如何将opencv mat写入gstreamer管道？

Question

我想在gstreamer管道中添加一些opencv进程,然后通过udpsink发送它.

我可以像这样从gstreamer读取帧:

// may add some plugins to the pipeline later
cv::VideoCapture cap("v4l2src ! video/x-raw, framerate=30/1, width=640, height=480, format=RGB ! videoconvert ! appsink");
cv::Mat frame;
while(ture){
  cap >> frame;
  // do some processing to the frame
}

但无法弄清楚的是如何将已处理的帧传递给以下管道: appsrc ! x264enc ! mpegtsmux ! udpsink host=localhost port=5000

我试过了

cv::VideoWriter writer = cv::VideoWriter("appsrc ! x264enc ! mpegtsmux ! udpsink host=localhost port=5000",  0, (double)30, cv::Size(640, 480), true);
writer << processedFrame;

但是,接收方没有收到任何信息.(我使用管道$gst-launch-1.0 udpsrc port=5000 ! tsparse ! tsdemux ! h264parse ! avdec_h264 ! videoconvert ! ximagesink sync=false作为接收器)

我的问题是,我可以将已处理的opencv Mat传递给gstreamer管道并让它进行一些编码,然后通过udpsink通过网络发送吗？如果是,我该如何实现？

附带问题,有什么办法可以调试VideoWriter吗？例如检查帧是否实际写入其中.

请注意,我在ubuntu 14.04上使用opencv 2.4.12和gstreamer 1.2.

任何帮助都很棒!

编辑: 为了提供更多信息,我测试了以下代码,它给了GStreamer Plugin: Embedded video playback halted; module appsrc0 reported: Internal data flow error.

#include <stdio.h>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/opencv.hpp>

int main(int argc, char *argv[]){
    cv::VideoCapture cap("v4l2src ! video/x-raw, framerate=30/1, width=640, height=480, format=RGB ! videoconvert ! appsink");
    if (!cap.isOpened()) {
        printf("=ERR= can't create capture\n");
        return -1;
    }
    cv::VideoWriter writer;
    // problem here
    writer.open("appsrc ! video/x-raw, framerate=30/1, width=640, height=480, format=RGB ! autovideoconvert ! ximagesink sync=false", 0, (double)30, cv::Size(640, 480), true);
    if (!writer.isOpened()) {
        printf("=ERR= can't create writer\n");
        return -1;
    }

    cv::Mat frame;
    int key;

    while (true) {
        cap >> frame;
        if (frame.empty()) {
            printf("no frame\n");
            break;
        }
        writer << frame;
        key = cv::waitKey( 30 );
    }

    cv::destroyWindow( "video" );
}

显然,appsrc管道有问题,但我不知道出了什么问题,因为管道gst-launch-1.0 v4l2src ! video/x-raw, framerate=30/1, width=640, height=480, format=RGB ! videoconvert ! ximagesink sync=false工作正常.

Answer 1

经过几个小时的搜索和测试,我终于得到了答案.关键是只videoconvert在使用之后appsrc,不需要设置上限.因此,编写器管道看起来像appsrc ! videoconvert ! x264enc ! mpegtsmux ! udpsink host=localhost port=5000.

下面是一个示例代码,它从gstreamer管道读取图像,执行一些opencv图像处理并将其写回管道.

使用此方法,您可以轻松地将任何opencv进程添加到gstreamer管道.

// Compile with: $ g++ opencv_gst.cpp -o opencv_gst `pkg-config --cflags --libs opencv`

#include <stdio.h>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/opencv.hpp>

int main(int argc, char** argv) {

    // Original gstreamer pipeline: 
    //      == Sender ==
    //      gst-launch-1.0 v4l2src 
    //      ! video/x-raw, framerate=30/1, width=640, height=480, format=RGB 
    //      ! videoconvert
    //      ! x264enc noise-reduction=10000 tune=zerolatency byte-stream=true threads=4
    //      ! mpegtsmux 
    //      ! udpsink host=localhost port=5000
    //      
    //      == Receiver ==
    //      gst-launch-1.0 -ve udpsrc port=5000
    //      ! tsparse ! tsdemux 
    //      ! h264parse ! avdec_h264 
    //      ! videoconvert 
    //      ! ximagesink sync=false

    // first part of sender pipeline
    cv::VideoCapture cap("v4l2src ! video/x-raw, framerate=30/1, width=640, height=480, format=RGB ! videoconvert ! appsink");
    if (!cap.isOpened()) {
        printf("=ERR= can't create video capture\n");
        return -1;
    }

    // second part of sender pipeline
    cv::VideoWriter writer;
    writer.open("appsrc ! videoconvert ! x264enc noise-reduction=10000 tune=zerolatency byte-stream=true threads=4 ! mpegtsmux ! udpsink host=localhost port=9999"
                , 0, (double)30, cv::Size(640, 480), true);
    if (!writer.isOpened()) {
        printf("=ERR= can't create video writer\n");
        return -1;
    }

    cv::Mat frame;
    int key;

    while (true) {

        cap >> frame;
        if (frame.empty())
            break;

        /* Process the frame here */

        writer << frame;
        key = cv::waitKey( 30 );
    }
}

希望这可以帮助.;)