NDI Streams Break After August Windows Update: Switch Receive Mode Now

Microsoft’s August cumulative updates have introduced a hard-to-ignore problem for streamers and live‑production teams: NDI streams that previously ran flawlessly on local networks now stutter, drop frames, or produce choppy audio after installing KB5063878 (Windows 11) or KB5063709 (Windows 10). The issue is confirmed by Microsoft and acknowledged by NDI vendors, and the safest immediate mitigation for most users is to change NDI’s Receive Mode from RUDP to UDP (Legacy) or Single‑TCP so you can keep the security patches while restoring reliable streams. (bleepingcomputer.com, docs.ndi.video)

Background​

The August cumulative updates for Windows 11 (KB5063878, OS Build 26100.4946) and the companion Windows 10 releases landed during the normal Patch Tuesday cycle and include dozens of security fixes and quality improvements. Shortly after the rollout, broadcasters and streamers began reporting severe degradation when using NDI‑based workflows: stuttered video, dropped frames, and choppy audio even on otherwise healthy LANs. Microsoft added the symptom set to its Release Health messaging while engineering investigates. (support.microsoft.com, bleepingcomputer.com)
NDI (Network Device Interface) is a widely used protocol in professional and hobbyist streaming environments for moving high‑quality, low‑latency video and audio over standard Ethernet. Many multi‑PC capture rigs — game capture machines, graphics render boxes, and encoder PCs — rely on NDI to ferry Display Capture sources and camera feeds between hosts. Because NDI is a transport‑level protocol, an OS‑level regression in packet handling can ripple across every NDI application on a machine. (docs.ndi.video, neowin.net)

---

What exactly is failing?​

At the core of the problem is NDI’s default transport mode, Reliable UDP (RUDP). RUDP attempts to combine UDP’s low latency with application‑level retransmission to recover lost packets. After the August updates, Windows and some networking stacks appear to interact poorly with RUDP, producing retransmission storms, packet handling delays, or otherwise degraded throughput that looks like stutter or choppy playback in the receiving app. Importantly, traffic sent or received via standard UDP or Single‑TCP does not show the same failure pattern, which is why switching the NDI Receive Mode is a practical workaround. (bleepingcomputer.com, windowsforum.com)
Affected applications and workflows reported in community channels include OBS Studio when using NDI sources, NDI Tools (Access Manager, Studio Monitor), vMix, and other NDI‑aware production software. The problem is especially visible when the sending machine uses Display Capture rather than a camera feed — a common scenario for gamers and presenters. (bleepingcomputer.com, m.vmix.com)

---

Immediate fixes (what you should try now)​

These are ordered from least intrusive to most intrusive. For most streamers the first option (change NDI transport) is the best tradeoff between reliability and security.

1. Change NDI Receive Mode (recommended, non‑destructive)​

• Install the free NDI Tools pack (if not already installed).
• Launch NDI Access Manager on every receiving machine in your NDI flow.
• Open the Advanced tab.
• Change Receive Mode from Reliable UDP (RUDP) (the default) to Single‑TCP or UDP (Legacy).
• Click OK, then restart every NDI‑receiving application so it reads the updated settings.

This change avoids the OS‑level regression in RUDP while leaving the Windows security updates in place. Single‑TCP tends to be the most universally stable fallback across complicated networks and middleboxes, while UDP (Legacy) preserves lower latency on clean Ethernet LANs but sacrifices RUDP’s retransmission features. After switching, always reboot or restart the NDI processes on each host because NDI reads Access Manager’s configuration file only at app startup. (docs.ndi.video, m.vmix.com)
Practical tradeoffs:

• Single‑TCP: Highest reliability across NATs/firewalls and troublesome switches; potential for slightly increased latency and head‑of‑line blocking during packet loss.
• UDP (Legacy): Lowest latency on a well‑managed LAN; no retransmissions — lost packets remain lost, which can affect image quality but usually avoids the disruptive retransmission behavior triggered by the regression.
• RUDP: Previously best balance but currently affected by the update-induced regression.

2. Roll back the cumulative update (last resort)​

If you cannot change the transport on remote/third‑party machines (for example, remote contributors you cannot access or appliances that cannot be reconfigured), uninstalling the problematic KB is an option — but it is the riskiest.

• Open Settings > Windows Update > Update history > Uninstall updates.
• Find Security Update for Microsoft Windows (KB5063878) on Windows 11 or KB5063709 for Windows 10 and select Uninstall.
• Alternatively, administrators can use wusa /uninstall /kb:5063878 (elevated Command Prompt) to script removal.
• Reboot the machine.

Uninstalling removes the security fixes included in the update, exposing systems to the vulnerabilities the patch addressed. Treat this as a temporary, controlled remediation: remove the patch only on devices that need it for live shows and that have compensating protections (network segmentation, limited internet exposure). Microsoft’s own guidance emphasizes using a rollback only when reconfiguration is infeasible. (support.microsoft.com, bleepingcomputer.com)

3. Pause updates if you haven’t installed the patch yet​

If the KB hasn’t been installed and you need time to test, you can pause updates temporarily:

• Open Settings > Windows Update and use the Pause updates control to delay installations (Windows exposes a variable pause window; exact options depend on the build and edition).
• Enterprise customers should use Windows Update for Business or WSUS to withhold the update from production rings until it’s confirmed fixed.

Pausing updates is a stopgap and not a security strategy; it buys time to validate vendor workarounds or to schedule safe rollback windows. Microsoft’s published guidance on pausing is straightforward, but some enterprise mechanisms (KIR, Group Policy) may be necessary for broad deployments. (support.microsoft.com, theverge.com)

4. Enterprise options: Known Issue Rollback and Group Policy​

Large organizations should watch Microsoft’s Release Health and their management tooling. Microsoft has previously released Known Issue Rollback (KIR) group policies to address regressive behaviors caused by updates; similarly, WSUS and SCCM can defer or block the LCU for affected rings while a fix is produced. For many broadcast operations, the correct approach is to keep production systems on a validated baseline and run the August LCU on a staging ring first. (neowin.net, support.microsoft.com)

---

Step‑by‑step: Change NDI Receive Mode (detailed)​

• Download and install NDI Tools from NDI’s distribution page.
• Launch NDI Access Manager (from Start Menu or the NDI Tools launcher).
• Click the Advanced tab.
• Find Receive Mode and choose Single‑TCP or UDP (Legacy).
• Click OK to save.
• Restart every NDI‑receiving program (OBS, Studio Monitor, vMix, etc.) so they re‑read %programdata%/NDI/ndi-config.v1.json on startup.
• Repeat on every receiving host in the NDI chain.

Important notes:

• Remember to change the setting on every receiving machine; leaving a mixed environment where some hosts still use RUDP can produce asymmetric behavior.
• If you later remove the update or the vendor releases a fix, you can revert to Auto or Reliable UDP. Always validate with a rehearsal before going live. (docs.ndi.video, windowsforum.com)

---

Why switching transport works — a technical explainer​

RUDP is an application‑layer approach that wraps UDP datagrams with retransmission and ordering logic. It keeps latency down by retransmitting only lost packets and by attempting to avoid full head‑of‑line blocking. The August update appears to alter socket behavior, timing, or driver interactions in a way that upsets RUDP’s assumptions — for example, by changing packet batching, scheduling, or how retransmits are processed. The result can be bursts of retransmissions or delayed packet handling that look like stuttering.
Switching to Single‑TCP replaces the custom reliability mechanism with TCP’s built‑in ordered, reliable stream — eliminating RUDP’s edge cases at the cost of potentially higher latency during network congestion. Choosing UDP (Legacy) removes reliability logic entirely, avoiding retransmission storms but making the flow susceptible to packet loss. Because the regression is specific to RUDP, both alternate transports bypass the faulty path and restore consistent playback. Microsoft, NDI, and third‑party vendors have converged on this practical explanation while the deep root‑cause investigation continues. (bleepingcomputer.com, windowsforum.com)
Caveat: Microsoft has not yet published a full, line‑by‑line root‑cause analysis naming the exact kernel function or driver misbehavior; the above is an accurate synthesis of vendor findings and network engineering principles rather than a verbatim Microsoft technical post‑mortem. Flagging uncertainty here is important until a formal Windows engineering write‑up is released. (windowsforum.com)

---

Risks, trade‑offs and live‑show hygiene​

Switching transport is a configuration change — not a silver bullet. Understand the operational tradeoffs and run rehearsals.

• Security vs. Availability: Uninstalling the KB removes the protection that Microsoft’s security update delivered. For mission‑critical live events, isolating the machine on a private VLAN and removing external access can mitigate risk while you run the old code. Use rollback only when absolutely necessary. (support.microsoft.com)
• Latency and lip sync: Single‑TCP will typically reintroduce a small latency penalty. For multi‑camera, tightly timed switching, this may require audio delay adjustments or switching rehearsal to verify lip sync. (windowsforum.com)
• Packet loss sensitivity: UDP (Legacy) offers minimal added latency but if your LAN experiences packet drops the image will degrade gracefully — sometimes preferable to retransmission storms. Test on your actual switch fabric. (docs.ndi.video)
• App restart requirements: NDI applications read Access Manager’s configuration at startup, so you cannot change Receive Mode in the Access Manager and expect already‑running apps to adapt. Plan a restart window and notify contributors. (docs.ndi.video)

---

Operational checklist for broadcasters (ready to print and use)​

• Identify affected hosts: run winver or check Settings > Windows Update > Update history > Uninstall updates to confirm presence of KB5063878/KB5063709. (support.microsoft.com)
• For each receiving machine:
• Install NDI Tools.
• Set Receive Mode to Single‑TCP or UDP (Legacy).
• Restart NDI apps and verify source discovery.
• Run a full show rehearsal: check switching, transitions, OBS scenes, and audio sync.
• If remote guests are affected and cannot reconfigure: escalate to controlled rollback only for the minimal set of machines, using network segmentation to limit exposure. (m.vmix.com, bleepingcomputer.com)
• Monitor Microsoft Release Health and vendor channels for a permanent patch; plan to revert test hosts to the updated state once a validated patch is available. (bleepingcomputer.com, windowsforum.com)

---

Longer‑term hardening: how to avoid update surprises​

• Maintain a staging ring that mirrors production: run new cumulative updates on a subset of non‑critical machines for 1–2 weeks before each broadcast season begins.
• Use separate NICs or segmented VLANs for NDI traffic: isolating media traffic reduces interaction effects with management or internet‑facing flows.
• Keep a simple recovery playbook (change transport, restart apps, rollback KB, apply network segmentation) and test it quarterly.
• Automate configuration checks: verify NDI access manager settings across your estate and enforce preferred Receive Mode via deployment tools where possible.
• Keep vendor tools and drivers up to date (NDI Tools, capture card firmware, NIC drivers) because many regressions are multi‑factor and can be avoided by coordinated updates. (conferenceroomsystems.freshdesk.com, docs.ndi.video)

---

What vendors and Microsoft are saying (and what to watch for)​

Microsoft’s Release Health dashboard and the Windows update KB pages list the symptom set and confirm an investigation is underway; vendors such as NewTek (NDI), vMix, and community knowledge bases have issued practical guidance that centers on switching Receive Mode as the safe temporary mitigation. Expect Microsoft to either reissue a corrected LCU or deliver a Known Issue Rollback or targeted fix once the engineering teams identify and validate the remediation. Streamers should monitor the Windows Update Release Health and vendor advisories for an official patch and testing guidance. (bleepingcomputer.com, m.vmix.com)
If a permanent fix arrives, vendors will typically recommend:

• Validate the patch on a test machine first.
• Revert the NDI Receive Mode to Auto or RUDP only after confirming stability across your topology.
• Rehearse a full production show to validate performance under load.

---

Final assessment and recommendations​

The intersection of an OS‑level update and a widely used streaming protocol has produced a practical, high‑impact regression for live producers — but the problem is solvable without compromising security for most users. The clearest, safest plan for the majority of streamers is:

• Immediately change NDI Receive Mode to Single‑TCP or UDP (Legacy) on every receiving host. This restores reliability while keeping Windows security updates in place. (docs.ndi.video, bleepingcomputer.com)
• Reserve uninstalling KB5063878/KB5063709 only for machines you cannot reconfigure and treat it as a temporary, controlled measure with compensating network protections. (bleepingcomputer.com)
• Implement a staging/test ring and rehearse patch windows so future regressions are discovered before they affect live shows. (m.vmix.com)

This sequence balances the operational need to deliver a reliable live broadcast with the security imperative of keeping systems patched. The community and vendors have converged on a practical mitigation; expect a formal Microsoft patch in short order, but plan your next live event on the assumption that workarounds will be necessary unless you can validate the fix in a test environment. (bleepingcomputer.com)

---

Keep this guide as your immediate show‑room checklist: change NDI Receive Mode, restart NDI apps, run a full rehearsal, and only remove the update as a carefully controlled emergency measure. Implementing those steps will restore most NDI‑based workflows and let production teams keep their machines protected while Microsoft and NDI vendors work toward a permanent resolution. (docs.ndi.video, m.vmix.com)

---

Source: Techweez How to Fix Broken Streaming After the Latest Windows Updates