I thought I would have a go at this as I've not done tracking before.
I downloaded some random dash cam footage from YouTube, and in about 15 minutes produced the following result:
Here are my nodes as screenshot:
And as text, which can be copied and pasted into Resolve or Fusion Studio:
Link to view and download nodes as textNote: I did this in Fusion Studio, hence the Loader and Saver nodes. In Resolve these would be MediaIn and MediaOut respectively.
Here's the method I followed:
1. I went through the 350 frames of footage and noted there was a point where the license plate was occluded (frames 240 to 284).
I therefore decided to follow the advice I saw recently in Brian / Prophetless' tutorial (link at the end), and do two separate tracking operations, before and after occlusion.
1. I connected a normal Tracker node to my Loader (MediaIn)
2. Starting at frame 270, I dragged the tracker to concentrate on the license plate, like so:
3. I set the Tracker to Adaptive Mode: Best Match (as I've seen in a Vito / Captain LeBuck tutorial)
4. I clicked Track Forward From Current Time, and it tracked reasonably well to the end
5. I then went to frame 240, re-positioned the tracker over the plate in this position, and then did Track
Backward From Current Time. It managed to track nearly all the way to the start, just the first few frames weren't great
6. I now had a gap between frames 240 and 284. Some of the time the license plate was fully occluded, but sometimes it was partially visible, so I wanted to try and fill in this gap.
I first tried adjusting the spline handles in the Spline Editor, as suggested in the Prophetless tutorial, but didn't get good results.
So instead I set the frame to 240, moved the tracker to another part of the car, and then switched Path Center to "Tracker Append". The idea here is to track a different part of the car, and the Tracker will apply this to the original track, automatically applying the offset.
This kind of worked, but still not great. But it did fill in some of my missing keyframes where the occlusion happened.
7. I created a Blur node, connected to Loader / MediaIn. Then I created a Polygon node, put the viewer on a frame around the middle where the number plate was clearly visible, and then drew a 4-point polygon mask around it.
8. I connected the Polygon to the Effect Mask of the Blur node, increased the Blur amount, and applied a small amount of soft edge to the mask. I put the Blur node into the Viewer and confirmed that on this frame, the number plate was properly blurred
9. On the Polygon node, I right-clicked on Center and chose "Path", giving me an animation path on the center. Now in Modifiers, I right-clicked on Path1 : Center, and chose Connect To -> Tracker 1 -> Unsteady Position.
My mask center was now following the Tracker position.
10. The one remaining issue is that the car's number plate gets bigger and smaller and changes perspective as the car moves across the front of the camera, and then away into the distance.
So I now keyframed the Polygon mask across the duration of the 350 frames. In total I placed about 25 keyframes, adjusting the mask size and sometimes position wherever it wasn't exactly covering the plate, or was also blurring other parts of the car.
I had to add 10 keyframes in a row on the first few frames, because this part hadn't been fully tracked - maybe I could have fixed that up in the tracker instead.
My general principle for applying keyframes was to check every 50 frames or so (out of 350) to see if the position was OK there, adjust it if needed, and then check half way between each existing keyframe, and so on.
11. I also applied 4 x Level keyframes, to turn the mask off in the section where the number plate was fully occluded.
And that's it. This certainly wasn't super clean, because I felt like I had to add a few more Polygon mask keyframes than I would have liked. Probably I could have got a better track and reduced this number. Also, there's a few places where the mask shifts around a bit, which could have used a couple more mask keyframes to clean up. I didn't bother for this example.
But still, I think this is a viable and fairly quick method; the whole thing only took about 15 minutes and it was the first time I'd ever done it. I feel like it wouldn't have taken much longer even if there had been a lot more footage.
Hope that's some use to the OP. Even if not, I was glad to get a practical reason to try out the tracker for the first time
Here's the tutorial I watched which showed the basic tracker and mask-attachment techniques:
Mon Aug 31, 2020 8:00 pm
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