Sharing a video to the Nextcloud app alters the resulting video file

Steps to reproduce

1. Record a video (e.g. 5 seconds) with iPhone camera, settings 4K (60 fps high efficiency)
2. Check the file size in iOS Photos app -> 50 MB
3. Upload the video to your nextcloud instance with these 3 methods and check the resulting file size:

• Via Auto-Upload -> Result: 50 MB (unchanged)
• Nextcloud app -> Upload video -> Result: 50 MB (unchanged)
• iOS Photos -> Share -> Nextcloud -> Result: 18 MB (file changed)

I don´t know if this behaviour is due to iOS photos or Nextcloud or Apple being Apple. All i´m seeing is the result...

Expected behaviour

The video file should not change when using different methods, especially without any hint or message.

Actual behaviour

Sharing through iOS Photos app alters the video file. To be exact:

• Original: 50 MB, 4K, 60 fps, H.265
• Auto-Upload: 50 MB, 4K, 60 fps, H.265
• Via Nextcloud App: 50 MB, 4K, 60 fps, H.265
• Shared via Photos: 18 MB, 4K, 30 fps, H.264

Original

Shared

Environment data

iOS version: iOS 18.4.1

Nextcloud iOS app version: 6.6.2.2

No source file or test is named. First reproduce the iOS Photos Share flow and compare the resulting video with Auto-Upload and direct upload, including codec and frame rate; done means sharing preserves the original video characteristics or clearly reports any conversion.