Adaptive post-filtering for reducing noise in highly compressed image/video coding
AssigneeSeiko Epson Corporation
InventorChangick Kim
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Abstract
A technique to reduce ringing artifacts in highly compressed block-based image/video coding is applied to each reconstructed frame output from the decoder. For each pixel block of a reconstructed frame, low-pass filtering is then adaptively applied according certain calculated differences between adjacent pixel values. For each pixel, a determination is made as to what type of horizontal filter, if any, is to be applied. Depending on the results of that determination, the pixel may remain unfiltered or may have a 2- or 3-tap horizontal filter applied to it. A similar process is undertaken to determine what type of vertical filter, if any, is to be applied, no filter, a 2-tap or a 3-tap vertical filter.
Claims21
A method for reducing ringing noise in a decompressed image, comprising the steps of:
- obtaining reconstructed frame blocks of the decompressed image;
- for each reconstructed frame block, selectively performing a first type of filtering on each pixel of that reconstructed frame block based on certain relationships between that pixel and its left and right adjacent pixels, wherein, for each pixel of that block, a first filter is applied to perform the first type of filtering if a first condition is satisfied, a second filter is applied to perform the first type of filtering if the first condition is not satisfied but a second condition is satisfied;
- and
- for each reconstructed frame block, selectively performing a second type of filtering on each pixel of that reconstructed frame block based on certain relationships between that pixel and its upper and lower adjacent pixels, wherein, for each pixel of that block, the first filter is applied to perform the second type of filtering if a third condition is satisfied, the second filter is applied to perform the second type of filtering if the third condition is not satisfied but a fourth condition is satisfied.
An apparatus for reducing ringing noise in a decompressed image, the apparatus comprising:
- an input circuit configured to receive reconstructed frame blocks of the decompressed image;
- and
- processing circuitry configured to
- selectively perform, for each reconstructed frame block, a first type of filtering on each pixel of that reconstructed frame block based on certain relationships between that pixel and its left and right adjacent pixels, wherein, for each pixel of that block, a first filter is applied to perform the first type of filtering if a first condition is satisfied, a second filter is applied to perform the first type of filtering if the first condition is not satisfied but a second condition is satisfied, and
- selectively perform, for each reconstructed frame block, a second type of filtering on each pixel of that reconstructed frame block based on certain relationships between that pixel and its upper and lower adjacent pixels, wherein, for each pixel of that block, the first filter is applied to perform the second type of filtering if a third condition is satisfied, the second filter is applied to perform the second type of filtering if the third condition is not satisfied but a fourth condition is satisfied.
A machine-readable medium having a program of instructions for directing a machine to perform a process of reducing ringing noise in a decompressed image, the program of instructions comprising:
- instructions for obtaining reconstructed frame blocks of the decompressed image;
- instructions for selectively performing, for each reconstructed frame block, a first type of filtering on each pixel of that reconstructed frame block based on certain relationships between that pixel and its left and right adjacent pixels, wherein, for each pixel of that block, a first filter is applied to perform the first type of filtering if a first condition is satisfied, a second filter is applied to perform the first type of filtering if the first condition is not satisfied but a second condition is satisfied;
- and
- instructions for selectively performing, for each reconstructed frame block, a second type of filtering on each pixel of that reconstructed frame block based on certain relationships between that pixel and its upper and lower adjacent pixels, wherein, for each pixel of that block, the first filter is applied to perform the second type of filtering if a third condition is satisfied, the second filter is applied to perform the second type of filtering if the third condition is not satisfied but a fourth condition is satisfied.
Dependencies are inferred from the claim text.