a #GstBuffer
0 for progressive or field 1 and 1 for field 2
if true then bar data specifies letterbox, otherwise pillarbox
If is_letterbox is true, then the value specifies the last line of a horizontal letterbox bar area at top of reconstructed frame. Otherwise, it specifies the last horizontal luminance sample of a vertical pillarbox bar area at the left side of the reconstructed frame
If is_letterbox is true, then the value specifies the first line of a horizontal letterbox bar area at bottom of reconstructed frame. Otherwise, it specifies the first horizontal luminance sample of a vertical pillarbox bar area at the right side of the reconstructed frame.
the #GstVideoBarMeta on buffer.
See Table 6.11 Bar Data Syntax
https://www.atsc.org/wp-content/uploads/2015/03/a_53-Part-4-2009.pdf
Attaches #GstVideoBarMeta metadata to buffer with the given parameters.