can now be computed for regions that are big enough. A linear regression is then
performed in order to estimate c and d in equation (6).
The correlation coefficient is used as an indication of
whether the video has been altered. Parameters c and d
bring more information than variance alone would. For
example, in certain cases, comparing variances cannot
help us distinguish two different types of noise. Indeed,
several combinations of c, µ and d will result in the
same variance. Results presented further on will confirm this.
In the case where movement occurs from one frame
to the next, we can no longer perform the subtraction