Template matching for JVET intra prediction

1. A method of decoding Joint Video Experts Team (JVET) video, comprising:

defining a coding unit (CU) template within a decoded area of a video frame, said CU template being positioned above and/or to the left of a current decoding position for which data was intra predicted;

defining a search window within said decoded area, said search window being adjacent to said CU template;

generating a plurality of candidate prediction templates based on pixel values in said search window, each of said plurality of candidate prediction templates being generated using different intra prediction modes;

calculating a matching cost between said CU template and each of the plurality of candidate prediction templates;

selecting an intra prediction mode that generated the candidate prediction template that had the lowest matching cost relative to said CU template; and

generating a prediction CU for said current decoding position based on said intra prediction mode.

2. The method of claim 1 , wherein said CU template is shaped with a row of pixels immediately above the top of the current decoding position and a column of pixels immediately to the left of the current decoding position.

3. The method of claim 2 , wherein said row of pixels has a length that is one pixel less than the length of the current decoding position and said column of pixels has a height that is one pixel less than the height of the current decoding position.

4. The method of claim 1 , wherein calculating said matching costs comprises calculating the sum of absolute differences between said CU template and each of said plurality of candidate prediction templates.

5. The method of claim 1 , wherein said search window is spaced apart from the current decoding position by the CU template and extends beyond the ends of the CU template.

6. The method of claim 1 , wherein the steps of defining said CU template and said search window, calculating said matching costs, selecting intra prediction mode, and generating said prediction CU based on said intra prediction mode are performed when information identifying an intra prediction mode for the current decoding position is absent from a bitstream.

7. The method of claim 1 , further comprising adding said prediction CU to a reconstructed residual CU to generate a reconstructed CU for output video.

8. The method of claim 1 , wherein the different intra prediction modes for which candidate prediction templates are considered are at least a subset of the allowed JVET intra prediction modes.

9. A method of decoding Joint Video Experts Team (JVET) video, comprising:

defining a plurality of coding unit (CU) templates within a decoded area of a video frame, each of the CU templates being positioned above and/or to the left of a current decoding position for which data was intra predicted and being spaced apart from the current decoding position by a different number of reference lines;

defining a search window within said decoded area for each of said plurality of CU templates, each search window being within an associated reference line;

generating one or more candidate prediction templates for each of said plurality of CU templates based on pixel values in the search window associated with the CU template, each of said plurality of candidate prediction templates being generated using an intra prediction modes;

calculating a matching cost between each of said plurality of CU templates and each of said plurality of candidate prediction templates;

selecting an intra prediction mode that generated a candidate prediction template with a lowest matching cost relative to one of said plurality of CU templates; and

generating a prediction CU for said current decoding position based on said selected intra prediction mode.

10. The method of claim 9 , wherein each of said plurality of CU templates is shaped with a row of pixels immediately above an associated reference line and a column of pixels immediately to the left of the associated reference line.

11. The method of claim 9 , wherein calculating said matching costs comprises calculating the sum of absolute differences between the CU templates and their associated plurality of candidate prediction templates.

12. The method of claim 9 , wherein each search window extend beyond the ends of the associated CU template.

13. The method of claim 9 , wherein the steps of defining said CU templates and said search windows, calculating said matching costs, selecting said intra prediction mode, and generating said prediction CU based on said intra prediction mode are performed when in-formation identifying an intra prediction mode for the current decoding position is absent from a bitstream.

14. The method of claim 9 , further comprising adding said prediction CU to a reconstructed residual CU to generate a reconstructed CU for output video.

15. The method of claim 9 , wherein the different intra prediction modes for which candidate prediction templates are considered are at least a subset of the allowed JVET intra prediction modes.

16. A method of decoding Joint Video Experts Team (JVET) video, comprising:

receiving a bitstream identifying a plurality of coding units (CUs), at least some of which were encoded with intra prediction, wherein said bitstream omits an indication of which intra prediction mode was used to encode those CUs;

defining at least one CU template within a decoded area of a video frame, the at least one CU template being positioned above and/or to the left of a current decoding position for a coding unit encoded with intra prediction;

defining at least one search window within said decoded area, said at least one search window being adjacent to said at least one CU template within said decoded area;

generating a plurality of candidate prediction templates for said at least one CU template based on pixel values in the search window associated with said at least one CU template, each of said plurality of candidate prediction templates being generated using different intra prediction modes;

calculating a matching cost between said at least one CU template and each of said plurality of candidate prediction templates;

selecting an intra prediction mode that generated the candidate prediction template that had the lowest matching cost relative to said at least one CU template;

generating a prediction CU for said current decoding position based on said intra prediction mode;

decoding a reconstructed residual CU from said bitstream for said current decoding position; and

generating a reconstructed CU by adding said prediction CU to said reconstructed residual CU.

17. The method of claim 16 , wherein said at least one CU template is shaped with a row of pixels immediately above the top of the current decoding position and a column of pixels immediately to the left of the current decoding position.

18. The method of claim 16 , wherein each of said at least one CU templates is shaped with a row of pixels immediately above a different associated reference line and a column of pixels immediately to the left of the associated reference line.

19. The method of claim 16 , wherein calculating said matching costs comprises calculating the sum of absolute differences between said at least one CU template and each of said plurality of candidate prediction templates.

20. The method of claim 16 , wherein the different intra prediction modes for which candidate prediction templates are considered are at least a subset of the allowed JVET intra prediction modes.