High precision up-sampling in scalable coding of high bit-depth video

In a decoder, a method performed by a processor for re-sampling image data in a scalable video system from a first layer to a second layer, the method comprising:

• determining scaling and rounding parameters in response to bit-depth requirements of the scalable video system;
• generating first re-sampled data by filtering image data from the first layer, wherein filtering of the image data from the first layer is performed across a first spatial direction;
• generating first intermediate data by scaling the first re-sampled data with a first shift parameter;
• generating second re-sampled data by filtering the first intermediate data, wherein the filtering of the first intermediate data is performed across a second spatial direction using a rounding parameter;
• generating second intermediate data by scaling the second re-sampled data with a second shift parameter;
• and
• generating output re-sampled data for the second layer by clipping the second intermediate data,
• wherein the second shift parameter is based on a bit depth value of the image data in the first layer and determining the rounding parameter comprises computing
• offset=1<<(nShift2−1),
• wherein offset is the rounding parameter, <<denotes a binary shift to the left, and nShift2 is the second shift parameter.