add launch exampl

examples/launch/main.go

@@ -0,0 +1,66 @@
+// This is a simplified go-reimplementation of the gst-launch-<version> cli tool.
+// It has no own parameters and simply parses the cli arguments as launch syntax.
+// When the parsing succeeded, the pipeline is run until the stream ends or an error happens.
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/tinyzimmer/go-gst/examples"
+	"github.com/tinyzimmer/go-gst/gst"
+)
+
+func runPipeline(mainLoop *gst.MainLoop) error {
+	gst.Init(nil)
+
+	if len(os.Args) == 1 {
+		return errors.New("Pipeline string cannot be empty")
+	}
+
+	// Build a pipeline string from the cli arguments
+	pipelineString := strings.Join(os.Args[1:], " ")
+
+	/// Let GStreamer create a pipeline from the parsed launch syntax on the cli.
+	pipeline, err := gst.NewPipelineFromString(pipelineString)
+	if err != nil {
+		return err
+	}
+
+	// Add a message handler to the pipeline bus, printing interesting information to the console.
+	pipeline.GetPipelineBus().AddWatch(func(msg *gst.Message) bool {
+		switch msg.Type() {
+		case gst.MessageEOS: // When end-of-stream is received stop the main loop
+			mainLoop.Quit()
+		case gst.MessageError: // Error messages are always fatal
+			err := msg.ParseError()
+			fmt.Println("ERROR:", err.Error())
+			if debug := err.DebugString(); debug != "" {
+				fmt.Println("DEBUG:", debug)
+			}
+			mainLoop.Quit()
+		default:
+			// All messages implement a Stringer. However, this is
+			// typically an expensive thing to do and should be avoided.
+			fmt.Println(msg)
+		}
+		return true
+	})
+
+	// Start the pipeline
+	pipeline.SetState(gst.StatePlaying)
+
+	// Block on the main loop
+	mainLoop.Run()
+
+	// Destroy the pipeline
+	return pipeline.Destroy()
+}
+
+func main() {
+	examples.RunLoop(func(loop *gst.MainLoop) error {
+		return runPipeline(loop)
+	})
+}