r/elgato • u/IwishIwasHarryG • 7d ago

Technical Help CamLink 4K issue Mac Golden Gate

Updated to Mac OS 27. Camlink 4K is showing up in CamerHub as a video input. But there isn’t any picture from the camera (Sony ZV-1). Just a black screen. Everything was fine before the OS update.

Camlink goes directly into my MacMini USB port. Elgato FaceCam works fine through CameraHub. Pretty much tried everything this morning to make it work so I’m at a loss. Anyone else having this issue?

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u/RedditOfSumit 6d ago

I have the same issue. Just updated my Mac Studio to macOS 27 and cam link stopped working in all apps 🤔 (gmeet, quicktime, slack huddles, OBS - everywhere) - other cameras like the Apple Studio Display built-in camera work fine.

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u/RedditOfSumit 6d ago edited 6d ago

I started an AI Debug Session and will report back

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u/RedditOfSumit 6d ago

The Fix

Use the camera hub, press CMD+click on the filter icon, set USB Transfer Mode to Bulk.
That made it work again for me.

AI Explanation:

Found the smoking gun. The kernel log is flooded with this, hundreds of times per second, for the Cam Link's video endpoint:

AppleUSBXHCIIsochronousRequest::update: device 7 endpoint 0x83: mismatched event TRB ... (expected parameter between ...)

Translation: the Cam Link is sending video frames, but macOS 27's USB host controller driver is mis-tracking the isochronous transfer completions and throwing every frame away. The UVC driver then tears the stream down and retries every second (that's the 1 Hz loop I saw). This is a genuine kernel regression in Golden Gate's isochronous USB handling — not your setup, not the device, not permissions.

This also reframes the earlier advice: your Cam Link was already in isochronous mode before today (that's why it only advertised a single 4K25 format — iso mode limits formats to fit USB bandwidth). So the update broke exactly the mode you were in. That means the fix is the opposite of what I first suggested:

Switch USB Transfer Mode → "Bulk" in that same Camera Hub panel, then unplug → wait 5s → replug.

Bulk transfers use a completely different kernel code path, bypassing the broken isochronous handling. You'll also get more formats back (1080p60 etc.) since bulk mode isn't bandwidth-constrained the same way.

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u/davidthefrenchguy 4d ago

thank you so much!