VideoCapture::get(CV_CAP_PROP_POS_MSEC) returns -1

#videocapture

asked 2014-03-26 12:29:35 -0600

us62
1 ●1 ●3

updated 2014-03-26 12:32:12 -0600

I am trying to get the timestamp at which the frame was captured using VideoCapture::get(CV_CAP_PROP_POS_MSEC) but i get the value -1. Am i doing something wrong or is there another way of retrieving the timestamp at which a particular frame was captured from the camera?
If i just take the millisecond count using GetTickCount() function from windows API just before capturing a frame, will it represent an accurate timestamp for the captured frame ?

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answered 2014-03-26 12:40:05 -0600

xaffeine
829 ●2 ●12 ●25

On question 2, if you want to use cv::getTickCount() to estimate a time stamp, you should call it immediately after a grab, not before, since grab() may wait for a frame to be available.

I'll leave question 1 to others, other than to say I wouldn't surprised if prop_pos_msec doesn't work for live streams.