# Virtual Background: unknown message in single thread vb worker

**URL:** <https://devforum.zoom.us/t/virtual-background-unknown-message-in-single-thread-vb-worker/110043>\
**Category:** Video SDK\
**Created:** [May 15, 2024, 9:46pm UTC](https://devforum.zoom.us/t/virtual-background-unknown-message-in-single-thread-vb-worker/110043 "2024-05-15T21:46:31Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![curran.birdwell](https://avatars.discourse-cdn.com/v4/letter/c/9fc29f/32.png) [@curran.birdwell](https://devforum.zoom.us/u/curran.birdwell)\
**Post date:** [May 15, 2024, 9:46pm UTC](https://devforum.zoom.us/t/virtual-background-unknown-message-in-single-thread-vb-worker/110043/1 "2024-05-15T21:46:31Z")

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- _Video SDK Type and Version_\*  
1.11.0, 1.10.7

**Description**  
I’m currently trying to implement blurred backgrounds. I’m doing this without SharedArrayBuffer. Console logs indicate the virtual Background worker is failing. The video does start, but with no blur or background image. The current relevant code is very simple:  
await zoomClient.init(‘en-US’, ‘Global’, { patchJsMedia: true, enforceVirtualBackground: true });  
await zoomSession.startVideo({ virtualBackground: { imageUrl: ‘blur’ } });

**Error?**  
On initializing and connecting to zoom, I receive the first error “unknown message in single thread vb worker: undefined”, then when starting video I receive the second error "unknown message in single thread vb worker: vb "

unknown message in single thread vb worker: undefined  
value @ 33a15246-0f4e-4591-a68f-aded56b8d0f2:1

unknown message in single thread vb worker: vb  
value @ 33a15246-0f4e-4591-a68f-aded56b8d0f2:1

**Troubleshooting Routes**  
I upgraded the version from 1.10.7 to 1.11.0. I also tested with an input image which resulted in the same messages.

**Browser**  
Chrome version: 124.0.6367.119

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<div class="post-metadata">

**Author:** ![vic.yang](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/vic.yang/32/24656_2.png) [@vic.yang](https://devforum.zoom.us/u/vic.yang)\
**Post date:** [May 17, 2024, 3:43am UTC](https://devforum.zoom.us/t/virtual-background-unknown-message-in-single-thread-vb-worker/110043/2 "2024-05-17T03:43:22Z")

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Hey @curran.birdwell

Thanks for your feedback.

Could you share the session ID that’s experiencing issues with us for troubleshooting purposes?

Thanks  
Vic

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<div class="post-metadata">

**Author:** ![curran.birdwell](https://avatars.discourse-cdn.com/v4/letter/c/9fc29f/32.png) [@curran.birdwell](https://devforum.zoom.us/u/curran.birdwell)\
**Post date:** [May 17, 2024, 7:13pm UTC](https://devforum.zoom.us/t/virtual-background-unknown-message-in-single-thread-vb-worker/110043/3 "2024-05-17T19:13:45Z")

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Hey @vic.yang  
It’s happening on all my sessions most recently session: VjVH16roT5O1d0lbioDm/g==   
Thanks

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<div class="post-metadata">

**Author:** ![vic.yang](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/vic.yang/32/24656_2.png) [@vic.yang](https://devforum.zoom.us/u/vic.yang)\
**Post date:** [May 20, 2024, 8:10am UTC](https://devforum.zoom.us/t/virtual-background-unknown-message-in-single-thread-vb-worker/110043/4 "2024-05-20T08:10:02Z")

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Hey @curran.birdwell

Thank you for sharing the session ID. We are currently analyzing the issue.

Thanks  
Vic

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<div class="post-metadata">

**Author:** ![curran.birdwell](https://avatars.discourse-cdn.com/v4/letter/c/9fc29f/32.png) [@curran.birdwell](https://devforum.zoom.us/u/curran.birdwell)\
**Post date:** [June 10, 2024, 3:22pm UTC](https://devforum.zoom.us/t/virtual-background-unknown-message-in-single-thread-vb-worker/110043/5 "2024-06-10T15:22:55Z")

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Hey @vic.yang,  
Any updates?  
Thanks