Package gst-plugin-gtk is missing in required dependencies

Versions

• OS: Gentoo
• Gajim version: 1.3.1_p2 & 1.3.2
• GTK version: 4.2.1
• Python-nbxmpp version: 2.0.2-r1

Steps to reproduce the problem

1. Click on the Gajim menu button on the top left and select Preferences
2. Click on Audio/Video
3. Activate Live Preview

Expected behavior

See a live preview of whatever my webcam sees.

Actual behavior

Getting the error message "Something went wrong. Video feature disabled"

Additional information

My webcam is detected and works with V4L2 on a variety of software, including Zoom, Google Meet, and the following command: mpv --no-cache --no-osc --no-input-default-bindings --profile-low-latency --input-conf=/dev/null --title=webcam $(ls /dev/video[0,2,4,6,8] | tail -n 1) which makes me think the issue has to be Gajim specific or located somewhere in the chain from Gajim to getting webcam footage.

Clicking on Help -> Features shows that every feature has a checkmark.

Gajim has the following USE flags on my system (+ = enabled, - = disabled):

• +crypt : End to end encryption and GPG encryption
• -geolocation : Sharing your location
• +jingle : Audio and video calls
• -python_single_target_python3_7 : Build for Python 3.7 only
• +python_single_target_python3_8 : Build for Python 3.8 only
• -python_single_target_python3_9 : Build for Python 3.9 only
• -remote : Controlling Gajim instance from command line with gajim-remote
• +rst : Generating XHTML output from RST code
• +spell : Spellchecking of composed messages
• +upnp : Ability to request your router to forward port for file transfer
• +webp : Support WebP avatars

On the Audio/Video tab, I have the following settings set:

Server

• Use STUN server: On

Audio

• Audio Input Device: Pulse: Default device
• Audio Output Device: Pulse: Default device

Video

• Video Input Device: V4L2: Default device (I also tried specifying the webcam exactly with this option, and still doesn't work any better)
• Video Framerate: Default
• Video Resolution: Default
• Show My Video Stream: On
• Live Preview: On/Off (This is the problem option, turning it on gives the error, if I leave the preferences window and come back, it's turned Off again.)

Errors logged on stdout when started from terminal

05/10/2021 22:53:28 (E) gajim.gui.preview          Failed to obtain a working Gstreamer GTK+ sink, video support will be disabled

This error makes me believe the error is somewhere between Gajim and Gstreamer.

End message

I do not know if voice calls or video calls actually work at all as I have no friends with whom to test it.

I have raised a bug request on the Gentoo package repository to have the version bumped up to 1.3.2, but I doubt a simple version bump will fix this issue entirely.

Thanks for any help, Kusoneko.