Multi-metric filtering

Patent metadata

Field	Value
Publication number	US-9258563-B2
Application number	US-201514592841-A
Country	US
Kind code	B2
Filing date	Jan 8, 2015
Priority date	Feb 23, 2011
Publication date	Feb 9, 2016
Grant date	Feb 9, 2016

Abstract

A filter unit of a video encoder or video decoder can determine a first metric for a group of pixels within a block of pixels, determine a second metric for the group of pixels, determine a filter based on the first metric and the second metric, and generate a filtered image by applying the filter to the group of pixels. The first metric and second metric can be an activity metric and a direction metric, respectively, or can be other metrics such as an edge metric, horizontal activity metric, vertical activity metric, or diagonal activity metric.

First claim

The invention claimed is:

1. A method of video decoding, the method comprising:
decoding, from a video bitstream, a second metric for a pixel within a block of pixels, wherein the second metric is indicative of one of a horizontal direction, a vertical direction, a 45-degree direction, or a 135-degree direction;
determining a first metric for the pixel by comparing, with reference to the second metric, a pixel value of the pixel to pixel values of neighboring pixels within the block of pixels;
determining a filter based on the second metric and the first metric; and
applying the filter to the pixel.

2. The method of claim 1 , wherein all pixels within the block of pixels are associated with the second metric.

3. The method of claim 2 , further comprising:
decoding, from the video bitstream, a filter value, wherein the filter is applied to the pixel using the filter value.

4. The method of claim 1 , wherein:
the neighboring pixels are selected as a right neighbor pixel and a left neighbor pixel if the second metric is indicative of the horizontal direction,
the neighboring pixels are selected as an upper neighbor pixel and a lower neighbor pixel if the second metric is indicative of the vertical direction,
the neighboring pixels are selected as an upper-right neighbor pixel and a lower-left neighbor pixel if the second metric is indicative of the 45-degree direction, and
the neighboring pixels are selected as an upper-left neighbor pixel and a lower-right neighbor pixel if the second metric is indicative of the 135-degree direction.

5. The method of claim 1 , further comprising:
applying a deblocking filter to an image including a plurality of blocks of pixels before determining the first metric for the pixel.

6. The method of claim 1 , wherein the filter has an associated filter support shape with respect to the pixel.

7. The method of claim 1 , wherein the second metric is coded in the video bitstream as a syntax element.

8. The method of claim 1 , wherein the second metric is decoded from the video bitstream with context adaptive binary arithmetic coding (CABAC).

9. The method of claim 1 , wherein determining the first metric for the pixel comprises:
comparing the pixel to a first neighboring pixel within the block of pixels;
incrementing an edge metric variable in response to a pixel value of the pixel being greater than a pixel value of the first neighboring pixel; and
decrementing the edge metric variable in response to the pixel value of the pixel being less than the pixel value of the first neighboring pixel.

10. The method of claim 1 , wherein the first metric is an integer.

11. The method of claim 1 , wherein the second metric is indicative of one of the horizontal direction, the vertical direction, the 45-degree direction, the 135-degree direction, or no direction, such that if the second metric is indicative of no direction, no filter is applied to the pixel.

12. The method of claim 1 , wherein the decoding does not use line buffers for pixel values of blocks neighboring the block of pixels.

13. The method of claim 1 , wherein applying the filter to the pixel smoothes differences in intensity of the pixel value with respect to an adjacent pixel value to reduce unwanted artifacts.

14. The method of claim 1 , the method being executable on a wireless communication device, wherein the device comprises:
a memory configured to store the first metric, the second metric, and the pixel within the block of pixels;
one or more processors configured to execute instructions to decode the second metric, determine the first metric, determine the filter, and apply the filter to the pixel;
a receiver configured to receive modulated information over a channel; and
a modem configured to demodulate the modulated information to produce the video bitstream.

15. The method of claim 14 , wherein the wireless communication device is a cellular telephone and the modulated information is demodulated according to a cellular communication standard.

16. The method of claim 1 , wherein the first metric is an activity metric, said activity metric having five classes.

17. The method of claim 1 , wherein the first metric is an activity metric var(i, j) defined according to the following equation:

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Assignees

• Qualcomm Inc

Inventors

• Chong In Suk
• Karczewicz Marta

Classifications

• H04N19/176 Primary

  the region being a block, e.g. a macroblock · CPC title

• H04N19/70

  characterised by syntax aspects related to video coding, e.g. related to compression standards · CPC title

• H04N19/82

  involving filtering within a prediction loop · CPC title

• H04N19/61

  in combination with predictive coding · CPC title

• H04N19/85

  using pre-processing or post-processing specially adapted for video compression · CPC title