I did a RAM dump and was able to find two offsets with battle video data.
data(0x32991DDC, 0x2BC0, filename='Video', pid=0x29)
data(0x32AC55E4, 0x2BC0, filename='Video', pid=0x29)
I tested it once with the latter command in my copy of Ultra Moon and was able to dump the video and read it with...