fix camera listing

[poulpeit]

This PR has been made in order to fix an issue on capture device listing in the settings menu on linux.

Video devices are listed in /sys/class/video4linux with "video<ID>".
When adding or removing a new webcam, a new folder video<ID> is created or deleted, but there is some edge cases where ID are not contiguous (example: plug two devices and remove the first one).

As the code is currently a range(0, <number of folder>), in these edge cases, capture devices are not properly detected.

To fix this, I changed get_input_devices to properly list every folders.
As a side effect, I had to set enumerate into get_input_devices instead of get_all_video_capture_devices

Please note that, as I don't have any Windows available, tests were made only on Linux, but these changes should not break Autosplit on Windows.

[Avasam]

Thanks! I do have a duplicate cam listing issue on my Linux machine, so I can test this. Maybe not now though as I just came back from organising and running a gaming convention + show. Will need some time to recover.

[poulpeit]

OK, I thought duplicate cam listing was an issue on my side, but obsiously no :)

I dug a bit and saw that this is a normal behavior. As explained on https://askubuntu.com/a/1191209 Linux kernel creates a second device for metadata and stuff.
Listing every video devices on /sys/class/video4linux will by design show the second device.

Instead of listing /sys/class/video4linux, I found that we should ask for capabilities for every device. This can be done by using ioctl, asking for VIDIOC_QUERYCAP data and check if the V4L2_CAP_VIDEO_CAPTURE flag is set.
A bit of explaination here: https://www.linuxtv.org/downloads/legacy/video4linux/API/V4L2_API/spec/rn01re56.html

I changed the source code in order to check for this.
It seems to be a bit slower to get every video devices on the settings window, but nothing really annoying.