1. " With our vocabulary tree apporach, the representation of an image patch is simply one or two integers, which should be contrasted to the hundreds of bytes or floats used for a descriptor vector."

then on the next page...

" For D-dimensional descriptors represented as char the size of the tree is Dk^L bytes. With our current implementation, a tree with D = 128, L= 6, and k= 10, ..., uses 143MB of memory."

I am confused of what the descriptor vectors consist of. I thought it was only 1 or 2 integers per image patch. Does dimension of the descriptor vector (e.g D = 128) mean the number of pixels in the image patch, and the 128 elements of descriptor vector take the value of one of the 2 integers.. ? Thank you for clarifying.