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Kamoso shows a black screen; camera works fine in other apps

User avatar selplacei
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I'm on Kubuntu 20.04 LTS, all packages are up to date as of writing this post. The camera is a Microsoft LifeCam VX-3000.
When starting Kamoso, it shows a solid black background instead of whatever the camera sees. The camera works fine with VLC (vlc v4l2:// :input-slave=alsa:// :v4l-vdev="/dev/video0") and in Firefox (tested with Jitsi Meet and webcamera.io). Here's the output when running kamoso from the terminal:
Code: Select all
new device "USB camera" "/sys/devices/pci0000:00/0000:00:01.2/0000:01:00.0/usb1/1-2/1-2:1.0/video4linux/video0" "/dev/video0"
Playing device changed "/dev/video0"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/private/globaltoolbar/ToolBarPageHeader.qml:44:9: QML ActionToolBar: Binding loop detected for property "actions"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/private/globaltoolbar/ToolBarPageHeader.qml:44:9: QML ActionToolBar: Binding loop detected for property "actions"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/private/globaltoolbar/ToolBarPageHeader.qml:44:9: QML ActionToolBar: Binding loop detected for property "actions"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/private/globaltoolbar/PageRowGlobalToolBarUI.qml:113: TypeError: Cannot read property 'globalToolBarStyle' of null
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/private/globaltoolbar/PageRowGlobalToolBarUI.qml:58:17: Unable to assign [undefined] to QQmlListProperty<QObject>
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/private/globaltoolbar/PageRowGlobalToolBarUI.qml:49:13: Unable to assign [undefined] to bool

(kamoso:2915): GStreamer-CRITICAL **: 17:02:11.840: gst_pad_get_current_caps: assertion 'GST_IS_PAD (pad)' failed

(kamoso:2915): GLib-GObject-CRITICAL **: 17:02:11.840: g_object_set: assertion 'G_IS_OBJECT (object)' failed

(kamoso:2915): GLib-GObject-CRITICAL **: 17:02:11.840: g_object_set: assertion 'G_IS_OBJECT (object)' failed
error debugMessage: No file name specified for reading.
error on: "filesrc location=\"\" ! decodebin ! imagefreeze ! videoconvert ! identity name=last" "gstfilesrc.c(524): gst_file_src_start (): /GstPipeline:pipeline0/GstFileSrc:filesrc0"
error debugMessage: No file name specified for reading.
error on: "filesrc location=\"\" ! decodebin ! imagefreeze ! videoconvert ! bulge name=last" "gstfilesrc.c(524): gst_file_src_start (): /GstPipeline:pipeline1/GstFileSrc:filesrc1"
error debugMessage: GStreamer error: negotiation problem.
error: "camerabingeneral.c(86): gst_camerabin_add_element_full (): /GstCameraBin:camerabin/GstWrapperCameraBinSrc:video_balance:\nlinking src-crop failed"
Stop

(kamoso:2915): GLib-GObject-CRITICAL **: 17:02:11.957: g_object_notify: assertion 'G_IS_OBJECT (object)' failed

(kamoso:2915): GLib-GObject-CRITICAL **: 17:02:11.957: g_object_notify: assertion 'G_IS_OBJECT (object)' failed
error debugMessage: Internal data stream error.
error: "gstbasesrc.c(3072): gst_base_src_loop (): /GstCameraBin:camerabin/GstWrapperCameraBinSrc:video_balance/GstV4l2Src:v4l2src:\nstreaming stopped, reason not-negotiated (-4)"
Stop

(kamoso:2915): GLib-GObject-CRITICAL **: 17:02:12.013: g_object_notify: assertion 'G_IS_OBJECT (object)' failed

(kamoso:2915): GLib-GObject-CRITICAL **: 17:02:12.014: g_object_notify: assertion 'G_IS_OBJECT (object)' failed

(kamoso:2915): GLib-GObject-CRITICAL **: 17:02:12.014: g_object_notify: assertion 'G_IS_OBJECT (object)' failed
error debugMessage: Internal data stream error.
error: "gstbasesrc.c(3072): gst_base_src_loop (): /GstCameraBin:camerabin/GstWrapperCameraBinSrc:video_balance/GstV4l2Src:v4l2src:\nstreaming stopped, reason not-negotiated (-4)"
Stop

(kamoso:2915): GLib-GObject-CRITICAL **: 17:02:12.070: g_object_notify: assertion 'G_IS_OBJECT (object)' failed

(kamoso:2915): GLib-GObject-CRITICAL **: 17:02:12.070: g_object_notify: assertion 'G_IS_OBJECT (object)' failed

(kamoso:2915): GLib-GObject-CRITICAL **: 17:02:12.070: g_object_notify: assertion 'G_IS_OBJECT (object)' failed

(kamoso:2915): GLib-GObject-CRITICAL **: 17:02:12.070: g_object_notify: assertion 'G_IS_OBJECT (object)' failed
error debugMessage: Internal data stream error.
error: "gstbasesrc.c(3072): gst_base_src_loop (): /GstCameraBin:camerabin/GstWrapperCameraBinSrc:video_balance/GstV4l2Src:v4l2src:\nstreaming stopped, reason not-negotiated (-4)"
Stop
Stop


I tried installing a bunch of packages related to GStreamer and Phonon, as well as restarting my PC several times, with no change in this behavior. Not sure what to search for except "kamoso black screen" or "kamoso not working", so please point me in the right direction if I'm missing something obvious.
User avatar Mamarok
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I don't have a camera so can't test: is this a new behavior since a specific update?


Currently running Kubuntu 20.04, Plasma 5.18.5, Frameworks 5.68.0, Qt 5.12.8, kernel 5.4.0-42
FWIW: it is always useful to state the exact Plasma version and distribution when asking questions in this forum, makes it easier for us to help ...
User avatar selplacei
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Mamarok wrote:I don't have a camera so can't test: is this a new behavior since a specific update?


The behavior is occurring on a freshly installed machine, and I haven't tried to use the camera before that, so I can't say for sure.

Also, I've tested another (more modern) camera and it works just fine. So it seems to be using a different technology or have a driver-related issue. I'll also test the VX-3000 on another Kubuntu machine when it's done upgrading, will update this post when done.

 
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