Is it to possible to have parallel access of Pi's camera to take stills, when it is streaming through FFMpEG video streaming ?, if not, then how both ( still and streaming) can be processed at the same time, pl reply.
Only one process can access the camera module at a given time, so you couldn't have, say,
raspivid feeding data to ffmpeg and simultaneously use
raspistill to capture images. That said, the underlying firmware does support the concept of a "splitter" component which can be used to accomplish something similar (e.g. by connecting one port of the splitter to a video encoder, and another to an image encoder).
An example of using this from python is given in this recipe.
This can be possible if you use opencv.. Video grab funtion might help.. you can get furthur details on this link.. http://docs.opencv.org/modules/highgui/doc/reading_and_writing_images_and_video.html#videocapture-grab