A method of extracting feature descriptors for a video, the video including a sequence of pictures, the method comprising: identifying a first key picture and a second key picture later in the sequence than the first key picture; extracting a first set of feature descriptors from the first key picture and a second set of feature descriptors from the second key picture; identifying a set of pairs of feature descriptors, where each pair includes one descriptor from the first set and one descriptor from the second set; generating motion information describing a motion field between the first key picture and the second key picture; and filtering the set of pairs of feature descriptors based on correlation with the motion information to produce and output a subset of persistent descriptors, wherein identifying the first and second key pictures comprises analyzing picture correlation of the sequence of pictures and dividing the sequence of pictures into segments exhibiting high picture correlation among respective pictures of a segment, each segment having a respective first key picture and a respective second key picture, wherein filtering the set of pairs of feature descriptors includes, for each pair, determining, based on the motion information and a location of pair's descriptor from the first key picture, an estimated location in the second key picture; determining whether the pair's descriptor from the second key picture is located within a search window centered on the estimated location; and if so, retaining the pair in the subset of persistent descriptors, and if not, excluding the pair from the subset of persistent descriptors. identifying a first key picture and a second key picture later in the sequence than the first key picture; extracting a first set of feature descriptors from the first key picture and a second set of feature descriptors from the second key picture; identifying a set of pairs of feature descriptors, where each pair includes one descriptor from the first set and one descriptor from the second set; generating motion information describing a motion field between the first key picture and the second key picture; and filtering the set of pairs of feature descriptors based on correlation with the motion information to produce and output a subset of persistent descriptors, wherein identifying the first and second key pictures comprises analyzing picture correlation of the sequence of pictures and dividing the sequence of pictures into segments exhibiting high picture correlation among respective pictures of a segment, each segment having a respective first key picture and a respective second key picture, wherein filtering the set of pairs of feature descriptors includes, for each pair, determining, based on the motion information and a location of pair's descriptor from the first key picture, an estimated location in the second key picture; determining whether the pair's descriptor from the second key picture is located within a search window centered on the estimated location; and if so, retaining the pair in the subset of persistent descriptors, and if not, excluding the pair from the subset of persistent descriptors. determining, based on the motion information and a location of pair's descriptor from the first key picture, an estimated location in the second key picture; determining whether the pair's descriptor from the second key picture is located within a search window centered on the estimated location; and if so, retaining the pair in the subset of persistent descriptors, and if not, excluding the pair from the subset of persistent descriptors. if so, retaining the pair in the subset of persistent descriptors, and if not, excluding the pair from the subset of persistent descriptors. <EOS>