Remove background from a video sequence
by Per Ottesen
on
Jan 23, 2008 at 8:34:38 pm
I have a greyscaled video (not so good quality), where I would like to remove the background, so I can isolate some few people who are walking in the sequence.
I have a frame with no people on, so I will be able to use this for a kind of extraction, but how ???
The video is taken from a camcorder that are locked on a wall, so there is no camera movement/zoom.
Re: Remove background from a video sequence by Kevin Camp on Jan 23, 2008 at 8:48:31 pm
there is an effect called difference matte that does what you are looking for. its a standard effect, just bring the clean still and the image sequence into the same comp, apply the effect to the sequence and select the still as the difference layer.
ae will try to remove the pixels that are the same, leaving you with jus tthe subject... in theory. things like noise and compression artifacts will make this process more difficult, so getting a great key with not-so-great-footage and this method may be tricky...
Re: Remove background from a video sequence by Per Ottesen on Jan 24, 2008 at 7:54:31 am
Hi Kevin!
I've tried this dfference matte, but since the materiale has so poor quality, and has no color but only greyscale, the people are being removed also, when the background is removed.
I have earlier seen an effect, where it was possible to paint the content of one frame on another frame in the sequence, but I don't know if that's possible in AE.
IF it is, I maybe could isolate the background, increase the contrast and then have more clear differences to use the difference matte on.
Re: Remove background from a video sequence by Peter Rongsted on Jan 24, 2008 at 11:40:08 am
If you have enough contrast between the people walking and the background you may be able to crush the whites and blacks together with a levels and a curves effect. Thus trying to create a luma matte.
May not work if the quality is too poor, but worth a try.
Re: Remove background from a video sequence by Kevin Camp on Jan 24, 2008 at 3:57:46 pm
i'm pretty sure i read a few rotoscoping tutorials here that may be the best way to go for bad footage. i remember they used vector paint to paint a matte to isolate the subject. unfortunately, i can't get to the tutorials page to find the tutorial(s) i'm thinks of (i'm not sure if it is a firewall problem on my end, or a cow problem).
i was able to google the cow library and turn up these:
hopefully you can get to the tutorials page to see if these may help you. one of the ones i was thinking was working with sports footage, if that helps.
