Number of lines in region.
X coordinate within the region which is anchored to the video viewport.
Y coordinate within the region which is anchored to the video viewport.
Scroll value of the region.
X coordinate within the video viewport to which the region anchor point is anchored.
https://www.w3.org/TR/webvtt1/#webvtt-region-viewport-anchor
Y coordinate within the video viewport to which the region anchor point is anchored.
https://www.w3.org/TR/webvtt1/#webvtt-region-viewport-anchor
Width of the region.
ID of the region.
https://www.w3.org/TR/webvtt1/#webvtt-region-identifier