Stereo depth estimation

A method of smoothing an input stream of disparity cost vectors, the method comprising, in an in-stream processing system:

• receiving at a processing block of the in-steam processing system (i) an input stream of disparity cost vectors, and (ii) a version of the input stream delayed by a predetermined amount, the disparity cost vectors associated with respective pixels of a target image stream, having been determined by applying stereo image processing to the target image stream and a reference image stream;
• and
• for each of the pixels, applying cost smoothing to that pixel's disparity cost vector, as received in the delayed stream, based on the disparity cost vector(s) of one or more neighbouring pixels, as received in the input stream, the neighbouring pixels being subsequent to that pixel in the target image stream, which is accounted for by said delaying of the input stream.

A non-transitory computer-readable storage medium having stored thereon register-transfer level code or other circuit description code operable to configure a field programmable gate array to implement:

• a delay block having an input for receiving an input stream of disparity cost vectors, and configured to provide a delayed stream of disparity cost vectors at an output of the delay block, by delaying the input stream by a predetermined amount;
• and
• a processing block having a cost input connected to receive the delayed stream of disparity cost vectors and a smoothing input connected to receive the input stream of disparity cost vectors, and configured to apply cost smoothing to the delayed stream based on the input stream, so as to generate, at an output of the processing block, a stream of reverse pass disparity cost vectors.