RGB TO YCBCR

YCBCR基本原理：

部分传感器自己定义：

重点RGB转换YCBCR公式：

 

代码分几个模块分析：

1.RGB565 to RGB 888，但会造成饱和度稍微强一些，用损失图像精度来换取资源消耗

assign rgb888_r         = {img_red  , img_red[4:2]  };
assign rgb888_g         = {img_green, img_green[5:4]};
assign rgb888_b         = {img_blue , img_blue[4:2] };

2.同步输出数据接口信号，处理后的

assign post_frame_vsync = pre_frame_vsync_d[2]      ;
assign post_frame_hsync = pre_frame_hsync_d[2]      ;
assign post_frame_de    = pre_frame_de_d[2]         ;
assign img_y            = post_frame_hsync ? img_y1 : 8'd0;
assign img_cb           = post_frame_hsync ? img_cb1: 8'd0;
assign img_cr           = post_frame_hsync ? img_cr1: 8'd0;

3.加、乘、还原数据

//step1 pipeline mult
always @(posedge clk or negedge rst_n) begin
    if(!rst_n) begin
        rgb_r_m0 <= 16'd0;
        rgb_r_m1 <= 16'd0;
        rgb_r_m2 <= 16'd0;
        rgb_g_m0 <= 16'd0;
        rgb_g_m1 <= 16'd0;
        rgb_g_m2 <= 16'd0;
        rgb_b_m0 <= 16'd0;
        rgb_b_m1 <= 16'd0;
        rgb_b_m2 <= 16'd0;
    end
    else begin
        rgb_r_m0 <= rgb888_r * 8'd77 ;
        rgb_r_m1 <= rgb888_r * 8'd43 ;
        rgb_r_m2 <= rgb888_r << 3'd7 ;
        rgb_g_m0 <= rgb888_g  * 8'd150;
        rgb_g_m1 <= rgb888_g * 8'd85 ;
        rgb_g_m2 <= rgb888_g * 8'd107;
        rgb_b_m0 <= rgb888_b * 8'd29 ;
        rgb_b_m1 <= rgb888_b << 3'd7 ;
        rgb_b_m2 <= rgb888_b * 8'd21 ;
    end
end

//step2 pipeline add
always @(posedge clk or negedge rst_n) begin
    if(!rst_n) begin
        img_y0  <= 16'd0;
        img_cb0 <= 16'd0;
        img_cr0 <= 16'd0;
    end
    else begin
        img_y0  <= rgb_r_m0 + rgb_g_m0 + rgb_b_m0;
        img_cb0 <= rgb_b_m1 - rgb_r_m1 - rgb_g_m1 + 16'd32768;
        img_cr0 <= rgb_r_m2 - rgb_g_m2 - rgb_b_m2 + 16'd32768;
    end

end

//step3 pipeline div 右移8位
always @(posedge clk or negedge rst_n) begin
    if(!rst_n) begin
        img_y1  <= 8'd0;
        img_cb1 <= 8'd0;
        img_cr1 <= 8'd0;
    end
    else begin
        img_y1  <= img_y0 [15:8];
        img_cb1 <= img_cb0[15:8];
        img_cr1 <= img_cr0[15:8];
    end
end

4.延时3拍以同步数据信号，同步信号，输出图像到输入图像有3ns的延迟

assign post_frame_vsync = pre_frame_vsync_d[2]      ;
assign post_frame_hsync = pre_frame_hsync_d[2]      ;
assign post_frame_de    = pre_frame_de_d[2]         ;
assign img_y            = post_frame_hsync ? img_y1 : 8'd0;
assign img_cb           = post_frame_hsync ? img_cb1: 8'd0;
assign img_cr           = post_frame_hsync ? img_cr1: 8'd0;

always@(posedge clk or negedge rst_n) begin
    if(!rst_n) begin
        pre_frame_vsync_d <= 3'd0;
        pre_frame_hsync_d <= 3'd0;
        pre_frame_de_d    <= 3'd0;
    end
    else begin
        pre_frame_vsync_d <= {pre_frame_vsync_d[1:0], pre_frame_vsync};
        pre_frame_hsync_d <= {pre_frame_hsync_d[1:0], pre_frame_hsync};
        pre_frame_de_d    <= {pre_frame_de_d[1:0]   , pre_frame_de   };
    end
end