These techniques are also referred in the literature as forward error control or concealment, and they could be generally described as preventive. In other words, should a transmission error occur, the decoder is left alone to deal with the problem, by exploiting the concealment redundancy added at the coding stage. This can be done either by exploiting niches that standards intentionally left to add such information, or by slightly modifying standards and providing an error-resilient version of them. A brief overview of the techniques follows.