Modifying a coded bitstream

Abstract

Implementations may relate to various aspects of modifying, or using, a coded bitstream, or to recovering watermarking information from data. In one implementation, a coded bitstream is modified to allow for the application of a watermark to the coded bitstream without changing the coding of any other syntax elements in the bitstream. This is performed by identifying conditions necessary to change a coded syntax element without disrupting the interpretation of subsequent coded elements. The coded syntax element is replaced with another coded value if the modified value generates the same decoding variables as the original value would have generated. Particular implementations focus on syntax elements coded using entropy coding, including, for example, Context-based Adaptive Binary Arithmetic Coding (CABAC). Regardless of the type of coding or watermarking, various implementations may provide for recovering watermarking information. Particular implementations recover watermarking information using detection data and feature information.