Troubleshooting Auto-Tracks

No matter how sophisticated tracking becomes, some sequences are inevitably going to cause problems. There are a number of controls on the Settings tab that can help achieve a better result. Try adjusting these settings and re-tracking to improve your results.

Tip:  You can also add User Tracks to improve the result further. See Manual Tracking for more information.

Feature Settings

These controls determine the number and position of auto-detected features that C_Tracker analyzes per frame. Enable Preview Features so that you can see how altering the controls affects the positioning of features across the image.

Note:  Tracking takes longer with Preview Features enabled, so don't forget to disable it before re-tracking.

• Number of Features - sets the number of features you want to track in each frame.

In most cases, the default 300 should be sufficient, but in difficult sequences you may consider using a higher number.

A low Number of Features.	A high Number of Features.

Tip:  Check enforce to keep the number of tracks constant, even if it means stopping some tracks and seeding new ones when Track forwards and backwards is enabled.

• Feature Spread - sets the spread of features over the image.

A high value selects points that are distinct in local regions, whereas lower values select more prominent points in areas of high contrast.

A low Feature Spread.	A high Feature Spread.

• Feature Separation - sets the distribution of features in relation to each other.

To force feature separation and spread features evenly over the image at even distances, enter a high feature separation value.

A low Feature Separation.	A high Feature Separation.

Tip:  Check enforce to separation, even if it means fewer overall tracks.

Check Refine Feature Locations to lock detected features to local corners. If you activate this, C_Tracker finds the closest corner point in your footage and locks the feature to it.

Tracking Settings

You can improve a set of feature tracks using the following controls and then retrack to improve your chances of getting a good solve:

• Track forwards and backwards - enabling this control can improve stablization results, but tracks take longer to generate.

• Patch Size - sets the size of the pattern that C_Tracker looks for when analysing the sequence.

Reducing this value helps to match the pattern more closely, but higher values can produce more stable tracks.

• Minimum Length - sets a threshold value for the minimum acceptable track length. Tracks that fail to stick to the associated feature for this amount of frames are rejected.

In long slow camera moves, it is best to solve from long tracks generated in the shot. If there are lots of short tracks, this can lead to noise on the calculated camera. Try removing the short tracks before solving.

A low Minimum Length.	A high Minimum Length.

• Track Error Threshold - C_Tracker’s tolerance to change along the track is determined by this control.

Increasing this threshold makes tracking more tolerant to image changes, potentially producing longer tracks.

A low Track Error Threshold.	A high Track Error Threshold.

Note:  The Track Error Threshold is also applied to User Tracks by default. If you don't want User Tracks to be subject to this threshold, disable the apply to user tracks control.

• Track Smoothness - sets the threshold for smooth track generation. Adjusting this value can be useful in preventing poor tracks in complex sequences.

Increasing the smoothness value removes tracks that fail over time.

• Track Consistency - sets the threshold for how inconsistent a feature track can be before C_Tracker discards it and reseeds in a different location.

Higher values allow for less inconsistency.

When you're happy with the number and distribution of tracked features, you can solve the camera and then use the results for stabilizing or match-moving. See Solving Cameras for more information.