Hierarchical inter-layer prediction in multi-loop scalable video coding

1. A method for encoding a video sequence in a scalable video encoder to generate a scalable bitstream, the method comprising:

encoding the video sequence in a first layer encoder of the scalable video encoder to generate a first layer sub-bitstream that includes a first temporal hierarchy of two or more temporal levels;

encoding the video sequence in a second layer encoder of the scalable video encoder to generate a second layer sub-bitstream that includes a second temporal hierarchy of two or more temporal levels, wherein portions of the video sequence being encoded in the second layer encoder are predicted using reference portions of the video sequence encoded in the first layer encoder;

combining the first layer sub-bitstream and the second layer sub-bitstream in the scalable bitstream; and

signaling an indication of a highest temporal level in the first temporal hierarchy of the first layer sub-bitstream that is used for inter-layer prediction in the scalable bitstream.

2. The method of claim 1 , wherein the first layer encoder is a base layer encoder of the scalable video encoder.

3. The method of claim 1 , wherein the first layer encoder is an enhancement layer encoder of the scalable video encoder.

4. The method of claim 1 , wherein the indication of the highest temporal level is signaled in a video parameter set.

5. The method of claim 1 , further comprising:

signaling in the scalable bitstream an indication of a maximum decoded picture buffer (DPB) size needed for decoding the second layer sub-bitstream and the first layer sub-bitstream when the second layer sub-bitstream is a target sub-bitstream for decoding.

6. The method of claim 5 , wherein the indication of a maximum DPB size comprises an indication of a maximum DPB size needed for decoding the first layer sub-bitstream as a reference sub-bitstream.

7. A method for decoding a scalable bitstream in a scalable video decoder to generate a video sequence, the method comprising:

decoding from the scalable bitstream an indication of a highest temporal level in a first temporal hierarchy of a reference layer sub-bitstream that includes reference data used for inter-layer prediction of portions of a first enhancement layer sub-bitstream, the first temporal hierarchy including two or more temporal levels, the first enhancement layer sub-bitstream including a second temporal hierarchy of two or more temporal levels;

decoding the first enhancement layer sub-bitstream to generate the video sequence; and

decoding the reference layer sub-bitstream without decoding pictures in the reference layer sub-bitstream in temporal layers above the indicated highest temporal level.

8. The method of claim 7 , wherein the reference layer sub-bitstream is a base layer sub-bitstream.

9. The method of claim 7 , wherein the reference layer sub-bitstream is a second enhancement layer sub-bitstream.

10. The method of claim 7 , wherein the indication of the highest temporal level is signaled in a video parameter set.

11. The method of claim 7 , further comprising:

decoding from the scalable bitstream an indication of a maximum decoded picture buffer (DPB) size needed for decoding the first enhancement layer sub-bitstream and the reference layer sub-bitstream when the first enhancement layer sub-bitstream is a target sub-bitstream for decoding.

12. The method of claim 11 , wherein the indication of a maximum DPB size comprises an indication of a maximum DPB size needed for decoding the reference layer sub-bitstream as a non-target sub-bitstream.

13. The method of claim 11 , further comprising:

using the maximum DPB size indication to determine if the apparatus has sufficient DPB storage to decode the first enhancement layer sub-bitstream.

14. An apparatus configured to decode a scalable bitstream, the apparatus comprising:

means for decoding from the scalable bitstream an indication of a highest temporal level in a first temporal hierarchy of a reference layer sub-bitstream comprising reference data used for inter-layer prediction of portions of a first enhancement layer sub-bitstream, the first temporal hierarchy including two or more temporal levels, the first enhancement layer sub-bitstream including a second temporal hierarchy of two or more temporal levels;

means for decoding the first enhancement layer sub-bitstream to generate the video sequence; and

means for decoding the reference layer sub-bitstream wherein pictures in the reference layer sub-bitstream in temporal layers above the indicated highest temporal level are not decoded.

15. The apparatus of claim 14 , wherein the reference layer sub-bitstream is a base layer sub-bitstream.

16. The apparatus of claim 14 , wherein the reference layer sub-bitstream is a second enhancement layer sub-bitstream.

17. The apparatus of claim 14 , wherein the indication of the highest temporal level is signaled in a video parameter set.

18. The apparatus of claim 14 , further comprising:

decoding from the scalable bitstream an indication of a maximum decoded picture buffer (DPB) size needed for decoding the first enhancement layer sub-bitstream and the reference layer sub-bitstream when the first enhancement layer sub-bitstream is a target sub-bitstream for decoding.

19. The apparatus of claim 18 , wherein the indication of a maximum DPB size comprises an indication of a maximum DPB size needed for decoding the reference layer sub-bitstream as a non-target sub-bitstream.

20. The apparatus of claim 18 , further comprising:

means for using the maximum DPB size indication to determine if the scalable video decoder has sufficient DPB storage to decode the first enhancement layer sub-bitstream.