adds further details to videowriter_basic #65

opencv/examples/cpp/README.md

@@ -1,23 +1,5 @@
 # CPP Examples 
 
-## clean, build and execute 
-```
-cd .. && rm -rf build  && bash build.bash  && cd build
-./*APP 
-```
-
-## execute 
-```
-cd build
-./*APP
-vlc live.avi
-```
-## clean 
-
-```  
-cd .. && rm -rf build
-```
-
 
 ## Reference 
 * Modern C++ Course: OpenCV 4 C++ in GNU/Linux (Tutorial 3, I. Vizzo, 2020)

opencv/examples/cpp/videowriter_basic/CMakeLists.txt

@@ -11,8 +11,7 @@ set(${PROJECT_NAME}_SRC
 find_package(OpenCV 4 REQUIRED)
 include_directories(${OpenCV_INCLUDE_DIRS})
 
-#########################################################
-# Executable
+#Executable
 add_executable( ${PROJECT_NAME} ${${PROJECT_NAME}_SRC} )
 target_link_libraries( ${PROJECT_NAME} ${OpenCV_LIBS} )
 

opencv/examples/cpp/videowriter_basic/README.md

@@ -1,6 +1,65 @@
 # Video Recording
 
+## video features
+```
+v4l2-ctl --list-formats-ext
+ioctl: VIDIOC_ENUM_FMT
+	Type: Video Capture
+
+	[0]: 'MJPG' (Motion-JPEG, compressed)
+		Size: Discrete 1280x720
+			Interval: Discrete 0.033s (30.000 fps)
+		Size: Discrete 960x540
+			Interval: Discrete 0.033s (30.000 fps)
+		Size: Discrete 848x480
+			Interval: Discrete 0.033s (30.000 fps)
+		Size: Discrete 640x480
+			Interval: Discrete 0.033s (30.000 fps)
+		Size: Discrete 640x360
+			Interval: Discrete 0.033s (30.000 fps)
+	[1]: 'YUYV' (YUYV 4:2:2)
+		Size: Discrete 640x480
+			Interval: Discrete 0.033s (30.000 fps)
+		Size: Discrete 640x360
+			Interval: Discrete 0.033s (30.000 fps)
+```
+
+v4l2-ctl --all
+```
+...
+Video input : 0 (Input 1: ok)
+Format Video Capture:
+	Width/Height      : 640/480
+	Pixel Format      : 'YUYV' (YUYV 4:2:2)
+	Field             : None
+	Bytes per Line    : 1280
+	Size Image        : 614400
+	Colorspace        : sRGB
+	Transfer Function : Rec. 709
+
+```
+
+
+## clean, build and execute 
+```
+bash build.bash
+```
+
+
+## execute 
+```
+./build/videowriter
+vlc live.avi
+```
+
+## clean 
+```  
+rm -rf build live.avi
+```
+
+
 ## Reference 
+https://docs.opencv.org/4.9.0/df/d94/samples_2cpp_2videowriter_basic_8cpp-example.html#a5  
 https://github.com/Myzhar/simple-opencv-kalman-tracker
 https://www.myzhar.com/blog/tutorials/tutorial-opencv-ball-tracker-using-kalman-filter/
 https://www.youtube.com/watch?v=sG-h5ONsj9s&feature=emb_title

opencv/examples/cpp/videowriter_basic/build.bash

@@ -1,4 +1,5 @@
 ## how to compile
+rm -rf build 
 mkdir build && cd build
 cmake ..
 make 

opencv/examples/cpp/videowriter_basic/src/main.cpp

@@ -5,30 +5,46 @@
 #include <stdio.h>
 using namespace cv;
 using namespace std;
+
+#define VID_WIDTH 640
+#define VID_HEIGHT 480
+#define VIDEO_IN "/dev/video0"
+
 int main(int, char**)
 {
     Mat src;
     // use default camera as video source
-    VideoCapture cap(0);
+    VideoCapture cap(VIDEO_IN);
     // check if we succeeded
     if (!cap.isOpened()) {
         cerr << "ERROR! Unable to open camera\n";
         return -1;
     }
+
     // get one frame from camera to know frame size and type
     cap >> src;
     // check if we succeeded
     if (src.empty()) {
         cerr << "ERROR! blank frame grabbed\n";
         return -1;
     }
+
+    cout << "Original video size " << src.size() << endl;
+    Size targetSize(VID_WIDTH, VID_HEIGHT);
+    cap.set(cv::CAP_PROP_FRAME_WIDTH, VID_WIDTH);
+    cap.set(cv::CAP_PROP_FRAME_HEIGHT, VID_HEIGHT);
+    cout << "Target video size " << targetSize << endl;
+
+    cout << "Source type " << src.type() << endl;
     bool isColor = (src.type() == CV_8UC3);
+
     //--- INITIALIZE VIDEOWRITER
     VideoWriter writer;
     int codec = VideoWriter::fourcc('M', 'J', 'P', 'G');  // select desired codec (must be available at runtime)
-    double fps = 25.0;                          // framerate of the created video stream
+    double fps = 30.0;                          // framerate of the created video stream
     string filename = "./live.avi";             // name of the output video file
-    writer.open(filename, codec, fps, src.size(), isColor);
+    //writer.open(filename, codec, fps, src.size(), isColor);
+    writer.open(filename, codec, fps, targetSize, isColor);
     // check if we succeeded
     if (!writer.isOpened()) {
         cerr << "Could not open the output video file for write\n";
@@ -47,7 +63,7 @@ int main(int, char**)
         // encode the frame into the videofile stream
         writer.write(src);
         // show live and wait for a key with timeout long enough to show images
-        imshow("Live", src);
+        imshow("Live Video Stream", src);
         if (waitKey(5) >= 0)
             break;
     }

opencv/installation/installation.bash

@@ -14,7 +14,7 @@ unzip opencv_contrib.zip
 # Create build directory and switch into it
 mkdir -p build && cd build
 # Configure
-cmake -DOPENCV_EXTRA_MODULES_PATH=../opencv_contrib-4.x/modules ../opencv-4.x
+cmake -DOPENCV_EXTRA_MODULES_PATH=../opencv_contrib-4.x/modules ../opencv-4.x -DWITH_FFMPEG=ON -DOPENCV_GENERATE_PKGCONFIG=ON
 
 ### leaving the folling lines for reference
 #cmake -D CMAKE_BUILD_TYPE=RELEASE \