freeze frame when cam switch

At every switch line and switch off, there is a freeze frame (16 frames exactly) on the file recorded.
I edit with fcpx but expect more (sound connection trouble and less work).

Idea ?
Thanks

My Config :
MBPretina2012 + 2 cam firewire/thunderbolt + audiousb
BoinxTV : layer cam1 backward still active and layer cam2 forward (line or off)

Whenever a camera isn’t visible (or no more used for rendering) BoinxTV switches off the processing of the cam in order to save performance. If you switch it back on, it takes some frames until all buffers are filled. the solution to this is, to install a Placer layer above all other layers, and configure it that way, that it places the video outside the video frame, so that it isn’t visible in the recoding anymore, but keeps alive the camera processing. (Settings for the Placer: “Video Source”=the cam in question, “Show As”=Custom, “Zoom”=1%, “X-Position”= as far left or right as it goes, don’t forget to push the layer live!). Since the rendering of the video in that layer is offscreen, it won’t take much performance. You have to create such a “Keep camera alive” layer for each source you won’t let go away.