Apparatus and method for adaptive filtering
An apparatus and a method for adaptive filtering includes an antenna that receives analog video broadcast signal data; an analog-to-digital converter coupled to the antenna and converting the received analog video broadcast signal data to digital video signal data; a frame buffer memory storing the digital video signal data; an instruction memory storing adaptive filtering instructions; and an adaptive filter coupled to the memory and the analog-to-digital converter, wherein the adaptive filter: reads the adaptive filter instructions from the memory; executes the adaptive filter instructions; averages an input pixel with a corresponding pixel stored in the frame buffer memory; calculates a forgetting factor for each pixel in the plurality of pixel values stored in the frame buffer memory; and filters noise from each pixel of the plurality of pixel values stored in the frame buffer memory based on the forgetting factor.
1. A system for adaptively filtering noise from an analog video broadcast signal, said system comprising:
an antenna that receives analog video broadcast signal data;
an analog-to-digital converter operatively connected to said antenna and converting the received analog video broadcast signal data to digital video signal data;
a frame buffer memory storing only a plurality of horizontal lines of said digital video signal data, wherein said plurality of horizontal lines comprise a plurality of pixel values of an input frame;
an instruction memory storing adaptive filtering instructions; and
an adaptive filter coupled to said memory and said analog-to-digital converter, wherein said adaptive filter:
reads said adaptive filter instructions from said memory;
executes said adaptive filter instructions;
calculates a forgetting factor for each pixel in said plurality of pixel values stored in said frame buffer memory based on estimation of channel power and noise power;
averages an input pixel with a corresponding pixel of said horizontal lines stored in said frame buffer memory based on the forgetting factor;
filters noise from each pixel of said plurality of pixel values stored in said frame buffer memory based on said forgetting factor; and
calculates a motion detection measure for each said input pixel in said input frame, wherein said motion detection measure equals an absolute value of a difference between said input pixel and a corresponding input pixel in a previous input frame positioned immediately before said input frame stored in said frame buffer memory, and wherein the averaging of said input pixel is proportionally adjusted by a scaled version of motion amount for each said input pixel when said motion detection measure is greater than zero.
2. The system of claim 1 , further comprising an analog signal equalizing system coupled to said analog-to-digital converter, wherein said analog signal equalizing system equalizes said received analog video broadcast signal data.
3. The system of claim 2 , wherein said analog equalizing system comprises at least one of an automatic gain controller and an equalizer.
4. The system of claim 3 , wherein said analog equalizing system comprises an automatic gain controller and said adaptive filter compensates said forgetting factor for said noise measured by said equalizer.
5. The system of claim 3 , wherein said analog equalizing system comprises an equalizer and said adaptive filter compensates said forgetting factor for said channel power measured by said equalizer.
6. The system of claim 1 , wherein said analog video broadcast signal data comprises at least one of an odd analog video signal data and an even analog video signal data.
7. The system of claim 6 , wherein said analog-to-digital converter converts said odd analog video signal to odd digital video signal data and said analog-to-digital converter converts said even analog video signal data to digital video signal data.
8. The system of claim 7 , wherein said frame buffer memory comprises a display frame.
9. The system of claim 8 , further comprising a display device, wherein said adaptive filter averages said input pixel to a corresponding pixel in said frame buffer and send the average to said display device and to the corresponding pixel location in said frame buffer memory.
10. The system of claim 9 , wherein a horizontal input line is repositioned when said horizontal input line corresponds to an odd frame, wherein said repositioning averages an upper and a lower input line using a corresponding horizontal line stored in said frame buffer memory.
11. The system of claim 1 , wherein said adaptive filter adjusts said forgetting factor using said estimation of channel power and said estimation of noise power.
12. A method of adaptively filtering noise in analog video broadcast signal data, said method comprising:
receiving said analog signal data;
converting said analog video broadcast signal data to first digital signal data comprising a plurality of first pixel values;
providing second digital signal data stored in a frame buffer memory, wherein said second digital signal data comprises a plurality of second pixel values;
calculating a forgetting factor for every pixel in said first digital signal data;
averaging said first digital signal data and said second digital signal data using said forgetting factor to determine a first weight to adjust said first digital signal data and a second weight to adjust said second digital signal data; and
detecting motion between said first digital signal data and said second digital signal data and automatically adjusting said forgetting factor when motion is detected, wherein the detecting of motion comprises calculating a motion detection measure for each input pixel in an input frame, wherein said motion detection measure equals an absolute value of a difference between said input pixel and a corresponding input pixel in a previous input frame positioned immediately before said input frame stored in said frame buffer memory, and wherein the averaging of said input pixel is proportionally adjusted by a scaled version of motion amount for each said input pixel when said motion detection measure is greater than zero.
13. The method of claim 12 , wherein said first weight is calculated as α and said second weight is calculated as 1−α, where α comprises said forgetting factor, and wherein a displayed frame is computed based on multiplication of α and first signal data and further based on multiplication of 1−α and said second digital signal data.
14. The method of claim 12 , wherein said analog video broadcast signal data comprises at least one of an odd analog video signal data and an even analog video signal data.
15. The method of claim 14 , further comprising converting said odd analog video signal to said first digital signal data, wherein said second digital signal data comprises a digitized copy of said even analog video signal data.
16. The method of claim 15 , wherein said first digital signal data comprises a plurality of horizontal lines; and each of said plurality of horizontal lines comprises a plurality of pixel values, and said method further comprises averaging a first horizontal line of said plurality of horizontal lines and a second horizontal line of said horizontal lines to obtain an intermediate line.
17. The method of claim 12 , further comprising detecting a scene change between said first digital signal data and said second digital signal data and automatically setting said forgetting factor to one when said scene change is detected.
18. The method of claim 12 , further comprising adjusting said forgetting factor using a estimation of channel power and an estimation of noise power.
19. The method of claim 12 , further comprising equalizing said received analog video broadcast signal.
20. The method of claim 12 , wherein said analog video broadcast signal data is configured for a mobile receiver comprising any of a National Television Systems Committee (NTSC) standard, a Phase Alternate Line (PAL), and a Sequential Color with Memory (SECAM) standard.