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/lpcm.go

@@ -0,0 +1,124 @@
+package format
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/pion/rtp"
+
+	"github.com/aler9/gortsplib/v2/pkg/rtpcodecs/rtplpcm"
+)
+
+// LPCM is an uncompressed, Linear PCM format.
+type LPCM struct {
+	PayloadTyp   uint8
+	BitDepth     int
+	SampleRate   int
+	ChannelCount int
+}
+
+// String implements Format.
+func (t *LPCM) String() string {
+	return "LPCM"
+}
+
+// ClockRate implements Format.
+func (t *LPCM) ClockRate() int {
+	return t.SampleRate
+}
+
+// PayloadType implements Format.
+func (t *LPCM) PayloadType() uint8 {
+	return t.PayloadTyp
+}
+
+func (t *LPCM) unmarshal(payloadType uint8, clock string, codec string, rtpmap string, fmtp string) error {
+	t.PayloadTyp = payloadType
+
+	switch codec {
+	case "l8":
+		t.BitDepth = 8
+
+	case "l16":
+		t.BitDepth = 16
+
+	case "l24":
+		t.BitDepth = 24
+	}
+
+	tmp := strings.SplitN(clock, "/", 32)
+	if len(tmp) != 2 {
+		return fmt.Errorf("invalid clock (%v)", clock)
+	}
+
+	sampleRate, err := strconv.ParseInt(tmp[0], 10, 64)
+	if err != nil {
+		return err
+	}
+	t.SampleRate = int(sampleRate)
+
+	channelCount, err := strconv.ParseInt(tmp[1], 10, 64)
+	if err != nil {
+		return err
+	}
+	t.ChannelCount = int(channelCount)
+
+	return nil
+}
+
+// Marshal implements Format.
+func (t *LPCM) Marshal() (string, string) {
+	var codec string
+	switch t.BitDepth {
+	case 8:
+		codec = "L8"
+
+	case 16:
+		codec = "L16"
+
+	case 24:
+		codec = "L24"
+	}
+
+	return codec + "/" + strconv.FormatInt(int64(t.SampleRate), 10) +
+		"/" + strconv.FormatInt(int64(t.ChannelCount), 10), ""
+}
+
+// Clone implements Format.
+func (t *LPCM) Clone() Format {
+	return &LPCM{
+		PayloadTyp:   t.PayloadTyp,
+		BitDepth:     t.BitDepth,
+		SampleRate:   t.SampleRate,
+		ChannelCount: t.ChannelCount,
+	}
+}
+
+// PTSEqualsDTS implements Format.
+func (t *LPCM) PTSEqualsDTS(*rtp.Packet) bool {
+	return true
+}
+
+// CreateDecoder creates a decoder able to decode the content of the format.
+func (t *LPCM) CreateDecoder() *rtplpcm.Decoder {
+	d := &rtplpcm.Decoder{
+		BitDepth:     t.BitDepth,
+		SampleRate:   t.SampleRate,
+		ChannelCount: t.ChannelCount,
+	}
+	d.Init()
+	return d
+}
+
+// CreateEncoder creates an encoder able to encode the content of the format.
+func (t *LPCM) CreateEncoder() *rtplpcm.Encoder {
+	e := &rtplpcm.Encoder{
+		PayloadType:  t.PayloadTyp,
+		BitDepth:     t.BitDepth,
+		SampleRate:   t.SampleRate,
+		ChannelCount: t.ChannelCount,
+	}
+	e.Init()
+	return e
+}