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AE motion tracks differently when using "Analyze 1 frame forward" vs "Analyze forward"?

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Mike Imam
AE motion tracks differently when using "Analyze 1 frame forward" vs "Analyze forward"?
on Aug 18, 2012 at 2:03:29 pm

Hi all,

Strange problem here: I'm trying to motion track the position of a point in my footage. Lighting is not ideal so AE CS5 is having a bit of trouble "sticking" to my selected point, and I have to constantly stop the tracking when using "Analyze forward" to reposition my track point. Weirdly though, when I stop the tracking, move back one frame (using command-right arrow), then press "Analyze 1 frame forward" instead of the "Analyze forward" button, AE usually finds the point and it tracks well.

Any idea why this is happening? In theory there should be no difference between the two functions except that one moves ahead automatically and the other is one frame at a time? It would save me a ton of time if I didn't have to stop the tracking every few frames. Any techniques or help would be appreciated in improving the tracking.

Side note: I tried viewing only the blue channel by selecting it in my Layer window (my track points are blue), but it seems to have not made a difference (despite choosing RGB as the channel in tracker options)? Let me know if this is a waste of time.

Thanks!


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Roland R. Kahlenberg
Re: AE motion tracks differently when using "Analyze 1 frame forward" vs "Analyze forward"?
on Aug 18, 2012 at 7:56:09 pm

[Mike Imam] "Side note: I tried viewing only the blue channel by selecting it in my Layer window (my track points are blue), but it seems to have not made a difference (despite choosing RGB as the channel in tracker options)? Let me know if this is a waste of time."

It's a waste of time. Best to pre-process the footage in a pre-comp to enhance the contrast of the image. If you think this can be achieved by only tracking the blue channel then use Shift Channels to move all the RGB channels to assume just the blue channel.

[Mike Imam] "In theory there should be no difference between the two functions except that one moves ahead automatically and the other is one frame at a time?"

In theory, if they were the same, there would only be a single option - ie track single frame or track multiple frames. So, theoretically, they are not the same. As you have noticed there is a difference in the results between the two.

Artificial intelligence (AI) is built into every tracking algorithm. What you have experienced is simply a side-effect of this AI. In practice, when the tracking algorithm loses its track with automatic tracking, it is a good idea to go back to the last good frame and then to proceed with single-frame tracks for 1-3 frames and then to proceed again with multi-frame tracking. It seems that the 1-3 single frame tracks provides the tracking algorithm with more confidence for a multi-frame track.

Just remember to apply this technique in the future and you will have many more successful tracks. You should also set the Options to Stop Tracking when Confidence Level is below 95%. This will ensure that the algorithm will stop automatically at a 'bad' frame rather than you having to eyeball the tracking result in realtime.

HTH
RoRK

Intensive AE & Mocha Training in Singapore and Malaysia
Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer


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Mike Imam
Re: AE motion tracks differently when using "Analyze 1 frame forward" vs "Analyze forward"?
on Aug 19, 2012 at 2:43:50 pm

Makes total sense. This is helpful. Thanks for the very complete answer!


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Roland R. Kahlenberg
Re: AE motion tracks differently when using "Analyze 1 frame forward" vs "Analyze forward"?
on Aug 19, 2012 at 4:39:24 pm

You're welcome Mike. BTW, you can disable or tweak the view of the tracking path in the Prefs>Display Motion Path section. Simply select the option that provides the clearest view of the Attach Point and Track/Search regions.

Cheers
RoRK

Intensive AE & Mocha Training in Singapore and Malaysia
Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer


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