Ability to select the desired VideoWriter output codec on Open()

Signed-off-by: deadprogram <[email protected]>

cmd/savevideo/main.go

@@ -45,7 +45,7 @@ func main() {
 		return
 	}
 
-	writer, err := gocv.VideoWriterFile(saveFile, 25, img.Cols(), img.Rows())
+	writer, err := gocv.VideoWriterFile(saveFile, "MJPG", 25, img.Cols(), img.Rows())
 	if err != nil {
 		fmt.Printf("error opening video writer device: %v\n", saveFile)
 		return

videoio.cpp

@@ -44,9 +44,10 @@ void VideoWriter_Close(VideoWriter vw) {
     delete vw;
 }
 
-void VideoWriter_Open(VideoWriter vw, const char* name, double fps, int width,
+void VideoWriter_Open(VideoWriter vw, const char* name, const char* codec, double fps, int width,
       int height) {
-    vw->open(name, CV_FOURCC('M', 'J', 'P', 'G'), fps, cv::Size(width, height), true);
+    int codecCode = cv::VideoWriter::fourcc(codec[0], codec[1], codec[2], codec[3]);
+    vw->open(name, codecCode, fps, cv::Size(width, height), true);
 }
 
 int VideoWriter_IsOpened(VideoWriter vw) {

videoio.go

@@ -219,15 +219,25 @@ type VideoWriter struct {
 }
 
 // VideoWriterFile opens a VideoWriter with a specific output file.
-func VideoWriterFile(name string, fps float64, width int, height int) (vw *VideoWriter, err error) {
+// The "codec" param should be the four-letter code for the desired output
+// codec, for example "MJPG".
+//
+// For further details, please see:
+// http://docs.opencv.org/3.3.0/dd/d9e/classcv_1_1VideoWriter.html#a0901c353cd5ea05bba455317dab81130
+//
+func VideoWriterFile(name string, codec string, fps float64, width int, height int) (vw *VideoWriter, err error) {
 	vw = &VideoWriter{
 		p:  C.VideoWriter_New(),
 		mu: &sync.RWMutex{},
 	}
 
 	cName := C.CString(name)
 	defer C.free(unsafe.Pointer(cName))
-	C.VideoWriter_Open(vw.p, cName, C.double(fps), C.int(width), C.int(height))
+
+	cCodec := C.CString(codec)
+	defer C.free(unsafe.Pointer(cCodec))
+
+	C.VideoWriter_Open(vw.p, cName, cCodec, C.double(fps), C.int(width), C.int(height))
 	return
 }
 

videoio.h

@@ -29,7 +29,7 @@ void VideoCapture_Grab(VideoCapture v, int skip);
 // VideoWriter
 VideoWriter VideoWriter_New();
 void VideoWriter_Close(VideoWriter vw);
-void VideoWriter_Open(VideoWriter vw, const char* name, double fps, int width,
+void VideoWriter_Open(VideoWriter vw, const char* name, const char* codec, double fps, int width,
   int height);
 int VideoWriter_IsOpened(VideoWriter vw);
 void VideoWriter_Write(VideoWriter vw, Mat img);

videoio_test.go

@@ -31,7 +31,7 @@ func TestVideoWriterFile(t *testing.T) {
 	}
 	defer img.Close()
 
-	vw, _ := VideoWriterFile("/tmp/test.avi", 25, img.Cols(), img.Rows())
+	vw, _ := VideoWriterFile("/tmp/test.avi", "MJPG", 25, img.Cols(), img.Rows())
 	defer vw.Close()
 
 	if !vw.IsOpened() {