In one example, an apparatus for processing video data comprises a video coder configured to, for each of the one or more chrominance components, calculate a chrominance quantization parameter for a common edge between two blocks of video data based on a first luminance quantization parameter for the first block of video data, a second luminance quantization parameter for the second block of video data, and a chrominance quantization parameter offset value for the chrominance component. The video coder is further configured to determine a strength for a deblocking filter for the common edge based on the chrominance quantization parameter for the chrominance component, and apply the deblocking filter according to the determined strength to deblock the common edge.