Itseez/opencv — pull request #740 by evil0sheep (2013-04-02 17:36:37+00:00)
Title: Added v4l2 support for getting capture property CV_CAP_PROP_POS_MSEC

Returns the millisecond timestamp of the last frame grabbed or 0 if no frames have been grabbed. Used to successfully synchronize 2 Logitech C310 USB webcams to within 16 ms of one another.