linux-pipewire: Use list-based format selector for video capture

[tytan652]

Description

Change the video capture source UX to choose between formats provided as is by PipeWire and avoid providing non-functional combination.

Also it avoid the user to check every format to find the right resolution.

Negotiation is now made with the user selected format (the choice was ignored before).

Also fixes a typo in the name of a structure.

Note

Formatting of the strings case can be discussed, and FPS values (mainly multiple choices per format) could be added.

Before:

After first commit:

After second and third commit:

Motivation and Context

Inspired by #10895 and the fact the actual code was not respecting the user chosen format and potentially showing non-available resolution for some formats.

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)

• Tweak (non-breaking change to improve existing functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[Warchamp7]

We had a lot of discussion about the string formatting for #10895 so I'd like to copy that as closely as possible for this.

[tytan652]

@Warchamp7

[RytoEX]

@Warchamp7 does this now copy #10895 as closely as possible to be acceptable?

[Warchamp7]

• Change fps to FPS
• Sort discrete FPS values from low to high
• Include aspect ratio after resolution like we do in mac-avcapture: Use list-based format selector #10895
  • aspectRatioStringFromDimensions

[tytan652]

@Warchamp7 requested changes are done.

[stephematician]

Not that this is intended to be addressed with this PR (or perhaps a sensible default would be to assume 'N/A' FPS) - but 'ranged' FPS is not supported. E.g. start a loopback device and feed it some frames:

sudo modprobe v4l2loopback video_nr=10 max_buffers=4
gst-launch-1.0 videotestsrc horizontal_speed=4 ! \
    'video/x-raw,format=YUY2,width=640,height=480,framerate=30/1' ! \
    v4l2sink device=/dev/video10

This can be viewed using V4L2 input, but doesn't work with pipewire (camera) capture.

Also; I see errors in my log related to reading the format: test-v4l2loopback-pw.log - and the dropdown for format and FPS are empty.

[tytan652]

but 'ranged' FPS is not supported

It is already explicitly marked/logged unsupported on master.

[stephematician]

but 'ranged' FPS is not supported

It is already explicitly marked/logged unsupported on master.

ACK - and given that these devices work with plain V4L2 input; there's probably nothing that needs to be done here.

Confirming that if we use gstreamer's pipewiresink instead (not v4l2loopback) i.e.

gst-launch-1.0 videotestsrc ! 'video/x-raw,format=YUY2,width=640,height=480,framerate=30/1' ! \
    identity drop-allocation=1 ! \
    pipewiresink mode='render' \
    stream-properties='props,node.name=virtual_input.gst.test-source,media.class=Video/Source,media.role=Camera'

We get exactly what we expect in OBS; one format + FPS available: