add *codec* to codec-related examples

examples/client-read-codec-h264-save-to-disk/main.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"github.com/aler9/gortsplib"
+	"github.com/aler9/gortsplib/pkg/rtph264"
+	"github.com/aler9/gortsplib/pkg/url"
+)
+
+// This example shows how to
+// 1. connect to a RTSP server and read all tracks on a path
+// 2. check if there's a H264 track
+// 3. save the content of the H264 track into a file in MPEG-TS format
+
+func main() {
+	c := gortsplib.Client{}
+
+	// parse URL
+	u, err := url.Parse("rtsp://localhost:8554/mystream")
+	if err != nil {
+		panic(err)
+	}
+
+	// connect to the server
+	err = c.Start(u.Scheme, u.Host)
+	if err != nil {
+		panic(err)
+	}
+	defer c.Close()
+
+	// find published tracks
+	tracks, baseURL, _, err := c.Describe(u)
+	if err != nil {
+		panic(err)
+	}
+
+	// find the H264 track
+	h264TrackID, h264track := func() (int, *gortsplib.TrackH264) {
+		for i, track := range tracks {
+			if h264track, ok := track.(*gortsplib.TrackH264); ok {
+				return i, h264track
+			}
+		}
+		return -1, nil
+	}()
+	if h264TrackID < 0 {
+		panic("H264 track not found")
+	}
+
+	// setup RTP/H264->H264 decoder
+	rtpDec := &rtph264.Decoder{}
+	rtpDec.Init()
+
+	// setup H264->MPEGTS muxer
+	mpegtsMuxer, err := newMPEGTSMuxer(h264track.SafeSPS(), h264track.SafePPS())
+	if err != nil {
+		panic(err)
+	}
+
+	// called when a RTP packet arrives
+	c.OnPacketRTP = func(ctx *gortsplib.ClientOnPacketRTPCtx) {
+		if ctx.TrackID != h264TrackID {
+			return
+		}
+
+		// convert RTP packets into NALUs
+		nalus, pts, err := rtpDec.Decode(ctx.Packet)
+		if err != nil {
+			return
+		}
+
+		// encode H264 NALUs into MPEG-TS
+		mpegtsMuxer.encode(nalus, pts)
+	}
+
+	// setup and read all tracks
+	err = c.SetupAndPlay(tracks, baseURL)
+	if err != nil {
+		panic(err)
+	}
+
+	// wait until a fatal error
+	panic(c.Wait())
+}