Apparatus and method for improving video encoding

An apparatus for determining a quantization parameter for a second rate-control pass of a video encoder for a group of pictures based on an encoding bitrate and further quantization parameter of a first rate-control pass of the video encoder for the group of pictures, the apparatus comprising:

• a processor and memory, the memory storing instruction code for execution by the processor configuring the apparatus to:
• determine, for each of positions spatially distributed over frames of the group of pictures, a dissimilarity measure or a similarity measure of a comparison of a first frame portion at the respective position, and a second portion of a reference frame to which a motion vector of an estimated motion field at the respective position points;
• form a representative scalar value based on the dissimilarity measures or similarity measures determined for the positions;
• determine a preliminary quantization parameter for the second rate-control pass based on the encoding bitrate, the further quantization parameter of the first rate-control pass and an intended bitrate for the second rate-control pass, and
• adjust the preliminary quantization parameter using the representative scalar value (216) to obtain the quantization parameter for a second rate-control pass.