YUV编码格式（二）

YUV常见格式的像素分布

YUV444：

YUV422：

YUV420：

YUV常见格式的数据量的计算

YUV444：

        Data(YUV)=Data(Y)*3
        Data(YUV)=Data(RGB)

YUV422：

        Data(YUV)=Data(Y)*2
        Data(YUV)=(Data(RGB)/3)*2

YUV420：

        Data(YUV)=Data(Y)*1.5
        Data(YUV)=Data(RGB)/2

YUV420存储格式

Planar（平面）：

YUV420P又叫plane平面模式，Y , U , V分别在不同平面，也就是有三个平面，它是YUV标准格式4:2:0，主要分为：YU12和YV12:
YU12: YYYYYYYY UUVV => YUV420P
YV12: YYYYYYYY VVUU => YUV420P
（下图为YU12存储格式示意图，将U行与V行互换则是YV12存储格式示意图）

Packed（打包）：

YUV420SP格式的图像阵列又叫packed打包模式，首先是所有Y值，然后是UV或者VU交替存储，NV12和NV21属于YUV420SP格式：
NV12: YYYYYYYY UVUV =>YUV420SP

NV21: YYYYYYYY VUVU =>YUV420SP

（android手机从摄像头采集的预览数据一般都是NV21）

YUV相关代码

YUV与RGB相互转换：

Y      =  (0.257 * R) + (0.504 * G) + (0.098 * B) + 16
Cr = V =  (0.439 * R) - (0.368 * G) - (0.071 * B) + 128
Cb = U = -(0.148 * R) - (0.291 * G) + (0.439 * B) + 128

B = 1.164(Y - 16) + 2.018(U - 128)
G = 1.164(Y - 16) - 0.813(V - 128) - 0.391(U - 128)
R = 1.164(Y - 16) + 1.596(V - 128)

分离YUV420各分量：

void split_yuv420(char *inputPath, int width, int height) {

    FILE *fp_yuv = fopen(inputPath, "rb+");

    FILE *fp_y = fopen("output_420_y.y", "wb+");
    FILE *fp_u = fopen("output_420_u.y", "wb+");
    FILE *fp_v = fopen("output_420_v.y", "wb+");

    unsigned char *data = (unsigned char *) malloc(width * height * 3 / 2);

    fread(data, 1, width * height * 3 / 2, fp_yuv);
    //Y
    fwrite(data, 1, width * height, fp_y);
    //U
    fwrite(data + width * height, 1, width * height / 4, fp_u);
    //V
    fwrite(data + width * height * 5 / 4, 1, width * height / 4, fp_v);

    //释放资源
    free(data);

    fclose(fp_yuv);
    fclose(fp_y);
    fclose(fp_u);
    fclose(fp_v);
}

NV12转YU12：

void NV12_to_YU12(	const unsigned char* image_src, 
					unsigned char* image_dst,
					int image_width, 
					int image_height)
{
	unsigned char* p = image_dst;
	memcpy(p, image_src, image_width * image_height * 3 / 2);
	const unsigned char* pNV = image_src + image_width * image_height;
	unsigned char* pU = p + image_width * image_height;
	unsigned char* pV = p + image_width * image_height + ((image_width * image_height)>>2);
	for (int i=0; i<(image_width * image_height)/2; i++){
		if ((i%2)==0) 
			pU++ = (pNV + i);
		else 
			pV++ = (pNV + i);
	}
}

NV21转YU12：

void NV21_to_YU12(const unsigned char* image_src,
				  unsigned char* image_dst,
				  int image_width,
				  int image_height) {

	unsigned char* p = image_dst;
	memcpy(p, image_src, image_width * image_height * 3 / 2);
	const unsigned char* pNV = image_src + image_width * image_height;
	unsigned char* pU = p + image_width * image_height;
	unsigned char* pV = p + image_width * image_height + ((image_width * image_height) >> 2);
	for (int i = 0; i < (image_width * image_height) / 2; i++) {
		if ((i % 2) == 0)
		{
			memcpy(pU, pNV + i, 1);
			pU++;
		}
		else {
			memcpy(pV, pNV + i, 1);
			pV++;
		}
	}
}

YU12转NV12：

void YU12_to_NV12(	unsigned char* Src, 
					unsigned char* Dst, 
					int Width, 
					int Height) {

	unsigned char* SrcU = Src + Width * Height;
	unsigned char* SrcV = SrcU + Width * Height / 4;
	memcpy(Dst, Src, Width * Height);
	unsigned char* DstU = Dst + Width * Height;
	for (int i = 0; i < Width * Height / 4; i++) {
		(*DstU++) = (*SrcU++);
		(*DstU++) = (*SrcV++);
	}
}

YU12转NV21：

void YU12_to_NV21(unsigned char *Src, 
				   unsigned char *Dst, 
				   int Width, 
				   int Height){

	unsigned char* SrcU = Src + Width * Height;
	unsigned char* SrcV = SrcU + Width * Height / 4;
	memcpy(Dst, Src, Width * Height);
	unsigned char* DstV = Dst + Width * Height;
	for (int i = 0; i < Width * Height / 4; i++)
	{
		(*DstV++) = (*SrcV++);
		(*DstV++) = (*SrcU++);
	}
}