Architecture

Objective

Make one local Windows computer available as OBS sources on another computer, with sender-side NVENC video encoding and independently mixable audio sources.

Current Mechanism

The repo owns configuration and scripts. FFmpeg owns capture, encoding, and SRT transport. OBS owns scene composition.

Inputs become outputs like this:

1. config/localcast.json declares the receiver IP, SRT ports, video capture shape, and named audio devices.
2. scripts/sender-discover.ps1 asks FFmpeg what Windows capture devices and encoders exist.
3. scripts/sender-start.ps1 validates the config and launches one FFmpeg process per source.
4. The video process captures the desktop and encodes H.264 using h264_nvenc.
5. Each audio process captures one DirectShow audio device and encodes Opus.
6. Each process sends MPEG-TS over SRT to a stable receiver URL.
7. OBS adds each URL as a Media Source.

Invariants

• Video encoding happens on the sender.
• OBS receives ordinary media-source URLs; it does not need a plugin for v1.
• Audio remains separately mixable in OBS.
• Ports are stable and derived from one base port plus explicit offsets.
• Secrets, if used, stay in local config and are not committed.

Intended Change

The first implementation creates the repeatable operating spine. Future native code is only justified if the SRT Media Source path fails one of the invariants above.

Cut Line

The following do not currently earn their keep:

• OBS fork
• OBS plugin
• custom receiver daemon
• synchronized multi-track container that hides audio sources from OBS mixing
• homegrown capture stack over Windows APIs

Source Notes

• OBS SRT guide: https://obsproject.com/kb/srt-protocol-streaming-guide
• FFmpeg devices docs: https://www.ffmpeg.org/ffmpeg-devices.html
• FFmpeg protocols docs: https://ffmpeg.org/ffmpeg-protocols.html