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Improving my code to skip pixels!

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flote21

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Hello buddys!

I am working with a image sensor which delivers 4 pixels (12 bits/pixel) every system clock.

The pixel output of the sensor is 6 Lines x 2112 pixels. And I want to throw away some pixels per line according to the parameter SHIFT_COL.

For example,
- if SHIFT_COL = 1, the 1st pixel of every line should be skipped resulting 2111 pixels.
- if SHIFT_COL = 2, the 2 first pixels of every line should be skipped resulting 2110 pixels
- and so on...

Here is the code that I have already programmed. But I think that it could be a better coding for this issue. Any suggestion?

Code: 
		-- Valid Pixels Management:
      -- Receiving 4 pixels on every clock cycle and skip some of them
		-- according to the parameter SHIFT_COL
		SHIFT_DAV  <= '0';
		if VID_I_DAV = '1' then  -- New "4pixels" 	          			
		  VID_I_CNT <= VID_I_CNT + 4;		  
		  SHIFT_SEL    <= SHIFT_SEL + 1;
		  -- Binning 6x6 => Max. 10 pixels to shift!
		  if FPGA_MODE_l = "100" then                         							
				case SHIFT_COLr is
					when x"0000" => -- No shifting 
						if SHIFT_SEL = 0 then 
							SHIFT_DATA_REG <= VID_I_DATA;
							SHIFT_DAV  <= '1';
							SHIFT_SEL  <= (others=>'0');
							SHIFT_CNT <= SHIFT_CNT + 4;
						end if;			
					when x"0001" => -- Shifting 1 column
						if SHIFT_SEL = 0 then 							
							SHIFT_PIX_REG1  <= VID_I_DATA(23 downto 12);
							SHIFT_PIX_REG2  <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG3  <= VID_I_DATA(47 downto 36);														
						elsif SHIFT_SEL = 1 then 							
							SHIFT_PIX_REG1  <= VID_I_DATA(23 downto 12);
							SHIFT_PIX_REG2  <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG3  <= VID_I_DATA(47 downto 36);														
							SHIFT_DATA_REG <= VID_I_DATA(11 downto 0) & SHIFT_PIX_REG3 & SHIFT_PIX_REG2 & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';
							SHIFT_CNT <= SHIFT_CNT + 4;
						elsif SHIFT_SEL = 2 then
							SHIFT_PIX_REG1  <= VID_I_DATA(23 downto 12);
							SHIFT_PIX_REG2  <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG3  <= VID_I_DATA(47 downto 36);														
							SHIFT_DATA_REG <= VID_I_DATA(11 downto 0) & SHIFT_PIX_REG3 & SHIFT_PIX_REG2 & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';						
							SHIFT_SEL   <= x"1";
							SHIFT_CNT <= SHIFT_CNT + 4;
						end if;									 
					when x"0002" => -- Shifting 2 columns
						if SHIFT_SEL = 0 then 
							SHIFT_PIX_REG1 <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG2 <= VID_I_DATA(47 downto 36);
						elsif SHIFT_SEL = 1 then 
							SHIFT_PIX_REG1 <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG2 <= VID_I_DATA(47 downto 36);
							SHIFT_DATA_REG <= VID_I_DATA(23 downto 0) & SHIFT_PIX_REG2 & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';
							SHIFT_CNT <= SHIFT_CNT + 4;
						elsif SHIFT_SEL = 2 then
							SHIFT_PIX_REG1 <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG2 <= VID_I_DATA(47 downto 36);
							SHIFT_DATA_REG <= VID_I_DATA(23 downto 0) & SHIFT_PIX_REG2 & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';						
							SHIFT_SEL   <= x"1";
							SHIFT_CNT <= SHIFT_CNT + 4;
						end if;									 					
					when x"0003" => -- Shifting 3 columns
						if SHIFT_SEL = 0 then 
							SHIFT_PIX_REG1 <= VID_I_DATA(47 downto 36);
						elsif SHIFT_SEL = 1 then 
							SHIFT_PIX_REG1 <= VID_I_DATA(47 downto 36);
							SHIFT_DATA_REG <= VID_I_DATA(35 downto 0) & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';
							SHIFT_CNT <= SHIFT_CNT + 4;
						elsif SHIFT_SEL = 2 then
							SHIFT_PIX_REG1 <= VID_I_DATA(47 downto 36);
							SHIFT_DATA_REG <= VID_I_DATA(35 downto 0) & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';						
							SHIFT_SEL   <= x"1";
							SHIFT_CNT <= SHIFT_CNT + 4;
						end if;
					--
					when x"0004" => -- Shifting 4 columns
						if SHIFT_SEL = 1 then 
							SHIFT_DATA_REG <= VID_I_DATA;
							SHIFT_DAV  <= '1';
							SHIFT_SEL  <= x"1";
							SHIFT_CNT <= SHIFT_CNT + 4;
						end if;			
					when x"0005" => -- Shifting 5 columns
						if SHIFT_SEL = 1 then 							
							SHIFT_PIX_REG1  <= VID_I_DATA(23 downto 12);
							SHIFT_PIX_REG2  <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG3  <= VID_I_DATA(47 downto 36);														
						elsif SHIFT_SEL = 2 then 							
							SHIFT_PIX_REG1  <= VID_I_DATA(23 downto 12);
							SHIFT_PIX_REG2  <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG3  <= VID_I_DATA(47 downto 36);														
							SHIFT_DATA_REG <= VID_I_DATA(11 downto 0) & SHIFT_PIX_REG3 & SHIFT_PIX_REG2 & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';
							SHIFT_CNT <= SHIFT_CNT + 4;
						elsif SHIFT_SEL = 3 then
							SHIFT_PIX_REG1  <= VID_I_DATA(23 downto 12);
							SHIFT_PIX_REG2  <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG3  <= VID_I_DATA(47 downto 36);														
							SHIFT_DATA_REG <= VID_I_DATA(11 downto 0) & SHIFT_PIX_REG3 & SHIFT_PIX_REG2 & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';						
							SHIFT_SEL   <= x"2";
							SHIFT_CNT <= SHIFT_CNT + 4;
						end if;									 
					when x"0006" => -- Shifting 6 columns
						if SHIFT_SEL = 1 then 
							SHIFT_PIX_REG1 <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG2 <= VID_I_DATA(47 downto 36);
						elsif SHIFT_SEL = 2 then 
							SHIFT_PIX_REG1 <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG2 <= VID_I_DATA(47 downto 36);
							SHIFT_DATA_REG <= VID_I_DATA(23 downto 0) & SHIFT_PIX_REG2 & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';
							SHIFT_CNT <= SHIFT_CNT + 4;
						elsif SHIFT_SEL = 3 then
							SHIFT_PIX_REG1 <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG2 <= VID_I_DATA(47 downto 36);
							SHIFT_DATA_REG <= VID_I_DATA(23 downto 0) & SHIFT_PIX_REG2 & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';						
							SHIFT_SEL   <= x"2";
							SHIFT_CNT <= SHIFT_CNT + 4;
						end if;									 					
					when x"0007" => -- Shifting 7 columns
						if SHIFT_SEL = 1 then 
							SHIFT_PIX_REG1 <= VID_I_DATA(47 downto 36);
						elsif SHIFT_SEL = 2 then 
							SHIFT_PIX_REG1 <= VID_I_DATA(47 downto 36);
							SHIFT_DATA_REG <= VID_I_DATA(35 downto 0) & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';
							SHIFT_CNT <= SHIFT_CNT + 4;
						elsif SHIFT_SEL = 3 then
							SHIFT_PIX_REG1 <= VID_I_DATA(47 downto 36);
							SHIFT_DATA_REG <= VID_I_DATA(35 downto 0) & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';						
							SHIFT_SEL   <= x"2";
							SHIFT_CNT <= SHIFT_CNT + 4;
						end if;									 											
					--
					when x"0008" => -- Shifting 8 columns
						if SHIFT_SEL = 2 then 
							SHIFT_DATA_REG <= VID_I_DATA;
							SHIFT_DAV  <= '1';
							SHIFT_SEL   <= x"2";
							SHIFT_CNT <= SHIFT_CNT + 4;
						end if;			
					when x"0009" => -- Shifting 9 column
						if SHIFT_SEL = 2 then 							
							SHIFT_PIX_REG1  <= VID_I_DATA(23 downto 12);
							SHIFT_PIX_REG2  <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG3  <= VID_I_DATA(47 downto 36);														
						elsif SHIFT_SEL = 3 then 							
							SHIFT_PIX_REG1  <= VID_I_DATA(23 downto 12);
							SHIFT_PIX_REG2  <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG3  <= VID_I_DATA(47 downto 36);														
							SHIFT_DATA_REG <= VID_I_DATA(11 downto 0) & SHIFT_PIX_REG3 & SHIFT_PIX_REG2 & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';
							SHIFT_CNT <= SHIFT_CNT + 4;
						elsif SHIFT_SEL = 4 then
							SHIFT_PIX_REG1  <= VID_I_DATA(23 downto 12);
							SHIFT_PIX_REG2  <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG3  <= VID_I_DATA(47 downto 36);														
							SHIFT_DATA_REG <= VID_I_DATA(11 downto 0) & SHIFT_PIX_REG3 & SHIFT_PIX_REG2 & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';						
							SHIFT_SEL   <= x"3";
							SHIFT_CNT <= SHIFT_CNT + 4;
						end if;									 
					when x"000A" => -- Shifting 10 columns
						if SHIFT_SEL = 2 then 
							SHIFT_PIX_REG1 <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG2 <= VID_I_DATA(47 downto 36);
						elsif SHIFT_SEL = 3 then 
							SHIFT_PIX_REG1 <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG2 <= VID_I_DATA(47 downto 36);
							SHIFT_DATA_REG <= VID_I_DATA(23 downto 0) & SHIFT_PIX_REG2 & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';
							SHIFT_CNT <= SHIFT_CNT + 4;
						elsif SHIFT_SEL = 4 then
							SHIFT_PIX_REG1 <= VID_I_DATA(35 downto 24);
							SHIFT_PIX_REG2 <= VID_I_DATA(47 downto 36);
							SHIFT_DATA_REG <= VID_I_DATA(23 downto 0) & SHIFT_PIX_REG2 & SHIFT_PIX_REG1;
							SHIFT_DAV <= '1';						
							SHIFT_SEL   <= x"3";
							SHIFT_CNT <= SHIFT_CNT + 4;
						end if;									 					
					when others => null;
				end case;			  
		  end if;		
		end if;

Thanks anyway!
 

why not have a simple counter, that counters to 2112.
When count < SHIFT_COL, data_valid = '0', else it is '1'
 

Hi Thank you for your help!

I was wrong in the initial post. What I want to have is always 2112 pixels. So when for example, SHIFT_COL = 1 and the input of the sensor is so:
HTML: 
           Input                                      Output
Pixel1 Pixel2 Pixel3 Pixel4           Pixel1   Pixel2   Pixel3   Pixel4
   0       1        2       3           1         2       3         4
   4       5        6       7           5         6       7         8
   8       9        10      11    =>    9         10      11        12
..                                     ..
..                                     ..
 2108   2109   2110  2111              2109     2110    2111    2112

As you can see the amount of pixels is always the same: 2112.

A lot of thanks




TrickyDicky said:
why not have a simple counter, that counters to 2112.
When count < SHIFT_COL, data_valid = '0', else it is '1'
Click to expand...
 
Last edited:

This is just a simple delay of the valid. You would have a shift register and only enable the output 2 clocks later.
 

If I just make a delay of the valid I am skipping 4 pixels and I want to have a resolution of 1 pixel skipped.

TrickyDicky said:
This is just a simple delay of the valid. You would have a shift register and only enable the output 2 clocks later.
Click to expand...
 

what is the incoming clock speed?
What is the input interface?
6x2112 is a very strange sensor size - why so odd?
why are pixel packed into 4 pels per word? where are they sourced from?

I think this problem has come up before - and you generally ignored my questions then. Maybe you'll answer this time

Basically, I cannot think of a simple elegent solution from the top of my head.
Have you got a good testbench to test your solution?
 

1) what is the incoming clock speed?
148.5 MHz.
2) What is the input interface?
4 channels LVDS
3)6x2112 is a very strange sensor size - why so odd?
It is a special CMOS sensor for industrial applications. The sensor window is 1110x2112. But I can set up a Region Of Interest (ROI) of 6x21112.
4)why are pixel packed into 4 pels per word? where are they sourced from?
Because the sensor interface is 4 LVDS channels and one pixel per channel is given in every sys_clk in PARALLEL. The sensor is working in that way and I can´t modify the pixel output of the sensor...

I think this problem has come up before - and you generally ignored my questions then. Maybe you'll answer this time

I am sorry, I thought that I have already clarified this issue. Anyway if you have more questions I will answer as far af I know.

Have you got a good testbench to test your solution?
Yes I have done a good test bench where I can simulate the output of the sensor. And the my code posted works perfectly. But I want to know if there is another solution more generic. Because my code is only able to skip 10 pixels maximum. I want to implement some kind of elegant algorithm to save resources and skip whatever amount of pixels...

TrickyDicky said:
what is the incoming clock speed?
What is the input interface?
6x2112 is a very strange sensor size - why so odd?
why are pixel packed into 4 pels per word? where are they sourced from?

I think this problem has come up before - and you generally ignored my questions then. Maybe you'll answer this time

Basically, I cannot think of a simple elegent solution from the top of my head.
Have you got a good testbench to test your solution?
Click to expand...
 

This is a very custom set up, so its not very easy to give any improvements without the whole architecture.
But i could probably use a counter in there to get the base offset - then you can shift as much as you like.
 
Yes I was thinking to do something like that buffering the input pixels with a FIFO and using a cunter to throw away the pixels which are not useful...

Thanks dude!


TrickyDicky said:
This is a very custom set up, so its not very easy to give any improvements without the whole architecture.
But i could probably use a counter in there to get the base offset - then you can shift as much as you like.
Click to expand...
 

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