From: Bryce Chester Newman <bryce.newman@gettyimages.com>

Export the poster_time_location if available.
The poster_time_location is calculated using
the poster_time / time_scale = X seconds.
The value of poster_time_location indicates
where in the video the poster frame is.

Addresses feedback
from https://www.mail-archive.com/ffmpeg-devel@ffmpeg.org/msg138122.html.

Signed-off-by: Bryce Chester Newman bryce.newman@gettyimages.com

Submitted-As: https://master.gitmailbox.com/ffmpegdev/pull.41.ffstaging.FFmpeg.1664813294282.ffmpegagent@gmail.com