1. A method for encoding watermark information into media data containing a series of digital samples in a sample domain, the method comprising: dividing the series of digital samples into a plurality of sections in the sample domain, each section comprising a corresponding plurality of samples; processing the corresponding plurality of samples in each section to obtain a single energy value associated with each section; grouping the sections into groups, each group containing an ordered plurality of three or more sections wherein first and second sections are adjacent to one another in the sample domain and a third section is adjacent to the second section in the sample domain, but spaced apart from the first section in the sample domain; assigning a nominal bit value to each group according to a bit assignment rule, the bit assignment rule based on the energy values of the sections in the group; assigning a watermark bit value to each group; for each group, comparing the watermark bit value to the nominal bit value and, if the nominal bit value and the watermark bit value of the watermark information bit do not match, modifying one or more energy values of one or more corresponding sections in the group such that re-application of the bit assignment rule would assign the watermark bit value to the group; wherein assigning the nominal bit value to each group according to the bit assignment rule comprises: categorizing each group into one of a plurality of categories according to a categorization rule based on the energy value of the first section relative to the energy value of the second section and the energy value of the third section relative to the energy values of the first and second sections; and for each category, assigning a nominal zero bit value or a nominal one bit value to each group according to a unique category bit assignment rule associated with the category; wherein, for a particular group, the categorization rule comprises: categorizing the particular group into a first shape category if the energy value of the second section is greater than an energy value of the first section and the energy value of the third section is greater than the energy values of the first and second sections; categorizing the particular group into a second shape category if the energy value of the second section is less than an energy value of the first section and the energy value of the third section is less than the energy values of the first and second sections; categorizing the particular group into a third shape category if the energy value of the second section is greater than an energy value of the first section and the energy value of the third section is between the energy values of the first and second sections; categorizing the particular group into a fourth shape category if the energy value of the second section is greater than an energy value of the first section and the energy value of the third section is less than the energy values of the first and second sections; categorizing the particular group into a fifth shape category if the energy value of the second section is less than an energy value of the first section and the energy value of the third section is between the energy values of the first and second sections; and categorizing the particular group into a sixth shape category if the energy value of the second section is less than an energy value of the first section and the energy value of the third section is greater than the energy values of the first and second sections.