// This file is part of OpenCV project.
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// It is subject to the license terms in the LICENSE file found in the top-level directory
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// of this distribution and at http://opencv.org/license.html.
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//
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// Copyright (C) 2019 Intel Corporation
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#ifndef OPENCV_GAPI_STREAMING_CAP_HPP
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#define OPENCV_GAPI_STREAMING_CAP_HPP
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/**
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* YOUR ATTENTION PLEASE!
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*
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* This is a header-only implementation of cv::VideoCapture-based
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* Stream source. It is not built by default with G-API as G-API
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* doesn't depend on videoio module.
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*
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* If you want to use it in your application, please make sure
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* videioio is available in your OpenCV package and is linked to your
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* application.
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*
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* Note for developers: please don't put videoio dependency in G-API
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* because of this file.
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*/
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#include <opencv2/videoio.hpp>
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#include <opencv2/gapi/garg.hpp>
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namespace cv {
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namespace gapi {
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namespace wip {
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/**
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* @brief OpenCV's VideoCapture-based streaming source.
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*
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* This class implements IStreamSource interface.
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* Its constructor takes the same parameters as cv::VideoCapture does.
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*
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* Please make sure that videoio OpenCV module is avaiable before using
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* this in your application (G-API doesn't depend on it directly).
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*
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* @note stream sources are passed to G-API via shared pointers, so
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* please gapi::make_src<> to create objects and ptr() to pass a
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* GCaptureSource to cv::gin().
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*/
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class GCaptureSource: public IStreamSource
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{
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public:
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explicit GCaptureSource(int id) : cap(id) { prep(); }
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explicit GCaptureSource(const std::string &path) : cap(path) { prep(); }
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// TODO: Add more constructor overloads to make it
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// fully compatible with VideoCapture's interface.
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protected:
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cv::VideoCapture cap;
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cv::Mat first;
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bool first_pulled = false;
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void prep()
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{
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// Prepare first frame to report its meta to engine
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// when needed
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GAPI_Assert(first.empty());
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cv::Mat tmp;
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if (!cap.read(tmp))
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{
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GAPI_Assert(false && "Couldn't grab the very first frame");
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}
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// NOTE: Some decode/media VideoCapture backends continue
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// owning the video buffer under cv::Mat so in order to
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// process it safely in a highly concurrent pipeline, clone()
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// is the only right way.
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first = tmp.clone();
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}
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virtual bool pull(cv::gapi::wip::Data &data) override
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{
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if (!first_pulled)
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{
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GAPI_Assert(!first.empty());
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first_pulled = true;
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data = first; // no need to clone here since it was cloned already
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return true;
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}
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if (!cap.isOpened()) return false;
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cv::Mat frame;
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if (!cap.read(frame))
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{
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// end-of-stream happened
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return false;
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}
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// Same reason to clone as in prep()
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data = frame.clone();
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return true;
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}
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virtual GMetaArg descr_of() const override
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{
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GAPI_Assert(!first.empty());
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return cv::GMetaArg{cv::descr_of(first)};
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}
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};
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} // namespace wip
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} // namespace gapi
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} // namespace cv
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#endif // OPENCV_GAPI_STREAMING_CAP_HPP
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