CV_CAP_PROP_FPS return -nan

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Hello all,

I am trying to get FPS (Framrate per sec) by using VideoCapture and CV_CAP_PROP_FPS. But for many videos, I am getting FPS as -nan.

OPENCV VERSION: 2.4.10 FFMPEG VERSION: 2.7.6

Can You Guys Please help me to sort out these issues??

Thanks in advance...........