# US 2020/0288144 A1 · Method and apparatus for encoding a picture

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- Number: US 2020/0288144 A1
- Document ID: US20200288144A1
- Status: Published application
- Kind: A1
- Application number: 16/464,267
- Filed: 2017-11-23
- Published: 2020-09-10
- Earliest claimed: 2016-11-25
- Applicants: Interdigital Ce Patent Holdings
- Inventors: Fabrice LELEANNEC; Tangi POIRIER; Franck GALPIN; Fabien RACAPE; Thierry VIELLARD; Fabrice URBAN
- Web page: https://patentgrep.com/patent/US20200288144A1

## CPC

- H04N 19/147: according to rate distortion criteria (rate-distortion as a criterion for motion estimation H04N19/567)
- H04N 19/19: using optimisation based on Lagrange multipliers
- H04N 19/119: Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks
- H04N 19/124: Quantisation
- H04N 19/176: the region being a block, e.g. a macroblock
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

A method and an apparatus for encoding a picture are disclosed. A first rate-distortion cost is determined (42) for a current block of said picture when said current block is not split into subblocks, from a distortion computed for each subblock of said current block, said distortion being scaled by an inverse of a lagrangian parameter determined (40) according to a quantization parameter assigned to said subblock. It is then determined (44) whether said current block is split or not according at least to the determined first rate-distortion cost, and the current block is encoded (45) according to the result of determining whether a current block is split or not into subblocks.

## Claims

### Claim at position 1

1-7. (canceled)

### Claim 8

A method for encoding a picture, comprising:
determining a first rate-distortion cost RDnon-split for a current block of said picture when said current block is not split into subblocks, from a distortion computed from each distortion for each subblock i of said current block, said distortion being scaled by an inverse of a lagrangian parameter λs(i) determined according to a quantization parameter qi assigned to said each subblock i;
determining a first rate-distortion cost RDsplit for said current block when said current block is not split as the sum of rate-distortion costs of all subblocks in the current block using the assigned quantization parameters qi and the Lagrange parameters λs(i),
determining that the current block is split if RDnon-split is larger than RDsplit,
encoding the current block using a common quantization parameter q0 if the current block is not split or the subblocks in the current block using the assigned quantization parameters qi if the current block is split.

### Claim 9 (depends on 8)

The method according to claim 8, wherein determining a first rate-distortion cost RDnon-split for said current block when said current block is not split further comprises:
assigning to said current block, the quantization parameter q0 being a minimum value of the quantization parameters qi initially assigned to the subblocks of the current block.

### Claim 10 (depends on 8)

The method according to claim 8, wherein determining a first rate-distortion cost RDnon-split for said current block when said current block is not split further comprises:
assigning to said current block, the quantization parameter q0 being the quantization parameter from among the quantization parameters qi initially assigned to the subblocks that results in the lowest RDnon-split.

### Claim 11 (depends on 9)

The method according to claim 9, wherein if said current block is not split for encoding, encoding the current block comprises quantifying datas for said current block using said assigned quantization parameter q0.

### Claim 12 (depends on 9)

The method according to claim 9, wherein when it is determined not to split said current block for encoding, encoding said current block comprises updating a quantization parameter map, wherein said quantization parameter map comprises indexes representative of quantization parameters assigned to the subblocks of said picture.

### Claim 13 (depends on 8)

The method according to claim 8, wherein said first rate-distortion cost RDnon-split for said current block when said current block is not split is determined according to following the equation:
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where RSB(q0) corresponds to the total bits cost for encoding the current block and Di(q0) corresponds to the distortion computed for each subblock of said current block.

### Claim 14

An apparatus for encoding a picture, comprising at least one processor and at least one memory, said at least one processor being configured to:
determine a first rate-distortion cost RDnon-split for a current block of said picture when said current block is not split into subblocks, from a distortion computed for each distortion for each subblock i of said current block, said distortion being scaled by an inverse of a lagrangian parameter λs(i) determined according to a quantization parameter qi assigned to said each subblock
determine a first rate-distortion cost RDsplit for said current block when said current block is not split as the sum of rate-distortion costs of all subblocks in the current block using assigned quantization parameters qi and the Lagrange parameters λs(i);
determine that the current block is split if RDnon-split is larger than RDsplit;
encode the current block using a common quantization parameter q0 if the current block is not split or the subblocks in the current block using the assigned quantization parameters qi if the current block is split.

### Claim 15 (depends on 14)

The apparatus according to claim 14, wherein the quantization parameter q0 assigned to said current block when said current block is not split is the minimum value of the quantization parameters qi initially assigned to the subblocks of the current block.

### Claim 16 (depends on 14)

The apparatus according to claim 14, wherein the quantization parameter q0 assigned to said current block when said current block is not split, is the quantization parameter from among the quantization parameters qi initially assigned to the subblocks that results in the lowest RDnon-split.

### Claim 17 (depends on 15)

The apparatus according to claim 15, wherein if said current block is not split for encoding, the processor is configured to encode the current block by quantifying datas for said current block using said assigned quantization parameter q0.

### Claim 18 (depends on 14)

The apparatus according to claim 14, wherein when it is determined not to split said current block for encoding, the processor is configured to encode the current block by updating a quantization parameter map, wherein said quantization parameter map comprises indexes representative of quantization parameters assigned to the subblocks of said picture.

### Claim 19 (depends on 8)

The apparatus according to claim 8, wherein said first rate-distortion cost RDnon-split for said current block when said current block is not split is determined according to following the equation:
R
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where RSB(q0) corresponds to the total bits cost for encoding the current block and Di(q0) corresponds to the distortion computed for each subblock of said current block.

### Claim 20 (depends on 1)

A computer program comprising software code instructions for performing the method according to claim 1, when the computer program is executed by a processor.