[英]How to convert RGB to NV12 color space using IPP
Video encoders like Intel® Media SDK require NV12 video input format. 像Intel®MediaSDK这样的视频编码器需要NV12视频输入格式。
NV12 format is YUV 4:2:0 format ordered in memory with a Y plane first, followed by packed chroma samples in interleaved UV plane. NV12格式是YUV 4:2:0格式,在存储器中排序,首先是Y平面,然后是交错UV平面中的打包色度样本。
Example: 例:
YYYYYY
YYYYYY
UVUVUV
RGB color format, refers to Pixel-Order RGB (byte per pixel, lower byte is Red): RGB颜色格式,指像素级RGB(每像素字节,低字节为红色):
RGBRGBRGBRGBRGB
RGBRGBRGBRGBRGB
I did some Web research, and found out that regarding NV12, YUV is defined as YCbCr color space. 我做了一些网络研究,发现对于NV12, YUV被定义为YCbCr色彩空间。 There are currently at least 2 possible YCbCr formats apply NV12:
目前至少有两种可能的YCbCr格式适用于NV12:
My question is: Is there as IPP function that converts RGB color space to NV12? 我的问题是: 是否有将IP色彩空间转换为NV12的IPP功能?
I found out that IPP function exists: 我发现IPP功能存在:
ippiRGBToYCbCr420_8u_C3P2R ippiRGBToYCbCr420_8u_C3P2R
It was hard to find, because the function name or description does not mention NV12. 很难找到,因为功能名称或描述没有提到NV12。
The function uses BT.601 standard. 该功能使用BT.601标准。
Here is a code sample for converting RGB to NV12 in BT.601 standard: 以下是在BT.601标准中将RGB转换为NV12的代码示例:
void Rgb2NV12(const unsigned char I[], int image_width, int image_height, unsigned char J[])
{
IppStatus ipp_status;
int srcStep = image_width*3;
int dstYStep = image_width;
int dstCbCrStep = image_width;
IppiSize roiSize = {image_width, image_height};
const Ipp8u* pSrc = (Ipp8u*)I;
Ipp8u *pDstY = (Ipp8u*)J; //Y color plane is the first image_width*image_height pixels of J.
Ipp8u *pDstCbCr = (Ipp8u*)&J[image_width*image_height]; //In NV12 format, UV plane starts below Y.
ipp_status = ippiRGBToYCbCr420_8u_C3P2R(pSrc, srcStep, pDstY, dstYStep, pDstCbCr, dstCbCrStep, roiSize);
//if (ipp_status != ippStsNoErr), Handle errors...
}
Converting RGB to NV12 with BT.709 standard: 使用BT.709标准将RGB转换为NV12:
As for 2019, BT.709 (HDTV) standard is probably more relevant than BT.601 (SDTV). 至于2019年,BT.709(HDTV)标准可能比BT.601(SDTV)更具相关性。
IPP lacks a function for direct conversion from RGB to NV12 in BT.709 standard. IPP缺乏在BT.709标准中从RGB直接转换为NV12的功能。
There is a function that converts BGR to NV12 . 有一个功能可以将BGR转换为NV12 。
The solution includes two stages: 该解决方案包括两个阶段:
ippiSwapChannels_8u_C3R
for RGB to BGR conversion. ippiSwapChannels_8u_C3R
进行RGB到BGR转换。 ippiBGRToYCbCr420_709CSC_8u_C3P2R
for BGR to NV12 conversion. ippiBGRToYCbCr420_709CSC_8u_C3P2R
进行BGR到NV12的转换。 The sample function requires some extra memory space for storing the intermediate BGR image. 样本函数需要一些额外的存储空间来存储中间BGR图像。
A pointer to the sketch memory is passed to the function (the memory should be allocated outside the function). 指向草图存储器的指针被传递给函数(存储器应该在函数外部分配)。
Here is a code sample for converting RGB to NV12 in BT.709 standard: 以下是在BT.709标准中将RGB转换为NV12的代码示例:
//sketch_buff - Temporary buffer for storing image in BGR format.
// Size of sketch_buff must be at least image_width*image_height*3 bytes.
void Rgb2NV12_709(const unsigned char I[],
const int image_width,
const int image_height,
unsigned char sketch_buff[],
unsigned char J[])
{
IppStatus ipp_status;
int srcStep = image_width*3;
int dstBgrStep = image_width*3;
int dstYStep = image_width;
int dstCbCrStep = image_width;
IppiSize roiSize = {image_width, image_height};
const Ipp8u* pRGB = (Ipp8u*)I;
Ipp8u* pBGR = (Ipp8u*)sketch_buff; //BGR image is stored in sketch_buff
Ipp8u *pDstY = (Ipp8u*)J; //Y color plane is the first image_width*image_height pixels of J.
Ipp8u *pDstCbCr = (Ipp8u*)&J[image_width*image_height]; //In NV12 format, UV plane starts below Y.
const int bgrOrder[3] = {2, 1, 0};
//Swap Red and Blue color channels - convert from RGB to BGR
//Store the result into sketch_buff (sketch buffer is allocated outside the function)
ipp_status = ippiSwapChannels_8u_C3R(pRGB, srcStep, pBGR, dstBgrStep, roiSize, bgrOrder);
//if (ipp_status != ippStsNoErr), Handle errors...
//Convert BGR to NV12 in BT.709 standard
ipp_status = ippiBGRToYCbCr420_709CSC_8u_C3P2R(pBGR, srcStep, pDstY, dstYStep, pDstCbCr, dstCbCrStep, roiSize);
//if (ipp_status != ippStsNoErr), Handle errors...
}
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