MODIFYING A CODED BITSTREAM

Various implementations are provided for, for example, determining watermarking data, performing the watermarking, and processing watermarked data. At least one implementation watermarks AVC bitstream that uses CAVLC entropy coding. The watermarking data may be determined in a pre-processing stage and stored for later use in watermark a bitstream. One method accesses variable-length encoded data including an encoding of information identifying an actual reference used to predictively encode an image. The encoding of the information has a particular value. The method determines an alternative value that is different from the particular value, such that the alternative value is an encoding of alternative information that identifies a different reference from the actual reference. The alternative value is for use in watermarking the variable-length encoded data.