Implement audio-video sync in diskwriter.

We used to simply synchronise on the first keyframe.  This
could lead to important time offets, since every audio frame
is a keyframe, while we only request video keyframes every
four seconds.

Fix that by parsing the RTCP synchronisation data and adjusting
timestamp offsets accordingly.  If we have no RTCP sync, we simply
assume that the first frames received are synchronised.

diskwriter/diskwriter_test.go

@@ -0,0 +1,157 @@
+package diskwriter
+
+import (
+	"testing"
+	"time"
+
+	"github.com/jech/galene/rtptime"
+)
+
+func TestAdjustOriginLocalNow(t *testing.T) {
+	now := time.Now()
+
+	c := &diskConn{
+		tracks: []*diskTrack{
+			&diskTrack{},
+		},
+	}
+	for _, t := range c.tracks {
+		t.conn = c
+	}
+	c.tracks[0].setOrigin(132, now, 100)
+
+	if !c.originLocal.Equal(now) {
+		t.Errorf("Expected %v, got %v", now, c.originLocal)
+	}
+
+	if c.originRemote != 0 {
+		t.Errorf("Expected 0, got %v", c.originRemote)
+	}
+
+	if c.tracks[0].origin != some(132) {
+		t.Errorf("Expected 132, got %v", value(c.tracks[0].origin))
+	}
+}
+
+func TestAdjustOriginLocalEarlier(t *testing.T) {
+	now := time.Now()
+	earlier := now.Add(-time.Second)
+
+	c := &diskConn{
+		originLocal: earlier,
+		tracks: []*diskTrack{
+			&diskTrack{},
+		},
+	}
+	for _, t := range c.tracks {
+		t.conn = c
+	}
+	c.tracks[0].setOrigin(132, now, 100)
+
+	if !c.originLocal.Equal(earlier) {
+		t.Errorf("Expected %v, got %v", earlier, c.originLocal)
+	}
+
+	if c.originRemote != 0 {
+		t.Errorf("Expected 0, got %v", c.originRemote)
+	}
+
+	if c.tracks[0].origin != some(32) {
+		t.Errorf("Expected 32, got %v", value(c.tracks[0].origin))
+	}
+}
+
+func TestAdjustOriginLocalLater(t *testing.T) {
+	now := time.Now()
+	later := now.Add(time.Second)
+
+	c := &diskConn{
+		originLocal: later,
+		tracks: []*diskTrack{
+			&diskTrack{},
+		},
+	}
+	for _, t := range c.tracks {
+		t.conn = c
+	}
+	c.tracks[0].setOrigin(32, now, 100)
+
+	if !c.originLocal.Equal(later) {
+		t.Errorf("Expected %v, got %v", later, c.originLocal)
+	}
+
+	if c.originRemote != 0 {
+		t.Errorf("Expected 0, got %v", c.originRemote)
+	}
+
+	if c.tracks[0].origin != some(132) {
+		t.Errorf("Expected 132, got %v", value(c.tracks[0].origin))
+	}
+}
+
+func TestAdjustOriginRemote(t *testing.T) {
+	now := time.Now()
+	earlier := now.Add(-time.Second)
+
+	c := &diskConn{
+		tracks: []*diskTrack{
+			&diskTrack{
+				remoteNTP: rtptime.TimeToNTP(earlier),
+				remoteRTP: 32,
+			},
+		},
+	}
+	for _, t := range c.tracks {
+		t.conn = c
+	}
+	c.tracks[0].setOrigin(132, now, 100)
+
+	if !c.originLocal.Equal(now) {
+		t.Errorf("Expected %v, got %v", now, c.originLocal)
+	}
+
+	d := now.Sub(rtptime.NTPToTime(c.originRemote))
+	if d < -time.Millisecond || d > time.Millisecond {
+		t.Errorf("Expected %v, got %v (delta %v)",
+			rtptime.TimeToNTP(now),
+			c.originRemote, d)
+	}
+
+	if c.tracks[0].origin != some(132) {
+		t.Errorf("Expected 132, got %v", value(c.tracks[0].origin))
+	}
+}
+
+func TestAdjustOriginLocalRemote(t *testing.T) {
+	now := time.Now()
+	earlier := now.Add(-time.Second)
+
+	c := &diskConn{
+		tracks: []*diskTrack{
+			&diskTrack{},
+		},
+	}
+	for _, t := range c.tracks {
+		t.conn = c
+	}
+	c.tracks[0].setOrigin(132, now, 100)
+
+	c.tracks[0].setTimeOffset(rtptime.TimeToNTP(earlier), 32, 100)
+
+	c.tracks[0].setOrigin(132, now, 100)
+
+	if !c.originLocal.Equal(now) {
+		t.Errorf("Expected %v, got %v", now, c.originLocal)
+	}
+
+	d := now.Sub(rtptime.NTPToTime(c.originRemote))
+	if d < -time.Millisecond || d > time.Millisecond {
+		t.Errorf("Expected %v, got %v (delta %v)",
+			rtptime.TimeToNTP(now),
+			c.originRemote, d)
+	}
+
+	if c.tracks[0].origin != some(132) {
+		t.Errorf("Expected 132, got %v", value(c.tracks[0].origin))
+	}
+}