convert Tracks into Medias and Formats (#155)

* split tracks from medias

* move tracks into dedicated package

* move media into dedicated package

* edit Medias.Marshal() in order to return SDP

* add medias.Find() and simplify examples

* improve coverage

* fix rebase errors

* replace TrackIDs with MediaIDs

* implement media-specific and track-specific callbacks for reading RTCP and RTP packets

* rename publish into record, read into play

* add v2 tag

* rename tracks into formats

pkg/format/h264_test.go

@@ -0,0 +1,72 @@
+package format
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestH264Attributes(t *testing.T) {
+	format := &H264{
+		PayloadTyp:        96,
+		SPS:               []byte{0x01, 0x02},
+		PPS:               []byte{0x03, 0x04},
+		PacketizationMode: 1,
+	}
+	require.Equal(t, "H264", format.String())
+	require.Equal(t, 90000, format.ClockRate())
+	require.Equal(t, uint8(96), format.PayloadType())
+	require.Equal(t, []byte{0x01, 0x02}, format.SafeSPS())
+	require.Equal(t, []byte{0x03, 0x04}, format.SafePPS())
+
+	format.SafeSetSPS([]byte{0x07, 0x08})
+	format.SafeSetPPS([]byte{0x09, 0x0A})
+	require.Equal(t, []byte{0x07, 0x08}, format.SafeSPS())
+	require.Equal(t, []byte{0x09, 0x0A}, format.SafePPS())
+}
+
+func TestH264Clone(t *testing.T) {
+	format := &H264{
+		PayloadTyp:        96,
+		SPS:               []byte{0x01, 0x02},
+		PPS:               []byte{0x03, 0x04},
+		PacketizationMode: 1,
+	}
+
+	clone := format.Clone()
+	require.NotSame(t, format, clone)
+	require.Equal(t, format, clone)
+}
+
+func TestH264MediaDescription(t *testing.T) {
+	t.Run("standard", func(t *testing.T) {
+		format := &H264{
+			PayloadTyp: 96,
+			SPS: []byte{
+				0x67, 0x64, 0x00, 0x0c, 0xac, 0x3b, 0x50, 0xb0,
+				0x4b, 0x42, 0x00, 0x00, 0x03, 0x00, 0x02, 0x00,
+				0x00, 0x03, 0x00, 0x3d, 0x08,
+			},
+			PPS: []byte{
+				0x68, 0xee, 0x3c, 0x80,
+			},
+			PacketizationMode: 1,
+		}
+
+		rtpmap, fmtp := format.Marshal()
+		require.Equal(t, "H264/90000", rtpmap)
+		require.Equal(t, "packetization-mode=1; "+
+			"sprop-parameter-sets=Z2QADKw7ULBLQgAAAwACAAADAD0I,aO48gA==; profile-level-id=64000C", fmtp)
+	})
+
+	t.Run("no sps/pps", func(t *testing.T) {
+		format := &H264{
+			PayloadTyp:        96,
+			PacketizationMode: 1,
+		}
+
+		rtpmap, fmtp := format.Marshal()
+		require.Equal(t, "H264/90000", rtpmap)
+		require.Equal(t, "packetization-mode=1", fmtp)
+	})
+}