Best Practice for Custom Nx Witness Player (RTSP + GStreamer, Overlay Sync & Performance)

Hi,

I'm working on a custom client integration with Nx Witness and would appreciate some guidance on best practices.

Context

• We are building a WPF-based client
• Pulling RTSP streams from Nx Server (not directly from cameras)
• Using GStreamer (D3D11) for decoding and rendering
• Parsing metadata (JSON) from the stream and rendering analytics overlays (bounding boxes)

Main Challenges

1. Accurate overlay synchronization
   Matching overlays to the exact displayed frame (currently using PTS and buffers, but it impacts performance)
2. Performance
   GPU → CPU copies and buffering logic are expensive

Questions

1. Player / SDK
   • Does Nx provide any internal or supported video player component / SDK (similar to other VMS systems)?
   • Or is RTSP + external player (GStreamer/VLC) the recommended approach for custom clients?
2. Overlay synchronization
   • What is the recommended way to sync analytics overlays with video?
   • Is PTS / clock-based synchronization the correct approach?
3. Scalability / Performance
   • Are there recommendations for how many simultaneous analytics video streams can be displayed?
   • Any best practices for multi-stream performance (GPU usage, decoding, etc.)?
4. Metadata
   • Is consuming metadata from the RTSP stream sufficient?
   • Or is there an advantage to using NX Metadata SDK / API for better accuracy or synchronization?

Goal

We aim to achieve behavior similar to Nx Desktop Client:

• Smooth playback
• Accurate overlay timing
• Minimal latency
• Efficient multi-stream handling

Any guidance, documentation, or examples would be greatly appreciated.

Thanks!