webcamoid crashes on startup

[whitis]

sudo apt-get install -y webcamoid
webcamoid &
# Segmentation Fault (core dumped)
# no video cameras currently plugged in, which may have helped excite the bug, though
# it is unlikely the program got far enough for that to even be an issue.

ldd /usr/bin/webcamoid
 linux-vdso.so.1 (0x00007fffcf1f7000)
 libavkys.so.8 => /usr/lib/x86_64-linux-gnu/libavkys.so.8 (0x00007fd72ee53000)
 libQt5Quick.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5 (0x00007fd72e80a000)
 libQt5Widgets.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5 (0x00007fd72dfc3000)
 libQt5Gui.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5 (0x00007fd72d85a000)
 libQt5Qml.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5 (0x00007fd72d25d000)
 libQt5Network.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Network.so.5 (0x00007fd72ced1000)
 libQt5Core.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Core.so.5 (0x00007fd72c786000)
 libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fd72c3fd000)
 libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fd72c1e5000)
 libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fd72bdf4000)
 libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fd72ba56000)
 libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fd72b837000)
 libGL.so.1 => /usr/lib/x86_64-linux-gnu/libGL.so.1 (0x00007fd72b5ab000)
 libpng16.so.16 => /usr/lib/x86_64-linux-gnu/libpng16.so.16 (0x00007fd72b379000)
 libharfbuzz.so.0 => /usr/lib/x86_64-linux-gnu/libharfbuzz.so.0 (0x00007fd72b0db000)
 libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007fd72aebe000)
 libicui18n.so.60 => /usr/lib/x86_64-linux-gnu/libicui18n.so.60 (0x00007fd72aa1d000)
 libicuuc.so.60 => /usr/lib/x86_64-linux-gnu/libicuuc.so.60 (0x00007fd72a666000)
 libdouble-conversion.so.1 => /usr/lib/x86_64-linux-gnu/libdouble-conversion.so.1 (0x00007fd72a455000)
 libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fd72a251000)
 libglib-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007fd729f3a000)
 /lib64/ld-linux-x86-64.so.2 (0x00007fd72f3d0000)
 libGLX.so.0 => /usr/lib/x86_64-linux-gnu/libGLX.so.0 (0x00007fd729d09000)
 libGLdispatch.so.0 => /usr/lib/x86_64-linux-gnu/libGLdispatch.so.0 (0x00007fd729a53000)
 libfreetype.so.6 => /usr/lib/x86_64-linux-gnu/libfreetype.so.6 (0x00007fd72979f000)
 libgraphite2.so.3 => /usr/lib/x86_64-linux-gnu/libgraphite2.so.3 (0x00007fd729572000)
 libicudata.so.60 => /usr/lib/x86_64-linux-gnu/libicudata.so.60 (0x00007fd7279c9000)
 libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007fd727757000)
 libX11.so.6 => /usr/lib/x86_64-linux-gnu/libX11.so.6 (0x00007fd72741f000)
 libxcb.so.1 => /usr/lib/x86_64-linux-gnu/libxcb.so.1 (0x00007fd7271f7000)
 libXau.so.6 => /usr/lib/x86_64-linux-gnu/libXau.so.6 (0x00007fd726ff3000)
 libXdmcp.so.6 => /usr/lib/x86_64-linux-gnu/libXdmcp.so.6 (0x00007fd726ded000)
 libbsd.so.0 => /lib/x86_64-linux-gnu/libbsd.so.0 (0x00007fd726bd8000)
 librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fd7269d0000)
 gdb /usr/bin/webcamoid
GNU gdb (Ubuntu 8.1-0ubuntu3.2) 8.1.0.20180409-git
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from /usr/bin/webcamoid...(no debugging symbols found)...done.
(gdb) run
Starting program: /usr/bin/webcamoid
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffeb140700 (LWP 24309)]
[New Thread 0x7fffe0c83700 (LWP 24310)]
[New Thread 0x7fffdbfff700 (LWP 24311)]
[New Thread 0x7fffda974700 (LWP 24312)]
[New Thread 0x7fffd9d15700 (LWP 24314)]

Thread 1 "webcamoid" received signal SIGSEGV, Segmentation fault.
0x00007ffff575eff3 in QObject::event(QEvent*) ()
   from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
(gdb) where
#0 0x00007ffff575eff3 in QObject::event(QEvent*) ()
    at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#1 0x00007fffc71d3a48 in MultiSrcElement::setState(AkElement::ElementState) ()
    at /usr/lib/x86_64-linux-gnu/avkys/libMultiSrc.so
#2 0x00007fffc71d3320 in MultiSrcElement::codecLibUpdated(QString const&) ()
    at /usr/lib/x86_64-linux-gnu/avkys/libMultiSrc.so
#3 0x00007fffc71d3812 in MultiSrcElement::MultiSrcElement() ()
    at /usr/lib/x86_64-linux-gnu/avkys/libMultiSrc.so
#4 0x00007fffc71d2a60 in MultiSrc::create(QString const&, QString const&) ()
    at /usr/lib/x86_64-linux-gnu/avkys/libMultiSrc.so
#5 0x00007ffff7b9b50a in AkElement::createPtr(QString const&, QString const&) () at /usr/lib/x86_64-linux-gnu/libavkys.so.8
#6 0x00007ffff7b9b684 in AkElement::create(QString const&, QString const&) ()
    at /usr/lib/x86_64-linux-gnu/libavkys.so.8
#7 0x00007fffcbdf22cd in Pipeline::parse(QString const&) ()
    at /usr/lib/x86_64-linux-gnu/avkys/libBin.so
#8 0x00007fffcbdea3fc in BinElement::setDescription(QString const&) ()
    at /usr/lib/x86_64-linux-gnu/avkys/libBin.so
#9 0x00007fffcbdf68f5 in () at /usr/lib/x86_64-linux-gnu/avkys/libBin.so
#10 0x00007fffcbdf6a53 in BinElement::qt_metacall(QMetaObject::Call, int, void**) () at /usr/lib/x86_64-linux-gnu/avkys/libBin.so
#11 0x00007ffff573dba5 in QMetaProperty::write(QObject*, QVariant const&) const () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
---Type <return> to continue, or q <return> to quit---
#12 0x00007ffff5766628 in QObject::setProperty(char const*, QVariant const&) ()
    at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#13 0x000055555557dbf6 in ()
#14 0x0000555555563db8 in ()
#15 0x00005555555615d5 in ()
#16 0x00007ffff4b34b97 in __libc_start_main (main=
    0x5555555613a0, argc=1, argv=0x7fffffffdb38, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffdb28)
    at ../csu/libc-start.c:310
#17 0x000055555556181a in ()
(gdb) q

strace webcamoid
[...]
stat("/usr/lib/x86_64-linux-gnu/avkys/submodules/MultiSrc/libffmpeg.so", {st_mode=S_IFREG|0644, st_size=174240, ...}) = 0
lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/usr/lib", {st_mode=S_IFDIR|0755, st_size=36864, ...}) = 0
lstat("/usr/lib/x86_64-linux-gnu", {st_mode=S_IFDIR|0755, st_size=311296, ...}) = 0
lstat("/usr/lib/x86_64-linux-gnu/avkys", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/usr/lib/x86_64-linux-gnu/avkys/submodules", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/usr/lib/x86_64-linux-gnu/avkys/submodules/MultiSrc", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/usr/lib/x86_64-linux-gnu/avkys/submodules/MultiSrc/libffmpeg.so", {st_mode=S_IFREG|0644, st_size=174240, ...}) = 0
--- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0x10} ---
+++ killed by SIGSEGV (core dumped) +++
Segmentation fault (core dumped)
# this shows that the last system call was an attempt to stat libffmpeg.so but that finished so
# it might have little to do with the segfault although MultiSrc does seem to be mentioned in both
# stack trace and strace in close proximity to the segfault.

ls -lgF /usr/lib/x86_64-linux-gnu/avkys/submodules/MultiSrc/libffmpeg.so
-rw-r--r-- 1 root 174240 Jan 5 2018 /usr/lib/x86_64-linux-gnu/avkys/submodules/MultiSrc/libffmpeg.so

md5sum /usr/lib/x86_64-linux-gnu/avkys/submodules/MultiSrc/libffmpeg.so
de663d0952938cafa56bbf0f03f0704c /usr/lib/x86_64-linux-gnu/avkys/submodules/MultiSrc/libffmpeg.so

 dpkg -l | fgrep -i ffmpeg
ii chromium-codecs-ffmpeg-extra 80.0.3987.87-0ubuntu0.18.04.1 amd64 Extra ffmpeg codecs for the Chromium Browser
ii ffmpeg 7:3.4.6-0ubuntu0.18.04.1 amd64 Tools for transcoding, streaming and playing of multimedia files
ii ffmpeg-doc 7:3.4.6-0ubuntu0.18.04.1 all Documentation of the FFmpeg multimedia framework
ii ffmpegthumbs 4:17.12.3-0ubuntu1 amd64 video thumbnail generator using ffmpeg
ii libavcodec-extra 7:3.4.6-0ubuntu0.18.04.1 all FFmpeg library with extra codecs (metapackage)
ii libavcodec-extra57:amd64 7:3.4.6-0ubuntu0.18.04.1 amd64 FFmpeg library with additional de/encoders for audio/video codecs
ii libavdevice57:amd64 7:3.4.6-0ubuntu0.18.04.1 amd64 FFmpeg library for handling input and output devices - runtime files
ii libavfilter6:amd64 7:3.4.6-0ubuntu0.18.04.1 amd64 FFmpeg library containing media filters - runtime files
ii libavformat57:amd64 7:3.4.6-0ubuntu0.18.04.1 amd64 FFmpeg library with (de)muxers for multimedia containers - runtime files
ii libavresample3:amd64 7:3.4.6-0ubuntu0.18.04.1 amd64 FFmpeg compatibility library for resampling - runtime files
ii libavutil55:amd64 7:3.4.6-0ubuntu0.18.04.1 amd64 FFmpeg library with functions for simplifying programming - runtime files
ii libffmpegthumbnailer4v5 2.1.1-0.1build1 amd64 shared library for ffmpegthumbnailer
ii libpostproc54:amd64 7:3.4.6-0ubuntu0.18.04.1 amd64 FFmpeg library for post processing - runtime files
ii libswresample2:amd64 7:3.4.6-0ubuntu0.18.04.1 amd64 FFmpeg library for audio resampling, rematrixing etc. - runtime files
ii libswscale4:amd64 7:3.4.6-0ubuntu0.18.04.1 amd64 FFmpeg library for image scaling and various conversions - runtime files
ii libxine2-ffmpeg:amd64 1.2.8-2build2 amd64 MPEG-related plugins for libxine2

sudo apt-get install qt5-default ffmpeg
# up to date

lsb_release -rd
Description: Ubuntu 18.04.4 LTS
Release: 18.04

apt-cache policy webcamoid
webcamoid:
  Installed: 8.1.0+dfsg-7
  Candidate: 8.1.0+dfsg-7
  Version table:
 *** 8.1.0+dfsg-7 500
        500 http://us.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
        100 /var/lib/dpkg/status

apport has apparently sent details of the crash.

The following suggested bug also mentions MultiSrc but there is insufficient information to say they are related:
https://bugs.launchpad.net/bugs/1826093

The following suggested bug also involves a crash on startup
https://bugs.launchpad.net/bugs/1654618
That bug involves a missing package dependency that isn't even a package now. Further, there is no obvious indication that that package, or its absence, is involved.

lauchpad crashes on submit, fortunately, I was able to get form contents back.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: webcamoid 8.1.0+dfsg-7
ProcVersionSignature: Ubuntu 5.3.0-40.32~18.04.1-generic 5.3.18
Uname: Linux 5.3.0-40-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.11
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Mon Mar 16 18:07:41 2020
InstallationDate: Installed on 2019-05-02 (319 days ago)
InstallationMedia: Ubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: webcamoid
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.