Webcam n'est plus détectée sous ubuntu 14.04

Bonjour,
Asus Intel Core i5-7200U
ubuntu 14.04 + Windows 10
webcam n'est plus détectée sous ubuntu sachant qu'elle fonctionnait auparavant
alors que sous Windows est détectée
j'essaie bcp de tests mais en vain
cheese ne donne rien
J'ai déjà suivi ce site :

https://forums.commentcamarche.net/forum/affich-31113438-probleme-webcam-sur-linux-mint-17

voici les résultats trouvés :

~$ lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 004: ID 0bda:b721 Realtek Semiconductor Corp.
Bus 001 Device 003: ID 13d3:5a01 IMC Networks
Bus 001 Device 002: ID 275d:0ba6
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub


~$ ls /dev/video*
ls: cannot access /dev/video*: No such file or directory


~$ gstreamer-properties
(gstreamer-properties:3425): Gtk-WARNING **: Unknown property: GtkDialog.has-separator
(gstreamer-properties:3425): Gtk-WARNING **: Unknown property: GtkDialog.has-separator
gstreamer-properties-Message: Skipping unavailable plugin 'artsdsink'
gstreamer-properties-Message: Skipping unavailable plugin 'esdsink'
gstreamer-properties-Message: Skipping unavailable plugin 'sunaudiosink'
gstreamer-properties-Message: Skipping unavailable plugin 'glimagesink'
gstreamer-properties-Message: Skipping unavailable plugin 'sdlvideosink'
gstreamer-properties-Message: Skipping unavailable plugin 'v4lmjpegsrc'
gstreamer-properties-Message: Skipping unavailable plugin 'qcamsrc'
gstreamer-properties-Message: Skipping unavailable plugin 'v4lsrc'
gstreamer-properties-Message: Skipping unavailable plugin 'esdmon'
gstreamer-properties-Message: Skipping unavailable plugin 'sunaudiosrc'


~$ lspci
00:00.0 Host bridge: Intel Corporation Device 5904 (rev 02)
00:02.0 VGA compatible controller: Intel Corporation Device 5916 (rev 02)
00:04.0 Signal processing controller: Intel Corporation Device 1903 (rev 02)
00:14.0 USB controller: Intel Corporation Device 9d2f (rev 21)
00:14.2 Signal processing controller: Intel Corporation Device 9d31 (rev 21)
00:15.0 Signal processing controller: Intel Corporation Device 9d60 (rev 21)
00:15.1 Signal processing controller: Intel Corporation Device 9d61 (rev 21)
00:16.0 Communication controller: Intel Corporation Device 9d3a (rev 21)
00:17.0 SATA controller: Intel Corporation Device 9d03 (rev 21)
00:1c.0 PCI bridge: Intel Corporation Device 9d10 (rev f1)
00:1c.4 PCI bridge: Intel Corporation Device 9d14 (rev f1)
00:1c.5 PCI bridge: Intel Corporation Device 9d15 (rev f1)
00:1f.0 ISA bridge: Intel Corporation Device 9d58 (rev 21)
00:1f.2 Memory controller: Intel Corporation Device 9d21 (rev 21)
00:1f.3 Audio device: Intel Corporation Device 9d71 (rev 21)
00:1f.4 SMBus: Intel Corporation Device 9d23 (rev 21)
01:00.0 3D controller: NVIDIA Corporation GK208M [GeForce 920M] (rev a1)
02:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS5286 PCI Express Card Reader (rev 01)
02:00.2 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller (rev 06)
03:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8723BE PCIe Wireless Network Adapter


j'apprécie toute aide