
[0057]
Subsequently, when the prediction mode is forward prediction, a forward MC unit 208 obtains a predicted image, when backward prediction is performed, a predicted image is obtained by the Backward MC unit 209, and when the direct mode is used, the DirectMC unit is obtained. At 207, a predicted image is obtained. Here, in the case of skip, a motion vector when the difference is set to 0 in Expression (2) is used.
[0058]
Subsequently, in the case of not skip, the prediction error inverse quantization / decoding unit 210 dequantizes and decodes the prediction error, and creates a decoded image using the prediction error. In the case of skip, the predicted image becomes a decoded image as it is. The decoded image is stored in the reference image memory 206. In the case of forward prediction and backward prediction, the decoded motion vector is stored in the motion vector storage unit 205. The decoded prediction mode is stored in the prediction mode storage unit 204.
[0059]
The above procedure is repeated for all macroblocks.
[0060]
Next, a second embodiment will be described. In the second embodiment, it is assumed that a B picture is coded by switching among forward prediction, backward prediction, direct mode, and bi-predictive mode in block units.
[0061]
First, the encoding device will be described. FIG. 5 shows an outline of an image encoding device according to the second embodiment. The image coding apparatus according to the second embodiment includes an image input unit 301, a sub-division motion search / coding mode determination unit 302, a Skip prediction mode determination unit 303, a prediction mode storage unit 304, an area prediction mode determination unit 315, It has a motion vector storage unit 305, a reference image memory 306, a DirectMC unit 307, a Bi-predictive MC unit 316, a ForwardMC unit 308, a BackwardMC unit 309, a prediction error encoding / quantization unit 310, a decoding unit 311 and a switch unit 312 to 314. .
[0062]
The ForwardMC unit 308 performs forward prediction to obtain a predicted image, the BackwardMC unit 309 performs backward prediction to obtain a predicted image, and the DirectMC unit 307 performs direct mode prediction to obtain a predicted image. Predictive MC section 316 performs bi-predictive mode prediction to obtain a predicted image. It is assumed that the motion vector used in the direct mode by the DirectMC unit 307 is stored in the motion vector storage unit 305.
[0063]
The Skip prediction mode determination unit 303 determines the prediction modes of all the blocks in the Skip macro block from the prediction modes of the left, upper left, upper, and upper right blocks stored in the prediction mode storage unit 304. FIG. 6 shows a flow of the determination.
[0064]
First, it is determined whether there is a direct block at any of the left, upper left, upper, and upper right of the current block (step S20). If there is a direct block, the prediction mode of the block in the skip macro block is determined to be the direct mode (step S25).
[0065]
If there are no direct blocks on the left, upper left, upper, and upper right, the number Nf of forward predicted blocks and the number Nb of backward predicted blocks on the left, upper left, upper, and upper right are counted (step S21), and the number of forward predicted blocks is counted. It is determined whether both Nf and the number Nb of backward prediction blocks are 0 (step S22). If Nf = 0 and Nb = 0, the prediction mode of the block in the skip macroblock is determined to be the direct mode (step S25).
[0066]
If Nf = 0 and Nb = 0 are not satisfied, it is determined whether Nf> 0 and Nb> 0 (step S23). If Nf> 0 and Nb> 0, the prediction mode of the block in the skip macroblock is determined to be the bi-predictive mode (step S25).
[0067]
Next, it is determined whether or not Nf> 0 and Nb = 0 (step S24). If Nf> 0 and Nb = 0, the prediction mode of the block in the skip macroblock is set to the forward prediction mode. It is determined (step S27).
[0068]
If Nf> 0 and Nb = 0, then Nf = 0 and Nb> 0. In this case, the prediction mode of the block in the skip macroblock is determined as the backward prediction mode (step S28).
[0069]
The subdivision motion search / coding mode determination unit 302 performs a motion search for forward prediction and a motion search for backward prediction for each block. In the motion search, the prediction error and the code amount of the motion vector are evaluated using Expression (5) described later, and the position where the value becomes the smallest is determined as the motion vector in the prediction method. In the bi-predictive mode, a prediction error is obtained using a motion vector obtained by a motion search for forward prediction and backward prediction, and an evaluation value is obtained by Expression (6). The above processing is performed on all the blocks in the macro block.
[0070]
The region prediction mode determination unit 315 compares the evaluation values of the bi-predictive mode, the direct mode, the forward prediction, and the backward prediction obtained by the subdivision motion search / coding mode determination unit 302 for each block. Then, the prediction mode when the value is the smallest is obtained. The evaluation value summed by the macroblock at this time is M1. Further, the evaluation value of the prediction mode determined by the Skip prediction mode determination unit 303 is calculated by the equation (5) or (6). The evaluation value summed by the macroblock at this time is defined as M2.
[0071]
It is checked whether the evaluation value M1 and the evaluation value M2 satisfy Expression (7). If the evaluation value M1 and the evaluation value M2 satisfy the expression (7), the current macroblock is skipped. Note that A, B, and C in Expressions (5) and (6) are values that change depending on the quantization scale, p indicates a pixel, and e [p] indicates a prediction error in the pixel p. , B (MV) indicate the code amount of the motion vector MV. The motion vector MVf indicates a forward prediction motion vector, the motion vector MVb indicates a backward prediction motion vector, and the motion vector MV indicates a forward prediction motion vector or a backward prediction motion vector. THskip in equation (7) is a preset constant. Σ represents the sum of all pixels p in the block.
[0072]

The encoding method of the prediction mode is as follows. First, there is COD information (1 bit) indicating whether it is skip or not. In the case of skip, it is set to 1 and only that. If it is not skip, it is set to 0, and then information (variable length 4 bits) indicating forward prediction, backward prediction or bidirectional prediction of each block is encoded. A value of 1 indicates the direct mode, a value of 01 indicates the forward prediction, a value of 001 indicates the backward prediction, and a value of 0001 indicates the bi-predictive mode. This is coded continuously for four blocks.
[0073]
On this assumption, the current macroblock is encoded as follows. First, the Skip prediction mode determination unit 303 determines the prediction mode of each block in the Skip macroblock. Subsequently, an evaluation value in each prediction mode is obtained by the subdivision motion search / coding mode determination unit 302. At the same time, in the case of forward prediction and backward prediction, a motion vector is also obtained. The region prediction mode determination unit 315 determines the prediction mode of each block in the macro block, and further determines whether the block is a skip. The determined prediction mode is stored in the prediction mode storage unit 304.
[0074]
Subsequently, when it is determined to be forward prediction, a predicted image is obtained by the ForwardMC unit 308, and when it is determined to be backward prediction, a predicted image is obtained by the BackMC unit 309, and the direct mode is determined. In this case, a predicted image is obtained by the DirectMC unit 307, and when it is determined that the mode is the bi-predictive mode, the predicted image is obtained by the Bi-predictive MC unit 316. Here, in the case of skip, a motion vector when the difference is set to 0 in Expression (2) is used. Subsequently, in the case of not skip, the prediction error encoding / quantization unit 310 obtains a prediction error between the current image and the predicted image, encodes and quantizes the prediction error.
[0075]
When the decoding is not skip, the decoding unit 311 decodes the prediction error by dequantizing and decoding the prediction error, using the prediction image obtained by the ForwardMC unit 308, the BackwardMC unit 309, the DirectMC unit 307, or the Bi-predictiveMC unit 316. Ask for an image. In the case of skip, a predicted image obtained by the ForwardMC unit 308, the BackwardMC unit 309, the DirectMC unit 307, or the Bi-predictiveMC unit 316 is used as a decoded image. The decoded image is stored in the reference image memory 306. In the case of forward prediction, backward prediction, and bi-predictive mode, the motion vector is stored in the motion vector storage unit 305.
[0076]
The above procedure is repeated for all macroblocks.
[0077]
Next, the decoding device will be described. FIG. 7 shows an outline of an image decoding apparatus according to the second embodiment. Hereinafter, a procedure for decoding the encoded data obtained by the image encoding device according to the second embodiment shown in FIG. 5 will be described.
[0078]
The image decoding apparatus according to the second embodiment includes an encoded data input unit 401, a prediction mode decoding unit 402, a Skip prediction mode determination unit 403, a prediction mode storage unit 404, a motion vector storage unit 405, a reference image memory 406, and DirectMC. A unit 407, a ForwardMC unit 408, a BackwardMC unit 409, a Bi-predictiveMC unit 416, a prediction error inverse quantization / decoding unit 410, and switches 412 to 414.
[0079]
The ForwardMC unit 408 performs forward prediction to obtain a predicted image, the BackMC unit 409 performs backward prediction to obtain a predicted image, and the DirectMC unit 407 performs direct mode prediction to obtain a predicted image. Predictive MC section 416 performs bi-predictive mode prediction to obtain a predicted image. It is assumed that the motion vector used in the direct mode by the DirectMC unit 407 is stored in the motion vector storage unit 405.
[0080]
The Skip prediction mode determination unit 403 determines the prediction modes of all the blocks in the Skip macroblock from the prediction modes of the left, upper left, upper, and upper right macroblocks stored in the prediction mode storage unit 404 according to the flow of FIG. I do.
[0081]
On this assumption, the current macroblock is encoded as follows. First, the Skip prediction mode determination unit 403 determines the prediction mode of a block in the Skip macroblock. Subsequently, the prediction mode decoding unit 402 decodes the prediction mode. First, the COD information is decoded. If it is 1, it is a skip, and if it is 0, it is not a skip. When COD is 0, the prediction mode information of up to 4 bits is further decoded for each block. In the case of 1, direct mode is set, in the case of 01, forward prediction, in the case of 001, backward prediction, and in the case of 0001, bi-predictive prediction. When COD is 1, the prediction mode determined by the Skip prediction mode determination unit 403 is used. This is continuously decoded for four blocks.
[0082]
Subsequently, when the prediction mode is forward prediction, a forward MC unit 408 obtains a predicted image, when backward prediction is performed, a predicted image is obtained by a Backward MC unit 409, and when the direct mode is used, the DirectMC unit is obtained. At 407, a predicted image is obtained, and in the case of the bi-predictive mode, a predicted image is obtained at the Bi-predictive MC unit 416. Subsequently, in the case of not skip, the prediction error inverse quantization / decoding unit 410 dequantizes and decodes the prediction error, and creates a decoded image using the prediction error. In the case of skip, the predicted image becomes a decoded image as it is. The decoded image is stored in the reference image memory 406. In the case of forward prediction, backward prediction, and bi-predictive mode, the decoded motion vector is stored in the motion vector storage unit 405. The decoded prediction mode is stored in the prediction mode storage unit 404.
[0083]
The above procedure is repeated for all macroblocks.
[0084]
In the first and second embodiments, the skip prediction mode is determined by the skip prediction mode determination units 103 and 303 according to the flow of FIG. 2 or FIG. 6, but the determination flow is not limited to this. Absent.
[0085]
Further, the determination flow of the Skip prediction mode determination units 103 and 303 may be changed depending on the position in the screen. For example, in the case of a macroblock or a block on the outer periphery of the screen, it is also preferable that the Skip prediction mode determination units 103 and 303 perform prediction in the direct mode without following the flow of FIG. 2 or FIG.
[0086]
Furthermore, the determination flow of the Skip prediction mode determination units 103 and 303 may be changed depending on whether the display time of the reference frame in the backward prediction is later or later than the current frame. For example, when the display time of the reference frame in the backward prediction is later than the current frame, the display time of the reference frame in the backward prediction is later than the current frame according to the determination flow of FIG. 2 or FIG. It is also preferable to always use the direct mode.
[0087]
Further, in the present embodiment, the prediction error is encoded for each macroblock or block, but image information for a plurality of frames may be encoded collectively. For example, as described in the document “Ishikawa et al.,“ 3D / 2D Hybrid Coding of Moving Images Using Multi-Parameter Motion Compensation, ”IEICE Technical Report IE 2001-76, pp. 15-22, 2001” As described in the literature "J.-R. Ohm," Three-dimensional subband coding with motion compensation, "IEEE Trans., Image Process., Vol. 3, Vol. 3, pp. 559-57. The image information of the frame may be subjected to Wavelet conversion.
[0088]
As described above, according to the present embodiment, the inter-frame prediction method of a skip macro block of a B picture can be adaptively changed from the prediction method of an adjacent macro block or block.
[0089]
【The invention's effect】
According to the present invention, the inter-frame prediction method of a skip macro block of a B picture can be adaptively changed from the prediction method of an adjacent macro block or a block. Accordingly, even when the motion is not constant among the three frames including the conventional B picture and the prediction error cannot be reduced by the motion vector in the direct mode, the inter-frame prediction mode of the skip macroblock is set to other than direct. It is possible to improve the coding efficiency by utilizing the fact that the image content is correlated between adjacent regions.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of an image encoding device according to a first embodiment.
FIG. 2 is a diagram illustrating an example of a skip prediction mode determination flow according to the first embodiment.
FIG. 3 is a diagram illustrating an example of an operation flow of a motion search / coding mode determination unit according to the first embodiment.
FIG. 4 is a diagram illustrating an example of an image decoding device according to the first embodiment.
FIG. 5 is a diagram illustrating an example of an image encoding device according to a second embodiment.
FIG. 6 is a diagram illustrating an example of a skip prediction mode determination flow according to the second embodiment.
FIG. 7 is a diagram illustrating an example of an image decoding device according to a second embodiment.
FIG. 8 is a diagram illustrating an example of a prediction relationship.
FIG. 9 is a diagram for explaining a relationship between motion vectors in a direct mode.
[Explanation of symbols]
101, 301 Image input unit
102 Motion search / coding mode determination unit
202, 402 Prediction mode decoding unit
302 Subdivision motion search / coding mode determination unit
103, 203, 303, 403 Skip prediction mode determination unit
104, 204, 304, 404 prediction mode storage unit
105, 205, 305, 405 Motion vector storage unit
106, 206, 306, 406 Reference image memory
107, 207, 307, 407 DirectMC section
108,208,308,408 ForwardMC part
109, 209, 309, 409 Backward MC section
110,310 Prediction error coding / quantization unit
210, 410 prediction error inverse quantization / decoding unit
111, 311 decoding unit
112-114, 212-214, 312-314, 412-414 Switch section
315 Area prediction mode determination unit
316,416 Bi-predictive MC section

Claims (12)

A moving image encoding method for dividing an input image into regions and encoding image information using a bidirectional inter-frame predictive coding method or a forward inter-frame predictive coding method.
When encoding the current area as an area having no inter-frame prediction mode encoded data, motion vector encoded data, and prediction error encoded data,
A moving picture coding method characterized by changing an inter-frame prediction method of a current area according to whether or not an inter-frame prediction method of an adjacent area satisfies a preset condition. A moving image encoding method for dividing an input image into regions and encoding image information using a bidirectional interframe predictive coding method, a forward interframe predictive coding method, or a backward interframe predictive coding method,
When encoding the current area as an area having no inter-frame prediction mode encoded data, motion vector encoded data, and prediction error encoded data,
A moving picture coding method characterized by changing an inter-frame prediction method of a current area according to whether or not an inter-frame prediction method of an adjacent area satisfies a preset condition. In the moving picture coding method according to claim 1 or 2,
At the time of bidirectional inter-frame prediction encoding, a direct mode in which no motion vector is encoded and a bi-predictive mode in which forward and backward motion vectors are encoded are distinguished to determine an inter-frame prediction method of the current area. A moving picture coding method characterized in that: In the moving picture encoding method according to claim 1, claim 2, or claim 3,
When encoding the current area as an area having no inter-frame prediction mode encoded data, motion vector encoded data, and prediction error encoded data,
The method of changing the inter-frame prediction method of the re-divided area of the current area is performed according to whether the inter-frame prediction method of the adjacent re-divided area satisfies a preset condition for each sub-divided area obtained by further dividing the current area. Moving image encoding method. In a moving image decoding method for decoding image information using a bidirectional inter-frame predictive coding method or a forward inter-frame predictive coding method for each divided region of an image,
When decoding the current region as a region having no inter-frame prediction mode encoded data, motion vector encoded data, and prediction error encoded data,
A moving picture decoding method characterized by changing an inter-frame prediction method of a current area according to whether an inter-frame prediction method of an adjacent area satisfies a preset condition. In a moving image decoding method for decoding image information using a bidirectional inter-frame predictive coding method, a forward inter-frame predictive coding method, or a backward inter-frame predictive coding method for each divided region of an image,
When decoding the current region as a region having no inter-frame prediction mode encoded data, motion vector encoded data, and prediction error encoded data,
A moving picture decoding method characterized by changing an inter-frame prediction method of a current area according to whether an inter-frame prediction method of an adjacent area satisfies a preset condition. In the moving picture decoding method according to claim 5 or 6, the bidirectional inter-frame predictive decoding includes a direct mode in which no motion vector is decoded and a bi-predictive mode in which forward and backward motion vectors are decoded. A moving picture decoding method characterized by determining an inter-frame prediction method for a current area in distinction. In the moving picture decoding method according to claim 5, claim 6, or claim 7,
When decoding the current region as a region having no inter-frame prediction mode encoded data, motion vector encoded data, and prediction error encoded data,
The method of changing the inter-frame prediction method of the re-divided area of the current area is performed according to whether the inter-frame prediction method of the adjacent re-divided area satisfies a preset condition for each sub-divided area obtained by further dividing the current area. Moving image decoding method. A moving image encoding apparatus that divides an input image into regions and encodes image information using a bidirectional interframe predictive coding method, a forward interframe predictive coding method, or a backward interframe predictive coding method,
An image input unit for inputting an image for each area;
A prediction mode accumulation unit for accumulating an inter-frame prediction mode of an already encoded region, and a prediction mode accumulated in the prediction mode accumulation unit, wherein the current region is subjected to motion vector encoded data and prediction error encoding according to preset conditions. A skip prediction mode determination unit that determines an inter-frame prediction mode when the region has no data;
A motion search is performed between the input image and the reference image to determine a prediction error in the forward prediction mode, the backward prediction mode, or the bidirectional prediction mode, and the prediction error is used to determine which prediction mode to use for encoding. A motion vector to be coded according to the determined prediction mode, and for the prediction mode determined by the skip prediction mode determination section, motion search / coding to determine whether to encode the motion vector and the prediction error. A mode determination unit,
A forward motion compensation unit for creating a predicted image used for motion compensation in the forward prediction mode,
A backward motion compensator for creating a predicted image used for motion compensation in the backward prediction mode,
A bidirectional motion compensator for generating a predicted image used for motion compensation in the bidirectional prediction mode,
A prediction error encoding / quantizing unit for obtaining a prediction error, encoding and quantizing the prediction error,
A decoding unit that decodes the quantized encoded data to create a decoded image;
A reference image memory for storing the decoded image,
A motion vector storage unit for storing motion vectors;
A moving picture coding apparatus comprising: A moving image encoding apparatus that divides an input image into regions and encodes image information using a bidirectional interframe predictive coding method, a forward interframe predictive coding method, or a backward interframe predictive coding method,
An image input unit for inputting an image for each area;
A prediction mode storage unit for storing the inter-frame prediction mode of the already coded region;
A skip prediction mode for determining an inter-frame prediction mode when the current region is a region having no motion vector coded data and no prediction error coded data from a prediction mode stored in the prediction mode storage unit according to a preset condition. A judgment unit;
Performs motion search between the input image and the reference image, finds the prediction error in forward prediction mode, backward prediction mode, direct mode, or bipredictive mode, and encodes in any prediction mode using the prediction error Is determined, a motion vector to be encoded is determined according to the determined prediction mode, and for the prediction mode determined by the skip prediction mode determination unit, it is determined whether to encode the motion vector and the prediction error. A motion search / coding mode determination unit,
A forward motion compensation unit for creating a predicted image used for motion compensation in the forward prediction mode,
A backward motion compensator for creating a predicted image used for motion compensation in the backward prediction mode,
A direct motion compensation unit for creating a predicted image used for motion compensation in the direct mode,
A bi-predictive motion compensation unit for creating a predicted image used for motion compensation in a bi-predictive mode,
A prediction error encoding / quantizing unit for obtaining a prediction error, encoding and quantizing the prediction error,
A decoding unit that decodes the quantized encoded data to create a decoded image;
A reference image memory for storing the decoded image,
A motion vector storage unit for storing motion vectors;
A moving picture coding apparatus comprising: In a moving image encoding apparatus that divides an input image into regions, encodes image information by changing an inter-frame prediction method for each of the subdivided regions into which the region is further divided,
An image input unit for inputting an image for each area;
A prediction mode storage unit for storing the inter-frame prediction mode of the already coded region;
From the prediction modes stored in the prediction mode storage unit, an inter-frame prediction mode is determined according to a preset condition when the current subdivision region is a region having no motion vector coded data and no prediction error coded data. A skip prediction mode determination unit,
In the current subdivision region, a motion search is performed between an input image and a reference image, and a subdivision motion search / encoding for obtaining a prediction error in a forward prediction mode, a backward prediction mode, a direct mode, or a bipredictive mode. A mode determination unit,
Using the prediction error and the motion vector obtained by the subdivision motion search / coding mode determination unit for all subdivision regions in the current region, the prediction mode of each subdivision region in the region is determined. An area prediction mode determining unit for determining whether to skip,
A forward motion compensation unit for creating a predicted image used for motion compensation in the forward prediction mode,
A backward motion compensator for creating a predicted image used for motion compensation in the backward prediction mode,
A direct motion compensation unit for creating a predicted image used for motion compensation in the direct mode,
A bi-predictive motion compensation unit for creating a predicted image used for motion compensation in a bi-predictive mode,
A prediction error encoding / quantizing unit for obtaining a prediction error, encoding and quantizing the prediction error,
A decoding unit that decodes the quantized encoded data to create a decoded image;
A reference image memory for storing the decoded image,
A motion vector storage unit for storing motion vectors;
A moving picture coding apparatus comprising: In a moving image decoding apparatus that decodes image information using a bidirectional inter-frame predictive coding method, a forward inter-frame predictive coding method, or a backward inter-frame predictive coding method for each divided region of an image,
A prediction mode decoding unit for decoding a prediction mode;
A prediction mode storage unit for storing the inter-frame prediction mode of the already decoded area;
A skip prediction mode for determining an inter-frame prediction mode when the current region is a region having no motion vector coded data and no prediction error coded data from a prediction mode stored in the prediction mode storage unit according to a preset condition. A judgment unit;
A forward motion compensation unit for creating a predicted image used for motion compensation in the forward prediction mode,
A backward motion compensator for creating a predicted image used for motion compensation in the backward prediction mode,
A direct motion compensation unit for creating a predicted image used for motion compensation in the direct mode,
A bi-predictive / motion compensation unit for creating a predicted image used for motion compensation in a bi-predictive mode,
A prediction error inverse quantization / decoding unit for inversely quantizing and decoding the prediction error;
A reference image memory for storing the decoded image,
A motion vector storage unit for storing motion vectors;
A moving picture decoding apparatus comprising:

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