v4l2videodec: use visible size, not coded size, for downstream negotiation filter

gst_v4l2_probe_caps() returns the coded size, not the visible size. Subtract
the known padding from probed caps with the coded size before using them as
filter for caps negotiation with downstream elements.

https://bugzilla.gnome.org/show_bug.cgi?id=766382
1 file changed