EP0687104A2
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A method for detecting edge direction in an interlaced television image
Assignee: Nokia Technology GmbH
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Filing: 1995-05-26
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Granted: —
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Expires: 2015-05-26
Abstract
Abstract The invention relates to a method for detecting an edge and edge direction in an interlaced video signal received in the form of a sampled data. In a detection mask it is calculated the responses of several operators with respect to the examined position (X) in the center of the mask, which function in different subdirections. The responses are arranged in main groups according to the main directions, and for each main group it is found out a minimum response and its subdirection, after which it is found out the minimum of the minimum responses. In addition, for the examined position (X) it is determined its activity. The operators also include a horizontal operator. In a consistency check it is found out the dominant main direction for the edge using the main and subdirection information of the examined position (X) and its neighbouring positions, stored in memory, and the subdirection of the minimum response of said main direction group of the examined position is selected as the final edge direction.
Inventors
- 👤 Jouni Salonen
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 12:52
CPC Classifications
H; H04; H04N; H04N7/00; H04N7/01; H04N7/0117; H04N7/012; H04N5/00; H04N5/14
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
306 words
A method for detecting an edge and edge direction in an interlaced video signal received in the form of sampled data, in which method for each position (X) examined: - it is used a detection mask the top row of which comprises samples from a line (m) and the bottom row comprises samples of the corresponding horizontal positions from the next line (m+1) of the same field, - it is calculated several operator responses that function in different subdirections with respect to the examined position (X) in the center of the mask, - said operator responses in the subdirections are arranged in main groups according to the main directions and for each main group it is found out a minimum response (resp_left, resp_middle, resp_right) and its subdirection (dir_left, dir_middle, dir_right), which is stored in a memory, - it is found out the minimum of the minimum responses and the main direction (dir_totmin) of its main group is stored in a memory, characterized in that, in addition: - for the examined position (X) it is determined its activity, and only positions considered active are taken into account in the consistency check, - the operators also include a horizontal operator (horizontal), which compares the difference of samples in the vertical direction to the difference of samples in the horizontal direction, and the greater the difference in the vertical direction and the smaller the difference in the horizontal direction, the greater the probability that there is a horizontal edge, - it is performed a consistency check, in which it is searched the dominant main direction of an edge using the main and subdirection information of the examined position (X) and its neighbouring positions stored in the memory, and the subdirection of the minimum response of said main direction group of the examined position is selected as final edge direction.
Claim 2
Dependent Claim
179 words
The method of claim 1, characterized in that the operators, divided into main groups, are: middle group: vertical = | c3 - c10 | + | c4 - c11 | right1 = | c4 - c10 | + | c5 - c11 | left1 = | c3 - c11 | + | c4 - c12 | left group : left2 = | c2 - c11 | + | c3 - c12 | left3 = | c2 - c12 | + | c3 - c13 | left4 = | c1 - c12 | + | c2 - c13 | right group : right2 = | c5 - c10 | + | c6 - c11 | right3 = | c5 - c9 | + | c6 - c10 | right4 = | c6 - c9 | + | c7 - c10 | where c1, c2, c3, c4, c5, c6 and c7 are the samples on the top row of the window and, correspondingly, c8, c9, c10, c11, c12, c13 and c14 are the samples on the bottom row of the window.
Claim 3
Dependent Claim
28 words
The method of claim 2, characterized in that the horizontal operator is: horizontal = | c4 - c11 | - [(max(c3,c4,c5) - min(c3,c4,c5)) + (max(c10,c11,c12) - min(c10,c11,c12))] .
Claim 4
Dependent Claim
26 words
The method of claim 3, characterized in that when the horizontal operator exceeds a set first threshold value, there is considered to be a horizontal edge.
Claim 5
Dependent Claim
33 words
The method of claim 1, characterized in that the position examined is determined active if any one of the responses of the middle group operators is greater than a set second threshold value.
Claim 6
Dependent Claim
29 words
The method of claim 1, characterized in that it will be performed checks on the basis of which at least one of the main directions is discarded as unsuitable.
Claim 7
Independent Claim
74 words
The method of claims 2 and 6, characterized in that in the first check (Check A) it is compared the sum of the responses of operators left2 and left1 to the sum of the responses of operators right2 and right1, and if the former is greater than the latter, the minimum response of the left main direction is discarded, and in the opposite case the minimum response of the right main direction is discarded.
Claim 8
Dependent Claim
76 words
The method of claim 7, characterized in that in the second check (Check B): - it is performed a trial interpolation in the direction indicated by the subdirection information of the minimum response of the remaining main group, - the trial interpolated value (y) is compared to the sample above and below the examined position (X), and if the difference falls outside a set range, also the minimum response of the remaining main direction is discarded.
Claim 9
Independent Claim
102 words
The method of any one of the preceding claims, characterized in that the consistency check is performed in a window, the size of which has been selected, and to each memory position (em) of the window it is associated the information on the subdirection of the minimum responses of the main groups (dir_left, dir_middle, dir_right), the information on the minimum of the minimum responses of the main groups (dir_totmin), the activity information (activity), the horizontal response information (horizontal) and the information on whether the direction of the minimum of the minimum responses of the main groups (dir_totmin) is in a certain direction.
Claim 10
Dependent Claim
60 words
The method of claim 9, characterized in that in the window it is calculated the number of active positions and how many of each main direction there are, and in order for the main direction with the greatest number to be the dominant main direction said number has to be sufficient, e.g. at least half the number of active positions.
References Cited (Backward Citations)
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