Pose Liveness Detection
Liveness detection is the process whereby facial recognition software attempts to differentiate between genuine live faces and spoofed fake faces. (such as from a photo of a face) SAFR uses a face’s center pose quality to attempt to detect liveness.
Pose liveness detection operates as follows:
- State A: An unrecognized face needs to be recognized.
- State B: Proof of liveness will pursued as follows:
- The recognized face is tracked at the rate of at least 25 frames per second.
- Any loss of tracking (occurrence of lingering for more than 1 frame) or a detection gap > 40 ms in frame capture time results in the need to re-recognize the face and thus a return to State A.
- Pose quality must maintain a score of 0.5 or higher for 3 consecutive frames and at least one of the samples must have a profile pose confidence of 35% or less to trigger the transition to the next state, State C.
- State C: A smooth transition to profile pose will be pursued as follows:
- The face is tracked at the rate of at least 25 detections per second.
- Any loss of tracking (occurrence of lingering for more than 10 frames) or a detection gap > 40ms in frame capture time results in the need for re-recognition and thus return to State A.
- A momentary loss of tracking (recovered in less than 10 frames) will require a center pose quality difference from the prior frame of no less than 0.15.
- If change in identity is detected as part of prescribed re-recognition, State B will restarted.
- Pose quality must be observed to transition to score of 0.26 or lower for at least 3 consecutive frames and with 66% of at least 3 images but no more than 30 images immediately proceeding with scores observed > 0.26 and < 0.5 and in decreasing sequence to trigger transition to State D.
- For example:
0.45, 0.37, 0.23, 0.12, 0.24
- This algorithm can interpreted as requiring presence of descending strand of samples being at least 66% of the number of samples with min number being specified in preferences and max number being 30 (~1 second).
- State D: After the profile pose state has changed, a verification call is issued to obtain a similarity score to the identity obtained in State A.
- The verification call must indicate at least a 86% match.
- A response from recognition must also indicate that the face is in profile pose, based on profile pose confidence returned and threshold set.
- If both of above are met, liveness detection will conclude.
- If both aren’t true, re-recognition will continue immediately for as long as the pose quality score remains at 0.26 or lower until successful confirmation of pose and 86% identity match is confirmed.
- If pose score exceeds value of 0.26 for 3 consecutive frames, transition back to state B will occur.
- Any loss of tracking (occurrence of lingering) will result in need for re-recognition and thus return to State A.
See Also