NVIDIA Kit App Streaming Debug
Debug Kit livestream performance end-to-end before jumping into generic profiling. Always collect both server-side Kit logs and browser-side WebRTC evidence, then correlate by timestamp around the lag/freeze event.
Collect Kit Evidence
Run the Kit app with StreamSDK event tracing and verbose file logs. Keep --no-window for app-stream tests when resolution mismatch is suspected.
# Windows
.\repo.bat launch -- --no-window --/exts/omni.kit.livestream.app/primaryStream/enableEventTracing=true --/log/channels/omni.kit.livestream.streamsdk=verbose --/log/fileLogLevel=verbose
# Linux
./repo.sh launch -- --no-window --/exts/omni.kit.livestream.app/primaryStream/enableEventTracing=true --/log/channels/omni.kit.livestream.streamsdk=verbose --/log/fileLogLevel=verbose
If extension context is needed, also enable:
--/log/channels/omni.kit.livestream.webrtc=verbose
--/log/channels/omni.kit.livestream.app=verbose
Extract the known streaming failure markers:
rg -n -C 3 "Timeout of [0-9]+ms exceeded waiting for copy fence|Cannot stream video frame because the video stream is not connected|Still cannot stream video frame|Cannot stream video frame with resolution|NVST_R_BUSY|Client disconnected from WebRTC server" path/to/kit.log
Interpret them this way:
| Marker | Likely cause | Next check |
|---|---|---|
Timeout of 1000ms exceeded waiting for copy fence |
Renderer/GPU stall before the framebuffer copy completes | Correlate with frame time, GPU utilization, and Tracy/NSight render zones |
Cannot stream video frame because the video stream is not connected |
WebRTC session has not established, or video stream dropped | Check browser ICE state, connection events, and nearby disconnect logs |
Still cannot stream video frame... |
Connection did not recover inside the wait timeout, frame dropped | Treat as stream/session instability, not render cost by itself |
Cannot stream video frame with resolution ... differs... |
OS/window resize or AOV/render resolution changed after connect | Try --no-window, fixed resolution, disable viewport fill behavior, or use dynamic resize only if required |
NVST_R_BUSY |
StreamSDK is not accepting frames fast enough | If not adjacent to disconnect/reconnect, suspect encoder, network, or client backpressure |
Client disconnected from WebRTC server |
Client/session dropped | Align with browser ICE/NACK/PLI/freeze events |
Collect Browser Evidence
Open chrome://webrtc-internals before connecting to the stream. After a lag event, use Create dump and inspect packet loss, jitter, frames dropped, decode time, bitrate, freezes, NACK/PLI, and the selected ICE candidate pair.
For ~/proj/ov-web-rtc, run the dev client with npm run dev and capture console logs. Add or inspect an onStreamStats callback like:
onStreamStats: (message: StatsEvent) => {
const s = message.data.stats;
console.table({
fps: s.fps,
rtdMs: s.rtd,
decodeMs: s.avgDecodeTime,
frameLoss: s.frameLoss,
packetLoss: s.packetLoss,
bandwidthMbps: s.totalBandwidth,
bitrateMbps: s.currentBitrate,
utilizedPct: s.utilizedBandwidth,
resolution: `${s.streamingResolutionWidth}x${s.streamingResolutionHeight}`,
codec: s.codec,
});
}
Browser-side interpretation:
| Symptom | Likely bottleneck |
|---|---|
High avgDecodeTime, low packet loss |
Client decode/GPU/display bottleneck |
High packetLoss, frameLoss, NACK/PLI, jitter, or freezes |
Network or congestion problem |
utilizedBandwidth near 100%, bitrate near/above available bandwidth |
Bandwidth cap or congestion control |
| Low browser FPS with clean browser stats but Kit copy-fence/NVST warnings | Server render/copy/encoder/backpressure |
| Browser resolution differs from expected Kit stream resolution | Resize/configuration mismatch |
Profiling Follow-Up
Use Tracy only after logs indicate the server side is involved. Add the profiling args to the same Kit run:
--/app/profilerBackend=tracy --/app/profileFromStart=true --/profiler/gpu/tracyInject/enabled=true --/app/profilerMask=1 --/plugins/carb.profiler-tracy.plugin/fibersAsThreads=false --/profiler/channels/carb.events/enabled=false --/profiler/channels/carb.tasking/enabled=false --/rtx/addTileGpuAnnotations=true --/profiler/enabled=true --/profiler/gpu=true --enable omni.kit.profiler.window
Use the profiling skill for capture mechanics and nsys-analyze for trace analysis. Do not promise StreamSDK-internal zones when StreamSDK source is unavailable; correlate log timestamps with surrounding Kit zones such as SharedFrameBuffer::waitForCopy, SharedFrameBuffer::streamBuffer, render zones, and frame markers.
Report Shape
Summarize:
- Kit run args and log path.
- Browser artifacts: console stats and
webrtc-internalsdump. - Timeline around the lag event.
- Matched markers and likely bottleneck category: renderer/GPU, session/network, resize/config, StreamSDK/encoder backpressure, or client decode.
- Next action: config fix, network/client investigation, or server-side profiling.
Source references in this workspace: ~/proj/kit-livestream for omni.kit.livestream.app and omni.kit.livestream.webrtc; ~/proj/ov-web-rtc for browser stats and dev client logging.