Encoder for encoding, and decoder for decoding, a 2-dimensional digital image representation into a data stream using further encoding for one or more remaining bits below the quantization factor

An encoder for at least partially encoding a 2-dimensional digital image representation into a compressed data stream is shown. The encoder comprises a rate control unit configured to determine a difference between a bit budget used for differentially encoding groups of coefficients representing spatial components of the digital image representation and a maximum available bit budget to determine a remaining bit budget. Furthermore, a processor may be configured to generate, by encoding, the compressed data stream comprising differentially encoded groups of coefficients representing spatial components of the digital image representation. The processor may encode the compressed data stream above (or greater than) a quantization factor used to compress the groups of coefficients and, further, to encode one or more remaining bit below (or less than) the quantization factor according to the remaining bit budget and to reduce the remaining bit budget respectively.