refactoring, renaming and commenting

src/beauty/beauty-demo.cpp

@@ -189,7 +189,7 @@ int main(int argc, char **argv) {
 
     cv::VideoCapture capture(argv[1], cv::CAP_FFMPEG, { cv::CAP_PROP_HW_DEVICE, VA_HW_DEVICE_INDEX, cv::CAP_PROP_HW_ACCELERATION, cv::VIDEO_ACCELERATION_VAAPI, cv::CAP_PROP_HW_ACCELERATION_USE_OPENCL, 1 });
     //Copy OpenCL Context for VAAPI. Must be called right after VideoWriter/VideoCapture initialization.
-    va::init();
+    va::copy();
 
     if (!capture.isOpened()) {
         cerr << "ERROR! Unable to open video input" << endl;

src/common/subsystems.hpp

@@ -66,7 +66,7 @@ void egl_check_error(const std::filesystem::path &file, unsigned int line, const
 namespace va {
 cv::ocl::OpenCLExecutionContext context;
 
-void init() {
+void copy() {
     va::context = cv::ocl::OpenCLExecutionContext::getCurrent();
 }
 

src/font/font-demo.cpp

@@ -25,6 +25,7 @@ using std::stringstream;
 int main(int argc, char **argv) {
     using namespace kb;
 
+    //Initialize the application
     kb::init(WIDTH, HEIGHT);
 
     //Initialize VP9 HW encoding using VAAPI
@@ -34,39 +35,52 @@ int main(int argc, char **argv) {
     });
 
     //Copy OpenCL Context for VAAPI. Must be called right after VideoWriter/VideoCapture initialization.
-    va::init();
+    va::copy();
-
 
+    //If we render offscreen we don't need x11.
     if (!OFFSCREEN)
         x11::init();
+    //Passing 'true' to egl::init() creates a debug OpenGL-context.
     egl::init();
+    //Initialize OpenGL.
     gl::init();
+    //Initialize nanovg.
     nvg::init();
 
     cerr << "EGL Version: " << egl::get_info() << endl;
     cerr << "OpenGL Version: " << gl::get_info() << endl;
     cerr << "OpenCL Platforms: " << endl << cl::get_info() << endl;
 
+    //BGRA frame buffer.
     cv::UMat frameBuffer;
+    //BGR video frame.
     cv::UMat videoFrame;
 
+    //The text to display
     string text = cv::getBuildInformation();
+    //Create a istringstream that we will read and the rewind. over again.
     std::istringstream iss(text);
+    //Count the number of lines.
     off_t numLines = std::count(text.begin(), text.end(), '\n');
+
+    //Derive the transformation matrix M for the pseudo 3D effect from src and dst.
     vector<cv::Point2f> src = {{0,0},{WIDTH,0},{WIDTH,HEIGHT},{0,HEIGHT}};
     vector<cv::Point2f> dst = {{WIDTH/3,0},{WIDTH/1.5,0},{WIDTH,HEIGHT},{0,HEIGHT}};
     cv::Mat M = cv::getPerspectiveTransform(src, dst);
 
+    //Frame count.
     size_t cnt = 0;
+    //Y-position of the current line in pixels.
     float y;
 
     while (true) {
         y = 0;
 
-        //Activate the OpenCL context for OpenGL
+        //Activate the OpenCL context for OpenGL.
         gl::bind();
-        //Render using nanovg
+        //Begin a nanovg frame.
         nvg::begin();
+        //Clear the screen with black. The clear color can be specified.
         nvg::clear();
         {
             using kb::nvg::vg;
@@ -75,54 +89,67 @@ int main(int argc, char **argv) {
             nvgFillColor(vg, nvgHSLA(0.15, 1, 0.5, 255));
             nvgTextAlign(vg, NVG_ALIGN_CENTER | NVG_ALIGN_TOP);
 
-            //only draw lines that are visible
+            /** only draw lines that are visible **/
+
+            //Progress measured in lines.
             off_t progressLines = cnt / FONT_SIZE;
+            //How many lines to skip.
             off_t skipLines = (numLines - progressLines) - 1;
             skipLines = skipLines < 0 ? 0 : skipLines;
-            off_t maxLines = HEIGHT / FONT_SIZE;
+            //How many lines fit on the page.
-            off_t translateY = cnt - (numLines - skipLines) * FONT_SIZE;
+            off_t pageLines = HEIGHT / FONT_SIZE;
+            //How many pixels to translate the text down.
+            off_t translateY = cnt - ((numLines - skipLines) * FONT_SIZE);
             nvgTranslate(vg, 0, translateY);
 
             for (std::string line; std::getline(iss, line); ) {
+                //Check if all yet-to-crawl lines have been skipped.
                 if(skipLines == 0) {
-                    if(((translateY + y) / FONT_SIZE) < maxLines) {
+                    //Check if the current lines fits in the page.
+                    if(((translateY + y) / FONT_SIZE) < pageLines) {
                         nvgText(vg, WIDTH/2.0, y, line.c_str(), line.c_str() + line.size());
                         y += FONT_SIZE;
-                    } else
+                    } else {
+                        //We can stop reading lines if the current line exceeds the page.
                         break;
+                    }
                 } else {
                    --skipLines;
                 }
             }
         }
+        //End a nanovg frame
         nvg::end();
 
-        if(y == 0) //nothing drawn, exit
+        if(y == 0) {
+            //Nothing drawn, exit.
             break;
+        }
 
-        //rewind the istringstream
+        //Rewind the istringstream.
         iss.clear(std::stringstream::goodbit);
         iss.seekg(0);
 
-        //Aquire frame buffer from OpenGL
+        //Aquire frame buffer from OpenGL.
         gl::acquire_from_gl(frameBuffer);
-        //Fake 3D text effect
+        //Pseudo 3D text effect.
         cv::warpPerspective(frameBuffer, frameBuffer, M, videoFrame.size(), cv::INTER_LINEAR, cv::BORDER_CONSTANT, cv::Scalar());
         //Color-conversion from BGRA to RGB. OpenCV/OpenCL.
         cv::cvtColor(frameBuffer, videoFrame, cv::COLOR_BGRA2RGB);
-        //Transfer buffer ownership back to OpenGL
+        //Transfer buffer ownership back to OpenGL.
         gl::release_to_gl(frameBuffer);
 
-        //if x11 is enabled it displays the framebuffer in the native window. returns false if the window was closed.
+        //If x11 is enabled it displays the framebuffer in the native window. returns false if the window was closed.
         if(!gl::display())
             break;
 
-        //Activate the OpenCL context for VAAPI
+        //Activate the OpenCL context for VAAPI.
         va::bind();
         //Encode the frame using VAAPI on the GPU.
         writer << videoFrame;
 
         ++cnt;
+        //Wrap the cnt around if it becomes to big.
         if(cnt == std::numeric_limits<size_t>().max())
             cnt = 1;
 

src/nanovg/nanovg-demo.cpp

@@ -132,7 +132,7 @@ int main(int argc, char **argv) {
     });
 
     //Copy OpenCL Context for VAAPI. Must be called right after VideoWriter/VideoCapture initialization.
-    va::init();
+    va::copy();
 
     // Check if we succeeded
     if (!capture.isOpened()) {

src/optflow/optflow-demo.cpp

@@ -190,7 +190,7 @@ int main(int argc, char **argv) {
     });
 
     //Copy OpenCL Context for VAAPI. Must be called right after VideoWriter/VideoCapture initialization.
-    va::init();
+    va::copy();
 
     if (!capture.isOpened()) {
         cerr << "ERROR! Unable to open video input" << endl;

src/pedestrian/pedestrian-demo.cpp

@@ -50,7 +50,7 @@ int main(int argc, char **argv) {
             cv::CAP_PROP_HW_ACCELERATION_USE_OPENCL, 1
     });
 
-    va::init();
+    va::copy();
 
 
     if (!cap.isOpened()) {

src/tetra/tetra-demo.cpp

@@ -91,7 +91,7 @@ int main(int argc, char **argv) {
     });
 
     //Copy OpenCL Context for VAAPI. Must be called right after VideoWriter/VideoCapture initialization.
-    va::init();
+    va::copy();
 
     //If we are rendering offscreen we don't need x11
     if(!OFFSCREEN)

src/video/video-demo.cpp

@@ -96,7 +96,7 @@ int main(int argc, char **argv) {
     });
 
     //Copy OpenCL Context for VAAPI. Must be called right after VideoWriter/VideoCapture initialization.
-    va::init();
+    va::copy();
 
     if (!capture.isOpened()) {
         cerr << "ERROR! Unable to open video input" << endl;