A block processing procedure to determine coding-block or transform-block sizes for encoded and decoding video data. An encoder obtains unencoded video data and selects a region-of-interest in the video data. Image characteristics of the video data are determined from the region-of-interest and a block size is determined from those image characteristics. The video data is encoded using the block size without storing the block size in a header associated with the encoded data. A decoder obtains the encoded data and selects a second region-of-interest in the encoded data that corresponds to the unencoded data region-of-interest. Second image characteristics are determined from the second region-of-interest, where the second characteristics are the same as the characteristics determined for the unencoded data. A block size is determined from the second image characteristics without using a header associated with the encoded data. The encoded data is decoded based on the determined block size.