Method for controlling the encoder output bit rate in a block-based video encoder, wherein the transform coefficients derived from a pixel block are quantised using a variable quantisation parameter and are encoded, and wherein said quantisation parameter is related to the quantiser step size and said pixel blocks can be coded in intra mode (Intra) or in inter mode (Inter), said method including the steps: - determining (RHOITATBL, RHOIETBL) for each macroblock of a frame containing one or more of said blocks of transform coefficients, which percentage ρ of the quantised coefficients gets the amplitude 'zero' depending on an applied value of said quantisation parameter; - based on the resulting information about the ρ value/ quantisation parameter relationship for the macroblocks of said frame, controlling the encoder output bit rate R for said frame, when processing said macroblocks, by using said quantisation parameter value such that the control of the bit rate R is based on R ( ρ) = Θ *(100- ρ), Θ being a constant, characterised by: - when controlling the encoder output bit rate R by using said quantisation parameter value, the quantisation parameter value applied to the current macroblock is constrained by a pre-determined deviation from the average of the quantisation parameter values for all prior macroblocks in the current frame until the current macroblock, wherein said percentage ρ determination (RHOITATBL, RHOIETBL) for each macroblock of transform coefficients of a frame is carried out using two different types of look-up tables, a first type mapping the coding mode (Intra, Inter), the position (i, j) of a transform coefficient in a block and the magnitude value of transform coefficients to a corresponding candidate quantisation parameter value, a second type mapping the coding mode (Intra, Inter), the position (i, j) of a transform coefficient in a block and a candidate quantisation parameter to an applicable quantisation threshold value for a quantisation parameter. - determining (RHOITATBL, RHOIETBL) for each macroblock of a frame containing one or more of said blocks of transform coefficients, which percentage ρ of the quantised coefficients gets the amplitude 'zero' depending on an applied value of said quantisation parameter; - based on the resulting information about the ρ value/ quantisation parameter relationship for the macroblocks of said frame, controlling the encoder output bit rate R for said frame, when processing said macroblocks, by using said quantisation parameter value such that the control of the bit rate R is based on R ( ρ) = Θ *(100- ρ), Θ being a constant, - when controlling the encoder output bit rate R by using said quantisation parameter value, the quantisation parameter value applied to the current macroblock is constrained by a pre-determined deviation from the average of the quantisation parameter values for all prior macroblocks in the current frame until the current macroblock, wherein said percentage ρ determination (RHOITATBL, RHOIETBL) for each macroblock of transform coefficients of a frame is carried out using two different types of look-up tables, a first type mapping the coding mode (Intra, Inter), the position (i, j) of a transform coefficient in a block and the magnitude value of transform coefficients to a corresponding candidate quantisation parameter value, a second type mapping the coding mode (Intra, Inter), the position (i, j) of a transform coefficient in a block and a candidate quantisation parameter to an applicable quantisation threshold value for a quantisation parameter.