LOCALIZED CONTENT ADAPTIVE FILTER FOR LOW POWER SCALABLE IMAGE PROCESSING

• US 20080069469A1
• Filed: 09/15/2006
• Published: 03/20/2008
• Est. Priority Date: 09/15/2006
• Status: Active Grant

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: He, Zhongli, Prieto, Yolanda, Yan, Yong
• Granted Patent: US 7,760,960 B2
• Time in Patent Office: Days
• US Class Current: 382/261
• CPC Class Codes: H04N 19/117 Filters, e.g. for pre-processing or post-processing sub-band filter banks H04N19/635
• CPC Class Codes: H04N 19/187 the unit being a scalable video layer
• CPC Class Codes: H04N 19/33 in the spatial domain
• CPC Class Codes: H04N 19/635 characterised by filter definition or implementation details
• CPC Class Codes: H04N 19/80 Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation H04N19/635, H04N19/86 take precedence

Abstract

A localized content adaptive filter system including a tile buffer having an output providing first image information, a frequency analyzer providing a frequency information signal based on frequency content of the first image information, and an adaptive filter which is adjusted based on the frequency information signal. The frequency analyzer may include a wavelet transform filter and a frequency content analyzer. The adaptive filter may include filter select logic which receives the frequency information signal and second image information associated with the first image information, and which provides filtered image information. The filter select logic determines a filter based on the frequency information signal and the determined filter filters the second image information to provide the filtered image information. The filter select logic may include preconfigured filters in which a filter is selected by the frequency information, or a programmable filter which is programmed according to the frequency information.

Claims

1. A localized content adaptive filter system, comprising:

a tile buffer having an output providing first image information;

a frequency analyzer, coupled to said tile buffer, providing a frequency information signal based on frequency content of said first image information; and

an adaptive filter, coupled to said frequency analyzer, which is adjusted based on said frequency information signal.

2. The localized content adaptive filter system of claim 1, wherein:

said frequency analyzer comprises;

a wavelet transform filter having an input coupled to said output of said tile buffer and an output; and

a frequency content analyzer having an input coupled to said output of said wavelet transform filter and an output providing said frequency information signal; and

wherein said adaptive filter comprises filter select logic having a first input receiving said frequency information signal, a second input receiving second image information associated with said first image information, and an output providing filtered image information, and wherein said filter select logic determines a filter based on said frequency information signal and wherein said determined filter filters said second image information to provide said filtered image information.

3. The localized content adaptive filter system of claim 2, wherein said filter select logic comprises:

a filter selector having an input receiving said frequency information signal and an output providing a filter select signal; and

a filter list having a first input receiving said filter select signal, a second input receiving said second image information and an output providing said filtered image information, wherein said filter list comprises a plurality of preconfigured filters in which one filter is selected by said filter select signal for filtering said second image information.

4. The localized content adaptive filter system of claim 3, wherein said plurality of preconfigured filters are mapped to a plurality of thresholds which have been determined based on predetermined image information.

5. The localized content adaptive filter system of claim 2, wherein said wavelet transform filter comprises a Haar wavelet transform filter.

6. The localized content adaptive filter system of claim 2, wherein said frequency content analyzer determines relative energy of said first image information between a lower frequency range and a higher frequency range.

7. The localized content adaptive filter system of claim 2, wherein said frequency content analyzer comprises:

frequency threshold logic having an input coupled to said output of said wavelet transform filter and an output;

counter logic having an input coupled to said output of said frequency threshold logic and an output providing said frequency information signal;

wherein said wavelet transform filter provides sub-banded image information, wherein said frequency threshold logic binarizes said image information based on at least one frequency threshold level and provides binarized information, and wherein said counter logic counts said binarized information to determine relative frequency information.

8. The localized content adaptive filter system of claim 2, wherein:

said frequency content analyzer comprises;

frequency threshold logic having an input coupled to said output of said wavelet transform filter and an output; and

a threshold counter having an input coupled to said output of said frequency threshold logic and an output providing a corresponding one of a plurality of frequency count values; and

wherein said filter select logic comprises a programmable filter system that is programmed based on said corresponding one of said plurality of frequency count values.

9. The localized content adaptive filter system of claim 8, wherein said programmable filter system comprises:

a memory storing a plurality of frequency transition bandwidth values and a corresponding plurality of stopband attenuation values, wherein each of said plurality of frequency count values is mapped to a corresponding one of a plurality of filter value pairs in which each filter value pair comprises one each of said plurality of frequency transition bandwidth values and said plurality of stopband attenuation values; and

a programmable filter which is programmed based on a selected one of said plurality of filter value pairs.

10. The localized content adaptive filter system of claim 9, wherein said programmable filter is configured according to a predetermined filter window function.

11. The localized content adaptive filter system of claim 8, further comprising:

an inverse filter having an input receiving said filtered image information and an output providing reconstructed image information;

control logic which provides said reconstructed image information through said wavelet transform filter and said frequency content analyzer to provide a new frequency count value for each of at least one iteration; and

comparator logic which determines whether consecutive frequency count values are within a predetermined range of each other.

12. The localized content adaptive filter system of claim 1, wherein said second image information is provided to an input of said tile buffer.

13. An image processing system, comprising:

an up sampler having an input receiving first image information at a first spatial layer and an output providing up sampled image information; and

a first localized content adaptive filter, comprising;

a first tile buffer which stores said first image information;

a first wavelet transform filter having an input coupled to said first tile buffer and an output;

a first frequency content analyzer having an input coupled to said output of said first wavelet transform filter and an output providing a first frequency information signal indicative of frequency content of said first image information; and

first filter select logic having a first input receiving said first frequency information signal, a second input receiving said up sampled image information, and an output providing first filtered image information for a second spatial layer;

wherein said first filter select logic determines a first filter based on said first frequency information signal and wherein said first filter filters said up sampled image information to provide said first filtered image information.

14. The image processing system of claim 13, further comprising:

a decoder having an input receiving encoded image information at said first spatial layer and encoded residual information at said second spatial layer, and an output providing said first image information at said first spatial layer and residual information at said second spatial layer; and

an adder having a first input receiving said first filtered image information, a second input receiving said residual information and an output providing second image information at said second spatial layer.

15. The image processing system of claim 13, further comprising:

a second localized content adaptive filter, comprising;

a second tile buffer which stores second image information at said second spatial layer;

a wavelet transform filter having an input coupled to said second tile buffer and an output;

a second frequency content analyzer having an input coupled to said output of said second wavelet transform filter and an output providing a second frequency information signal indicative of frequency content of said second image information; and

second select logic having a first input receiving said second frequency information signal, a second input receiving said second image information, and an output providing second filtered image information for said first spatial layer;

wherein said filter select logic determines a second filter based on said second frequency information signal and wherein said second filter filters said second image information to provide said second filtered image information; and

a down sampler having an input receiving said second filtered image information and an output providing third image information at said first spatial layer.

16. The image processing system of claim 15, further comprising:

an encoder having an input receiving said third image information and residual image information at said second layer and an output providing first encoded image information at said first spatial layer and encoded residual information at said second spatial layer;

a decoder having an input receiving said first encoded image information and an output providing said first image information at said first spatial layer; and

an adder having a first input receiving said first filtered image information, a second input receiving said second image information, and an output providing said residual image information.

17. The image processing system of claim 16, further comprising an output buffer which combines said first encoded image information at said first spatial layer and said encoded residual information at said second spatial layer into a bitstream.

18. The image processing system of claim 13, wherein said first frequency content analyzer comprises:

frequency threshold logic having an input coupled to said output of said first wavelet transform filter and an output; and

counter logic having an input coupled to said output of said frequency threshold logic and an output providing said first frequency information signal.

19. The image processing system of claim 13, wherein said first filter select logic comprises:

a filter selector having an input receiving said first frequency information signal and an output providing a filter select signal; and

a filter list having a first input receiving said filter select signal, a second input receiving said up sampled image information and an output providing said first filtered image information, wherein said filter list comprises a plurality of preconfigured filters in which one filter is selected by said filter select signal for filtering said up sampled image information.

20. The image processing system of claim 13, wherein:

said first frequency content analyzer comprises;

frequency threshold logic having an input coupled to said output of said first wavelet transform filter and an output; and

a threshold counter having an input coupled to said output of said frequency threshold logic and an output providing a corresponding one of a plurality of frequency count values; and

wherein said first filter select logic comprises a programmable filter system that is programmed based on said corresponding one of said plurality of frequency count values.

21. A method of adaptively configuring a filter, comprising:

localizing input image information;

determining frequency content of the localized input image information; and

adjusting an adaptive filter based on the determined frequency content.

22. The method of claim 21, wherein said determining frequency content comprises transforming the localized input image information through a filter bank providing filtered information and analyzing frequency of the filtered information.

23. The method of claim 21, wherein said adjusting an adaptive filter comprises selecting a filter from a filter list.

24. The method of claim 21, wherein said adjusting an adaptive filter comprises programming the adaptive filter according to a predetermined filter window function.