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Term: Field order

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Term: Field order

Definition:

Field Order (also referred to as Field Dominance) determines which of the two fields that make up a frame is displayed first.

An analog frame is made up of two fields, each field containing every other line in the frame. On an interlaced display, such as a CRT, each field is displayed one after another. Digital files created from analog content, and early digital video content (such as MiniDV, DVCAM, DCVPro, etc�) are stored as interlaced to retain the original organization of the content. However, when an interlaced file is displayed on a progressive display (such as a computer monitor) both fields are displayed at the same time. Digital files containing interlaced content should define their Field Order to express which of the two fields would be displayed first in an interlaced system, despite them being displayed simultaneously in a progressive system. This field must be properly defined to playback a digital file in an interlaced display system. This field is also referenced during de-interlacing, either by a playback system with built-in de-interlacement, or when transcoding to a new de-interlaced file. Field Order must be defined in order for this de-interlacement to occur properly, or the resulting image will contain interlacing artifacts.

SMPTE standard 125M-1995 references fields as field 1 (odd) and field 2 (even); video editing and transcoding software usually refers to field order in interlace video as top or bottom field.

Values for field order include:

  • Upper field first, lower field first Top field first, bottom field first Field 1, Field 2
  • Field Order is often expressed as Top Field First (TFF) or Bottom Field First (BFF). It can also be expressed as Odd or Even. TFF and Odd both refer to the field containing odd numbered lines, and BFF or Even both refer to the field containing even numbered lines.
Category:
Video
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