optical flow to matte

[akar]

hello,

i have a shot with a gazillion frames filmed from a tripod, with a steady background. Now there are a lot of people and some animals walking trough that frame that i have to roto out.
I stabilized it because it was a bit shaky

it can't be keyed with nothing at all (i tried in nuke, some colleagues in flame) i tried with a clean plate that i painted, hard degraining on the shot, but still not a god matte.

i heard something about a way to use the vectors from an optical flow to do that.
Now i "tracked" with pftrack it made some vectors but i don't know how to use them to make a matte (i also got pftrack to calculate the z depth but it gave me crap)

i've looked into furnace rig removal, but i don't need a clean plate and i don't think it could gave me a matte for the movement, if i'm wrong please tell me.

hope u understood what i would need, any advice on how i could get a result without roto would help me,

thank u, have a god day

[Andreas.Jablonka]

do you NEED all frames? you could frame avarage all frames which could remove the people and leave a minor blur. but if your background action is important then forget this technique.

[akar]

thanks for the reply

unfortunately i NEED all the frames. i frame averaged the shot to help me with the clean plate, but the difference keyer did not gave me an acceptable result (it's a 2k film, but it's very noisy, low contrast, 8 bit footage).

I need to replace the bg and keep the people.

still hoping for a magic trick

[jkenko]

Well, what about Furnace's Edge matte? Isn't it your solution?

[akar]

thank u for the suggestion, but i don't know edge matte and it's only for shake and unfortunately that's a bit of a issue. If u used it, can u please tell me how good it really works.