Detection of moving interlaced text for film mode decision
A method for detecting moving interlaced text in a video sequence originating through telecine is disclosed. The method generally includes the steps of (A) checking a motion condition of a current block in a current field in the video sequence for motion both (i) from a previous field in the video sequence to the current field and (ii) from the current field to a next field in the video sequence, (B) checking an artifact condition of the current block for a plurality of symmetric interlaced artifacts in both (i) a forward temporal direction and (ii) a backward temporal direction and (C) asserting a block motion indicator for the current block if all of (i) the motion condition is true and (ii) the artifact condition is true.
1. A method for detecting moving interlaced text in a video sequence originating through telecine, comprising the steps of:
(A) checking a motion condition of a current block in a current field in said video sequence to detect motion both (i) from a previous field in said video sequence to said current field and (ii) from said current field to a next field in said video sequence;
(B) checking an artifact condition of said current block by calculating (i) a first difference between said current block and a next block in said next field, (ii) a first activity between said current block to said next block, (iii) a second difference between a previous block in said previous field and said current block and (iv) a second activity between said previous block to said current block, wherein said artifact condition is true if said first difference is greater than said first activity and said second difference is greater than said second activity;
(C) asserting a block motion indicator to designate that said current block contains said moving interlaced text if all of (i) said motion condition is true and (ii) said artifact condition is true; and
(D) deinterlacing said current block in response to said block motion indicator.
2. The method according to claim 1 , further comprising the step of:
checking an activity condition of said current block to detect a high activity in at least one spatial direction within said current block, wherein assertion of said block motion indicator is further based on said activity condition.
3. The method according to claim 1 , further comprising the step of:
checking a neighbor condition of a plurality of neighboring blocks in said current field around said current block to detect a low activity in at least one spatial direction within said current block, wherein assertion of said block motion indicator is further based on said neighbor condition.
4. The method according to claim 1 , further comprising the step of:
measuring a noise level of said current block, wherein said motion condition is determined based on a value of said motion relative to said noise level.
5. The method according to claim 4 , further comprising the step of:
checking a 3:2 pull-down telecine condition of said current field, wherein said motion condition is further determined based on said 3:2 pull-down telecine condition.
6. The method according to claim 1 , further comprising the step of:
generating a plurality of row level indicators of said moving interlaced text based on a plurality of said block motion indicators, wherein each of said block motion indicators is evaluated at one of a plurality of block positions in said current field.
7. The method according to claim 6 , further comprising the step of:
asserting a field motion indicator of said current field if said row level indicators detect rapid moving text.
8. The method according to claim 7 , further comprising the step of:
asserting said field motion indicator if said row level indicators detect slow moving text.
9. The method according to claim 8 , further comprising the step of:
deasserting said field motion indicator of said current field if said row level indicators of (i) said current field and (ii) a fixed number of previous fields in said video sequence do not detect said moving interlaced text.
10. The method according to claim 1 , further comprising the step of:
de-interlacing a portion of said current field having said moving interlaced text using a spatial filter process.
11. A method for detecting moving interlaced text in a video sequence originating through telecine, comprising the steps of:
(A) checking an activity condition of a current block in a current field in said video sequence to detect a first activity in at least one first spatial direction within said current block, wherein said first spatial direction intersects at least two pixels in said current block;
(B) checking a neighbor condition of a plurality of neighbor blocks in said current field and around said current block to detect a plurality of second activities in at least one second spatial direction within said neighbor blocks;
(C) asserting a block motion indicator to designate that said current block contains said moving interlaced text if all of (i) said activity condition indicates that said first activity has a high value and (ii) said neighbor condition indicates that each of said second activities has a respective low value; and
(D) deinterlacing said current block in response to said block motion indicator.
12. The method according to claim 11 , further comprising the step of:
checking a motion condition of said current block to detect motion both (i) from a previous field in said video sequence to said current field and (ii) from said current field to a next field in said video sequence, wherein assertion of said block motion indicator is further based on said motion condition.
13. The method according to claim 11 , further comprising the step of:
checking an artifact condition of said current block to detect (i) one or more first artifacts in a forward temporal direction and (ii) one or more second artifacts in a backward temporal direction, wherein said artifact condition is true if said first artifacts interlace in a symmetrical pattern with said second artifacts and assertion of said block motion indicator is further based on said artifact condition.
14. The method according to claim 11 , wherein said first spatial direction comprises a vertical direction.
15. The method according to claim 14 , wherein said first spatial direction comprises a horizontal direction.
16. The method according to claim 11 , wherein said first activity comprises a value above a threshold.
17. The method according to claim 11 , wherein said first activity of said current block comprises a value above that of said second activities of said neighbor blocks.
18. The method according to claim 11 , further comprising the step of:
measuring a noise level of said current block, wherein said first activity of said current block comprises a value above said noise level.
19. The method according to claim 11 , further comprising the step of:
measuring a noise level of said current block, wherein said second activity of said neighbor blocks comprises a value below said noise level.
20. A system comprising:
a memory configured to store a video sequence (i) originating through telecine and (ii) having moving interlaced text; and
a processor configured to (A) check a motion condition of a current block in a current field in said video sequence to detect motion both (i) from a previous field in said video sequence to said current field and (ii) from said current field to a next field in said video sequence, (B) check an artifact condition of said current block by calculating (i) a first difference between said current block and a next block in said next field, (ii) a first activity between said current block to said next block, (iii) a second difference between a previous block in said previous field and said current block and (iv) a second activity between said previous block to said current block, wherein said artifact condition is true if said first difference is greater than said first activity and said second difference is greater than said second activity, (C) assert a block motion indicator to designate that said current block contains said moving interlaced text if all of (i) said motion condition is true and (ii) said artifact condition is true.