voxl-camera-server default exposure results in black snapshots + snapshot filename aliasing

[AndriiHlyvko]

Hi dev-team, I found a few minor bugs in the voxl-camera-server related to snapshot capturing. The first bug is that when you use the default exposure setting of AE_ISP and you also don't have any video streams open and try to capture camera snapshots you will get very underexposed images. Here is an example taken using an IMX412 camera with default settings. It was taken in our office in the middle of the day.

Basically the fix I found for that is to explicitly tell the Camera3 HAL not to use auto exposure by setting the default ae_mode to AE_LME_MSV.

The other bug that I found is that you cannot capture snapshots faster than 1Hz. This is because the snapshot filenames are timestamps with 1s resolution. So when multiple snapshot commands come in in the same second they will have the same filename and overwrite each other on disk. The solution to that is to add a millis to the timestamp in the filename.

I made a merge request for this https://gitlab.com/voxl-public/voxl-sdk/services/voxl-camera-server/-/merge_requests/45

On a separate note I would like to add in a feature to voxl-camera-server that adds XMP metadata to the snapshot images. This will be helpful for embedding UAV state information like attitude in the jpeg snapshots so they can later be used for mapping. For example DJI uses XMP to save its attitude and gimbal information. Would the modalai team be interested in me bringing in this feature?

Thanks.