Streaming & WebRTC

GFN uses WebRTC (and its own native RTC variant) to stream game video and audio from the rig to the client. The streaming stack lives primarily in vendor_beautified.js.

Stream Backends

Backend	Registry Value	Description
LIBWEBRTC	StreamServerModeOverride=1	Standard libwebrtc
NATIVE_RTC	StreamServerModeOverride=2	NVIDIA's NativeRTC (default for all clients)

Default for all clients:

{
  "StreamServerMode": 2,
  "EnableNativeRTCAllClients": true,
  "EnableNativeRtcSeparateStreams": 1,
  "EnableWebRtcSeparateStreams": 1
}

Network Test (Pre-Session)

Before every session, the client runs a network quality test:

// From vendor_beautified.js
NetworkTest: {
  startNetworkTest()       // Initiate test
  stopNetworkTest()        // Cancel test
  getNetworkTestExceptionTelemetryEvent()
  getNetworkTestHttpTelemetryEvent()
}

// User-Agent for network test requests
USER_AGENT: "GFN-PC/1.0 (WebRTC) NetworkTest/0.0.51"

Results feed into networkTestSessionId tracked in telemetry.

ICE Connection

WebRTC ICE is used to establish the peer connection:

Error Code	Name	Description
0x8004000C	NVST_STREAMING_ICE_CONNECTION_FAILED	ICE establishment failed
0x8004000D	NVST_STREAMING_ICE_CONNECTION_DISCONNECTED	ICE connection lost

Codec Support

Codec selection is dynamic based on client/server capabilities:

Codec	Control Flag	Condition
H.264	Default	All clients
HEVC/H.265	HevcEnable=1	TV clients at 1440p/4K, 4K sessions
AV1	Enabled by default	Disabled on half-GPU instances

4K Encoding

For 4K sessions, two-pass encoding can be overridden per game:

{
  "name": "Disable4k2Pass_ForSpecificGames4K60",
  "filters": [
    { "key": "sessionRequestData.clientRequestMonitorSettings.framesPerSecond", "value": "60" },
    { "key": "sessionRequestData.appId", "value": "101606111,100838211,..." }
  ]
}

Frame Pacing

Minimum target frame time controls the effective FPS cap:

minTargetFrameTimeUs: 7936  →  1,000,000 / 7936 ≈ 126 FPS max

Applied on both macOS and Windows clients.

Separate Streams

When EnableNativeRtcSeparateStreams=1, video and audio use separate WebRTC tracks:

• EnableWebRtcSeparateStreams: libwebrtc path
• EnableNativeRtcSeparateStreams: NativeRTC path
• DisableNativeRtcSeparateStreams=0: Ensure separate streams not disabled

Surround Sound

Enabled for native Windows/macOS clients ≥ v2.0.52.0:

surroundBrowser: 1        // 7.1 surround audio
separateMicStream: 1      // Separate microphone stream

GRC (Game Ready Check)

Enabled for Windows and macOS clients:

{
  "name": "EnableGrc_WindowsMacOSX",
  "filters": [{ "key": "sessionRequestData.clientPlatformName", "value": "Windows,MacOSX" }]
}

Stream Server Configuration

Key registry values managed by GameStream:

Registry Key	Type	Description
StreamServerMode	REG_SZ	Stream backend mode
StreamServerModeOverride	REG_SZ	Per-session override
HdrSupported	REG_DWORD	HDR output enabled
Enable4k	REG_DWORD	4K resolution
Enable1440p	REG_DWORD	1440p resolution
Enable7_1ForGFN	REG_DWORD	7.1 audio
Allow120FpsModeSet	REG_DWORD	120 FPS
DynamicFrlFramePacing	REG_DWORD	Dynamic frame pacing
EnableStreamerMinidump	REG_DWORD	Crash dump collection
Av1Disable	REG_DWORD	Disable AV1 encoding
HevcEnable	REG_DWORD	Enable HEVC

Bundle Port

{
  "general.nativeRtcOnBundlePort": 1
}

NativeRTC uses a single bundled port for all media (mux audio+video).

NACK (Retransmission)

Hysteresis for retransmission requests, enabled for native clients:

{
  "name": "EnableNackHysteresisLength",
  "filters": [{ "key": "clientInfo.clientType", "value": "NATIVE" }],
  "settingParameters": [
    { "key": "video[0].nackHysteresisLengthUs", "value": "4000" }
  ]
}

UDS (Uplink Detection Statistics)

Enabled for Windows and macOS native clients:

{
  "vqos[0].statsProcessorThread.flags": 255,
  "vqos[0].sendEndOfSessionQosTelemetry": 1
}