The convolution kernel convolves around the input volume by shifting one column/row at a time. The amount by which the filter shifts is called the stride. In the preceding scenario, the stride was implicitly set to 1. If we shift the kernel by a stride of 2 (two columns or two rows), the number of output units shrinks:
The convolution operator reduces the size of the input. If we want to preserve the size of the input, we need to pad zeros evenly around the input. For a two-dimensional image, this means adding a border of zero pixels around the four sides of the image. The thickness of the border—that ...
