finish GstDiscoverer impl and add exampl

examples/discoverer/main.go

@@ -0,0 +1,81 @@
+// This example uses gstreamer's discoverer api
+// https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-base-libs/html/GstDiscoverer.html
+// To detect as much information from a given URI.
+// The amount of time that the discoverer is allowed to use is limited by a timeout.
+// This allows to handle e.g. network problems gracefully. When the timeout hits before
+// discoverer was able to detect anything, discoverer will report an error.
+// In this example, we catch this error and stop the application.
+// Discovered information could for example contain the stream's duration or whether it is
+// seekable (filesystem) or not (some http servers).
+package main
+
+import (
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/tinyzimmer/go-gst/gst"
+	"github.com/tinyzimmer/go-gst/gst/pbutils"
+)
+
+func main() {
+
+	gst.Init(nil)
+
+	if len(os.Args) < 2 {
+		fmt.Printf("USAGE: %s <uri>\n", os.Args[0])
+		os.Exit(1)
+	}
+
+	uri := os.Args[1]
+
+	discoverer, err := pbutils.NewDiscoverer(time.Second * 15)
+	if err != nil {
+		fmt.Println("ERROR:", err)
+		os.Exit(2)
+	}
+	// defer discoverer.Unref()
+
+	info, err := discoverer.DiscoverURI(uri)
+	if err != nil {
+		fmt.Println("ERROR:", err)
+		os.Exit(3)
+	}
+
+	printDiscovererInfo(info)
+}
+
+func printDiscovererInfo(info *pbutils.DiscovererInfo) {
+	fmt.Println("URI:", info.GetURI())
+	fmt.Println("Duration:", info.GetDuration())
+
+	printTags(info)
+	printStreamInfo(info.GetStreamInfo())
+
+	children := info.GetStreamList()
+	fmt.Println("Children streams:")
+	for _, child := range children {
+		printStreamInfo(child)
+	}
+}
+
+func printTags(info *pbutils.DiscovererInfo) {
+	fmt.Println("Tags:")
+	tags := info.GetTags()
+	if tags != nil {
+		fmt.Println("  ", tags)
+		return
+	}
+	fmt.Println("  no tags")
+}
+
+func printStreamInfo(info *pbutils.DiscovererStreamInfo) {
+	if info == nil {
+		return
+	}
+	fmt.Println("Stream: ")
+	fmt.Println("  Stream id:", info.GetStreamID())
+	if caps := info.GetCaps(); caps != nil {
+		fmt.Println("  Format:", caps)
+	}
+}