System and method for processing subpicture data

1. A method for rendering subpicture images comprising:

reading a subpicture image from a digital versatile disk (“DVD”);

identifying regions within said subpicture image for which a translucence level, α, is below a specified threshold value, wherein identifying further comprises locating, within a subpicture image buffer, an indication that α is below said specified threshold value, and an indication that said α value repeats until an end of a current line of said subpicture image; and

rendering on a video screen only those regions of said subpicture image for which α is above said specified threshold value.

2. The method as in claim 1 wherein said specified threshold value is zero.

3. The method as in claim 1 wherein said indication comprises fourteen sequential zeros followed by a palette entry code corresponding to α=0.

4. The method as in claim 1 implemented by a processor which supports hardware-assisted zero run length counting.

5. The method as in claim 1 further comprising:

detecting that one or more regions of said subpicture image have changed; and

regenerating on said video screen only said regions of said subpicture image which have changed, while maintaining all remaining regions.

6. The method as in claim 5 wherein said changed regions are comprised of new bitmap data.

7. The method as in claim 5 wherein said changed regions are comprised of new palette data.

8. The method as in claim 1 further comprising:

detecting that a highlight associated with a first region has been moved to a second region on said subpicture image; and

regenerating on said video screen only said first region without said highlight and said second region with said highlight, while maintaining all remaining regions.

9. The method as in claim 8 wherein said highlight is moved responsive to a user selection input via a remote control device.

10. A tangible computer readable medium, other than a carrier wave or other propagation medium, including computer program code which, when executed by a machine, causes said machine to perform the operations of:

reading a subpicture image from a digital versatile disk (“DVD”);

identifying regions within said subpicture image for which a translucence level, α, is below a specified threshold value, wherein identifying further comprises locating, within a subpicture image buffer, an indication that α is below said specified threshold value, and an indication that said α value repeats until an end of a current line of said subpicture image; and

rendering on a video screen only those regions of said subpicture image for which α is above said specified threshold value.

11. The computer readable medium as in claim 10 wherein said specified threshold value is zero.

12. The computer readable medium as in claim 10 wherein said indication comprises fourteen sequential zeros followed by a palette entry code corresponding to α=0.

13. The computer readable medium as in claim 10 including additional program code to cause said machine to perform the operations of:

detecting that one or more regions of said subpicture image have changed; and

regenerating on said video screen only said regions of said subpicture image which have changed, while maintaining all remaining regions.

14. The computer readable medium as in claim 13 wherein said changed regions are comprised of new bitmap data.

15. The computer readable medium as in claim 13 wherein said changed regions are comprised of new palette data.

16. The computer readable medium as in claim 10 including additional program code to cause said machine to perform the operations of:

detecting that a highlight associated with a first region has been moved to a second region on said subpicture image; and

regenerating on said video screen only said first region without said highlight and said second region with said highlight, while maintaining all remaining regions.

17. The computer readable medium as in claim 16 wherein said highlight is moved responsive to a user selection input via a remote control device.

18. A system comprising:

DVD reader means for reading a subpicture image from a digital versatile disk (“DVD”);

image analysis means for identifying regions within said subpicture image for which a translucence level, α, is below a specified threshold value, wherein said image analysis means identifies said regions by locating, within a subpicture image buffer, an indication that α is below said specified threshold value, and an indication that said α value repeats until an end of a current line of said subpicture image; and

image rendering means for rendering on a video screen only those regions of said subpicture image for which α is above said specified threshold value.

19. The system as in claim 18 wherein said specified threshold value is zero.

20. The system as in claim 18 wherein said indication comprises fourteen sequential zeros followed by a palette entry code corresponding to α=0.

21. The system as in claim 18 wherein said image analysis means detects that one or more regions of said subpicture image have changed and responsively regenerates on said video screen only said regions of said subpicture image which have changed, while maintaining all remaining regions.

22. The system as in claim 21 wherein said changed regions are comprised of new bitmap data.

23. The system as in claim 21 wherein said changed regions are comprised of new palette data.

24. The system as in claim 18 wherein said image analysis means detects that a highlight associated with a first region has been moved to a second region on said subpicture image; and regenerates on said video screen only said first region without said highlight and said second region with said highlight, while maintaining all remaining regions.

25. The system as in claim 24 wherein said highlight is moved responsive to a user selection input via a remote control device.