Intra 4×4 modes 3, 7 and 8 availability determination intra estimation and compensation

1. An apparatus comprising:

a first processing circuit configured to generate a plurality of reconstructed samples in response to one or more macroblocks of an input signal; and

a second processing circuit configured to determine availability of intra 4×4 prediction modes for each luma sub-block of a current macroblock in response to available reconstructed samples adjacent to said current macroblock, wherein (i) an intra 4×4 prediction mode 3 and an intra 4×4 prediction mode 7 are indicated as available when a first group of said reconstructed samples only adjacent to a top edge of a current luma sub-block of said current macroblock is available and a second group of said reconstructed samples only adjacent to a left edge of said current luma sub-block is not available and (ii) an intra 4×4 prediction mode 8 is indicated as available when said first group of said reconstructed samples only adjacent to said top edge of said current luma sub-block is not available and said second group of said reconstructed samples only adjacent to said left edge of said current luma sub-block is available.

2. The apparatus according to claim 1 , wherein said second circuit is further configured to indicate availability of said intra 4×4 prediction modes 3, 7 and 8 for each of said luma sub-blocks when both said first group of said reconstructed samples adjacent to said top edge of said current luma sub-block and said second group of said reconstructed samples adjacent to said left edge of said current luma sub-block are available.

3. The apparatus according to claim 1 , wherein said second processing circuit is implemented in a decoding loop of an encoder.

4. The apparatus according to claim 1 , wherein said first processing circuit and said second processing circuit comprise a decoder.

5. The apparatus according to claim 1 , wherein said apparatus comprises an H.264 decoder.

6. The apparatus according to claim 1 , wherein said second processing circuit comprises:

an intra prediction circuit configured to generate an intra predicted luma sub-block in response to said available reconstructed samples adjacent to a single edge of said current luma sub-block.

7. The apparatus according to claim 6 , wherein said second processing circuit further comprises:

a control circuit configured to generate one or more control signals in response to (i) said first group of said reconstructed samples adjacent to a top edge of said current luma sub-block being available, (ii) said second group of said reconstructed samples adjacent to a left edge of said current luma sub-block being available and (iii) both said first group and said second group of said reconstructed samples being available.

8. The apparatus according to claim 7 , wherein said control circuit is further configured to determine a position of said top edge and said left edge of said current luma sub-block.

9. The apparatus according to claim 8 , wherein said first group of said reconstructed samples comprises a plurality of reconstructed samples in a line adjacent to said top edge of said current luma sub-block.

10. The apparatus according to claim 8 , wherein (i) said second group of said reconstructed samples comprises a plurality of reconstructed samples in a line adjacent to said left edge of said current luma sub-block.

11. The apparatus according to claim 7 , wherein said control circuit comprises:

a plurality of first logic gates configured to generate a first control signal in response to (i) said first group of said reconstructed samples being available and (ii) both said first group and said second group of said reconstructed samples being available; and

a plurality of second logic gates configured to generate a second control signal in response to (i) said second group of said reconstructed samples being available and (ii) both said first group and said second group of said reconstructed samples being available.

12. An apparatus comprising:

means for generating a plurality of reconstructed samples in response to one or more macroblocks of an input signal; and

means for determining availability of intra 4×4 prediction modes for each luma sub-block of a current macroblock in response to available reconstructed samples adjacent to said current macroblock, wherein (i) an intra 4×4 prediction mode 3 and an intra 4×4 prediction mode 7 are indicated as available when a first group of said reconstructed samples only adjacent to a top edge of a current luma sub-block of said current macroblock is available and a second group of said reconstructed samples only adjacent to a left edge of said current luma sub-block is not available and (ii) an intra 4×4 prediction mode 8 is indicated as available when said first group of said reconstructed samples only adjacent to said top edge of said current luma sub-block is not available and said second group of said reconstructed samples only adjacent to said left edge of said current luma sub-block is available.

13. A method for intra prediction of a luma sub-block comprising the steps of:

(A) generating a plurality of reconstructed samples in response to one or more macroblocks of an input signal; and

(B) determining availability of intra 4×4 prediction modes for each luma sub-block of a current macroblock in response to available reconstructed samples adjacent to said current macroblock, wherein (i) an intra 4×4 prediction mode 3 and an intra 4×4 prediction mode 7 are indicated as available when a first group of said reconstructed samples only adjacent to a top edge of a current luma sub-block of said current macroblock is available and a second group of said reconstructed samples only adjacent to a left edge of said current luma sub-block is not available and (ii) an intra 4×4 prediction mode 8 is indicated as available when said first group of said reconstructed samples only adjacent to said top edge of said current luma sub-block is not available and said second group of said reconstructed samples only adjacent to said left edge of said current luma sub-block is available.

14. The method according to claim 13 , wherein the step (B) further comprises:

generating an intra predicted luma sub-block according to said intra 4×4 prediction mode 3 in response to (i) said first group of said reconstructed samples adjacent to a top edge of said current luma sub-block being available and (ii) both said first group and said second group of said reconstructed samples adjacent to said left edge of said current luma sub-block being available.

15. The method according to claim 13 , wherein the step (B) further comprises:

generating an intra predicted luma sub-block according to said intra 4×4 prediction mode 7 in response to (i) said first group of said reconstructed samples adjacent to said top edge of said current luma sub-block being available and (ii) both said first group and said second group of said reconstructed samples adjacent to said left edge of said current luma sub-block being available.

16. The method according to claim 13 , wherein the step (B) further comprises:

generating an intra predicted luma sub-block according to said intra 4×4 prediction mode 8 in response to (i) said second group of said reconstructed samples adjacent to said left edge of said current luma sub-block being available and (ii) both said second group and said first group of said reconstructed samples adjacent to said top edge of said current luma sub-block being available.

17. The method according to claim 13 , wherein the step (B) further comprises:

generating one or more control signals indicating availability of each of said intra 4×4 prediction modes 3, 7 and 8 in response to availability of said reconstructed samples adjacent to said current macroblock.

18. The method according to claim 17 , wherein the step (B) further comprises:

enabling intra 4×4 prediction modes 3 and 7 in response to said one or more control signals indicating said available reconstructed samples being adjacent to a top edge of said luma sub-block; and

enabling intra 4×4 prediction mode 8 in response to said one or more control signals indicating said available reconstructed samples being adjacent to a left edge of said luma sub-block.

19. The method according to claim 13 , wherein the step (B) further comprises:

determining a position of a top edge and a left edge of said current luma sub-block.

20. The method according to claim 19 , wherein the step (B) further comprises:

determining availability of a plurality of reconstructed samples in a line adjacent to said top edge of said current luma sub-block; and

determining availability of a plurality of reconstructed samples in a line adjacent to said left edge of said luma sub-block.

21. The method according to claim 20 , further comprising the steps of:

providing an indication that a diagonal down-left prediction mode and a vertical-left prediction mode are available in response to said plurality of reconstructed samples in said line adjacent to said top edge of said current luma sub-block being available;

providing an indication that a horizontal-up prediction mode is available in response to said plurality of reconstructed samples in said line adjacent to said left edge of said current luma sub-block being available; and

providing an indication that at least said diagonal down-left prediction mode, said vertical-left prediction mode and said horizontal-up prediction mode are available in response to said plurality of reconstructed samples in said line adjacent to said top edge of said current luma sub-block and said line adjacent to said left edge of said current luma sub-block being available.

22. A computer readable medium comprising computer executable instructions for causing a computer to perform the method according to claim 13 .