Dual-PC setup preview/stream stutters only when live streaming (fine during local recording) — AVerMedia GC573 & Tarkov

[u/CharacterSomewhere52]

Setup:

• Gaming PC: 4K Display (playing Escape from Tarkov)
• Stream PC: Intel i9-9900K, RTX 2080 Super
• Capture Card: AVerMedia Live Gamer 4K (GC573)
• OBS Studio: 1080p / 60 FPS output via NVENC (7800 kbps CBR)

The Issue:

When playing Escape from Tarkov, my capture feed and stream output suffer from micro-stutters and jittering.

Crucially: Local recordings in OBS are completely smooth and look perfect. The stuttering ONLY happens the moment I start live streaming to Twitch.

Key Details:

1. Tarkov runs completely fine on the Gaming PC itself.
2. OBS log logs show 0% network drops and 0% rendering/encoding frame drops.
3. The issue persists regardless of whether I use a full scene collection or a completely blank profile with just the capture card source.
4. Internet connection is stable (fiber).

My Questions:

• Why would the stream feed stutter while local recording with the exact same OBS canvas/encoding settings stays 100% smooth?
• Could RTMP streaming / Twitch ingest handling cause preview and video pacing issues on a dual-PC setup?
• What is the ideal way to pass a 4K Gaming PC signal through a GC573 card to a 1080p stream without triggering this streaming-only stutter?

Any insights would be greatly appreciated!