Methods and apparatuses for encoding and decoding video using temporal motion vector prediction

1. A method of encoding a video into a coded video bitstream with temporal motion vector prediction, the method comprising:

determining a value of a flag for indicating whether temporal motion vector prediction is used or not used for the inter-picture prediction of a sub-picture unit of a picture; and

writing the flag having said value into a header of the sub-picture unit or a header of the picture;

wherein if the flag indicates that temporal motion vector prediction is used, the method further comprises:

creating a first list of motion vector predictors comprising a plurality of motion vector predictors including at least one temporal motion vector predictor derived from at least one motion vector from a collocated reference picture;

selecting a motion vector predictor out of the first list for a prediction unit in the sub-picture unit; and

writing a first parameter into the coded video bitstream for indicating the selected motion vector predictor out of the first list; and

wherein if a temporal layer of the picture is determined to be the lowest or base layer, the value of the flag is set to indicate that temporal motion vector prediction is not used; otherwise, the value of the flag is set to indicate that temporal motion vector prediction is used.

2. The method according to claim 1 , wherein if the flag indicates that temporal motion vector prediction is not used, the method further comprises:

creating a second list of motion vector predictors comprising a plurality of motion vector predictors without any temporal motion vector predictors;

selecting a motion vector predictor out of the second list for a prediction unit in the sub-picture unit; and

writing a second parameter into the coded video bitstream for indicating the selected motion vector predictor out of the second list.

3. The method according to claim 1 , wherein the value of the flag is determined based on a Picture Order Count (POC) value of the picture.

4. The method according to claim 3 , wherein if the POC value of the picture is determined greater than any POC values of reference pictures in a Decoder Picture Buffer (DPB), the value of the flag is set to indicate that temporal motion vector prediction is not used; otherwise, the value of the flag is set to indicate that temporal motion vector prediction is used.

5. The method according to claim 1 , wherein the value of the flag is determined based on a sub-picture unit type of an inter-picture sub-picture unit in the picture.

6. The method according to claim 5 , wherein if the sub-picture unit type is a Predictive (P) type, the value of the flag is set to indicate that temporal motion vector prediction is not used; otherwise, the value of the flag is set to indicate that temporal motion vector prediction is used.

7. The method according to claim 1 , wherein the value of the flag is determined based on whether the picture containing the sub-picture unit is a Random Access Point (RAP) picture.

8. The method according to claim 7 , wherein if the picture is the RAP picture and the sub-picture unit belongs to a non-base layer of the picture, the value of the flag is set to indicate that temporal motion vector prediction is not used; otherwise, the value of the flag is set to indicate that temporal motion vector prediction is used.

9. The method according to claim 1 , wherein the flag is written to the header of the sub-picture unit.

10. The method according to claim 1 , wherein the method further comprises writing one or more parameters into the header of the sub-picture unit to specify the order of reference pictures in one or more reference picture lists used for inter prediction of the sub-picture unit.

11. The method according to claim 1 , wherein the method further comprises:

performing a motion compensated inter-picture prediction using the selected motion vector predictor to produce the prediction unit;

subtracting the prediction unit from a block of original samples to produce a block of residual samples; and

encoding the block of residual samples corresponding to the prediction unit into the coded video bitstream.

12. The method according to claim 2 , wherein the second list comprises one less motion vector predictor than the first list, and the motion vector predictors of the first and second lists are the same other than the temporal motion vector predictor.

13. The method according to claim 2 , wherein the first and second parameters are represented in the coded video bitstream using different predetermined bit representations.

14. The method according to claim 2 , wherein the first and second lists comprise the same predetermined number of motion vector predictors, and the second list comprises a motion vector predictor which is not present in the first list and is derived without using motion vectors from any reference pictures.

15. The method according to claim 1 , wherein the flag is used to indicate whether temporal motion vector prediction is used or not used for the inter-picture prediction of a sub-picture unit independently of other sub-picture units in the picture.

16. The method according to claim 1 , wherein the sub-picture unit is a slice of the picture.

17. An apparatus for encoding a video into a coded video bitstream with temporal motion vector prediction, the apparatus comprising:

a processor; and

a non-transitory memory having stored thereon executable instructions, which when executed by the processor, cause the processor to function as:

a control unit operable to determine a value of a flag for indicating whether temporal motion vector prediction is used or not used for the inter-picture prediction of a sub-picture unit of a picture;

a writing unit operable to write the flag having said value into a header of the sub-picture unit or a header of the picture;

a motion vector prediction unit; and

an inter-picture prediction unit for performing inter-picture prediction based on a selected motion vector predictor from the motion vector prediction unit,

wherein the motion vector prediction unit is configured to receive the flag and based on the flag being a first value, the motion vector prediction unit is operable to create a first list of motion vector predictors comprising a plurality of motion vector predictors including at least one temporal motion vector predictor derived from at least one motion vector from a collocated reference picture, and select a motion vector predictor out of the first list for a prediction unit in the sub-picture unit;

the writing unit is further operable to write a first parameter into the coded video bitstream for indicating the selected motion vector predictor out of the first list; and

if a temporal layer of the picture is determined to be the lowest or base layer, the value of the flag is set to indicate that temporal motion vector prediction is not used otherwise, the value of the flag is set to indicate that temporal motion vector prediction is used.