xcb_shm_create_segment can't be called for size with v4l

Gulo

New Member
I have OBS working with both a standard install through apt and as a snap.
OBS launches just fine and is able to connect to my NDI stream pulling both audio and video.

The problem is when I go to launch V4L Video Output it opens a title bar that is super wide and I get the error message:
Code:
qt.qpa.xcb: xcb_shm_create_segment() can't be called for size 17179344900, maximumallowed size is 4294967295
OBS then crashes with a Segmentation fault (core dumped)
This happens on both the standard install and the snap install.

From what I have been reading, this might be caused by my monitor resolution. I haven't had the chance to disconnect all but one of my monitors to run a test yet. But I will attempt that in the next day or two.
Here is my log file from the OBS standard:

Is there a fix for this, or a way specify the window size for it to open to?

OS: Ubuntu 20.04
Window Manager: Fluxbox
Monitors: 3 monitors managed with xrandr (one monitor is 4K)
Video Card: AMD Radeon RX 5500
OBS Snap version: 26.0.2-modified (64-bit)
OBS Standard version: 26.0.2 (64-bit)

Here is the OBS Standard output:
Code:
~/ $ obs
Attempted path: share/obs/obs-studio/locale/en-US.ini
Attempted path: /usr/share/obs/obs-studio/locale/en-US.ini
Attempted path: share/obs/obs-studio/locale.ini
Attempted path: /usr/share/obs/obs-studio/locale.ini
Attempted path: share/obs/obs-studio/themes/Dark.qss
Attempted path: /usr/share/obs/obs-studio/themes/Dark.qss
info: CPU Name: AMD Ryzen 9 3900X 12-Core Processor
info: CPU Speed: 3139.440MHz
info: Physical Cores: 12, Logical Cores: 24
info: Physical Memory: 64296MB Total, 5642MB Free
info: Kernel Version: Linux 5.4.0-53-generic
info: Distribution: "Ubuntu" "20.04"
info: Window System: X11.0, Vendor: The X.Org Foundation, Version: 1.20.8
info: Portable mode: false
Attempted path: share/obs/obs-studio/themes/Dark/no_sources.svg
Attempted path: /usr/share/obs/obs-studio/themes/Dark/no_sources.svg
QMetaObject::connectSlotsByName: No matching signal for on_advAudioProps_clicked()
QMetaObject::connectSlotsByName: No matching signal for on_advAudioProps_destroyed()
QMetaObject::connectSlotsByName: No matching signal for on_actionGridMode_triggered()
QMetaObject::connectSlotsByName: No matching signal for on_program_customContextMenuRequested(QPoint)
QMetaObject::connectSlotsByName: No matching signal for on_transitionRemove_clicked()
info: OBS 26.0.2 (linux)
info: ---------------------------------
info: ---------------------------------
info: audio settings reset:
        samples per sec: 48000
        speakers:        2
info: ---------------------------------
info: Initializing OpenGL...
info: Loading up OpenGL on adapter X.Org Radeon RX 5500 XT (NAVI14, DRM 3.35.0, 5.4.0-53-generic, LLVM 10.0.0)
info: OpenGL loaded successfully, version 4.6 (Core Profile) Mesa 20.0.8, shading language 4.60
info: ---------------------------------
info: video settings reset:
        base resolution:   1920x1080
        output resolution: 1280x720
        downscale filter:  Bicubic
        fps:               30/1
        format:            NV12
        YUV mode:          709/Partial
info: NV12 texture support not available
info: Audio monitoring device:
        name: Default
        id: default
info: ---------------------------------
warning: Failed to load 'en-US' text for module: 'decklink-ouput-ui.so'
libDeckLinkAPI.so: cannot open shared object file: No such file or directory
warning: A DeckLink iterator could not be created.  The DeckLink drivers may not be installed
info: No blackmagic support
info: [obs-browser]: Version 2.8.7
error: os_dlopen(libnvidia-encode.so.1->libnvidia-encode.so.1): libnvidia-encode.so.1: cannot open shared object file: No such file or directory

info: FFMPEG VAAPI supported
info: [obs-ndi] hello ! (version 4.9.1)
info: [obs-ndi] Trying ''
info: [obs-ndi] Trying '/usr/lib'
info: [obs-ndi] Found NDI library at '/usr/lib/libndi.so.4'
info: [obs-ndi] NDI runtime loaded successfully
info: [obs-ndi] NDI library initialized successfully (NDI SDK LINUX 00:05:02 Apr  1 2020 4.5.1)
info: VLC found, VLC video source enabled
info: ---------------------------------
info:   Loaded Modules:
info:     vlc-video.so
info:     v4l2sink.so
info:     text-freetype2.so
info:     rtmp-services.so
info:     obs-x264.so
info:     obs-vst.so
info:     obs-transitions.so
info:     obs-outputs.so
info:     obs-ndi.so
info:     obs-libfdk.so
info:     obs-filters.so
info:     obs-ffmpeg.so
info:     obs-browser.so
info:     linux-v4l2.so
info:     linux-pulseaudio.so
info:     linux-jack.so
info:     linux-decklink.so
info:     linux-capture.so
info:     linux-alsa.so
info:     image-source.so
info:     frontend-tools.so
info:     decklink-ouput-ui.so
info: ---------------------------------
error: os_dlopen(../obs-plugins/obs-browser->../obs-plugins/obs-browser.so): ../obs-plugins/obs-browser.so: cannot open shared object file: No such file or directory

info: ==== Startup complete ===============================================
info: All scene data cleared
info: ------------------------------------------------
info: pulse-input: Server name: 'pulseaudio 13.99.1'
info: pulse-input: Audio format: s16le, 44100 Hz, 2 channels
info: pulse-input: Started recording from 'alsa_output.usb-Schiit_Audio_I_m_Fulla_Schiit-00.iec958-stereo.monitor'
info: [Loaded global audio device]: 'Desktop Audio'
info: pulse-input: Server name: 'pulseaudio 13.99.1'
info: pulse-input: Audio format: s16le, 44100 Hz, 2 channels
info: pulse-input: Started recording from 'alsa_input.pci-0000_0d_00.4.analog-stereo'
info: [Loaded global audio device]: 'Mic/Aux'
info: [obs-ndi] started A/V threads for source 'GULOCAM (GuloCam)'
info: [obs-ndi] A/V thread for 'GuloNDI' started
info: pulse-am: Server name: 'pulseaudio 13.99.1'
info: pulse-am: Audio format: s16le, 44100 Hz, 2 channels
info: pulse-am: Started Monitoring in 'alsa_output.usb-Schiit_Audio_I_m_Fulla_Schiit-00.iec958-stereo.monitor'
info: Switched to scene 'Scene'
info: ------------------------------------------------
info: Loaded scenes:
info: - scene 'Scene':
info:     - source: 'GuloNDI' (ndi_source)
info:         - monitoring: monitor and output
info: ------------------------------------------------
Attempted path: share/obs/obs-studio/images/overflow.png
Attempted path: /usr/share/obs/obs-studio/images/overflow.png
info: adding 42 milliseconds of audio buffering, total audio buffering is now 42 milliseconds (source: Mic/Aux)

qt.qpa.xcb: xcb_shm_create_segment() can't be called for size 17178820624, maximumallowed size is 4294967295
Segmentation fault (core dumped)
~/ $
Here is the OBS Snap output:
Code:
~/ $ /snap/bin/obs-studio
Attempted path: share/obs/obs-studio/locale/en-US.ini
Attempted path: /usr/share/obs/obs-studio/locale/en-US.ini
Attempted path: share/obs/obs-studio/themes/Dark.qss
Attempted path: /usr/share/obs/obs-studio/themes/Dark.qss
info: CPU Name: AMD Ryzen 9 3900X 12-Core Processor
info: CPU Speed: 2312.283MHz
info: Physical Cores: 12, Logical Cores: 24
info: Physical Memory: 64296MB Total, 5646MB Free
info: Kernel Version: Linux 5.4.0-53-generic
info: Distribution: "Ubuntu Core" "20"
info: Window System: X11.0, Vendor: The X.Org Foundation, Version: 1.20.8
info: Portable mode: false
Attempted path: share/obs/obs-studio/themes/Dark/no_sources.svg
Attempted path: /usr/share/obs/obs-studio/themes/Dark/no_sources.svg
QMetaObject::connectSlotsByName: No matching signal for on_advAudioProps_clicked()
QMetaObject::connectSlotsByName: No matching signal for on_advAudioProps_destroyed()
QMetaObject::connectSlotsByName: No matching signal for on_actionGridMode_triggered()
QMetaObject::connectSlotsByName: No matching signal for on_program_customContextMenuRequested(QPoint)
QMetaObject::connectSlotsByName: No matching signal for on_transitionRemove_clicked()
info: OBS 26.0.2-modified (linux)
info: ---------------------------------
/usr/share/libdrm/amdgpu.ids: No such file or directory
info: ---------------------------------
info: audio settings reset:
        samples per sec: 48000
        speakers:        2
info: ---------------------------------
info: Initializing OpenGL...
info: Loading up OpenGL on adapter X.Org AMD NAVI14 (DRM 3.35.0, 5.4.0-53-generic, LLVM 10.0.0)
info: OpenGL loaded successfully, version 4.6 (Core Profile) Mesa 20.0.8, shading language 4.60
info: ---------------------------------
info: video settings reset:
        base resolution:   1920x1080
        output resolution: 1280x720
        downscale filter:  Bicubic
        fps:               30/1
        format:            NV12
        YUV mode:          709/Partial
info: NV12 texture support not available
info: Audio monitoring device:
        name: Default
        id: default
info: ---------------------------------
info: [StreamFX] Loading Version 0.9.1.0-ad245401
info: [StreamFX] Loaded Version 0.9.1.0-ad245401
info: [adv-ss] trying '/home/gulo'
info: [adv-ss] trying '/usr/lib'
info: [adv-ss] trying '/usr/local/lib'
info: [adv-ss] trying '/usr/lib/x86_64-linux-gnu'
info: [adv-ss] trying '/usr/local/opt/curl/lib'
warning: [adv-ss] can't find the curl library
warning: Failed to load 'en-US' text for module: 'decklink-ouput-ui.so'
info: [pango]: Loaded system fontconfig
libDeckLinkAPI.so: cannot open shared object file: No such file or directory
warning: A DeckLink iterator could not be created.  The DeckLink drivers may not be installed
info: No blackmagic support
warning: Failed to load 'en-US' text for module: 'obs-audio-pan-filter.so'
info: [obs-audio-pan-filter] plugin loaded successfully (version 0.1.0)
info: [obs-browser]: Version 2.8.7
error: os_dlopen(libnvidia-encode.so.1->libnvidia-encode.so.1): libnvidia-encode.so.1: cannot open shared object file: No such file or directory

info: FFMPEG VAAPI supported
info: [obs-ndi] hello ! (version 4.9.1)
info: [obs-ndi] Trying ''
info: [obs-ndi] Trying '/usr/lib'
info: [obs-ndi] Trying '/usr/local/lib'
info: [obs-ndi] Found NDI library at '/usr/local/lib/libndi.so.4'
info: [obs-ndi] NDI runtime loaded successfully
info: [obs-ndi] NDI library initialized successfully (NDI SDK LINUX 18:32:11 Jun 30 2020 4.5.3)
warning: Signal declaration 'start' exists
warning: Signal declaration 'stop' exists
warning: Signal declaration 'pause' exists
warning: Signal declaration 'unpause' exists
warning: Errors/warnings for 'void error(char* msg)':

declaration (1, 12): Expected 'type'

error: Signal declaration invalid: void error(char* msg)
warning: Failed to load 'en-US' text for module: 'obs-vnc.so'
info: [obs-vnc] plugin loaded successfully (version 0.1.0)
info: [obs-websocket] you can haz websockets (version 4.8.0)
info: [obs-websocket] qt version (compile-time): 5.12.8 ; qt version (run-time): 5.12.8
info: [obs-websocket] module loaded!
info: VLC found, VLC video source enabled
info: ---------------------------------
info:   Loaded Modules:
info:     vlc-video.so
info:     v4l2sink.so
info:     text-freetype2.so
info:     spectralizer.so
info:     source-switcher.so
info:     scrab.so
info:     rtmp-services.so
info:     replay-source.so
info:     recursion-effect.so
info:     obs-x264.so
info:     obs-websocket.so
info:     obs-vst.so
info:     obs-vnc.so
info:     obs-vintage-filter.so
info:     obs-transitions.so
info:     obs-transition-matrix.so
info:     obs-rtspserver.so
info:     obs-rgb-levels-filter.so
info:     obs-outputs.so
info:     obs-ndi.so
info:     obs-libfdk.so
info:     obs-gstreamer.so
info:     obs-filters.so
info:     obs-ffmpeg.so
info:     obs-browser.so
info:     obs-audio-pan-filter.so
info:     move-transition.so
info:     linux-v4l2.so
info:     linux-pulseaudio.so
info:     linux-jack.so
info:     linux-decklink.so
info:     linux-capture.so
info:     linux-alsa.so
info:     libtext-pango.so
info:     image-source.so
info:     frontend-tools.so
info:     freeze-filter.so
info:     dynamic-delay.so
info:     dvd-screensaver.so
info:     dir-watch-media.so
info:     decklink-ouput-ui.so
info:     advanced-scene-switcher.so
info:     StreamFX.so
info: ---------------------------------
error: os_dlopen(../obs-plugins/obs-browser->../obs-plugins/obs-browser.so): ../obs-plugins/obs-browser.so: cannot open shared object file: No such file or directory

info: ==== Startup complete ===============================================
info: All scene data cleared
info: ------------------------------------------------
info: pulse-input: Server name: 'pulseaudio 13.99.1'
info: pulse-input: Audio format: s16le, 44100 Hz, 2 channels
info: pulse-input: Started recording from 'alsa_output.usb-Schiit_Audio_I_m_Fulla_Schiit-00.iec958-stereo.monitor'
info: [Loaded global audio device]: 'Desktop Audio'
info: pulse-input: Server name: 'pulseaudio 13.99.1'
info: pulse-input: Audio format: s16le, 44100 Hz, 2 channels
info: pulse-input: Started recording from 'alsa_input.pci-0000_0d_00.4.analog-stereo'
info: [Loaded global audio device]: 'Mic/Aux'
info: [obs-ndi] started A/V threads for source 'GULOCAM (GuloCam)'
info: [obs-ndi] A/V thread for 'GuloCam' started
info: Switched to scene 'Scene'
info: ------------------------------------------------
info: Loaded scenes:
info: - scene 'Scene':
info:     - source: 'GuloCam' (ndi_source)
info: ------------------------------------------------
info: [adv-ss] started
info: [obs-websocket] server started successfully on port 4444
info: [obs-websocket] io thread started
Attempted path: share/obs/obs-studio/images/overflow.png
Attempted path: /usr/share/obs/obs-studio/images/overflow.png
info: adding 42 milliseconds of audio buffering, total audio buffering is now 42 milliseconds (source: Desktop Audio)

qt.qpa.xcb: xcb_shm_create_segment() can't be called for size 17179344900, maximumallowed size is 4294967295
Segmentation fault (core dumped)
~/ $
 

Gulo

New Member
I finally got around to testing disabling of monitors. It turns out that I only have to disable my 4K monitor and the V4L Video Output opens without issue.

So it has to do with the resolution of my 4K monitor that is causing the problem.

So I still have the same problem, but now I have a work around for it. Is there a way to spoof the XCB resolution or to put a limiter in the launcher?
 
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