yuyv转yuv420p代码及验证代码

另一篇博客《YUV格式介绍》有yuyv和yuv420p的理论介绍，本篇博客为具体转换的实际代码以及验证用的代码，代码均来源于其他博客，经实际验证有效，在此记录防止遗忘。

yuyv转yuv420p：

unsigned char *yuyv_buf = (unsigned char *)malloc(2 * width * height * sizeof(unsigned char));
unsigned char *yuv420_buf = (unsigned char *)malloc(3 * width * height / 2 * sizeof(unsigned char));

int yuyv_to_yuv420p(const unsigned char *in, unsigned char *out, unsigned int width, unsigned int height)
{
    unsigned char *y = out;
    unsigned char *u = out + width*height;
    unsigned char *v = out + width*height + width*height/4;
 
    unsigned int i,j;
    unsigned int base_h;
    unsigned int is_y = 1, is_u = 1;
    unsigned int y_index = 0, u_index = 0, v_index = 0;
 
    unsigned long yuv422_length = 2 * width * height;
 
    //序列为YU YV YU YV，一个yuv422帧的长度 width * height * 2 个字节
    //丢弃偶数行 u v
    for(i=0; i<yuv422_length; i+=2){
        *(y+y_index) = *(in+i);
        y_index++;
    }
    for(i=0; i<height; i+=2){
        base_h = i*width*2;
        for(j=base_h+1; j<base_h+width*2; j+=2) {
            if(is_u){
                *(u+u_index) = *(in+j);
                u_index++;
                is_u = 0;
            }else{
                *(v+v_index) = *(in+j);
                v_index++;
                is_u = 1;
            }
        }
    }
    return 1;
}

验证的话只需要将数据转换成rgb看是否正长即可知道转换是否有问题：

yuyv转rgb：

void yuyv_to_rgb(unsigned char* yuv,unsigned char* rgb)
{
    unsigned int i;
    unsigned char* y0 = yuv + 0;   
    unsigned char* u0 = yuv + 1;
    unsigned char* y1 = yuv + 2;
    unsigned char* v0 = yuv + 3;
 
    unsigned  char* r0 = rgb + 0;
    unsigned  char* g0 = rgb + 1;
    unsigned  char* b0 = rgb + 2;
    unsigned  char* r1 = rgb + 3;
    unsigned  char* g1 = rgb + 4;
    unsigned  char* b1 = rgb + 5;
   
    float rt0 = 0, gt0 = 0, bt0 = 0, rt1 = 0, gt1 = 0, bt1 = 0;
 
    for(i = 0; i <= (WIDTH * HEIGHT) / 2 ;i++)
    {
        bt0 = 1.164 * (*y0 - 16) + 2.018 * (*u0 - 128); 
        gt0 = 1.164 * (*y0 - 16) - 0.813 * (*v0 - 128) - 0.394 * (*u0 - 128); 
        rt0 = 1.164 * (*y0 - 16) + 1.596 * (*v0 - 128); 
   
        bt1 = 1.164 * (*y1 - 16) + 2.018 * (*u0 - 128); 
        gt1 = 1.164 * (*y1 - 16) - 0.813 * (*v0 - 128) - 0.394 * (*u0 - 128); 
        rt1 = 1.164 * (*y1 - 16) + 1.596 * (*v0 - 128); 
    
      
                   if(rt0 > 250)      rt0 = 255;
        if(rt0< 0)        rt0 = 0;    
 
        if(gt0 > 250)     gt0 = 255;
        if(gt0 < 0)    gt0 = 0;    
 
        if(bt0 > 250)    bt0 = 255;
        if(bt0 < 0)    bt0 = 0;    
 
        if(rt1 > 250)    rt1 = 255;
        if(rt1 < 0)    rt1 = 0;    
 
        if(gt1 > 250)    gt1 = 255;
        if(gt1 < 0)    gt1 = 0;    
 
        if(bt1 > 250)    bt1 = 255;
        if(bt1 < 0)    bt1 = 0;    
                    
        *r0 = (unsigned char)rt0;
        *g0 = (unsigned char)gt0;
        *b0 = (unsigned char)bt0;
    
        *r1 = (unsigned char)rt1;
        *g1 = (unsigned char)gt1;
        *b1 = (unsigned char)bt1;
 
        yuv = yuv + 4;
        rgb = rgb + 6;
        if(yuv == NULL)
          break;
 
        y0 = yuv;
        u0 = yuv + 1;
        y1 = yuv + 2;
        v0 = yuv + 3;
  
        r0 = rgb + 0;
        g0 = rgb + 1;
        b0 = rgb + 2;
        r1 = rgb + 3;
        g1 = rgb + 4;
        b1 = rgb + 5;
    }   
}

yuv420p转rgb：

bool YV12ToBGR24_FFmpeg(unsigned char* pYUV,unsigned char* pBGR24,int width,int height)
{
    if (width < 1 || height < 1 || pYUV == NULL || pBGR24 == NULL)
        return false;
    //int srcNumBytes,dstNumBytes;
    //uint8_t *pSrc,*pDst;
    AVPicture pFrameYUV,pFrameBGR;
    
    //pFrameYUV = avpicture_alloc();
    //srcNumBytes = avpicture_get_size(PIX_FMT_YUV420P,width,height);
    //pSrc = (uint8_t *)malloc(sizeof(uint8_t) * srcNumBytes);
    avpicture_fill(&pFrameYUV,pYUV,PIX_FMT_YUV420P,width,height);

    //U,V互换
    uint8_t * ptmp=pFrameYUV.data[1];
    pFrameYUV.data[1]=pFrameYUV.data[2];
    pFrameYUV.data [2]=ptmp;

    //pFrameBGR = avcodec_alloc_frame();
    //dstNumBytes = avpicture_get_size(PIX_FMT_BGR24,width,height);
    //pDst = (uint8_t *)malloc(sizeof(uint8_t) * dstNumBytes);
    avpicture_fill(&pFrameBGR,pBGR24,PIX_FMT_BGR24,width,height);

    struct SwsContext* imgCtx = NULL;
    imgCtx = sws_getContext(width,height,PIX_FMT_YUV420P,width,height,PIX_FMT_BGR24,SWS_BILINEAR,0,0,0);

    if (imgCtx != NULL){
        sws_scale(imgCtx,pFrameYUV.data,pFrameYUV.linesize,0,height,pFrameBGR.data,pFrameBGR.linesize);
        if(imgCtx){
            sws_freeContext(imgCtx);
            imgCtx = NULL;
        }
        return true;
    }
    else{
        sws_freeContext(imgCtx);
        imgCtx = NULL;
        return false;
    }
}

拿到RGB数据后可以用Qt的QImage类保存成本地图片文件以查验转换是否成功。