VideoWriter depthMap

edit

you can try using pointer, opencv function or parallel_loop_body. Best method (relative to speed) will depend of your configuration (image type 16SC or 16UC and image size and your computer) :

class Parallel16BisTo2X8Bits: public ParallelLoopBody
{
private:

Mat &x;
Mat &result;
bool verbose;

public:

Parallel16BisTo2X8Bits(Mat& src, Mat &dst):
    x(src),
    result(dst),
    verbose(false)
{}
void Verbose(bool b){verbose=b;}
virtual void operator()(const Range& range) const
{

    if (verbose)
        cout << getThreadNum()<<"# :Start from row " << range.start << " to "  << range.end-1<<" ("<<range.end-range.start<<" loops)" << endl;

    if (x.type()==CV_16SC1)
        for (int i = range.start; i <  range.end; i++)
        {
            short *pts = (short*)x.ptr(i);
            uchar *ptc = result.ptr(i);
            for (int j=0;j<x.cols;j++,pts++)
            {
                *ptc++= *pts/256;
                *ptc++ = (*pts &0xFF);
                *ptc++=0;
            }

        }
    else
        for (int i = range.start; i <  range.end; i++)
        {
            ushort *pts = (ushort*)x.ptr(i);
            uchar *ptc = result.ptr(i);
            for (int j=0;j<x.cols;j++,pts++)
            {
                *ptc++= *pts/256;
                *ptc++ = (*pts &0xFF);
                *ptc++=0;
            }

        }

}
Parallel16BisTo2X8Bits& operator=(const Parallel16BisTo2X8Bits &) {
     return *this;
};
};

int main(int argc, char* argv[])
{

int type=CV_16SC1;
Mat x(1000,1023,type);
for (int i=0;i<x.rows;i++)
    for (int j=0;j<x.cols;j++)
        x.at<short>(i,j)=rand()%32767;

vector<Mat> m(3);
m[2] = Mat::zeros (x.rows,x.cols,CV_8UC1);
Mat lsb=Mat::zeros (x.rows,x.cols,type),msb=Mat::zeros (x.rows,x.cols,type),result=Mat::zeros(x.rows,x.cols,CV_8UC3);
// That's only for fun : compile ocl function speed time is equal to compiletime
int64 tpsIni = getTickCount();

bitwise_and(x,0xFF,lsb);
lsb.convertTo(m[1],CV_8UC1,1);
x.convertTo(m[0],CV_8UC1,1./256);

merge(m,result);
int64 tpsFin = getTickCount();
// Time using pointer 
result=Mat::zeros(x.rows,x.cols,CV_8UC3);
tpsIni = getTickCount();
if (type==CV_16UC1)
    for (int i = 0; i < x.rows; i++)
        {
            ushort *pts = (ushort*)x.ptr(i);
            uchar *ptc = (uchar*)result.ptr(i);
            for (int j=0;j<x.cols;j++,pts++,ptc++)
            {
                *ptc++= *pts/256;
                *ptc++ = (*pts &0xFF);
            }

        }
else
    for (int i = 0; i < x.rows; i++)
    {
        short *pts = (short*)x.ptr(i);
        uchar *ptc = (uchar*)result.ptr(i);
        for (int j=0;j<x.cols;j++,pts++,ptc++)
        {
            *ptc++= *pts/256;
            *ptc++ = (*pts &0xFF);
        }

    }
tpsFin = getTickCount();
cout << result.at<Vec3b>(64,32)<<endl;
cout << "Time pointer ="<<tpsFin-tpsIni<<"\n";
imshow("color(pointer)",result);
// Time using opencv fucntion with opencl
tpsIni = getTickCount();

{
bitwise_and(x,0xFF,lsb);
lsb.convertTo(m[1],CV_8UC1);
x.convertTo(m[0],CV_8UC1,1./256);

merge(m,result);

}
tpsFin = getTickCount();
imshow("color(ocv)",result);
cout << result.at<Vec3b>(64,32)<<endl;
cout << "Time opencv function with ocl ="<<tpsFin-tpsIni<<"\n";


Parallel16BisTo2X8Bits p(x,result);
cout << getNumThreads()<<endl;
tpsIni = getTickCount();
parallel_for_(Range(0,x.rows), p,4);
tpsFin = getTickCount();
imshow("color(parallel)",result);
cout << result.at<Vec3b>(64,32)<<endl;
cout << "Time opencv function with parallel ="<<tpsFin-tpsIni<<"\n";


waitKey();