YUV422显示视频格式解释

H.264编码器输入要YUV420，而解码器解码之后显示一般又要YUV422，并且视频采集芯片输出往往也是YUV422，下面以我一个实际使用为例说一下YUV422格式：

/* YUV4:2:2格式(这是初始化背景为纯色，所以用了同一个Y) *//* Black color in UYVY format */#define UYVY_BLACK/*Y Cr Y Cb*/ 0x10801080/*black*/ /*blue:0x286e28ef red:0x51ef515b green:0x90239036/*//* DM6446中的测试代码，整个宏像素赋值 */    for (bufIdx=0; bufIdx < NUM_DISPLAY_BUFS; bufIdx++) {        /* Clear the video buffer */        buf = (unsigned int *) virtDisplays[bufIdx];        for (i=0; i < displaySize / sizeof(unsigned int); i++) {            buf[i] = UYVY_BLACK;        }        /* Translate the virtual address to physical as resizer needs this */        physDisplays[bufIdx] = Memory_getPhysicalAddress(virtDisplays[bufIdx]);        DBG("virtDisplays[%d] LA:%#lx PA:%#lx\n",            bufIdx, (unsigned long) virtDisplays[bufIdx], physDisplays[bufIdx]);    }

可以看到YUV422存储顺序为Y Cr Y Cb Y Cr Y Cb Y Cr Y Cb……，Y是全部保留，而Cr，Cb则是在一行中交替采样，而不像YUV420，一行采样 Cb，下一行采用Cr。注意区别。

再说一下上面YCbCr的由来，是通过RGB转化的，具体代码如下：

RGB -> YCbCr代码void rgb2ycbcr(unsigned char r,unsigned char g,unsigned char b){    unsigned char ycbcr_res[3];     ycbcr_res[0]= (unsigned char)(r * 0.256789 + g * 0.504129 + b * 0.097906)+ 16;       ycbcr_res[1]= (unsigned char)(r *-0.148223 + g * -0.290992 + b * 0.439215)+ 128;      ycbcr_res[2]= (unsigned char)(r * 0.439215 + g * -0.367789 + b *-0.071426)+ 128;}

代码测试