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VideoCapture open camera slow#26601

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asmorkalov merged 1 commit intoopencv:4.xfrom
dai-xin:4.x
Jan 22, 2025
Merged

VideoCapture open camera slow#26601
asmorkalov merged 1 commit intoopencv:4.xfrom
dai-xin:4.x

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@dai-xin
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@dai-xin dai-xin commented Dec 10, 2024

Resolve the issue of slow camera opening when using dshow as the backend for VideoCapture.

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

  • I agree to contribute to the project under Apache 2 License.
  • To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
  • The PR is proposed to the proper branch
  • There is a reference to the original bug report and related work : Camera is very slow to open when using the MSMF VideoCapture backend #17687 , about DSHOW slow.
  • There is accuracy test, performance test and test data in opencv_extra repository, if applicable
    Patch to opencv_extra has the same branch name.
  • The feature is well documented and sample code can be built with the project CMake
    dshow-code.zip
    DSHOW_test.docx

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dai-xin commented Dec 10, 2024

image
I believe the key issue lies here: it first creates and opens the device, and then sets the properties. Setting the properties causes the device to close and reopen, which takes a considerable amount of time. My approach is to pass the parameters directly, similar to what is done in the setProperty method.

@asmorkalov asmorkalov self-assigned this Dec 10, 2024
@asmorkalov asmorkalov added this to the 4.11.0 milestone Dec 10, 2024
@asmorkalov asmorkalov requested a review from mshabunin December 16, 2024 10:50
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asmorkalov commented Dec 16, 2024

@mshabunin could you take a look?

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mshabunin commented Dec 17, 2024

I'm observing difference in actual fourcc set to a stream with this patch:

Without patch:

Open time: 3323.28 ms
FPS: 0 w:1600 h:896
Actual   : 0x47504a4d
Requested: 0x47504a4d
Frame: [1600 x 896] x 3 in 1000.76 ms
Total: 4324.04 ms

With patch:

Open time: 887.593 ms
FPS: 0 w:1600 h:896
Actual   : 0xe436eb7d
Requested: 0x47504a4d
Frame: [1600 x 896] x 3 in 999.927 ms
Total: 1887.52 ms

dshow.cpp.txt

@asmorkalov asmorkalov removed this from the 4.11.0 milestone Dec 19, 2024
@asmorkalov asmorkalov added this to the 4.12.0 milestone Jan 22, 2025
@asmorkalov asmorkalov merged commit 4a4031d into opencv:4.x Jan 22, 2025
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sturkmen72 commented Jan 22, 2025

I was not aware that the camera could be opened with parameters. I may update code samples related to VideoCapture accordingly.

        std::vector<int> params;
        params.push_back(cv::CAP_PROP_FRAME_WIDTH);
        params.push_back(size.width);
        params.push_back(cv::CAP_PROP_FRAME_HEIGHT);
        params.push_back(size.height);
        params.push_back(cv::CAP_PROP_FOURCC);
        params.push_back(fourcc);
        cap.open(0, cv::CAP_DSHOW, params);

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asmorkalov commented Jan 23, 2025

Great idea! Thanks a lot!

@asmorkalov asmorkalov mentioned this pull request Feb 19, 2025
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@asmorkalov asmorkalov asmorkalov approved these changes

@mshabunin mshabunin Awaiting requested review from mshabunin

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@dai-xin @asmorkalov @mshabunin @sturkmen72