Data buffer and data buffer control

A buffer occupancy difference between a current occupancy, representing a difference between read and write pointers, and a target occupancy is detected, and an interpolator is provided to interpolate a data item at an interpolated buffer position displaced by a read offset from a buffer address pointed to by the read pointer. In response to the occupancy difference exceeding a threshold occupancy difference, the read pointer is moved by a change amount so as to reduce the occupancy differences, the read offset displacement being progressively varied so as to define an interpolated data buffer location which progresses over the output of a transitional group of data items towards the location of the target read pointer, and when the occupancy difference is less that the threshold and the interpolated data buffer location is aligned with the target read pointer, inhibiting the interpolation process. The buffer may be a video buffer containing audio samples, and in response to detection of the occupancy, drops or repeats a video frame, and compensates over a transitional period for a reduction or increase in the output read rate. The transitional period may occur before the dropping or repeating of the video frame.