Error correcting code performance for watermark protection

The watermark signals are weakly inserted in images due to imperceptibility constraints which makes them prone to errors in the extraction stage. Although the error correcting codes can potentially improve their performance one must pay attention to the fact that the watermarking channel is in general very noisy. We have considered the trade-o of the BCH codes and repetition codes in various concatenation modes. At the higher rates that can be encountered in watermarking channels such as due to low-quality JPEG compression, codes like the BCH codes cease being useful. Repetition coding seems to be the last resort at these error rates of 25% and beyond. It has been observed that there is a zone of bit error rate where their concatenation turns out to be more useful. In fact the concatenation of repetition and BCH codes judiciously dimensioned, given the available number of insertion sites and the payload size, achieves a higher reliability level.