Method and apparatus for encoding a video

1. A method, comprising encoding a video comprising, for at least one block from a picture of said video:

determining a first rate-distortion cost comprising determining, for a first splitting mode of said block into a first set of at least one first subblock, coding parameters for said at least one first subblock;

determining at least one second rate-distortion cost comprising for determining, for at least one second splitting mode of said block into at least one second set of at least one second subblock, coding parameters for said at least one second subblock of said at least one second set, wherein determining coding parameters for said at least one second subblock of said at least one second set comprises associating a parameter to said at least one first subblock having a value that indicates that at least one coding parameter of said first subblock is used for determining coding parameters for the second subblock;

determining a splitting mode for coding said block according to the first rate-distortion cost and said at least one second rate-distortion cost;

encoding said block according to said best the determined splitting mode;

wherein the parameter associated with at least one first subblock is set to said value in response to a determination that:

the second subblock is located at a same position in the picture as the first subblock;

the second subblock has a same width and same height as the first subblock; and

the first subblock and the second subblock have a same causal neighborhood comprising data used to predict the subblock or to code a coding parameter for a first or second subblock.

2. The method of claim 1 wherein said first subblock and said second subblock have a same causal neighborhood of the subblock when said first subblock is a first subblock of a first set when said first set is ordered according to a scan order.

3. The method according to claim 1 , wherein said specific value indicates that coding parameters for said at least one first subblock are available and that coding parameters for said at least one second subblock are determined to be the same coding parameters as the coding parameters determined for said at least one first subblock.

4. The method according to claim 3 , wherein when said coding parameters of said at least one first subblock comprises a splitting configuration of said at least one first subblock, said at least one second subblock inherits from said splitting configuration.

5. The method according to claim 1 , wherein said specific value of said parameter indicates that coding parameters for said at least one second subblock are determined by searching for best coding parameters for coding said at least one second subblock from the coding parameters determined for said at least one first subblock.

6. The method according to claim 5 , wherein said coding parameters for said at least one first subblock are used only when a no-splitting mode of said at least one second subblock is evaluated.

7. The method according to claim 1 , further comprising:

computing an identifier for said at least one first subblock, said identifier allowing to identify said position, said width and said height of said at least one first subblock and a causal neighborhood of said at least one first subblock indicating at least whether coding parameters for a neighbor of said at least one first subblock have been previously determined,

for said at least one first subblock or said at least one second subblock, storing coding parameters determined for said at least one first subblock, in association with said identifier,

for said at least one second subblock, if said parameter associated to said at least one first subblock equals said specific value, using said identifier for reading stored coding parameters associated to said identifier, the coding parameters for said at least one second subblock being determined to be the read coding parameters.

8. An apparatus for encoding a video comprising, for at least one block from a picture of said video, a processor configured to:

determine a first rate-distortion cost comprising determining, for a first splitting mode of said block into a first set of at least one first subblock, coding parameters of said at least one first subblock;

determine at least one second rate-distortion cost comprising determining, for at least one second splitting mode of said block into at least one second set of at least one second subblock, coding parameters of said at least one second subblock of said at least one second set, wherein determining coding parameters for said at least one second subblock of said at least one second set comprises associating a parameter to said at least one first subblock having a value that indicates that at least one coding parameter of said first subblock is used for determining coding parameters for the second subblock;

determine a splitting mode for coding said block according to the first rate-distortion cost and the at least one second rate-distortion cost;

encode said block according to the determined splitting mode;

wherein the parameter associated with at least one first subblock is set to said value:

if the second subblock is located at a same position in the picture as the first subblock;

if the second subblock has a same width and same height as the first subblock; and

if the first subblock and the second subblock have a same causal neighborhood comprising data used to predict the subblock or to code a coding parameter for a first or second subblock.

9. The apparatus according to claim 8 , wherein said first subblock and said second subblock have a same causal neighborhood of the subblock when said first subblock is a first subblock of a first set when said first set is ordered according to a scan order.

10. The apparatus according to claim 9 , wherein said specific value indicates that coding parameters for said at least one first subblock are available and that coding parameters for said at least one second subblock are determined to be the same coding parameters as the coding parameters determined for said at least one first subblock.

11. The apparatus according to claim 9 , wherein when said coding parameters of said at least one first subblock comprises a splitting configuration of said at least one first subblock, said at least one second subblock inherits from said splitting configuration.

12. The apparatus according to claim 11 , wherein said specific value of said parameter indicates that coding parameters for said at least one second subblock are determined by searching for best coding parameters for coding said at least one second subblock from the coding parameters determined for said at least one first subblock.

13. The apparatus according to claim 12 , wherein said coding parameters for said at least one first subblock are used only when a no-splitting mode of said at least one second subblock is evaluated.

14. The apparatus according to claim 11 , further comprising a processor configured to:

compute an identifier for said at least one first subblock, said identifier allowing to identify said position, said width and said height of said at least one first subblock and a causal neighborhood of said at least one first subblock indicating at least whether coding parameters for a neighbor of said at least one first subblock have been previously determined,

for said at least one first subblock or said at least one second subblock, store coding parameters determined for said at least one first subblock, in association with said identifier,

for said at least one second subblock, if said parameter associated to said at least one first subblock equals said specific value, using said identifier for reading stored coding parameters associated to said identifier, the coding parameters for said at least one second subblock being determined to be the read coding parameters.

15. A non-transitory computer-readable medium including instructions for causing one or more processors to perform:

determining a first rate-distortion cost comprising determining, for a first splitting mode of said block into a first set of at least one first subblock, coding parameters of said at least one first subblock;

determining at least one second rate-distortion cost comprising determining, for at least one second splitting mode of said block into at least one second set of at least one second subblock, coding parameters of said at least one second subblock of said at least one second set, wherein determining coding parameters for said at least one second subblock of said at least one second set comprises associating a parameter to said at least one first subblock having a value that indicates that at least one coding parameter of said first subblock is used for determining coding parameters for the second subblock;

determining a splitting mode for coding said block according to the first rate-distortion cost and the at least one second rate-distortion cost,

encoding said block according to the determined splitting mode; wherein the parameter associated to with at least one first subblock is set to said value:

if the second subblock is located at a same position in the picture as said first subblock;

if the second subblock has a same width and same height as said first subblock; and

if the first subblock and the second subblock have a same causal neighborhood comprising data used to predict the subblock or to code a coding parameter for a first or second subblock.