Support CameraFeed format on macOS

[j20001970]

Implement CameraFeedMacOS::set_format and CameraFeedMacOS::get_formats.

When activating the feed, if selected_format is specified, try locking the device to set active format for it, and unlocking the device upon deactivated.

[shiena]

The format_changed signal is emitted from camera_feed.cpp, so emitting it from camera_macos.mm would result in double emission.
https://github.com/godotengine/godot/blob/master/servers/camera/camera_feed.cpp#L199
https://github.com/godotengine/godot/blob/master/servers/camera/camera_feed.cpp#L222
https://github.com/godotengine/godot/blob/master/servers/camera/camera_feed.cpp#L255

[j20001970]

I'm not clear on when format_changed should be emitted, the Linux driver emits the signal whenever a format is selected:

godot/modules/camera/camera_feed_linux.cpp

Lines 348 to 350 in a39a83a

	parameters = p_parameters.duplicate();
	selected_format = p_index;
	emit_signal(SNAME("format_changed"));

while camera_feed.cpp emit the signal when current camera frame size is different from the previous. Could someone clarify that whether format_changed should be emitted as soon as a format is selected for the camera feed?

[shiena]

Currently, the format_changed signal is emitted within set_ycbcr_images on the following line when the image size differs from the previous call, so combined with the call within set_format, it gets emitted twice per frame - we should choose one or the other. It's a dilemma which one should emit it, but I imagine what an app using CameraFeed would want to do when receiving the format_changed signal. Emitting from set_ycbcr_images allows receiving image data with the changed format. If emitted from set_format, there's a possibility that image data isn't available yet. Comparing these two, I think emitting from set_ycbcr_images would be better.
https://github.com/godotengine/godot/blob/master/modules/camera/camera_macos.mm#L185

[Calinou]

Tested locally on macOS 26 (MBP 16" 2024 with M4 Max), it works as expected.

However, some formats in the list look broken:

The following formats have an appearance like this, with green diagonal lines and what seems to be an incorrect stride (the image does update, but looks skewed):

• 1760x1328
• 1328x1760
• 1552x1552
• 1080x1920 (1920x1080 is fine)

[j20001970]

30959dc try to handle padded image data.

Please let me know if it fixes skewed image for some formats.

[Calinou]

30959dc try to handle padded image data.

Please let me know if it fixes skewed image for some formats.

Works great now 🙂 I can get all formats to display.

However, in https://github.com/shiena/godot-camerafeed-demo, switching formats occasionally leads to a black screen until I resize the window (the webcam display appears as a tiny square in the top-right corner). Sometimes, switching formats will still result in a black screen until I restart the project. No errors or warnings are printed in the output log. This is presumably a bug in the demo rather than in this PR though.

cc @shiena

[j20001970]

I didn't take into account that camera feed format could change while activated (current implementation just remember selected format index to use before next feed activation), maybe there are still parts that can be improved.

[j20001970]

I didn't take into account that camera feed format could change while activated (current implementation just remember selected format index to use before next feed activation), maybe there are still parts that can be improved.

With 76a317e and shiena/godot-camerafeed-demo@a10d76c, camera feeds should be able to change format while still active.

The problem of disappeared camera preview after stopping and starting the feed without changing format seems to be caused by rotation of camera preview in godot-camerafeed-demo.

The last issue that I'm aware of is that, after changing feed format, it does not take effect immediately. On my machine with a USB webcam, camera feed still output a frame or two in previously configured format, even when camera feed is deactivated then activated again.