# Workflow block velocity

**URL:** <https://discuss.roboflow.com/t/workflow-block-velocity/10132>\
**Category:** 🤝  Community Help\
**Created:** [June 4, 2025, 7:41pm UTC](https://discuss.roboflow.com/t/workflow-block-velocity/10132 "2025-06-04T19:41:53Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Thomas](https://avatars.discourse-cdn.com/v4/letter/t/e36b37/32.png) [@Thomas](https://discuss.roboflow.com/u/Thomas)\
**Post date:** [June 4, 2025, 7:41pm UTC](https://discuss.roboflow.com/t/workflow-block-velocity/10132/1 "2025-06-04T19:41:53Z")

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Hi  
I am running a workflow with inference workflows process-video on my local inference server.

I am trying to use the workflow block “velocity”, but I am continuously getting errors:

RuntimeError: Encountered the following errors while processing the video:  
{  
“error\_type”: “ExecutionEngineRuntimeError”,  
“error\_message”: “Requested Workflow output serialization, but for output `velocity` which evaluates into Python  
type: \<class ‘supervision.detection.core.Detections’\> cannot successfully apply any of registered serializers.”,  
“error\_context”: “inference\_thread”

It is not clear, how to vizualize the outputs of velocity. I am trying to use label visualizalization, but the error remains. the documentation of this building block seems a bit “light”, but I would appreciate any hints on how to get that running. (both for visualizing and for sinking the data for later analysis)

thx & cheers  
Thomas

- \*\*Project Type:\*\*inference on mp4 videos
- \*\*Operating System & Browser:\*\*roboflow inference server GPU latest running on Docker/Debian12
- \*\*Project Universe Link or Workspace/Project ID:\*\*beeometer

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**Author:** ![Grzegorz](https://yyz1.discourse-cdn.com/flex029/user_avatar/discuss.roboflow.com/grzegorz/32/2877_2.png) [@Grzegorz](https://discuss.roboflow.com/u/Grzegorz)\
**Post date:** [June 18, 2025, 1:11pm UTC](https://discuss.roboflow.com/t/workflow-block-velocity/10132/2 "2025-06-18T13:11:32Z")

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Hi @Thomas ,

Thank you for reporting this issue. Indeed, there was a problem with output representation of velocity block - this was fixed in `Inference` package and fix will be included in next release of `Inference`.

Thanks again,  
Grzegorz

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**Author:** ![Thomas](https://avatars.discourse-cdn.com/v4/letter/t/e36b37/32.png) [@Thomas](https://discuss.roboflow.com/u/Thomas)\
**Post date:** [June 18, 2025, 2:10pm UTC](https://discuss.roboflow.com/t/workflow-block-velocity/10132/3 "2025-06-18T14:10:36Z")

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Hi Grzegorz

cool, thanks for the quick fix…so that will be available in v0.50.5 ?

thx & cheers

Thomas

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**Author:** ![Grzegorz](https://yyz1.discourse-cdn.com/flex029/user_avatar/discuss.roboflow.com/grzegorz/32/2877_2.png) [@Grzegorz](https://discuss.roboflow.com/u/Grzegorz)\
**Post date:** [June 18, 2025, 3:58pm UTC](https://discuss.roboflow.com/t/workflow-block-velocity/10132/4 "2025-06-18T15:58:17Z")

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Hi @Thomas,

We are already at 0.50.5 - so next release, most likely this Friday

Thanks again,  
Grzegorz

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**Author:** ![system](https://canada1.discourse-cdn.com/flex029/uploads/roboflow1/original/1X/bb6edbfa56d0cf2ee603f061e9e09103502cc8cc.png) [@system](https://discuss.roboflow.com/u/system)\
**Post date:** [July 9, 2025, 3:58pm UTC](https://discuss.roboflow.com/t/workflow-block-velocity/10132/5 "2025-07-09T15:58:50Z")

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Closed on July 9, 2025, 3:58pm UTC

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