1. VECTOR MEDIAN VIDEO FILTER
SRI MOHAN KRISHNA
DAVID SANDEEP
Under the guidance of Mr. MATTIAS O’NILS

2. Introduction
Noise filtering - The process of estimating the original image information from noisy data
Vector median video filter is an Image restoration filter .
Goal of image restoration- improve image in a predefined sense.
Important aspect – having a prior knowledge of degradation phenomenon.

3. Basic function of a filter:
Restoration filter
g(x,y)
f(x,y)
f(x,y)
Ŋ(x,y)
g(x,y) = f(x,y) + Ŋ(x,y)
Restoration of f(x,y) form g(x,y) with a knowledge of Ŋ(x,y)

4. What is the need for a new filter?
Problem with averaging filter(mean filters)
- Blurs edges and details in image.
- Not effective for salt and pepper noise.
Median filter:
- Taking the median value instead of average or weighted average of pixels.
 sort all the pixel values in an increasing order,take the middle one.
- yeilds excellent results for images corrupted by salt and pepper noise

5. What is salt & pepper noise ?
a kind of impulsive noise
Pa for z= a
P(z) = Pb for z = b
for others
If Pa nearly eqaul to Pb
and Pa,Pb ≠ 0
Then impulsive noise resembles salt and pepper noise
Because of image digitization impulse noise tends to have extreme values i.e very large compared to strength of image signal
P(z) Pb Pa z a b

6. Median filter: 3 x 3 square window
shape
100
200
205
203
195
100
100
100
100
100
100
100
200
100
100
100
100
195
100
100
100
100
100
100

7. Directional Vector Median Filter
S11
S22
S33
S22
S13
S31
S12
S22
S32
First
Stage
Median
filter
Second
stage
Median
filter
S21
S22
S23
s22
Medians are calculated in four directions resulting in four values
In the second stage the median of the four values is calculated

8. Block diagram

9. 1. Address Generator Data flow rsync rsync_o Address1 1
rsync_o 1 1
Address
639
640 1 2 3 4 5
Genarates address where the input data is to be stored in block RAM’s

10. Block RAM’s address 1 2 3 4 5 639 640 Data_in = 20 Block RAM1 254 20 11 2 3 4 5
639
640
Data_in = 20
Block RAM1
254 20 1 1 1 1 1 1
Data_read1
254
Block RAM2
254
100 1 1 1 1 1 1
Data_read2
100
When read_write signal is enabled the data in the location specifed by address is read first and after that data to be written is placed in the location

11. Counter
The counter counts the row and column values with reference to the frame synchronisation and row synchronisation pulses.
Generates enable pulses for the edge detector block and
dvmf evaluator block.
If row synchronisation pulse turns high from low the column value is initialized 1.
If row sync pulse is high the value of column is incremented for every clock pulse
If frame synchronisation pulse changes high from low then row count is initialized to 1
Row count is incremented at row synchronisation positive edge transition.
The enable signal is generated when column count >0 and < 641

12. Edge detector
The edge detector detects the edges of the frame and informs to the DVMevaluator block
If fsync is high ,it informs it as upper edge of the frame and initialises the row count value to 0.
If rsync pulse changes from low to high it informs it as the left edge of frame and initialises the column count to 1 and increments row count.
If rsync pulse changes from high to low it informs that it is the right edge of the frame
If the row count = 480 then it informs that it is the bottom edge of the frame.

13. DVM Evaluator frame corner x Up/ Down Left / right 230 255 255 255
Pdata = 230
Pdata = 255
200
255
255
255
Data_read 1= 255
Data_read 1 = 200 x
200
255
Data_read 2 = X
Up/ Down
Left / right
200
170
180
255
150
200
100
130
210
215
200
150
255
200
180
210

14. results
Noisy input image
Matlab output
VHDL output

15. Results
The noise in the input image was removed successfully by the designed filter.
Maximum Frequency: 51 MHz
No of 641x8-bit dual-port block RAM’s used : 2
Number of 4 input LUTs :

16. Conclusion
The obtained results are compared with the MAT LAB output and the results are found to be absolutely comparable.
The only deviation obtained was at the first row where in the logic of VHDL specifies the first row output to be the pixel values of the last row of the previous frame.
The customer requirement of 30 MHz frequency has been met successfully.

17. ?