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opencv YOLOv2 vs darknet YOLOv2; is the results should be similar or different?

asked 2018-01-15 12:59:10 -0600

ZeroLogic gravatar image

This is the result of OpenCV YOLOv2 image description

While this is the result of using darknet YOLOv2 image description

May I know why opencv YOLOv2 is different from darknet's? Should both of the results are different? If I'm wrong in any way please do correct me.

cfg = "yolo.cfg" weights = "yolo.weights" names = "coco.names" threshold = 0.24

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Afaik OpenCV has YOLOv1 because it does not have these return layers that YOLOv2 needs and hence the lower accuracy?

StevenPuttemans gravatar imageStevenPuttemans ( 2018-01-16 00:58:19 -0600 )edit

as mentioned here, AlexeyAB states that: Now Darknet Yolo v2 is added to the OpenCV: opencv/opencv#9705 You can use it from master-branch or since OpenCV 3.4.0 will be released.

so which one is right? is OpenCV's v1 or v2?

ZeroLogic gravatar imageZeroLogic ( 2018-01-16 02:56:18 -0600 )edit

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answered 2018-01-16 03:13:58 -0600

dkurt gravatar image

Please add more details when you refer a public models. I've found at least 3 YOLOv2 at and they aren't similar. I hope YOLOv2 trained on COCO dataset with input size 608x608 is used. Am I right? OpenCV's sample works with 416x416 images for now so you need to modify a source code a bit:


Mat inputBlob = blobFromImage(frame, 1 / 255.F, Size(416, 416), Scalar(), true, false);


Mat inputBlob = blobFromImage(frame, 1 / 255.F, Size(608, 608), Scalar(), true, false);

One more thing that corresponding .cfg file has a confidence threshold inside:

thresh = .6

I don't know why Darknet ignore it but OpenCV consider this value to threshold detections with a low confidence. So you have to modify it too. In example,

thresh = .1

The result:

image description

Hidden objects has confidences about 0.4, 0.29, 0.37.

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noted, sorry for lack of information. thank you in highlighting the input size

ZeroLogic gravatar imageZeroLogic ( 2018-01-16 03:23:44 -0600 )edit

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Asked: 2018-01-15 12:59:10 -0600

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Last updated: Jan 16 '18