Implement XML metadata transmission

[unvermuthet]

The metadata part of the NDI SDK is unimplemented. The main use cases are tally messages. Since metadata can flow bi-directionally, both NDIOutput and VideoStreamNDI need to be able to send and receive metadata. An implementation would likely make use of

NDIOutput

• NDIlib_send_send_metadata for sending general metadata
• NDIlib_send_get_tally for getting the tally state
• NDIlib_send_add_connection_metadata
• NDIlib_send_clear_connection_metadata

VideoStreamNDI

• NDIlib_recv_send_metadata for sending general metadata
• NDIlib_recv_capture_v3 for receiving general metadata
• NDIlib_recv_set_tally for setting the tally state
• NDIlib_recv_add_connection_metadata
• NDIlib_recv_clear_connection_metadata

These functions are documented in the SDK's header files under ndi/.

Exposing this functionality to VideoStreamNDI will be a challenge since the actual NDI Receiver lives in VideoStreamPlaybackNDI, which isn't accessible. To solve this, I'd consider passing a Ref of VideoStreamNDI to VideoStreamPlaybackNDI on instantiation.

This should be a low-level implementation that just exposes the API. XML parsing and such should be left to the user.

This issue serves as a rough implementation guideline for now, as I will not work on this within the near future, unless incentivized. So feel free to pick this up! (Just leave a little note here to indicate your intention to me and others)

[Uliceau]

Hi, is this implementation still not planned by the contributors? Implementing metadata transmission would be appreciated and extremely useful.

[unvermuthet]

Hi! No, I'm not currently planning on adding this. I agree that it would be beneficial and frankly essential for a complete implementation, but I don't have time or motivation to work on this currently. I appreciate your interest!