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DNN : fix bug in extracting prior-box variances in detection output layer#20525

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opencv-pushbot merged 1 commit intoopencv:3.4from
jebastin-nadar:fix-prior-variances
Aug 13, 2021
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DNN : fix bug in extracting prior-box variances in detection output layer#20525
opencv-pushbot merged 1 commit intoopencv:3.4from
jebastin-nadar:fix-prior-variances

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@jebastin-nadar jebastin-nadar commented Aug 9, 2021

GetPriorBBoxes() assumes the input blob has shape (1, 2, num_priors * 4, 1) with the second channel being prior-box variances. But when _varianceEncodedInTarget is true, the input has shape (1, 1, num_prioirs * 4, 1), as checked by the following assertion

opencv/modules/dnn/src/layers/detection_output_layer.cpp

Line 239 in 424eaba

CV_Assert(inputs[2][1] == 1 + (int)(!_varianceEncodedInTarget));

Another reference in the reshape for the input of Detection output layer in faster-rcnn-vgg16.

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@asmorkalov asmorkalov requested a review from JulieBar August 9, 2021 07:13
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alalek commented Aug 9, 2021

@SamFC10 Thank you for contribution!
Is it possible to add accuracy test for this case?

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jebastin-nadar commented Aug 9, 2021

Is it possible to add accuracy test for this case?

There were some faster rcnn tests which crashed sporadically in my int8 PR (#20228) on Windows CI builders and local windows machine with the message - unknown file: error: SEH exception with code 0xc0000005 thrown in the test body. Tracing back, it was the illegal memory access in prior-box variances which caused these crashes. I don't know how to reproduce these sporadic crashes in a test. Will need some help.

@asmorkalov asmorkalov removed the request for review from JulieBar August 11, 2021 06:50
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alalek commented Aug 11, 2021

Tracing back, it was the illegal memory access in prior-box variances which caused these crashes.

This usually happens when memory is accessed without checking arrays layouts (through CV_Check* or CV_Assert macros). It makes sense to add these checks there.

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jebastin-nadar commented Aug 12, 2021

add these checks there

There is one already

opencv/modules/dnn/src/layers/detection_output_layer.cpp

Line 239 in 424eaba

CV_Assert(inputs[2][1] == 1 + (int)(!_varianceEncodedInTarget));

It was added in #11255 but the function GetPriorBBoxes() wasn't modified along with the added assertion.

@asmorkalov asmorkalov requested a review from rogday August 12, 2021 08:17
@vpisarev vpisarev self-requested a review August 13, 2021 08:29
@vpisarev vpisarev self-assigned this Aug 13, 2021
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vpisarev commented Aug 13, 2021

👍

@opencv-pushbot opencv-pushbot merged commit 9d3826c into opencv:3.4 Aug 13, 2021
@alalek alalek mentioned this pull request Aug 14, 2021
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@jebastin-nadar jebastin-nadar deleted the fix-prior-variances branch August 19, 2021 04:51
@alalek alalek mentioned this pull request Oct 15, 2021
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@vpisarev vpisarev vpisarev approved these changes

@rogday rogday Awaiting requested review from rogday

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