It is also possible, but more difficult, to perform reverse telecine without prior knowledge of where each field of video lies in the 2:3 pulldown pattern. This is the task faced by most consumer equipment such as line doublers and personal video recorders. Ideally, only a single field needs to be identified, the rest following the pattern in lock-step. However, the 2:3 pulldown pattern does not necessarily remain consistent throughout an entire program. Edits performed on film material after it undergoes 2:3 pulldown can introduce "jumps" in the pattern if care is not taken to preserve the original frame sequence (this often happens during the editing of television shows and commercials in NTSC format). Most reverse telecine algorithms attempt to follow the 2:3 pattern using image analysis techniques, e.g. by searching for repeated fields.