Force field for the output video frame.

The setfield filter marks the interlace type field for the output frames. It does not change the input frame, but only sets the corresponding property, which affects how the frame is treated by following filters (e.g. fieldorder or yadif).

This filter accepts a single option mode, which can be specified either by setting mode=VALUE or setting the value alone. Available values are:

auto

Keep the same field property.

bff

Mark the frame as bottom-field-first.

tff

Mark the frame as top-field-first.

prog

Mark the frame as progressive.