Adaptive upsampling for multi-layer video coding

1. A method for communicating video data, the method comprising:

selecting an upsampling filter for a video sequence to create enhancement layer pictures by:

applying a default upsampling filter to a base layer picture to obtain a processed base layer picture;

identifying blocks of the processed base layer picture that are selected for interlayer prediction of an enhancement layer frame; and

selecting one of the default upsampling filter and the plurality of candidate upsampling filters based on a comparison of block distortion measurements on the identified blocks associated with each of the default upsampling filter and the plurality of candidate upsampling filters;

encoding upsampling filter information, wherein the upsampling filter information comprises a plurality of coefficients of the selected upsampling filter; and

sending the encoded upsampling filter information and the enhancement layer pictures in an output video bitstream.

2. The method of claim 1 , wherein the selected upsampling filter is applied at a sequence level of the video sequence to create the enhancement layer bitstream.

3. The method of claim 1 , further comprising selecting a second upsampling filter from a plurality of candidate upsampling filters by:

determining whether knowledge of a content of the video sequence exists; and

upon determining that knowledge of the content of the video sequence exists, selecting a candidate upsampling filter that is designed for the content of the video sequence.

4. The method of claim 1 , further comprising selecting a second upsampling filter from a plurality of candidate upsampling filters by:

determining whether knowledge of a category related to the video sequence exists; and

upon determining that knowledge of the category related to the video sequence exists, selecting a candidate upsampling filter that is designed for the category related to the video sequence.

5. The method of claim 1 , wherein the selected upsampling filter is applied at a picture or slice level of the video sequence.

6. The method of claim 5 , further comprising selecting a second upsampling filter from a plurality of candidate upsampling filters by:

performing multi-pass encoding on an enhancement layer picture of the video sequence utilizing the plurality of candidate upsampling filters; and

selecting the second upsampling filter from the plurality of candidate upsampling filters based on the performance of the second upsampling filter during the multi-pass encoding.

7. The method of claim 6 , wherein the performance of the second upsampling filter is evaluated using a rate distortion cost.

8. The method of claim 1 , wherein selecting one of the default upsampling filter and the plurality of candidate upsampling filters based on a comparison of block distortion measurements comprises selecting one of the default upsampling filter and the plurality of candidate upsampling filters with the lowest associated distortion.

9. The method of claim 5 , further comprising selecting a second upsampling filter by:

performing multi-pass encoding on an enhancement layer picture of the video sequence for each of a first plurality of candidate upsampling filters; and

selecting one of the first plurality of candidate upsampling filters corresponding to a coding pass that best satisfies a criterion.

10. The method of claim 1 , further comprising:

for a previously received video sequence, generating a set of training data comprising a reconstructed base layer picture and an original enhancement layer input picture of the previously received video sequence; and

training the upsampling filter using a least squared method that uses the set of training data of the previously received video sequence.

11. A system comprising executable instruction that cause the system to perform operations comprising:

selecting an upsampling filter for a video sequence to create enhancement layer pictures by:

applying a default upsampling filter to a base layer picture to obtain a processed base layer picture;

identifying blocks of the processed base layer picture that are selected for interlayer prediction of an enhancement layer frame; and

selecting one of the default upsampling filter and the plurality of candidate upsampling filters based on a comparison of block distortion measurements on the identified blocks associated with each of the default upsampling filter and the plurality of candidate upsampling filters;

encoding upsampling filter information, the upsampling filter information comprising a plurality of coefficients of the selected upsampling filter; and

sending the encoded upsampling filter information and the enhancement layer pictures in an output video bitstream.

12. The system of claim 11 , wherein the selected upsampling filter is applied at a sequence level of the video sequence to create the enhancement layer bitstream.

13. The system of claim 11 , further comprising executable instruction that cause the system to perform further operations comprising:

selecting a second upsampling filter from a plurality of candidate upsampling filters by:

determining whether knowledge of a content of the video sequence exists; and

upon determining that knowledge of the content of the video sequence exists, selecting a candidate upsampling filter that is designed for the content of the video sequence.

14. The system of claim 11 , further comprising executable instruction that cause the system to perform further operations comprising:

selecting a second upsampling filter from a plurality of candidate upsampling filters by:

determining whether knowledge of a category related to the video sequence exists; and

upon determining that knowledge of the category related to the video sequence exists, selecting a candidate upsampling filter that is designed for the category related to the video sequence.

15. The system of claim 11 , wherein the selected upsampling filter is applied at a picture or slice level of the video sequence.

16. The system of claim 15 , further comprising executable instruction that cause the system to perform further operations comprising:

selecting a second upsampling filter from a plurality of candidate upsampling filters by:

performing multi-pass encoding on an enhancement layer picture of the video sequence utilizing the plurality of candidate upsampling filters; and

selecting the second upsampling filter from the plurality of candidate upsampling filters based on the performance of the second upsampling filter during the multi-pass encoding.

17. The system of claim 16 , wherein the performance of the second upsampling filter is evaluated using a rate distortion cost.

18. The system of claim 11 , wherein selecting one of the default upsampling filter and the plurality of candidate upsampling filters based on a comparison of block distortion measurements comprises selecting one of the default upsampling filter and the plurality of candidate upsampling filters with the lowest associated distortion.

19. The system of claim 5 , further comprising executable instruction that cause the system to perform further operations comprising:

selecting a second upsampling filter by:

performing multi-pass encoding on an enhancement layer picture of the video sequence for each of a first plurality of candidate upsampling filters; and

selecting one of the first plurality of candidate upsampling filters corresponding to a coding pass that best satisfies a criterion.

20. The system of claim 11 , further comprising executable instruction that cause the system to perform further operations comprising:

for a previously received video sequence, generating a set of training data comprising a reconstructed base layer picture and an original enhancement layer input picture of the previously received video sequence; and

training the upsampling filter using a least squared method that uses the set of training data of the previously received video sequence.