Temporal filtering techniques for image signal processing

摘要

Various techniques for temporally filtering raw image data acquired by an image sensor are provided. In one embodiment, a temporal filter determines a spatial location of a current pixel and identifies at least one collocated reference pixel from a previous frame. A motion delta value is determined based at least partially upon the current pixel and its collocated reference pixel. Next, an index is determined based upon the motion delta value and a motion history value corresponding to the spatial location of the current pixel, but from the previous frame. Using the index, a first filtering coefficient may be selected from a motion table. After selecting the first filtering coefficient, an attenuation factor may be selected from a luma table based upon the value of the current pixel, and a second filtering coefficient may subsequently be determined based upon the selected attenuation factor and the first filtering coefficient. The temporally filtered output value corresponding to the current pixel may then be calculated based upon the second filtering coefficient, the current pixel, and the collocated reference pixel.