Methods and apparatus for detecting edges within encoded images
AssigneeHitachi America, Ltd.
InventorsSharif Mohammad Sazzad, Frank Anton Lane
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Abstract
Edge detection methods and apparatus which utilize the dc dct differential data included in encoded images, e.g., an MPEG-2 encoded video stream, are described. Use of the dc dct differential data allows efficient methods for detecting the presence of edges within encoded images. The edge detection methods and apparatus of the present invention can be used where differential coding of the DC DCT coefficients is employed. Accordingly, the edge detection methods of the present invention are applicable to MPEG-2 encoded images as well as other differentially encoded images.
Claims25
A method of detecting an edge within an image represented by encoded image data including differential values, the method comprising the steps of:
- filtering a plurality of said differential values to produce a filter output value;
- and
- performing a threshold test as a function of the filter output value to determine whether the image represented by the encoded image data includes an edge.
A method of processing encoded image data including a first set of differential values, the method comprising the steps of:
- selecting from the first set of differential values differential values corresponding to vertically displaced image portions to generate a second set of differential values which is smaller than the first set;
- using the second set of differential values to determine whether a horizontal edge is present in the image represented by said encoded image data.
An image processing system comprising:
- means for receiving encoded image data representing an image, the encoded image data including a plurality of differential values;
- and
- means for processing the plurality of differential values to detect the presence of an edge in said image.
A machine readable medium comprising computer executable instructions for controlling a machine to:
- identify dc_dct_differential values included in a encoded data representing an image;
- and
- performing an edge detection operation to detect an edge in said image by examining the identified dc_dct_differential values.
Dependencies are inferred from the claim text.