Expressions

The 'alpha', 'x0' and 'y0' expressions can contain the following parameters.

'w'

'h'

input width and height

'n'

the number of input frame, starting from 0

'pts'

the PTS (Presentation TimeStamp) time of the filtered video frame, expressed in TB units, NAN if undefined

'r'

frame rate of the input video, NAN if the input frame rate is unknown

't'

the PTS (Presentation TimeStamp) of the filtered video frame, expressed in seconds, NAN if undefined

'tb'

time base of the input video