Application Flow

Application Flow

Overview

Every ovstream application follows the same core lifecycle, whether in Python or C:

1. Initialize SDK              → initialize / ovstream_initialize
2. Create server               → Server(ServerType.X) / ovstream_create_server
3. Register callbacks          → on_connection / on_message / on_input / on_unicode  (on_connection on all transports; on_message / on_input / on_unicode on WebRTC, native, SHM, CUDASHM)
4. Configure                   → ServerConfig(...) / ovstream_config_defaults + overrides
4a. (Optional, WebRTC/native)  → server.set_webrtc_ice_servers([...]) for STUN/TURN NAT traversal
5. Start                       → server.start(cfg) / ovstream_start
6. Stream loop:
   a. Produce frame (CUDA buffer or pre-encoded bitstream)
   b. Submit frame             → server.stream_video / ovstream_stream_video
   c. (Optional)                 server.set_webrtc_ice_servers([...]) again to refresh time-limited TURN credentials live
7. Stop                        → server.stop / ovstream_stop
8. Destroy server              → server.close / ovstream_destroy_server
9. Shutdown SDK                → shutdown / ovstream_shutdown

initialize / shutdown are ref-counted — call them once at process start/end (or matching pairs around a streaming subsystem). Creating multiple servers between one initialize and shutdown is fine.

Python

Source: examples/python/basic_stream/main.py snippet initialize-sdk

Followed by: examples/python/basic_stream/main.py snippet create-server

Followed by: examples/python/basic_stream/main.py snippet stream-loop

Followed by: examples/python/basic_stream/main.py snippet cleanup

The ovstream.Server class is a context manager; if you don't need initialize/shutdown to span multiple servers, the simplest pattern is:

ovstream.initialize()
with ovstream.Server(ovstream.ServerType.WEBRTC) as server:
    server.start(ovstream.ServerConfig(width=1920, height=1080))
    # ... stream frames ...
ovstream.shutdown()

C

Source: examples/c/basic_stream/main.cu snippet initialize-sdk

Followed by: examples/c/basic_stream/main.cu snippet create-server

Followed by: examples/c/basic_stream/main.cu snippet register-callbacks

Followed by: examples/c/basic_stream/main.cu snippet configure-server

Followed by: examples/c/basic_stream/main.cu snippet start-server

Followed by: examples/c/basic_stream/main.cu snippet stream-loop

Followed by: examples/c/basic_stream/main.cu snippet cleanup

Composing with another library (the headline pattern)

The point of ovstream's small surface area is that you compose it with whatever produces CUDA frames. The canonical example is examples/python/ovrtx_stream — ovrtx renders a USD scene, ovstream publishes the result over WebRTC. The two libraries don't know about each other; the app glues them together via the CUDA buffer that flows from one to the other.

If you're integrating ovstream into your own renderer, start from ovrtx_stream/main.py as a reference, then strip the ovrtx-specific pieces and replace them with your own frame producer.

Key Differences: Python vs C

Common Pitfalls

• Callback timing. Callbacks fire on internal network/SDK threads. Either keep callback bodies short and lock-free, or marshal to your main thread yourself. See callbacks-and-input skill.
• Buffer lifetime in streaming. stream_video stages the frame data into server-owned memory before returning, so the caller-supplied buffer is free to reuse or release immediately on return. Reusing a long-lived buffer across frames is still the common pattern because it avoids per-frame allocation; per-frame std::vectors or stack buffers are also legal. Producers that want to skip the staging copy and overlap their next render with the encoder's read should pass a CUDA event via frame.sync.
• RTSP has no input/message channel. Registering on_message / on_input on an RTSP server is silent — the registration succeeds but the callbacks never fire. WebRTC, native, SHM, and CUDASHM all carry a reverse channel; SHM and CUDASHM do so via a local control socket / named pipe alongside their pixel transports.
• Don't forget the ref-counted shutdown. Every initialize must be paired with a shutdown. Calling initialize twice and shutdown once leaks the backend lifetime.
• See error-handling skill for robust error checking patterns in both languages.