1 YCbCr顏色空間

YCbCr顏色空間是YUV顏色空間的縮放和偏移版本。Y定義為8bit,標稱顏色范圍為16-235；Cb和Cr標稱顏色表示范圍為16-240。YCbCr的采樣格式一般有44、42、41、和40。

1.1 44 YCbCr格式

圖1表示44格式YCbCr采樣點的定位。每個采樣點有Y、Cb和Cr值，每個顏色值的顏色分量為8bit（典型），因此每個采樣點24bit。

圖1 44采樣

1.2 42 YCbCr格式

圖 2表示42格式YCbCr采樣點定位。對于每兩個水平Y采樣點，有一個Cb和一個Cr采樣點。

圖2 42協調位置采樣

2 matlab YCbCr444轉YCbCr422

首先將rgb圖像轉為YCbCr444然后再由YCbCr444轉為YCbCr422。

close all clear all clc I=imread('1.bmp'); [H ,W ,D]=size(I); R=double(I(:,:,1)); G=double(I(:,:,2)); B=double(I(:,:,3)); Y0= double(zeros(H,W)); Cb0 =double(zeros(H,W)); Cr0 = double(zeros(H,W)); Cb1 =double(zeros(H,W/2)); Cr1 = double(zeros(H,W/2)); CbCr = double(zeros(H,W)); %RGB轉YCbCr444 for i = 1:H for j = 1:W Y0(i, j) = 0.299*R(i, j) + 0.587*G(i, j) + 0.114*B(i, j); Cb0(i, j) = -0.172*R(i, j) - 0.339*G(i, j) + 0.511*B(i, j) + 128; Cr0(i, j) = 0.511*R(i, j) - 0.428*G(i, j) - 0.083*B(i, j) + 128; end end for i=1:1:H for j=2:2:W Cb1(i,j/2)=(Cb0(i,j-1)+Cb0(i,j))/2; end end for i=1:1:H for j=2:2:W Cr1(i,j/2)=(Cr0(i,j-1)+Cr0(i,j))/2; end end for i=1:1:H for j=1:1:W if rem(j,2)==0 CbCr(i,j)=Cr1(i,j/2); else CbCr(i,j)=Cb1(i,(j+1)/2); end end end Iycbcr(:,:,1)=Y0; Iycbcr(:,:,2)=Cb0; Iycbcr(:,:,3)=Cr0; Iycbcr=uint8(Iycbcr); Y0=uint8(Y0); Cb0=uint8(Cb0); Cr0=uint8(Cr0); Cb1=uint8(Cb1); Cr1=uint8(Cr1); CbCr=uint8(CbCr); figure(1), subplot(211),imshow(I),title('RGB'); subplot(212),imshow(Iycbcr),title('YCbCr444'); figure(2), subplot(221),imshow(Cb1),title('Cb1'); subplot(222),imshow(Cr1),title('Cr1'); subplot(223),imshow(Cb0),title('Cb0'); subplot(224),imshow(Cr0),title('Cr0'); figure(3), subplot(211),imshow(Y0),title('Y0'); subplot(212),imshow(CbCr),title('CbCr');

Cb2和Cr2

CbCr交錯顯示

3 fpga的仿真實現

`timescale 1ns/1ps module YUV444_422 ( input clk, input rst_n, input iVsync, input iHsync, input iDVAL, input[23:0] YUV444_D, output reg oVsync, output reg oHsync, output reg oDVAL, output reg[15:0] YUV422_D ); reg iDVAL_reg0,iDVAL_reg1,iDVAL_reg2,iDVAL_reg3; reg iVsync_reg0,iVsync_reg1,iVsync_reg2,iVsync_reg3; reg iHsync_reg0,iHsync_reg1,iHsync_reg2,iHsync_reg3; reg[8:0] YUV444_Cr_Sum0; reg[8:0] YUV444_Cb_Sum0; wire [7:0] temp_Y,temp_Cb,temp_Cr; reg [7:0] temp_Y0,temp_Y1,temp_Y2,temp_Y3; reg [7:0] temp_Cb0,temp_Cb1; reg [7:0] temp_Cr0,temp_Cr1; reg[7:0] Cr,Cb,Crbuf; reg Sel; assign temp_Y=YUV444_D[23:16]; assign temp_Cb=YUV444_D[15:8]; assign temp_Cr=YUV444_D[7:0]; always@(posedge clk) begin iDVAL_reg0 <= iDVAL; iDVAL_reg1 <= iDVAL_reg0; iDVAL_reg2 <= iDVAL_reg1; iDVAL_reg3 <= iDVAL_reg2; oDVAL <= iDVAL_reg3; end always@(posedge clk ) begin iVsync_reg0 <= iVsync; iVsync_reg1 <= iVsync_reg0; iVsync_reg2 <= iVsync_reg1; iVsync_reg3 <= iVsync_reg2; oVsync <= iVsync_reg3; end always@(posedge clk) begin iHsync_reg0 <= iHsync; iHsync_reg1 <= iHsync_reg0; iHsync_reg2 <= iHsync_reg1; iHsync_reg3 <= iHsync_reg2; oHsync <= iHsync_reg3; end always@(posedge clk ) begin //delay 3 clock Y temp_Y0<=temp_Y; temp_Y1<=temp_Y0; temp_Y2<=temp_Y1; temp_Y3<=temp_Y2; //delay 2 clock Cb temp_Cb0<=temp_Cb; temp_Cb1<=temp_Cb0; //delay 2 clock Cr temp_Cr0<=temp_Cr; temp_Cr1<=temp_Cr0; //delay 1 clock YUV444_Cr_Sum0 <= temp_Cr1 + temp_Cr0;//cr0+cr1 YUV444_Cb_Sum0 <= temp_Cb1 + temp_Cb0;//cb0+cb1 //delay 2clock Cr <= YUV444_Cr_Sum0[8:1]; Cb <= YUV444_Cb_Sum0[8:1]; end always@(posedge clk or negedge rst_n) begin if(~rst_n) Sel <= 1'b0; else if(iDVAL_reg3) Sel <= ~Sel; else Sel <= 1'b0; end always@(posedge clk or negedge rst_n)begin if(~rst_n) YUV422_D <= 16'd0; else if(iDVAL_reg3) begin YUV422_D[15:8] <= temp_Y3; YUV422_D[7:0] <=(!Sel)?Cb:Crbuf; Crbuf <= Cr; end end endmodule

fpga實現CbCr22

責任編輯：xj

原文標題：YCbCr444轉YCbCr422

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