libv4l2: error setting pixformat: Dispositivo o risorsa occupata

(cheese:17200): cheese-WARNING **: Il device «/dev/video0» è occupato: gstv4l2object.c(2524): gst_v4l2_object_set_format (): /GstCameraBin:camerabin/GstWrapperCameraBinSrc:camera_source/GstBin:bin17/GstV4l2Src:video_source:
Call to S_FMT failed for YU12 @ 1280x720: Dispositivo o risorsa occupata