MinEnclosingCircle is not stable when object fast motion opencv android - opencv

Question

I have a project with opencv in android, i try to detect ball and i decide use MinEnclosingCircle, But i have problem when i move object so fast. I cannot get exactly radius of ball. Because of this phenomenon.
When object stand by, I get image like below:
But when i move ball from right to left, left to right so fast i get wrong radius because of this phenomenon
Could you please tell me how to solve this problem. So many thank for your help.
EDIT 1: More detail about image that i get
This is image not draw circle that i captured
And this is image which show contour of ball
It quite a dim, so i draw contour to see easier.

Answer 1

this works quite well I guess:
int main(int argc, char* argv[])
{
//cv::Mat input = cv::imread("C:/StackOverflow/Input/ballMaskClean2.png");
cv::Mat input = cv::imread("C:/StackOverflow/Input/ballMaskClean1.png");
cv::Mat mask;
cv::cvtColor(input, mask, CV_BGR2GRAY);
//cv::inRange(input, cv::Scalar(200, 200, 200), cv::Scalar(255, 255, 255), mask); // was used for your provided images with red circle inside
cv::imshow("mask", mask);
std::vector<std::vector<cv::Point> > contours;
cv::findContours(mask, contours, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_NONE);
cv::Mat cleanMask = cv::Mat::zeros(input.size(), CV_8UC1);
for (unsigned int i = 0; i < contours.size(); ++i)
{
cv::drawContours(cleanMask, contours, i, 255, -1); // draw filled
}
//cv::imwrite("C:/StackOverflow/Input/ballMaskClean.png", cleanMask);
cv::Mat dt;
cv::distanceTransform(cleanMask, dt, CV_DIST_L1, 3);
double minVal, maxVal;
cv::Point minLoc, maxLoc;
cv::minMaxLoc(dt, &minVal, &maxVal, &minLoc, &maxLoc);
double radius = maxVal;
cv::Point2f center = maxLoc;
cv::circle(input, center, radius, cv::Scalar(0, 255, 0), 2);
cv::imshow("output", input);
cv::imwrite("C:/StackOverflow/Input/ballCircle.png", input);
cv::waitKey(0);
return 0;
}
using these input I get that output: