Multichannel acoustic echo cancellation is basically composed of two parts. One part is a multichannel system identification problem which is nontrivial to solve. The other part, which is also nontrivial, is the so-called double-talk detection problem. Near-end speech detection is based on a test statistic. Recently, a new double-talk test statistic based on the normalized cross-correlation vector was proposed for the single-channel case. Obviously, in the multichannel case, there are several solutions, but what should be the optimal one is not yet known. Then, a fundamental question arises: how do we deal optimally with multiple channels? In this paper, we generalize the idea of normalized cross-correlation vector (single-channel) to the matrix case (multichannel), derive a frequency-domain version, and show how to combine both the multichannel frequency-domain adaptive filter and the multichannel double-talk detector.