Method for Deriving Coding Information for High Resolution Pictures from Low Resolution Pictures and Coding and Decoding Devices Implementing Said Method

• US 20090028245A1
• Filed: 02/14/2006
• Published: 01/29/2009
• Est. Priority Date: 02/18/2005
• Status: Active Grant

• Current Assignee: Thomson Licensing Dtv
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Vieron, Jerome, Francois, Edouard, Boisson, Guillaume, Marquant, Gwenaelle, Burdin, Nicolas, Lopez, Patrick
• Granted Patent: US 8,345,762 B2
• Time in Patent Office: Days
• US Class Current: 375/240.160
• CPC Class Codes: H04N 19/103 Selection of coding mode or of prediction mode
• CPC Class Codes: H04N 19/105 Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
• CPC Class Codes: H04N 19/109 among a plurality of temporal predictive coding modes
• CPC Class Codes: H04N 19/119 Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks
• CPC Class Codes: H04N 19/157 Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/187 the unit being a scalable video layer
• CPC Class Codes: H04N 19/30 using hierarchical techniques, e.g. scalability H04N19/63 takes precedence
• CPC Class Codes: H04N 19/33 in the spatial domain
• CPC Class Codes: H04N 19/40 using video transcoding, i.e. partial or full decoding of a coded input stream followed by re-encoding of the decoded output stream
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/513 Processing of motion vectors
• CPC Class Codes: H04N 19/57 Motion estimation characterised by a search window with variable size or shape
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

The invention relates to spatially scalable encoding and decoding processes using a method for deriving coding information. More particularly, it relates to a method for deriving coding information for high resolution pictures from the coding information of low resolution pictures. The method mainly comprises the following steps:

• • Computing geometrical parameters characterizing the position of said high layer macroblock relatively to the corresponding base layer macroblocks and deriving from these parameters a macroblock class;
  • Deriving a partition and possibly sub-partitions for each partition of said high layer macroblock from corresponding base layer macroblocks partition and sub-partitions on the basis of the geometrical parameters and HL MB class; and
  • Deriving motion information for said high layer macroblock from motion information of corresponding base layer macroblocks.

Claims

1. Method as part of a process of coding or decoding video signal for deriving coding information for at least one picture part of a high resolution picture from coding information of at least one picture part of a low resolution picture, each picture being divided into non-overlapping macroblocks, wherein, said coding information comprising at least partitioning information, at least one macroblock of said at least one low resolution picture part, called base layer macroblock, is associated with each macroblock of said at least one high resolution picture part, called high layer macroblock, so that said associated low resolution macroblock overlays at least partly said high resolution macroblock when said at least one low resolution picture part upsampled by a first predefined ratio in the horizontal direction and a second predefined ratio in the vertical direction is superposed with said at least one high resolution picture part and wherein said method comprises the following steps:

computing geometrical parameters for each high layer macroblock in said at least one high resolution picture part representative of the position of said high layer macroblock relatively to the base layer macroblock(s) associated with said high layer macroblock, called corresponding base layer macroblock(s); and

deriving partitioning information for each high layer macroblock in said at least one high resolution picture part from the partitioning information of the corresponding base layer macroblock(s) on the basis of said geometrical parameters.

2. Method according to claim 1, wherein the step for deriving partitioning information is preceded by a step for deriving a macroblock class for each high layer macroblock in said at least one high resolution picture part on the basis of said geometrical parameters, said macroblock class being representative of the splitting of said high layer macroblock by the borders of said corresponding base layer macroblock(s) and wherein said partitioning information is derived on the basis of said geometrical parameters and on said macroblock class.

3. Method according to claim 1, wherein a coordinate system is associated with each high resolution picture and wherein four geometrical parameters are computed for each high layer macroblock divided into non-overlapping blocks, in said high resolution picture coordinate system as follows:

a first geometrical parameter is the algebraic distance MbBorderX between the high layer macroblock center and the nearest vertical border of corresponding base layer macroblock(s), said distance being defined according to a first direction;

a second geometrical parameter is the algebraic distance between the high layer macroblock center and the nearest horizontal border of corresponding base layer macroblock(s), said distance being defined according to a second direction;

a third geometrical parameter is the algebraic distance between the high layer macroblock center and the nearest vertical border of a block of corresponding base layer macroblock(s), said distance being defined according to said first direction; and

a fourth geometrical parameter is the algebraic distance between the high layer macroblock center and the nearest horizontal border of a block of corresponding base layer macroblock(s), said distance being defined according to said second direction.

4. Method according to claim 1, wherein said coding information further comprises sub-partitioning information and wherein said method further comprises a step for deriving sub-partitioning information for high layer macroblocks in said at least one high resolution picture part from partitioning information and sub-partitioning information if any of the corresponding base layer macroblock(s) on the basis of said geometrical parameters.

5. Method according to claim 4, wherein said coding information further comprises motion information and wherein said method further comprises a step for deriving motion information for each high layer macroblock in said at least one high resolution picture part from motion information of the corresponding base layer macroblock(s).

6. Method according to claim 5, wherein said step for deriving motion information for each high layer macroblock in said at least one high resolution picture part consists in deriving motion information for each partition of said high layer macroblock and for each sub-partition of each said partition if any.

7. Method according to claim 6, wherein said motion information of one macroblock, one partition or one sub-partition comprises at least one motion vector having a first and a second component and at least one reference index associated with said motion vector selected among a first or a second list of reference indices, said indices identifying reference pictures.

8. Method according to claim 7, wherein, the step for deriving motion information, comprises a step for homogenizing, for each high layer macroblock in said at least one high resolution picture part, motion information between sub-partitions of same partition and wherein said step consists, for each list of reference indices, in:

identifying, for each partition of said high layer macroblock, the lowest index of said sub-partitions among the reference indices of said list of reference indices;

associating said lowest reference index with each of said sub-partitions whose current reference index is not equal to said lowest reference index, said current reference index becoming a previous reference index; and

associating, with each of said sub-partition whose previous reference index is not equal to said lowest index, the motion vector of one of its neighboring sub-partitions whose said previous reference index is equal to said lowest reference index.

9. Method according to claim 8, wherein the associated motion vector is the motion vector of the first neighboring sub-partition encountered when checking first the horizontal neighboring sub-partition, secondly the vertical neighboring sub-partition and thirdly the diagonal neighboring sub-partition.

10. Method according to any claim 8, wherein the motion vector components of motion vectors of each macroblock, partition, and sub-partition if any are scaled by the following equations:

$\hspace{1em}<br><br>\{\begin{array}{c}{d}_{\mathrm{sx}}=\left(\mathrm{dx}*\mathrm{scaled\_base}<br><br>\mathrm{\_width}+\mathrm{base\_width}/2*\mathrm{sign}<br><br>\left[d_x\right]\right)/\mathrm{base\_width}\\ d_{\mathrm{sy}}=\left(\mathrm{dy}*\mathrm{scaled\_base}<br><br>\mathrm{\_height}+\mathrm{base\_height}/2*\mathrm{sign}<br><br>\left[d_y\right]\right)/\mathrm{base\_height}\end{array}$

Where;

d_x and d_y represent the coordinates of the derived motion vector;

d_sx and d_sy represents the coordinates of the scaled motion vector;

sign [x] is equal to 1 when x is positive and −

1 when x is negative;

scaled_base_width and scaled_base_height are the width and the height of the high resolution image part respectively;

base_width and base_height are the width and height of the low resolution image part respectively.

11. Method according to any of claim 4, wherein said macroblocks have a size of 16 by 16 pixels, said block is of size 8 by 8 pixels and wherein said first predefined ratio equal said second predefined ratio.

12. Device for coding at least a sequence of high resolution pictures and a sequence of low resolution pictures, each picture being divided in macroblocks comprising:

a first coding unit for coding said low resolution pictures, said first coding unit generating coding information for said low resolution pictures and a base layer data stream;

an inheritance unit for deriving coding information for at least one picture part of a high resolution picture from coding information of at least one picture part of a low resolution picture; and

a second coding unit for coding said high resolution pictures using said derived coding information, said second coding unit generating an enhancement layer data stream;

wherein, said coding information comprising at least partitioning information, the inheritance unit comprises;

a unit for associating at least one macroblock of said at least one low resolution picture part, called base layer macroblock, with each macroblock of said at least one high resolution picture part, called high layer macroblock, so that said associated low resolution macroblock overlays at least partly said high resolution macroblock when said at least one low resolution picture part upsampled by a first predefined ratio in the horizontal direction and a second predefined ratio in the vertical direction is superposed with said at least one high resolution picture part;

a unit for computing geometrical parameters for each high layer macroblock in said at least one high resolution picture part on the basis of the position of said high layer macroblock relatively to the base layer macroblock(s) associated with said high layer macroblock, called corresponding base layer macroblock(s); and

a unit for deriving partitioning information for each high layer macroblock in said at least one high resolution picture part from the partitioning information of the corresponding base layer macroblock(s) on the basis of said geometrical parameters.

13. Device according to claim 12, wherein the device further comprises a module for combining said base layer data stream and said enhancement layer data stream into a single data stream.

14. Device according to claim 12, wherein said first coding unit is a MPEG-4 AVC video encoder.

15. Device for decoding at least a sequence of high resolution pictures and a sequence of low resolution pictures coded with the device according to claim 12, the coded pictures being represented by a data stream comprising:

a first decoding unit for decoding at least a first part of said data stream in order to generate low resolution pictures and coding information of said low resolution picture;

an inheritance unit for deriving coding information for at least one picture part of a high resolution picture from coding information of at least one picture part of a low resolution picture; and

a second decoding unit for decoding at least a second part of said data stream using said derived coding information in order to generate high resolution pictures;

wherein, said coding information comprising at least partitioning information, the inheritance unit comprises;

a unit for associating at least one macroblock of said at least one low resolution picture part, called base layer macroblock, with each macroblock of said at least one high resolution picture part, called high layer macroblock, so that said associated low resolution macroblock overlays at least partly said high resolution macroblock when said at least one low resolution picture part upsampled by a first predefined ratio in the horizontal direction and a second predefined ratio in the vertical direction is superposed with said at least one high resolution picture part;

a unit for computing geometrical parameters for each high layer macroblock in said at least one high resolution picture part on the basis of the position of said high layer macroblock relatively to the base layer macroblock(s) associated with said high layer macroblock, called corresponding base layer macroblock(s); and

a unit for deriving partitioning information for each high layer macroblock in said at least one high resolution picture part from the partitioning information of the corresponding base layer macroblock(s) on the basis of said geometrical parameters.

16. Device according to claim 15, wherein the device further comprises an extracting unit for extracting said first part of said data stream and said second part of said data stream from said data stream.

17. Device according to claim 15, wherein said first decoding unit a MPEG-4 AVC video decoder.