1. A method for processing a signal, said signal having been compression encoded according to a predetermined encoding type, subject to application of a quantization operation, and then decoded, said method comprising: estimating quantization noise introduced by the compression encoding based on the decoded signal and information obtained a priori relating to the type of compression encoding, estimating signal to quantization noise ratio, and determining, based on the estimated signal to quantization noise ratio, a filtering function to be applied to the decoded signal in order to apply an estimated quantization noise reduction process.