A picture in which the two fields in a frame are coded independently. Field pictures always come in sets of two fields, which are called top field and bottom field, respectively. When the first field is coded as a P- or a B-picture, the second picture must be coded in the same manner; however, if the first field is coded as an I-picture, the second field may be coded as either an I-picture or a P-picture (that is predicted from the first field).