 Format identifiers like 576i50 and 720p50 specify the frame rate for progressive scan formats, but for interlaced formats they typically specify the field rate (which is twice the frame rate).This can lead to confusion, because industry-standard SMPTE timecode formats always deal with frame rate, not field rate.To avoid confusion, SMPTE and EBU always use frame rate to specify interlaced formats, e.g., 480i60 is 480i/30, 576i50 is 576i/25, and 1080i50 is 1080i/25.