Added gstreamer pipeline sample

samples/cpp/gstreamer_pipeline.cpp

+#include "opencv2/core/utility.hpp"
+#include "opencv2/imgproc.hpp"
+#include "opencv2/imgcodecs.hpp"
+#include "opencv2/highgui.hpp"
+#include <string>
+#include <iostream>
+
+using namespace std;
+using namespace cv;
+
+string getGstDemuxPlugin(string container);
+string getGstAvDecodePlugin(string codec);
+
+int main(int argc, char *argv[])
+{
+    const string keys =
+          "{h help usage ? |           | print help messages   }"
+          "{p pipeline     |gst-default| pipeline name  (supported: 'gst-default', 'gst-vaapi', 'gst-libav', 'ffmpeg') }"
+          "{ct container   |mp4        | container name (supported: 'mp4', 'mov', 'avi', 'mkv') }"
+          "{cd codec       |h264       | codec name     (supported: 'h264', 'h265', 'mpeg2', 'mpeg4', 'mjpeg', 'vp8') }"
+          "{f file path    |           | path to file }"
+          "{fm fast        |           | fast measure fps }";
+
+    CommandLineParser parser(argc, argv, keys);
+
+    parser.about("This program shows how to read a video file with GStreamer pipeline with OpenCV.");
+
+    if (parser.has("help"))
+    {
+        parser.printMessage();
+        return 0;
+    }
+
+    bool   arg_fast_measure = parser.has("fast");              // fast measure fps
+    string arg_pipeline     = parser.get<string>("pipeline"),  // GStreamer pipeline type
+           arg_container    = parser.get<string>("container"), // container type
+           arg_codec        = parser.get<string>("codec"),     // codec type
+           arg_file_name    = parser.get<string>("file");      // path to videofile
+    VideoCapture cap;
+
+    if (!parser.check())
+    {
+        parser.printErrors();
+        return 0;
+    }
+
+    // Choose the constructed GStreamer pipeline
+    if (arg_pipeline.find("gst") == 0)
+    {
+        ostringstream pipeline;
+        pipeline << "filesrc location=\"" << arg_file_name << "\"";
+        pipeline << " ! " << getGstDemuxPlugin(arg_container);
+
+        if (arg_pipeline.find("default") == 4) {
+            pipeline << " ! decodebin";
+        }
+        else if (arg_pipeline.find("vaapi1710") == 4)
+        {
+            pipeline << " ! vaapidecodebin";
+            if (arg_container == "mkv")
+            {
+                pipeline << " ! autovideoconvert";
+            }
+            else
+            {
+                pipeline << " ! video/x-raw, format=YV12";
+            }
+        }
+        else if (arg_pipeline.find("libav") == 4)
+        {
+            pipeline << " ! " << getGstAvDecodePlugin(arg_codec);
+        }
+        else
+        {
+            parser.printMessage();
+            cout << "Unsupported pipeline: " << arg_pipeline << endl;
+            return -4;
+        }
+
+        pipeline << " ! videoconvert";
+        pipeline << "     n-threads=" << getNumThreads();
+        pipeline << " ! appsink sync=false";
+        cap = VideoCapture(pipeline.str(), CAP_GSTREAMER);
+    }
+    else if (arg_pipeline == "ffmpeg")
+    {
+        cap = VideoCapture(arg_file_name, CAP_FFMPEG);
+    }
+    else
+    {
+        parser.printMessage();
+        cout << "Unsupported pipeline: " << arg_pipeline << endl;
+        return -4;
+    }
+
+    // Choose a show video or only measure fps
+    cout << "_____________________________________" << '\n';
+    cout << "Start measure frame per seconds (fps)" << '\n';
+    cout << "Loading ..." << '\n';
+
+    Mat frame;
+    vector<double> tick_counts;
+
+    cout << "Start decoding: " << arg_file_name;
+    cout << " (" << arg_pipeline << ")" << endl;
+
+    while(true)
+    {
+        int64 temp_count_tick = getTickCount();
+        cap >> frame;
+        temp_count_tick = getTickCount() - temp_count_tick;
+        if (frame.empty()) { break; }
+        tick_counts.push_back(static_cast<double>(temp_count_tick));
+        if (arg_fast_measure && (tick_counts.size() > 1000)) { break; }
+
+    }
+    double time_fps = sum(tick_counts)[0] / getTickFrequency();
+
+    if (tick_counts.size() != 0)
+    {
+        cout << "Finished: " << tick_counts.size() << " in " << time_fps <<" sec ~ " ;
+        cout << tick_counts.size() / time_fps <<" fps " << endl;
+    }
+    else
+    {
+        cout << "Failed decoding: " << arg_file_name;
+        cout << " (" << arg_pipeline << ")" << endl;
+        return -5;
+    }
+    return 0;
+}
+
+// Choose a video container
+string getGstDemuxPlugin(string container) {
+    if      (container == "avi") { return "avidemux"; }
+    else if (container == "mp4") { return "qtdemux"; }
+    else if (container == "mov") { return "qtdemux"; }
+    else if (container == "mkv") { return "matroskademux"; }
+    return string();
+}
+
+// Choose a codec
+string getGstAvDecodePlugin(string codec) {
+    if      (codec == "h264")  { return "h264parse ! avdec_h264"; }
+    else if (codec == "h265")  { return "h265parse ! avdec_h265"; }
+    else if (codec == "mpeg2") { return "avdec_mpeg2video"; }
+    else if (codec == "mpeg4") { return "avdec_mpeg4"; }
+    else if (codec == "mjpeg") { return "avdec_mjpeg"; }
+    else if (codec == "vp8")   { return "avdec_vp8"; }
+    return string();
+}