But that was not enough, as a single HD frame contains the equivalent of 4 SD frames. This could have been "solved" by doubling the bandwidth of the D2-MAC signal, thus increasing the allowed horizontal resolution by the same factor. Instead, the standard D2-MAC channel bandwidth was preserved, and one pixel out of two was dropped from each line. This sub-sampling was done in a quincux pattern. Assuming pixels on a line independently numbered from 1 to 1440, only pixels 1,3,5... were retained from the first line, pixels 2, 4, 6... from the second, 1, 3, 5...again from the third, and so on. That way, information from all the columns of the HD frame were conveyed to the receiver. Each missing pixel was surrounded by 4 transmitted ones (except on the sides) and could be interpolated from them. The resulting 720 horizontal resolution was further truncated to the 697 samples per line limit of the D2-HDMAC video multiplex.