expose apiPreference in VideoWriter

videoio.cpp

@@ -54,6 +54,14 @@ void VideoWriter_Open(VideoWriter vw, const char* name, const char* codec, doubl
     vw->open(name, codecCode, fps, cv::Size(width, height), isColor);
 }
 
+void VideoWriter_OpenCap(VideoWriter vw, const char* name, int apiPreference, const char* codec, double fps, int width,
+                      int height, bool isColor) {
+    int codecCode = cv::VideoWriter::fourcc(codec[0], codec[1], codec[2], codec[3]);
+    vw->open(name, apiPreference, codecCode, fps, cv::Size(width, height), isColor);
+}
+
+
+
 int VideoWriter_IsOpened(VideoWriter vw) {
     return vw->isOpened();
 }

videoio.go

@@ -152,6 +152,43 @@ const (
 	VideoCaptureAutoFocus VideoCaptureProperties = 39
 )
 
+const (
+	CAP_ANY = 0
+	CAP_VFW = 200
+	CAP_V4L = 200
+	CAP_V4L2 = 200
+	CAP_FIREWIRE = 300
+	CAP_FIREWARE = 300
+	CAP_IEEE1394 = 300
+	CAP_DC1394 = 300
+	CAP_CMU1394 = 300
+	CAP_QT = 500
+	CAP_UNICAP = 600
+	CAP_DSHOW = 700
+	CAP_PVAPI = 800
+	CAP_OPENNI = 900
+	CAP_OPENNI_ASUS = 910
+	CAP_ANDROID = 1000
+	CAP_XIAPI = 1100
+	CAP_AVFOUNDATION = 1200
+	CAP_GIGANETIX = 1300
+	CAP_MSMF = 1400
+	CAP_WINRT = 1410
+	CAP_INTELPERC = 1500
+	CAP_OPENNI2 = 1600
+	CAP_OPENNI2_ASUS = 1610
+	CAP_GPHOTO2 = 1700
+	CAP_GSTREAMER = 1800
+	CAP_FFMPEG = 1900
+	CAP_IMAGES = 2000
+	CAP_ARAVIS = 2100
+	CAP_OPENCV_MJPEG = 2200
+	CAP_INTEL_MFX = 2300
+	CAP_XINE = 2400
+)
+
+
+
 // VideoCapture is a wrapper around the OpenCV VideoCapture class.
 //
 // For further details, please see:
@@ -284,6 +321,32 @@ func VideoWriterFile(name string, codec string, fps float64, width int, height i
 	return
 }
 
+func VideoWriterCap(name string, apiPreference int, codec string, fps float64, width int, height int, isColor bool) (vw *VideoWriter, err error) {
+
+	if fps == 0 || width == 0 || height == 0 {
+		return nil, fmt.Errorf("one of the numerical parameters "+
+			"is equal to zero: FPS: %f, width: %d, height: %d", fps, width, height)
+	}
+
+	vw = &VideoWriter{
+		p:  C.VideoWriter_New(),
+		mu: &sync.RWMutex{},
+	}
+
+	cName := C.CString(name)
+	defer C.free(unsafe.Pointer(cName))
+
+	cCodec := C.CString(codec)
+	defer C.free(unsafe.Pointer(cCodec))
+
+	cApiPreference := C.int(apiPreference)
+	////defer C.free(unsafe.Pointer(apiPreference))
+
+	C.VideoWriter_OpenCap(vw.p, cName, cApiPreference, cCodec, C.double(fps), C.int(width), C.int(height), C.bool(isColor))
+
+	return
+}
+
 // Close VideoWriter object.
 func (vw *VideoWriter) Close() error {
 	C.VideoWriter_Close(vw.p)

videoio.h

@@ -32,6 +32,8 @@ VideoWriter VideoWriter_New();
 void VideoWriter_Close(VideoWriter vw);
 void VideoWriter_Open(VideoWriter vw, const char* name, const char* codec, double fps, int width,
                       int height, bool isColor);
+void VideoWriter_OpenCap(VideoWriter vw, const char* name, int apiPreference, const char* codec, double fps, int width,
+                      int height, bool isColor);
 int VideoWriter_IsOpened(VideoWriter vw);
 void VideoWriter_Write(VideoWriter vw, Mat img);
 

videoio_test.go

@@ -4,6 +4,7 @@ import (
 	"io/ioutil"
 	"path/filepath"
 	"strings"
+	"fmt"
 	"testing"
 )
 
@@ -121,3 +122,49 @@ func TestVideoWriterFile(t *testing.T) {
 		t.Error("Invalid Write() in VideoWriter")
 	}
 }
+
+func TestVideoWriterCap(t *testing.T) {
+	dir, _ := ioutil.TempDir("", "gocvtests")
+	tmpfn := filepath.Join(dir, "test.mp4")
+
+	in_pipeline := fmt.Sprintf("videotestsrc ! video/x-raw,framerate=20/1 ! videoscale ! videoconvert ! appsink")
+	vr, in_err := OpenVideoCapture(in_pipeline)
+
+	if in_err != nil {
+		t.Error(in_err)
+	}
+
+	img := NewMat()
+	defer img.Close()
+	_ = vr.Read(&img)
+
+	_ = vr
+
+	out_pipeline := fmt.Sprintf("appsrc ! videoconvert ! x264enc ! mp4mux ! filesink location=%s", tmpfn)
+
+	vw, out_err := VideoWriterCap(out_pipeline, CAP_GSTREAMER, "avc1", 20, img.Cols(), img.Rows(), true)
+
+	if out_err != nil {
+		t.Fatal(in_err)
+	}
+	defer vw.Close()
+
+	if !vw.IsOpened() {
+		t.Error("Unable to open VideoWriterFile")
+	}
+
+	i := 0
+	for i < 100 {
+
+		img := NewMat()
+		defer img.Close()
+
+		_ = vr.Read(&img)
+
+		err := vw.Write(img)
+		if err != nil {
+			t.Error("Invalid Write() in VideoWriter")
+		}
+		i++
+	}
+}