Nicolas, Great analysis. This will help me. I will try to get to this tonight/tomorrow.
Do you have before and after vids? scott -------------- Original message ---------------------- From: Nicolas <[EMAIL PROTECTED]> > Hello, > > I did some tests with the motion effect, and I got a result which > satisfies me. In fact, that effect was easier to use than I thought. > Here is some feedback about it. > > I used the motion effect to stabilize DV footage. The camcorder was > installed on my helmet while I was following a group of motorbikes. My > motorbike's shocks are in good condition and the position of the > camcorder helps to reduce vibrations. However, the road was quite bumpy > and the footage is finally still jerky. My camcorder includes an optical > stabilization system (Panasonic OIS), but it's not that efficient in > such harsh conditions. > > Firstly I selected on the timeline the part of the footage I wanted to > stabilize, using the in and out points. Then, I applied the motion > effect on that part of the video. I did not use 2 tracks (top and > bottom). Motion tracking was done and applied on the same track. > > I tried the default options. I used the following parameters to define a > block on one of the motorbikes which was in front of me: > - translation block size > - block X, Y > And I rendered the video. Even if my computer got more than 10.500 > bogomips (dual-core over-clocked AMD64 X2 4600+), it was not convenient > to preview the result in the compositor. That is normal and described in > the official manual. Since the option "Draw vecors" was enabled, I was > able to see the block position and the vector shape on the video. > > I noticed the block was following the motorbike, and the picture was > stabilized. That was a good result for a first try. However there were > some problems. At the beginning of the video, the centre of the block > was positioned on the plate of the motorbike. Sometimes that centre > quickly moved to another part of the motorbike (the rear passenger > handle, located just behind the pilot). That resulted in the frame being > suddenly translated by a vector of several tens of pixels. Therefore the > video was quite stable, but sometimes there were large and quick shakes. > > I tried again and changed some parameters. I decided to select the > "Previous frame same block" option. That option is recommended for > stabilizing jerky camcorder footage. Its goal is not to "follow" an > object. The block stays exactly at the same place during all the effect > length. I enlarged the block and selected almost all of the upper half > part of the video. I also selected the "Stabilize subpixel" option. That > gives a finer stabilization. Finally I also rduced the "Maximum absolute > offset" value to limit the stabilization amplitude. I prefer to get a > non-perfect stabilization on some places on the video, than having a > very large black border on one side of the picture during big shakes. > > I rendered the video and got a better result. The image was stable and > there were no sudden translation anymore. Since the result was good, I > re-rendered after having deselected the "Draw vectors" option. The block > and vectors were not drawn anymore on the video. > > I then imported the resulting rendered .dv file into my project. I had > to zoom in the picture, in order to get ride of the black borders > generated around the picture. I had to tweak the projector keyframes. > > During my tests, I noticed increasing the "Translation search steps" > increases a LOT the rendering time. You can set it from 128 up to > 131072, and the rendering time is a lot longer when using the maximum > value. I reduced that value down to 128, and I compared the result with > what I got when using the maximum value (131072 steps). It is indeed > very easy to compare the result, since the translation x and y values > found by the motion effect are displayed in the console. What I did was > copy/paste the console output to text files, and compare them using the > diff utility. There was absolutely no difference at all in the result. I > then set the "Translation search steps" value at 128. I assume > increasing the value can be useful in some cases, but I do not know > which ones. > > The main problem I had was working with the stabilized video. The black > borders force one to zoom in and define projector keyframes to move the > projector around the screen. Since my original footage was quite shaky, > the black borders were large at some places. Moving the projector > implies having some camcorder movement, but since the projector > movements are slow, the result is far better than the jerky original > footage. The more your footage is jerky, the more you have to zoom in to > discard the black borders. That is why the result should be better with > high-def footage than with "normal DV" footage. I also had some problems > to stabilize panning movements. A large black border often appears on > one side of the video. > > Nicolas. > > _______________________________________________ > Cinelerra mailing list > [email protected] > https://init.linpro.no/mailman/skolelinux.no/listinfo/cinelerra _______________________________________________ Cinelerra mailing list [email protected] https://init.linpro.no/mailman/skolelinux.no/listinfo/cinelerra
