Intermittent remote video render failure (code 408 / subCode 43203) — audio OK, correlated with Firefox on the sender side

hi Bastien Lafont, thx for sharing urs issue here at Q&A portal,

the receiver waits for video frames, but the sender never sends usable frames in some Firefox cases.

The key clue is audio works and the call/participant stay connected. So this is prob not signaling or call setup. 408 / 43203 is happening at video render time bc ACS can’t get frames for that remote stream after retries. Since u reproduced it in a minimal app, that helps a lot. It makes an app-level bug less likely and points more to Firefox capture/encoding/WebRTC behavior or an ACS SDK/browser interop issue.

Worth testing Firefox with VP8/H264 differences if u can, camera permissions, hardware acceleration on/off, and Firefox safe mode/no extensions. I’d also compare Firefox ESR vs latest regular Firefox. If Chrome/Edge as sender don’t repro with the same camera/network, that’s a strong signal.

Grab ACS logs from both sides with setLogLevel('verbose'), plus browser console logs and about:webrtc stats from Firefox while the issue happens. The call id + stream id will be needed too. MS support can’t do much with only the 408, but they can trace the media path with call id/timestamps. https://learn.microsoft.com/en-us/azure/communication-services/concepts/voice-video-calling/known-issues-webjs & https://learn.microsoft.com/en-us/azure/communication-services/concepts/voice-video-calling/calling-sdk-features

My guess not ur integration. More likely ACS WebJS + Firefox sender video pipeline issue, esp if the receiver browser doesn’t matter. Open a support case with the repro repo, SDK version, Firefox version, OS, call ids, stream ids, UTC timestamps, and verbose logs from both clients.

rgds,

Alex

&

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Hello @Bastien Lafont

Thank you for reaching out Microsoft Q&A.

This 408/43203 error ("Failed to render video stream, rendering timed out while waiting for video frames") happens when the SDK subscribes to a remote video stream but doesn't receive actual frames within its timeout window, even though signaling reports the stream as available.

Audio works because it follows a separate path, but video frame delivery can lag slightly behind signaling — especially when the sender is on Firefox (which is still in Public Preview for ACS video calling). Common triggers include the sender's tab being backgrounded, minor network hiccups during initial keyframe delivery, or timing differences in Firefox's WebRTC encoding.

Recommendation:

The most effective mitigation is to wait for is Receiving before calling createView() and add light retry logic for this specific error. Here's a clean pattern based on the official guidance:

JavaScript

 remoteVideoStream.on('isAvailableChanged', async () => {

if (remoteVideoStream.isAvailable) {

// Optional: also wait for isReceiving

if (!remoteVideoStream.isReceiving) {

  await new Promise((resolve) => {

    const handler = () => { 

      if (remoteVideoStream.isReceiving) {

        remoteVideoStream.off('isReceivingChanged', handler);

        resolve();

      }

    };

    remoteVideoStream.on('isReceivingChanged', handler);

    // Safety timeout

    setTimeout(resolve, 3000);

  });

}



const renderer = new VideoStreamRenderer(remoteVideoStream);

try {

  const view = await renderer.createView({ scalingMode: 'Fit' });

  // Attach view.target to your UI

} catch (err) {

  if (err.code === 408 && err.subCode === 43203) {

    console.warn('Render timeout - retrying once...');

    // Retry once after short delay, or dispose & retry

    await new Promise(r => setTimeout(r, 800));

    // ... retry createView

  }

}
  }

});

 

Try the pattern above in your minimal app first.

If the issue continues, share a couple of affected Call IDs + console logs from both sides (especially the Firefox sender). We can dig deeper.

Keep the sender tab active/foreground during testing. 

Reference: [Manage video during calls - An Azure Communication Services article | Microsoft Learn](https://learn.microsoft.com/en-us/azure/communication-services/how-tos/calling-sdk/manage-video?pivots=platform-web#render-remote-participant-videoscreensharing-streams%22https://learn.microsoft.com/en-us/azure/communication-services/how-tos/calling-sdk/manage-video?pivots=platform-web#render-remote-participant-videoscreensharing-streams%22) 

[Video issues - CreateView timeout - Azure Communication Services - Troubleshooting Guide | Microsof…](https://learn.microsoft.com/en-us/azure/communication-services/resources/troubleshooting/voice-video-calling/video-issues/create-view-timeout%22https://learn.microsoft.com/en-us/azure/communication-services/resources/troubleshooting/voice-video-calling/video-issues/create-view-timeout%22)

If the above suggestion doesn't work then please comment below. We're happy to help you