opencv_trail_effect.cpp: hardcode V4L2 VideoCapture backend on linux

Hardcode the V4L2 backend on linux for now because the GStreamer one
lacks some functionality, see:
https://github.com/opencv/opencv/issues/18562

diff --git a/opencv_trail_effect.cpp b/opencv_trail_effect.cpp
index bc5b187..c78f326 100644 (file)
--- a/opencv_trail_effect.cpp
+++ b/opencv_trail_effect.cpp
@@ -131,7 +131,14 @@ int main(int argc, char *argv[])
        if (!input_file.empty()) {
                inputVideo.open(input_file);
        } else {
        if (!input_file.empty()) {
                inputVideo.open(input_file);
        } else {

+#ifdef __linux__
+               // XXX Hardcode the V4L2 backend on linux for now because the
+               // GStreamer one lacks some functionality, see:
+               // https://github.com/opencv/opencv/issues/18562
+               inputVideo.open(0, cv::CAP_V4L2);
+#else

                inputVideo.open(0);
                inputVideo.open(0);

+#endif

        }
 
        if (!inputVideo.isOpened()) {
        }
 
        if (!inputVideo.isOpened()) {