Method for coding video pictures by determining a sub-target value for the number of bits per sub-series of coefficients

A device for decoding a coded picture signal comprised of one or more coded picture blocks, the device comprising:

• a decoder for obtaining a series of quantized coefficients from a coded picture block;
• an inverse quantizer for reproducing transform coefficients from the quantized coefficients in response to an applied step size (s);
• a picture transformer for transforming the reproduced transform coefficients into a picture block;
• and
• means for receiving a parameter (L(n)) indicating how the series of quantized coefficients is divided into sub-series;
• wherein the inverse quantizer is adapted to reproduce the transform coefficients for each sub-series of quantized coefficients in accordance with a corresponding step size for the sub-series.

A picture signal comprising:

• coded picture blocks each having series of quantized coefficients;
• a step size with which the coefficients have been coded;
• a parameter (L(n)) indicating how each series of quantized coefficients of a picture block is divided into sub-series;
• and
• a step size (s(n)) for each sub-series of quantized coefficients.

A method of coding video pictures, the method comprising the steps of:

• dividing a video picture into one or more picture blocks;
• transforming a picture block into a series of coefficients;
• quantizing the series of coefficients with a step size;
• coding the series of coefficients;
• and
• controlling the step size in accordance with a target value (Rt(k)) for the number of bits per series of coefficients;
• wherein the series of coefficients is divided into sub-series each having a sub-target value (Rt(k,n)) for the number of bits per sub-series, and wherein the step size per sub-series is controlled in accordance with a corresponding sub-target value.

A method of decoding a coded picture signal comprised of one or more coded picture blocks, the method comprising the steps of:

• obtaining a series of quantized coefficients from a coded picture block;
• performing inverse quantizing on the series of quantized coefficients in response to an applied step size (s) so as to reproduce transform coefficients;
• transforming the reproduced transform coefficients into a picture block;
• and
• receiving a parameter (L(n)) which indicates how the series of quantized coefficients is divided into sub-series;
• wherein the transforming step reproduces transform coefficients for each sub-series in accordance with a corresponding step size for the sub-series.