xfade AVOptions:
transition <int> ..FV...... set cross fade transition (from -1 to 34) (default fade)
custom -1 ..FV...... custom transition
fade 0 ..FV...... fade transition
wipeleft 1 ..FV...... wipe left transition
wiperight 2 ..FV...... wipe right transition
wipeup 3 ..FV...... wipe up transition
wipedown 4 ..FV...... wipe down transition
slideleft 5 ..FV...... slide left transition
slideright 6 ..FV...... slide right transition
slideup 7 ..FV...... slide up transition
slidedown 8 ..FV...... slide down transition
circlecrop 9 ..FV...... circle crop transition
rectcrop 10 ..FV...... rect crop transition
distance 11 ..FV...... distance transition
fadeblack 12 ..FV...... fadeblack transition
fadewhite 13 ..FV...... fadewhite transition
radial 14 ..FV...... radial transition
smoothleft 15 ..FV...... smoothleft transition
smoothright 16 ..FV...... smoothright transition
smoothup 17 ..FV...... smoothup transition
smoothdown 18 ..FV...... smoothdown transition
circleopen 19 ..FV...... circleopen transition
circleclose 20 ..FV...... circleclose transition
vertopen 21 ..FV...... vert open transition
vertclose 22 ..FV...... vert close transition
horzopen 23 ..FV...... horz open transition
horzclose 24 ..FV...... horz close transition
dissolve 25 ..FV...... dissolve transition
pixelize 26 ..FV...... pixelize transition
diagtl 27 ..FV...... diag tl transition
diagtr 28 ..FV...... diag tr transition
diagbl 29 ..FV...... diag bl transition
diagbr 30 ..FV...... diag br transition
hlslice 31 ..FV...... hl slice transition
hrslice 32 ..FV...... hr slice transition
vuslice 33 ..FV...... vu slice transition
vdslice 34 ..FV...... vd slice transition
duration <duration> ..FV...... set cross fade duration (default 1)
offset <duration> ..FV...... set cross fade start relative to first input stream (default 0)
expr <string> ..FV...... set expression for custom transition