Source: http://patents.com/us-9432677.html
Timestamp: 2018-09-20 14:46:31
Document Index: 638135301

Matched Legal Cases: ['Application No. 03', 'Application No. 03156610', 'application No. 03019607', 'Application No. 2003', 'Application No. 2', 'Application No. 200510130221', 'Application No. 10', 'Application No. 2', 'application No. 03019607', 'Application No. 10', 'Application No. 03', 'Application No. 2', 'Application No. 07011670', 'Application No. 07011666', 'Application No. 2', 'Application No. 2', 'art 10']

US Patent # 9,432,677. Motion picture encoding device and motion picture decoding device - Patents.com
United States Patent 9,432,677
Nakagawa , et al. August 30, 2016
When a prediction is made between fields with different parity, the predicative efficiency of a chrominance vector is improved by adaptively switching the generation of a chrominance motion vector depending on encoding/decoding field parity (top/bottom) and a reference field parity (top/bottom), and the coding efficiency is improved accordingly.
Nakagawa; Akira (Kawasaki, JP), Miyoshi; Hidenobu (Kawasaki, JP)
Family ID: 1000002075603
14/472,616
US 20140369418 A1 Dec 18, 2014
11070663 Mar 3, 2005 9124886
10655397 Nov 29, 2011 8068542
Sep 6, 2002 [JP] 2002-261427
Aug 7, 2003 [JP] 2003-289350
Current CPC Class: H04N 19/186 (20141101); H04N 19/105 (20141101); H04N 19/139 (20141101); H04N 19/159 (20141101); H04N 19/16 (20141101); H04N 19/176 (20141101); H04N 19/51 (20141101); H04N 19/513 (20141101); H04N 19/52 (20141101); H04N 19/521 (20141101); H04N 19/61 (20141101)
Current International Class: H04N 7/12 (20060101); H04N 19/139 (20140101); H04N 19/16 (20140101); H04N 19/52 (20140101); H04N 19/159 (20140101); H04N 19/186 (20140101); H04N 19/105 (20140101); H04N 19/176 (20140101); H04N 19/51 (20140101); H04N 19/513 (20140101); H04N 19/61 (20140101)
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This application is a Continuation of application Ser. No. 11/070,663 filed Mar. 3, 2005, which is a Divisional of application Ser. No. 10/655,397 filed Sep. 5, 2003, which is based upon and claims the benefit of priority of the prior Japanese Patent Applications No. 2002-261427, filed on Sep. 6, 2002, and No. 2003-289350 filed on Aug. 7, 2003, the entire contents of which are incorporated herein by reference.
1. A motion picture encoding method for making an inter-field motion compensation prediction and for executing an encoding process on a motion picture signal, wherein each frame has two fields and a number of pixels of a chrominance vertical component is different than a number of pixels of a luminance vertical component, the motion picture encoding method comprising: generating a chrominance motion vector from a luminance motion vector based on an equation represented as MVCy=MVy/2+0.25 when a reference field is a top field and a coding field is a bottom field, wherein MVy represents a vertical component of a luminance motion vector which indicates a vertical direction movement of a luminance pixel of a field image, and MVCy represent a vertical component of a chrominance motion vector indicating a vertical direction movement of a chrominance pixel of the field image.
2. The motion picture encoding method according to claim 1, wherein the chrominance motion vector is generated from the luminance motion vector based on an equation represented as MVCy=MVy/2 when both the reference and coding fields are top fields or are bottom fields.
3. A motion picture encoding method for making an inter-field motion compensation prediction and for executing an encoding process on a motion picture signal, wherein each frame has two fields and a number of pixels of a chrominance vertical component is different than a number of pixels of a luminance vertical component, the motion picture encoding method comprising: generating a chrominance motion vector from a luminance motion vector based on an equation represented as MVCy=MVy/2-0.25 when a reference field is a bottom field and a coding field is a top field so that the generated chrominance motion vector and the luminance motion vector are thereby parallel, wherein MVy represents the luminance motion vector which indicates a vertical direction movement of a luminance pixel of a field, and MVCy represents the chrominance motion vector which indicates a vertical direction movement of a chrominance pixel of the field image.
4. The motion picture encoding method according to claim 3, wherein the chrominance motion vector is generated from the luminance motion vector based on an equation represented as MVCy=MVy/2 when both the reference and coding fields are top fields or are bottom fields.
5. A motion picture encoding method for making an inter-field motion compensation prediction and for executing an encoding process on a motion picture signal, wherein each frame has two fields and a number of pixels of a chrominance vertical component is different than a number of pixels of a luminance vertical component, the motion picture encoding method comprising: generating a chrominance motion vector from a luminance motion vector which depends on whether each of a reference field and a coding field is a top field or a bottom field, based on a first calculation when both the reference and coding fields are top fields or are bottom fields, based on a second calculation when the reference field is a top field and the coding field is a bottom field, and based on a third calculation when the reference field is a bottom field and the coding field is a top field.
6. The motion picture encoding method according to claim 5, wherein the first calculation is represented as MVCy=MVy/2, the second calculation is represented as MVCy=Mvy/2+0.25 and the third calculation is represented as MVCy=MVy/2-0.25 wherein MVy represents the luminance motion vector which indicates a vertical direction movement of a luminance pixel of a field image, and MVCy represents the chrominance motion vector which indicates a vertical direction movement of a chrominance pixel of the field image.
Generally, motion picture data is large in size. Therefore, when motion picture data is transmitted from a transmitting device to a receiving device or when it is stored in a storage device, highly efficient encoding is applied to motion picture data. In this case, "highly efficient encoding" is an encoding process of converting a specific data string into another data string, and compressing the amount of data.
FIGS. 2 and 3 show a format used to encode a field image that is commonly used in ISO/IEC MPEG-2/MPEG-4 (hereinafter called "MPEG-2" and "MPEG-4", respectively) and the final committee draft of ITU-T H.264/ISO/IEC MPEG-4 Part 10 (Advanced video coding (AVC)) ("Joint Final Committee Draft (JFCD) of Joint Video Specification (ITU-T REC, H.264|ISO/IEC 14496-10 AVC)", JVT-D157, or ISO/IEC JTC1/SO29/WG11 MPEG02/N492, July 2002, Klagenfurt, AT) (hereinafter called "AVC FCD"), which ITU-T and ISO/IEC jointly were standardizing as of August 2002. Specifically, each frame is composed of two fields: a top field and a bottom field. FIG. 2 shows the respective positions of a luminance pixels and a chrominance pixels, and a field to which each pixel belongs. As shown in FIG. 2, odd number-ordered luminance lines, such as a first luminance line (50a), a third luminance line (50b), a fifth luminance line (50c), a seventh luminance line (50d), etc., belong to the top field, and even number-ordered lines, such as a second luminance line (51a), a fourth luminance line (51b), a sixth luminance line (51c), a eighth luminance line (51d), etc., belong to the bottom field. Similarly, odd number-ordered chrominance lines, such as a first chrominance line (52a), a third chrominance line (52b), etc., belong to the top field, and even number-ordered chrominance line, such as a second chrominance (53a), a fourth chrominance line, etc., belong to the bottom field.
As shown in FIG. 3, the pixel position of a chrominance component deviates from the pixel position in a field of a luminance component by a quarter vertical pixel. This is because relationship of pixel positions as shown in FIG. 2 is achieved when a frame is constructed from both Top and Bottom fields. If it is based on a NTSC format, each time interval between adjacent top and bottom fields (64a: 65a, 65a: 64b, etc.) is approximately 1/60 seconds. Each time interval between two consecutive top fields (64a: 64b, etc.) or between two consecutive bottom field (65a: 65b, etc.) are approximately 1/30 seconds.
In FIG. 5 it is assumed that each frame, such as 84a, 84b, 84c, etc., is already reconstructed by two consecutive fields (top and bottom fields), as shown in FIG. 4. In this frame predictive mode, a frame to be encoded which is composed of top and bottom fields is encoded. As a reference image, one reference frame is constructed by two consecutive fields (top and bottom fields) stored for reference use, and is used to predict the target frame to be encoded. Then, these two frame images are encoded according to the process flow shown in FIG. 1. In the expression method of a motion vector of this frame predictive encoding mode, a zero vector, that is, (0,0) indicates a pixel located in the same spatial position. Specifically, the motion vector (0,0) of a luminance pixel 82 that belongs to frame#2 (84b) indicates the pixel position 81 of frame#1 (84a).
In a field predictive mode, an encoding target is one top field (94a, 94b, etc.) or bottom field (95a, 95b, etc.) that is inputted as an original image. As a reference image, a top field or bottom field that is stored before can be used. In this case, it is generally defined that the fact that an original image field parity and a reference field parity are the same means that the original image field and the reference field both are top fields or bottom fields. For example, in a prediction 90 between fields with the same parity shown in FIG. 6, an original image field (94b) and a reference field (94a) both are top fields. Similarly, it is generally defined that the fact that an original image field parity and a reference field parity are different means that one of original image and reference fields is a top field and the other is a bottom field. For example, in a prediction 91 between different parity fields shown in FIG. 6, the original image field is a bottom field (95a) and the reference field is a top field (94a). Then, these original image and reference fields are encoded according to the process flow shown in FIG. 1.
FIG. 7 defines the coordinates of a frame/field image widely used in MPEG-2 coding, MPEG-1 coding, AVC FCD coding, etc. White circles in FIG. 7 are pixel definition positions in target frames/fields. In the coordinates of this frame/field image, the upper left corner is designated as the origin (0, 0), and values 1, 2, 3, etc., are sequentially assigned to both horizontal and vertical pixel definition positions. Specifically, the coordinates of a pixel that are located at the n-th horizontal position and the m-th vertical position are (n,m). Similarly, the coordinates of a position interpolated among the pixels are also defined. Specifically, since a position 180 marked with a black circle in FIG. 7 is located at 1.5 pixels in the horizontal direction from the pixel located in the upper left corner and at 2 pixels in the vertical direction, the coordinates of the position 180 is expressed as (1.5, 2). In a field image, there are only a half of the pixels of a frame image in the vertical direction. However, even in this case, the coordinates of a pixel are defined in the same way as in FIG. 7, based on pixel positions located in each field.
FIG. 8 shows a conventional calculation method of a motion vector between corresponding pixels between fields. The definition of a motion vector requires the position of a coding field and the position of a reference field. A motion vector is defined between these two points. Thus, a motion vector between a coding field coordinates 201 (X.sub.s, Y.sub.s) and a reference field coordinates 202 (X.sub.d, Y.sub.d) is calculated. In the conventional calculation method of a motion vector between pixels corresponding to between-fields, a motion vector is calculated by the same method described below, regardless of whether the coding field or reference field is a top field or a bottom field. Specifically, coding field coordinates 201 (X.sub.s, Y.sub.s) and reference field coordinates 202 (X.sub.d, Y.sub.d) are inputted to a motion vector calculation unit 200, and as a motion vector 203 between these two points, (X.sub.d-X.sub.s, Y.sub.d-Y.sub.s) is given.
FIG. 9 shows a conventional method for calculating a pixel that is pointed by a motion vector defined between fields. In this case, it is assumed that a motion vector is calculated by the method shown in FIG. 8. The calculation of reference frame/field coordinates requires a coding frame/field position and a motion vector. In the case shown in FIG. 9, it is assumed that a motion vector 211 (X, Y) is given for coding field coordinates 212 (X.sub.s, Y.sub.s), and reference field coordinates can be calculated using both the motion vector 212 (X, Y) and the coding field coordinates 212 (X.sub.s, Y.sub.s). In the conventional calculation method of a motion vector between corresponding pixels between fields, a reference field position is calculated by the same method described below, regardless of whether the coding field or reference field is a top field or a bottom field. Specifically, a motion vector 211 (X, Y) and coding field coordinates 212 (X.sub.s, Y.sub.s) are inputted to a pixel corresponding unit 210, and as reference field coordinates 213, coordinates (X.sub.s+X, Y.sub.s+Y) is given.
Specifically, if a luminance motion vector 221 and a chrominance motion vector 222 are (MV_x,MV_y) and (MVC_x, MVC_y), respectively, a chrominance motion vector generation unit 220 can calculate a chrominance motion vector 222 according to the following equation. (MVC_x, MVC_y)=(MV_x/2,MV_y/2) (1) This conventional calculation method can be used regardless of whether a motion vector is used for prediction between fields with the same parity or between fields with different parity.
In AVC FCD, as the accuracy of the motion vector of a luminance component, 1/4 pixel accuracy can be applied. Therefore, as a result of equation (1), as the accuracy of the motion vector of a chrominance component, a vector having 1/8 pixel accuracy, that is, accuracy at the decimal fraction, can be used.
In FIG. 11, a black circle and a white circle represent an integer pixel and an interpolated pixel, respectively. In this case, the horizontal coordinate of an interpolated pixel G(256) is obtained by internally dividing each horizontal coordinate between points A(250) and C(252) at a ratio .alpha.:1-.alpha., and the vertical coordinate can be obtained by internally dividing each vertical coordinate between points A(250) and B(251) at .beta.:1-.beta.. In this case, .alpha. and .beta. are a value between 0 and 1. An interpolated pixel G(256) defined by such positions can be roughly calculated as follows using integer pixels A(250), B(251), C(252) and D(253), which are located around the interpolated pixel G(256), and using .alpha. and .beta.. G=(1-.alpha.)(1-.beta.)A+(1-.alpha.).beta.B+.alpha.(1-.beta.)C+.alpha..be- ta.D (2)
In the case of this field encoding mode, in a prediction in which an original image field and a reference field are different, that is, between fields with different parity, the respective zero vectors of the motion vector of a luminance component and that of a chrominance component are not parallel in the definition of AVC FCD. Specifically, if a prediction is made using the motion vector of a chrominance component calculated using the motion vector of a luminance component according to the conventional definition, a pixel located in a position spatially deviated from that of the luminance component is to be referenced. This fact is described below with reference to FIG. 12. In FIG. 12, it is assumed that a top field 130, a bottom field 131 and a top field 132 continue timewise. In this case, bottom field 131 is to be encoded using top field 130. In this inter-field encoding, the vertical motion vector in the same line of each field is defined to be zero. Therefore, if a zero vector (0,0) is assigned to a luminance pixel 133a that belongs to the second line of bottom field 131, this pixel can be predicted from a pixel 135a in top field 130. Similarly, when a zero vector (0,0) is assigned to a chrominance pixel 133a which belongs to the first line of the bottom field 131, this pixel is predicted from the pixel 137a which is in the first line of chrominance of the top field 130. Similarly, a luminance pixel 133b in the third line and a chrominance pixel 134b, which belong to top field 132 are predicted from pixels 135b in the third line of luminance and 137b in the second line of chrominance in bottom field 131, respectively. Since essentially it is preferable that a chrominance motion vector and a luminance motion vector are parallel, chrominance pixels 134a and 134b should be predicted from the positions 136a and 136b, respectively, if a luminance motion vector is as it is.
FIG. 13 shows a conventional problem caused if a chrominance motion vector is conventionally calculated using a luminance motion vector when a reference field and a coding field are a bottom field and a top field, respectively. In AVC FCD, since, as is clear from equation (1), it is specified that the number of vertical and horizontal pixels of a chrominance component are a half of those of a luminance component, a motion vector used to calculate the predictive pixel of a chrominance should be scaled down to a half of the motion vector of a luminance component. This is regardless of whether a motion vector is used for prediction between frames, between fields with the same parity or between fields with different parity.
In this case, a chrominance motion vector that belongs to the same block is calculated to be (0,1/2), according to equation (1). If a prediction is made using motion vector (0, 1/2) as a predictive value of a coding field top field chrominance-pixel 142 in the first line, a pixel position 143 is used as predicted value, which shifts downward by half a pixel from a pixel in the first line of a bottom reference field chrominance component.
In this case, a luminance motion vector (0,1) and a chrominance vector (0,1/2) are not parallel. It is preferable to use a bottom reference field chrominance predictive pixel position 145 to which a chrominance motion vector parallel to a luminance motion vector is applied.
In this case, a chrominance motion vector that belongs to the same block is calculated to be (0,1/2), according to equation (1). If a prediction is made using motion vector (0, 1/2) as a predictive value of a bottom coding field chrominance pixel 152, a pixel position 153 is used as predicted value which is shifted by half a pixel from a top reference field chrominance pixel position 153 in the first line.
In this case, a luminance motion vector (0,1) and a chrominance vector (0,1/2) are not parallel. It is preferable to use a top reference field chrominance predictive pixel position 155 to which a chrominance motion vector parallel to a luminance motion vector is applied.
Specifically, if the reference field parity and coding field parity are the same, the first chrominance motion vector generation unit calculates a chrominance motion vector as follows, assuming that a luminance motion vector indicating the vertical displacement of one luminance pixel of a field image by the value "1" of the vector component as units and a chrominance motion vector indicating the vertical displacement of one chrominance pixel of a field image by the value "1" of the vector component as units are MVy and MVCy, respectively. MVCy=Mvy/2 (3)
If the reference field parity and coding field parity are top and bottom fields, respectively, the second chrominance motion vector generation unit calculates a chrominance motion vector as follows, assuming that a luminance motion vector indicating the vertical displacement of one luminance pixel of a field image by the value "1" of the vector component as units and a chrominance motion vector indicating the vertical displacement of one chrominance pixel of a field image by the value "1" of the vector component as units are MVy and MVCy, respectively. MVCy=Mvy/2+0.25 (4)
If the reference field parity and coding field parity are bottom and top fields, respectively, the third chrominance motion vector generation unit calculates a chrominance motion vector as follows, assuming that a luminance motion vector indicating the vertical displacement of one luminance pixel of a field image by the value "1" of the vector component as units and a chrominance motion vector indicating the vertical displacement of one chrominance pixel of a field image by the value "1" of the vector component as units are MVy and MVCy, respectively. MVCy=Mvy/2-0.25 (5)
Sometimes, the respective units of luminance and chrominance vectors vary, depending on its definition. In the case that it is defined that a luminance motion vector indicates the displacement of one luminance moving pixel when the component of the luminance motion vector changes by value 4 and that a chrominance motion vector indicates the displacement of one chrominance moving pixel when the component of the chrominance motion vector changes by value 8, if the reference field parity and coding field parity are the same, the first chrominance motion vector generation unit calculates a chrominance motion vector as follows, assuming that a luminance motion vector and a chrominance motion vector are MVy and MVCy, respectively. MVCy=Mvy (6)
In the same definition, if the parity of reference field and coding field are top and bottom fields, respectively, the second chrominance motion vector generation unit calculates a chrominance motion vector as follows, assuming that a luminance motion vector and a chrominance motion vector are MVy and MVCy, respectively. MVCy=Mvy+2 (7)
In the same definition, if the reference field parity and coding field parity are bottom and top fields, respectively, the third chrominance motion vector generation unit calculates a chrominance motion vector as follows, assuming that a luminance motion vector and a chrominance motion vector are MVy and MVCy, respectively. MVCy=Mvy-2 (8)
The operation of the present invention shown in FIG. 15 is described below. Firstly it is assumed that a given luminance motion vector 231 is (MV_x,MV_y). This luminance vector is inputted to all of a first chrominance motion vector generation unit 233, a second chrominance motion vector generation unit 234 and a third chrominance motion vector generation unit 235. Then, their respective outputs are inputted to a selection unit 230. The selection unit 230 selects one of the respective outputs of the first, second and third chrominance motion vector generation units, based on information about the coding field parity 237 of the inputted motion vector and its reference field parity 238, and outputs it as a color motion vector 232 (MVC_x,MVC_y).
FIG. 16 shows the operation of the first chrominance motion vector generation unit. In this preferred embodiment, a luminance motion vector 261 (MV_x,MV_y) is inputted to a first chrominance motion vector generation unit 260, and a first chrominance motion vector candidate 262 (MVC1_x, MVC1_y) is outputted. The chrominance motion vector generation unit 260 calculates the first chrominance motion vector candidate 262 as follows using the luminance motion vector 261. (MVC1_x, MVC1_y)=(MV_x/2, MV_y/2) (9) Then, the calculated first chrominance motion vector candidate 262 is outputted to the selection unit.
FIG. 17 shows the operation of the second chrominance motion vector generation unit. In this preferred embodiment, a luminance motion vector 271 (MV_x,MV_y) is inputted to a second chrominance motion vector generation unit 270, and a second chrominance motion vector candidate 272 (MVC2_x,MVC2_y) is outputted. The chrominance motion vector generation unit 270 calculates the second chrominance motion vector candidate 272 as follows using the luminance motion vector 271. (MVC2_x, MVC2_y)=(MV_x/2, MV_y/2+1/4) (10) Then, the calculated second chrominance motion vector candidate 272 is outputted to the selection unit.
FIG. 18 shows the operation of the third chrominance motion vector generation unit. In this preferred embodiment, a luminance motion vector 281 (MV_x,MV_y) is inputted to a third chrominance motion vector generation unit 280, and a third chrominance motion vector candidate 282 (MVC2_x, MVC2_y) is outputted. The chrominance motion vector generation unit 280 calculates the third chrominance motion vector candidate 282 as follows using the luminance motion vector 281. (MVC3_x,MVC3_y)=(MV_x/2,MV_y/2-1/4) (11) Then, the calculated third chrominance motion vector candidate 282 is outputted to the selection unit.
In this case, the first, second or third chrominance motion vector candidates 244, 245 and 246 are connected to 262 shown in FIG. 16, 272 shown in FIGS. 17 and 282 shown in FIG. 18, respectively. Then, a selector 243 selects one of the first, second and third chrominance motion vector candidates 244, 245 and 246, based on the selection information 249, and outputs (MVC_x,MVC_y) as its chrominance motion vector 242.
.times..times..times. ##EQU00001## Then, this value is outputted as the chrominance motion vector 242 shown in FIG. 19. If this vector (0,1/4) is applied to the top coding field chrominance pixel 162, a bottom reference field chrominance pixel position 163 is used as a predicted value. In FIG. 20, the vertical positional relation between pixels corresponds to a real pixel. As is clear from FIG. 20, a luminance motion vector (0, 1) and a chrominance motion vector (0, 1/4) are parallel. Thus, the color deviation between luminance and chrominance components, which is a conventional problem, can be solved by the present invention.
.times..times..times. ##EQU00002## Then, this value is outputted as the chrominance motion vector 242 shown in FIG. 19. If this vector (0,3/4) is applied to the bottom coding field chrominance pixel 172, a top reference field chrominance pixel position 173 is used as a predictive position. In FIG. 21, the vertical positional relation between pixels corresponds to a real one. As is clear from FIG. 21, a luminance motion vector (0,1) and a chrominance motion vector (0, 3/4) are parallel. Thus, the color deviation between luminance and chrominance components, which is a conventional problem, can be solved by the present invention.
In the case that it is defined that a luminance motion vector indicates the displacement of one luminance moving pixel when the value of the luminance motion vector changes by four and that a chrominance motion vector indicates the displacement of one chrominance moving pixel when the value of the chrominance motion vector changes by eight, a chrominance motion vector generation unit 260a calculates a candidate first chrominance motion vector 262a using a luminance motion vector 261a as follows. (MVC1_x,MVC1_y)=(MV_x,MV_y) (14) Then, the calculated first chrominance motion vector candidate 262a is outputted to a selection unit.
The chrominance motion vector generation unit 270a calculates a second chrominance motion vector candidate 272a using a luminance motion vector 271a as follows. (MVC2_x,MVC2_y)=(MV_x,MV_y+2) (15) Then, the calculated second chrominance motion vector candidate 272a is outputted to a selection unit.
The chrominance motion vector generation unit 280a calculates a third chrominance motion vector candidate 282a using a luminance motion vector 281a as follows. (MVC3_x,MVC3_y)=(MV_x,MV_y-2) (16) Then, the calculated third chrominance motion vector candidate 282a is outputted to a selection unit.
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