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c++ - 如何将 Opencv VideoWriter 与 GStreamer 一起使用？

问题描述

我正在尝试使用 Opencv VideoWriter 传输 h264 流，以使用 VideoCapture 在网络上的另一台电脑上获取它。但是，我被困在 VideoWriter 上。执行此代码会返回错误，并且 out.isOpened () 始终为 false。

    int FOURCC = cv::VideoWriter::fourcc('H', '2', '6', '4');
    cv::VideoWriter out;
    out.open ("appsrc ! videoconvert ! x264enc tune=zerolatency bitrate=500 speed-preset=superfast ! rtph264pay ! udpsink host=127.0.0.1 port=5000",
        cv::CAP_GSTREAMER,
        FOURCC,
        16,
        cv::Size (640, 480),
        true);

    if (!out.isOpened ()) {
        qDebug () << "\ n ***** Failed to open videowriter *****";
        return -1;
    }

[ WARN:0] global D:\Libs\opencv-4.3.0\modules\videoio\src\cap_gstreamer.cpp (1274) cv::CvVideoWriter_GStreamer::close_ OpenCV | GStreamer warning: No source in GStreamer pipeline. Ignore
[ERROR:0] global D:\Libs\opencv-4.3.0\modules\videoio\src\cap.cpp (527) cv::VideoWriter::open VIDEOIO(GSTREAMER): raised OpenCV exception:
OpenCV(4.3.0) D:\Libs\opencv-4.3.0\modules\videoio\src\cap_gstreamer.cpp:144: error: (-215:Assertion failed) ptr in function 'cv::`anonymous-namespace'::GSafePtr<struct _GstElement>::get'

***** Failed open videowriter *****

即使是一个简单的例子也会给我一个错误并且 out.isOpened() 错误。

    out.open("autovideosrc ! videoconvert ! appsink",
             cv::CAP_GSTREAMER,
             FOURCC,
             16,
             cv::Size(640, 480),
             true);

[ WARN:0] global D:\Libs\opencv-4.3.0\modules\videoio\src\cap_gstreamer.cpp (1500) cv::CvVideoWriter_GStreamer::open    OpenCV | GStreamer warning: OpenCV backend does not support this file type (extension): autovideosrc ! videoconvert !   appsink
[ WARN:0] global D:\Libs\opencv-4.3.0\modules\videoio\src\cap_gstreamer.cpp (1274) cv::CvVideoWriter_GStreamer::close_  OpenCV | GStreamer warning: No source in GStreamer pipeline. Ignore

    ***** Failed to open videowriter *****

opencv 4.3.0 的版本是从源代码编译的，支持 gstreamer。cv::getBuildInformation () 说：

    Video I/O:
      DC1394: NO
      FFMPEG: YES (prebuilt binaries)
        avcodec: YES (58.54.100)
        avformat: YES (58.29.100)
        avutil: YES (56.31.100)
        swscale: YES (5.5.100)
        avresample: YES (4.0.0)
      GStreamer: YES (1.16.2)
      DirectShow: YES
      Media Foundation: YES
        DXVA: YES

如何流式传输流？VideoWriter应该指定哪些参数？我尝试了谷歌的各种提示，但没有一个对我有帮助。我会很感激一个简单的例子，说明如何从一侧的 VideoWriter 发送流并从另一侧的 VideoCapture 接收它。我正在使用 Windows 10 x64 和 Qt5.13 MSVC2017

标签： c++opencvgstreamer

解决方案

您需要将原始视频提供给appsrc. 设置fourcc 为h264强制VideoWriter编码视频而不是 gstreamer 管道。您可以将您的设置fourcc为 0 以推送原始视频。以下应该工作。

cv::VideoWriter out;
out.open ("appsrc ! videoconvert ! x264enc tune=zerolatency bitrate=500 speed-preset=superfast ! rtph264pay ! udpsink host=127.0.0.1 port=5000",
    cv::CAP_GSTREAMER,
    0,
    16,
    cv::Size (640, 480),
    true);

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