我使用的是海康DS-2CD852MF-E, 200万,网络摄像机,已经比较老了,不过SDK在海康官网下载的,开发流程都差不多.
海康摄像机回调解码后的视频数据格式为YV12,顺便说一下YV12的数据格式 YYYY V U. 我这个是720P,即1280 * 720分辨率. 那么Y分量的数量为 1280 * 720 = 921600 字节, V = U 数量为Y的1/4, 即921600 / 4 = 230400字节,所以一帧720P的YV12数据量为1382400字节,与断点调试查看nSize一致.
这篇博客实现方法均来自网上找的代码,不是自己写的.仅作为一个记录.有一篇博客YUV与RGB格式转换里面就是YV12转到BGR的实现,看着它的代码改的.
1.用OpenCV 颜色空间转换函数
Mat pImgYCrCb, pImg;
pImgYCrCb.create(720, 1280,CV_8UC3);
pImg.create(720, 1280,CV_8UC3);
yv12toYUV(pImgYCrCb.data, (uchar*)pBuf, pFrameInfo->nWidth,pFrameInfo->nHeight,pImgYCrCb.step);
cvtColor(pImgYCrCb, pImg, CV_YCrCb2RGB);//转化为RGB图像,pImg是输出的帧
void yv12toYUV(uchar *outYuv, uchar *inYv12, int width, int height,int widthStep)
{
int col,row;
unsigned int Y,U,V;
int tmp;
int idx;
for (row=0; row<height; row++)
{
idx=row * widthStep;
int rowptr=row*width;
for (col=0; col<width; col++)
{
tmp = (row/2)*(width/2)+(col/2);
Y=(unsigned int) inYv12[row*width+col];
U=(unsigned int) inYv12[width*height+width*height/4+tmp];
V=(unsigned int) inYv12[width*height+tmp]; outYuv[idx+col*3] = Y;
outYuv[idx+col*3+1] = U;
outYuv[idx+col*3+2] = V;
}
}
}
2.另一种opencv cvtColor实现,较为简单
Mat dst(pFrameInfo->nHeight,pFrameInfo->nWidth,CV_8UC3);//这里nHeight为720,nWidth为1280,8UC3表示8bit uchar 无符号类型,3通道值
Mat src(pFrameInfo->nHeight + pFrameInfo->nHeight/2,pFrameInfo->nWidth,CV_8UC1,(uchar*)pBuf);
cvtColor(src,dst,CV_YUV2BGR_YV12);
imshow("bgr",dst);
waitKey(1);
3.只保留Y分量,观看黑白视频
uchar Y[921600];
memcpy(Y, pBuf, 921600);
if (Videofile==NULL)
{
sprintf_s(filename,"is_Y.yuv",0);
fopen_s(&Videofile,filename,"wb");
}
fwrite(Y,921600,1,Videofile);
4.ffmpeg转换
int sizeRGB = pFrameInfo->nWidth * pFrameInfo->nHeight * 3;
uchar* pBGR24 = new unsigned char[sizeRGB];//开辟存储一副图像大小的内存空间,因为这里是RGB图像,所以需要 1280 * 720 * 3的大小
memset(pBGR24, 0, sizeRGB);
YV12ToBGR24_FFmpeg((uchar*)pBuf, pBGR24,1280, 720);
Mat BGR24_IMG(pFrameInfo->nHeight,pFrameInfo->nWidth,CV_8UC3,pBGR24);
imshow("bgr24", BGR24_IMG);
waitKey(1);
delete []pBGR24;
bool YV12ToBGR24_FFmpeg(unsigned char* pYUV,unsigned char* pBGR24,int width,int height)
{
if (width < 1 || height < 1 || pYUV == NULL || pBGR24 == NULL)
return false;
AVPicture pFrameYUV,pFrameBGR;
avpicture_fill(&pFrameYUV,pYUV,AV_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;
avpicture_fill(&pFrameBGR,pBGR24,AV_PIX_FMT_BGR24,width,height); struct SwsContext* imgCtx = NULL;
imgCtx = sws_getContext(width,height,AV_PIX_FMT_YUV420P,width,height,AV_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;
}
}
注意这里ffmpeg会出现函数被否决,需要用新接口替换,也可以忽略这个警告,并且头文件需要用extern “C”包含
extern "C"
{
#include <libavcodec\avcodec.h>
#include <libswscale\swscale.h>
#include <libavutil\pixfmt.h>
#include <libavutil\imgutils.h>
}
#pragma warning(disable: 4996)//忽略被否决的警告
