Estimator for estimating a probability distribution of a quantization index

A coding apparatus for coding a source signal, the coding apparatus comprising:

• a source coder for coding the source signal into a sequence of quantization indices, the source coder configured to provide a current quantization index and current side information;
• a lossless coder configured to encode the quantization indices into code words in dependency on a probability distribution of the quantization indices;
• and
• an estimator for estimating a probability distribution of the current quantization index generated from the source coder, the source signal being described by a signal model, the estimator being configured to obtain auxiliary parameters based on a configuration of the source coder and the current side information and the signal model, the estimator being further configured to adaptively update a probability distribution of a quantization index upon the basis of a probability density function relating to a previous state of the estimator, the auxiliary parameters, the current quantization index and the current side information.

A decoding apparatus for decoding a source signal being encoded by a source coder using quantization indices, the decoding apparatus comprising:

• a receiver configured to receive a bit stream with code words and current side information;
• an estimator for estimating a probability distribution of a current quantization index generated from the source coder, the source signal being described by a signal model, the estimator being configured to obtain auxiliary parameters based on a configuration of the source coder and current side information and the signal model, the estimator being further configured to adaptively update a probability distribution of a quantization index upon the basis of a probability density function relating to a previous state of the estimator, the auxiliary parameters, the current quantization index and the current side information;
• and
• a decoder for decoding a sequence of quantization indices and for providing the current quantization index for a reconstruction of the source signal based on the probability distribution of a quantization index.