Hi I have YCbCr video data in two color spaces in sequence(on the same 8bit data bus). I want to separate Y component from CbCr. can you help me please! thank You

If the video is 422 YCbCr you just extract every other data value with a toggling signal. so you get Y1 Cb1 Y2 Cr1 Y3 Cb2 Y4 Cr2 etc etc

Thank You Tricky for again replying me! toggling signal?? I am working in dsp builder v6.0. please guide me how is it possible in dsp builder?? actually I want to buffer a full frame (640x480) in real time video and then I have to divide it into blockset i.e 8x8 or 16x16 or 32x32. (I have to do all this in dsp builder) 1st of all I have to separate Y from CbCr.

Your YCbCr signal probably has a data rate of 27MHz (pixel rate x2). You need to create a signal that toggles at 13.5MHz to pick out every Y value from the data stream, because thats how fast it change. All you need is a signal that looks something like this in VHDL: process(clk, reset) begin if reset = '1' then y_valid <= '0'; elsif rising_edge(clk) y_valid <= not y_valid; end if; end process; So in DSP builder you just need a register with the input being in inverted version of its output.

--- Quote Start --- A register with the input being in inverted version of its output. --- Quote End --- Why input being in inverted version of its output?? I can not understand it.

You are creating a toggle. You want to select the Y values while ignoring the C values you can use this toggle as the write enable on another register or memory.

separate Y from CbCr in YCbCr | Altera Community

12 Replies

Altera_Forum
Honored Contributor
15 years ago
You need Y, Cb and Cr if you are going to colour space convert to RGB. Setting Y to 0 just kills an RGB output. The conversion is done via a matrix transform. But depending on what your input and output are for affects the matrix.

Raw video off a DAC is likely to have Y values in the range 16 to 235. PC monitors often expect the range 0 to 255 for RGB for peak values, so you can either rescale the input to 0 to 255 or use a different matrix for the colour space conversion.

The standard matrix for conversion is:

(R) = ( 1.0 , 0.0 , 1.140 , 0.0 ) (Y ) (G) = ( 1.0 , -0.396 , -0.581 , 0.0 ) * (Cb-128) (B) = ( 1.0 , 2.029 , 0.0 , 0.0)) (Cr-128) So R = Y + 1.14(Cr-128) G = Y - 0.396(Cb-128) - 0.581(Cr-128) B = Y + 2.029(Cb-128)
Altera_Forum
Honored Contributor
15 years ago
TO_BE_DONE

Forum Discussion

separate Y from CbCr in YCbCr

12 Replies

Recent Discussions

Using Quartus with softHSM

The quartus license works with version 25.0 but not with version 17.0

Quartus did not start

Docker image for Quartus Pro 26.1 missing ?

Timing analysis - long combinational path