Multiple inter predictors with decoder side motion vector derivation for video coding

1. A method of decoding video data, the method comprising:

determining merge candidates for a block of video data;

determining if a merge candidate of the merge candidates includes a base prediction signal and an additional inter prediction signal;

disabling at least one decoder side motion vector derivation technique for use on the base prediction signal of the block of video data based on determining that the merge candidate includes the additional inter prediction signal, wherein the at least one decoder side motion vector derivation technique comprises a multi-pass decoder side motion vector refinement technique;

determining an overall prediction signal with a multiple hypothesis prediction technique using the base prediction signal and the additional inter prediction signal; and

decoding the block of video data using the overall prediction signal.

2. The method of claim 1 , wherein the additional inter prediction signal is an inherited additional inter prediction signal.

3. The method of claim 1 , wherein the additional inter prediction signal is indicated by a syntax element signaled in a video bitstream related to the block of video data.

4. The method of claim 3 , further comprising:

decoding the syntax element indicating the additional inter prediction signal.

5. The method of claim 1 , wherein the at least one decoder side motion vector derivation technique is a bi-directional optical flow technique and a decoder side motion vector refinement technique.

6. The method of claim 1 , wherein the multiple hypothesis prediction technique determines a weighted superposition of the base prediction signal and the additional inter prediction signal.

7. The method of claim 1 , wherein the multiple hypothesis prediction technique determines a weighted superposition of more than two motion-compensated prediction signals.

8. A device configured to decode video data, the device comprising:

a memory configured to store a block of video data; and

one or more processors in communication with the memory, the one or more processors configured to:

determine merge candidates for the block of video data;

determine if a merge candidate of the merge candidates includes a base prediction signal and an additional inter prediction signal;

disable at least one decoder side motion vector derivation technique for use on the base prediction signal of the block of video data based on the determination that the merge candidate includes the additional inter prediction signal, wherein the at least one decoder side motion vector derivation technique comprises a multi-pass decoder side motion vector refinement technique;

determine an overall prediction signal with a multiple hypothesis prediction technique using the base prediction signal and the additional inter prediction signal; and

decode the block of video data using the overall prediction signal.

9. The device of claim 8 , wherein the additional inter prediction signal is an inherited additional inter prediction signal.

10. The device of claim 8 , wherein the additional inter prediction signal is indicated by a syntax element signaled in a video bitstream related to the block of video data.

11. The device of claim 10 , wherein the one or more processors are further configured to decode the syntax element indicating the additional inter prediction signal.

12. The device of claim 8 , wherein the at least one decoder side motion vector derivation technique is a first decoder side motion vector derivation technique, wherein the processors are further configured to enable a second decoder side motion vector derivation technique that is different than the first decoder side motion vector derivation technique if second decoder side motion vector derivation technique conditions are met.

13. The device of claim 12 , wherein the first decoder side motion vector derivation technique is a bi-directional optical flow technique and the second decoder side motion vector derivation technique is a decoder side motion vector refinement technique.

14. The device of claim 12 , wherein the first decoder side motion vector derivation technique is a decoder side motion vector refinement technique and the second decoder side motion vector derivation technique is a bi-directional optical flow technique.

15. The device of claim 8 , wherein the multiple hypothesis prediction technique determines a weighted superposition of the base prediction signal and the additional inter prediction signal.

16. The device of claim 8 , wherein the multiple hypothesis prediction technique determines a weighted superposition of more than two motion-compensated prediction signals.

17. The device of claim 8 , further comprising a display for displaying a picture of video data that includes the block of video data.

18. A device configured to decode video data, the device comprising:

a memory configured to store a block of video data; and

one or more processors in communication with the memory, the one or more processors configured to:

determine merge candidates for the block of video data;

determine if a merge candidate of the merge candidates includes a base prediction signal and an additional inter prediction signal;

disable at least one decoder side motion vector derivation technique for use on the base prediction signal of the block of video data based on the determination that the merge candidate includes the additional inter prediction signal, wherein the at least one decoder side motion vector derivation technique is a first decoder side motion vector derivation technique, and wherein the processors are further configured to enable a second decoder side motion vector derivation technique that is different than the first decoder side motion vector derivation technique if second decoder side motion vector derivation technique conditions are met;

determine an overall prediction signal with a multiple hypothesis prediction technique using the base prediction signal and the additional inter prediction signal; and

decode the block of video data using the overall prediction signal.

19. The device of claim 18 , wherein the first decoder side motion vector derivation technique is a bi-directional optical flow technique and the second decoder side motion vector derivation technique is a decoder side motion vector refinement technique.

20. The device of claim 18 , wherein the first decoder side motion vector derivation technique is a decoder side motion vector refinement technique and the second decoder side motion vector derivation technique is a bi-directional optical flow technique.