Download pdf - Time lapse and stabilising a sequence of images (GStreamer Conference 2011)

Image Stabilisation

Guillaume EmontIgalia

Image StabilisationHoliday pictures

that picture is not by me(it is © 2011 Ugo Riboni)

...but I was there!

with a plan!

What the balloon sees

Let's go higher

Higher!

HIGHER!

I said: HIIIGHEEEER!

Ok, that will do

We wanted to take pictures for 7 days

The balloon agreed to 4 hours and a half

There was an intimate ceremonywith family and friends

Nice pics! ...now what?

Time lapse!

-- [timelapse-theory.png] [fit] [text-align=center] <span font="20">(image from wikipedia under GFDL)</span> -- [timelapse-theory.png] [fit] [text-align=center] Crazier: one frame per minute!

Removing the training wheels:No tripod.

(luckily, we have OpenCV)

Stabilisation in post-processing:

1. detect the movement (optical flow)

Optical flow: position changes of features

Stabilisation in post-processing:

2. compensate

Compensation:

OpenCV provides nice tools(but we won't talk about them here)

Optical flow: a few algorithms

Horn-Schunck

Lucas-Kanade

gst-launch-0.10 filesrc location=shaky-hippo.ogg ! decodebin ! ffmpegcolorspace ! opticalflowcorrector algorithm=1 ! ffmpegcolorspace ! xvimagesink

Err, yeah but...What about the balloon pictures?

Horn-Schunck

Lucas-Kanade

SpeededUpRobustFeature

SURF

Woohoo!

Bonus track

TODO:Check out the optical flow work by David Jordan (used for slow motion)and try to apply it to stabilisation

TODO:better compensation (tesselation?)

TODO:try more algorithms (BRIEF and ORB)

TODO:automatic optimal choice of algorithm and parameters

TODO:reimplement in C and put in -bad?

TODO:for videos: movement prediction/averaging(follow the intended movement of the cameraman)

questions?

Image credits:training wheels: CC BY-NC-SA 2.0 Dale Basler http://www.flickr.com/photos/baslercast/surf: CC BY-NC-SA 2.0 Guilherme Meneghelli http://www.flickr.com/people/iberere/last one: CC BY-NC-SA 2.0 Martin Ibert http://www.flickr.com/photos/mar_ibert/

Thanks! http://www.gitorious.org/gststabilizerhttp://balloonfreaks.mooo.com/http://emont.org/blog/http://www.igalia.com/[email protected]