mediaengine.go

// +build !js

package webrtc

import (
	"fmt"
	"strconv"
	"strings"

	"github.com/pion/rtp"
	"github.com/pion/rtp/codecs"
	"github.com/pion/sdp/v2"
)

// PayloadTypes for the default codecs
const (
	DefaultPayloadTypeG722 = 9
	DefaultPayloadTypeOpus = 111
	DefaultPayloadTypeVP8  = 96
	DefaultPayloadTypeVP9  = 98
	DefaultPayloadTypeH264 = 102
)

// MediaEngine defines the codecs supported by a PeerConnection
type MediaEngine struct {
	codecs []*RTPCodec
}

// RegisterCodec registers a codec to a media engine
func (m *MediaEngine) RegisterCodec(codec *RTPCodec) uint8 {
	// pion/webrtc#43
	m.codecs = append(m.codecs, codec)
	return codec.PayloadType
}

// RegisterDefaultCodecs is a helper that registers the default codecs supported by Pion WebRTC
func (m *MediaEngine) RegisterDefaultCodecs() {
	m.RegisterCodec(NewRTPOpusCodec(DefaultPayloadTypeOpus, 48000))
	m.RegisterCodec(NewRTPG722Codec(DefaultPayloadTypeG722, 8000))
	m.RegisterCodec(NewRTPVP8Codec(DefaultPayloadTypeVP8, 90000))
	m.RegisterCodec(NewRTPH264Codec(DefaultPayloadTypeH264, 90000))
	m.RegisterCodec(NewRTPVP9Codec(DefaultPayloadTypeVP9, 90000))
}

// PopulateFromSDP finds all codecs in a session description and adds them to a MediaEngine, using dynamic
// payload types and parameters from the sdp.
func (m *MediaEngine) PopulateFromSDP(sd SessionDescription) error {
	sdpsd := sdp.SessionDescription{}
	err := sdpsd.Unmarshal([]byte(sd.SDP))
	if err != nil {
		return err
	}
	for _, md := range sdpsd.MediaDescriptions {
		for _, format := range md.MediaName.Formats {
			pt, err := strconv.Atoi(format)
			if err != nil {
				return fmt.Errorf("format parse error")
			}
			payloadType := uint8(pt)
			payloadCodec, err := sdpsd.GetCodecForPayloadType(payloadType)
			if err != nil {
				return fmt.Errorf("could not find codec for payload type %d", payloadType)
			}
			var codec *RTPCodec
			clockRate := payloadCodec.ClockRate
			parameters := payloadCodec.Fmtp
			switch payloadCodec.Name {
			case G722:
				codec = NewRTPG722Codec(payloadType, clockRate)
			case Opus:
				codec = NewRTPOpusCodec(payloadType, clockRate)
			case VP8:
				codec = NewRTPVP8Codec(payloadType, clockRate)
				codec.SDPFmtpLine = parameters
			case VP9:
				codec = NewRTPVP9Codec(payloadType, clockRate)
				codec.SDPFmtpLine = parameters
			case H264:
				codec = NewRTPH264Codec(payloadType, clockRate)
				codec.SDPFmtpLine = parameters
			default:
				// ignoring other codecs
				continue
			}
			m.RegisterCodec(codec)
		}
	}
	return nil
}

func (m *MediaEngine) getCodec(payloadType uint8) (*RTPCodec, error) {
	for _, codec := range m.codecs {
		if codec.PayloadType == payloadType {
			return codec, nil
		}
	}
	return nil, ErrCodecNotFound
}

func (m *MediaEngine) getCodecSDP(sdpCodec sdp.Codec) (*RTPCodec, error) {
	for _, codec := range m.codecs {
		if codec.Name == sdpCodec.Name &&
			codec.ClockRate == sdpCodec.ClockRate &&
			(sdpCodec.EncodingParameters == "" ||
				strconv.Itoa(int(codec.Channels)) == sdpCodec.EncodingParameters) &&
			codec.SDPFmtpLine == sdpCodec.Fmtp { // pion/webrtc#43
			return codec, nil
		}
	}
	return nil, ErrCodecNotFound
}

// GetCodecsByKind returns all codecs of a chosen kind in the codecs list
func (m *MediaEngine) GetCodecsByKind(kind RTPCodecType) []*RTPCodec {
	var codecs []*RTPCodec
	for _, codec := range m.codecs {
		if codec.Type == kind {
			codecs = append(codecs, codec)
		}
	}
	return codecs
}

// Names for the default codecs supported by Pion WebRTC
const (
	G722 = "G722"
	Opus = "opus"
	VP8  = "VP8"
	VP9  = "VP9"
	H264 = "H264"
)

// NewRTPG722Codec is a helper to create a G722 codec
func NewRTPG722Codec(payloadType uint8, clockrate uint32) *RTPCodec {
	c := NewRTPCodec(RTPCodecTypeAudio,
		G722,
		clockrate,
		0,
		"",
		payloadType,
		&codecs.G722Payloader{})
	return c
}

// NewRTPOpusCodec is a helper to create an Opus codec
func NewRTPOpusCodec(payloadType uint8, clockrate uint32) *RTPCodec {
	c := NewRTPCodec(RTPCodecTypeAudio,
		Opus,
		clockrate,
		2, //According to RFC7587, Opus RTP streams must have exactly 2 channels.
		"minptime=10;useinbandfec=1",
		payloadType,
		&codecs.OpusPayloader{})
	return c
}

// NewRTPVP8Codec is a helper to create an VP8 codec
func NewRTPVP8Codec(payloadType uint8, clockrate uint32) *RTPCodec {
	c := NewRTPCodec(RTPCodecTypeVideo,
		VP8,
		clockrate,
		0,
		"",
		payloadType,
		&codecs.VP8Payloader{})
	return c
}

// NewRTPVP9Codec is a helper to create an VP9 codec
func NewRTPVP9Codec(payloadType uint8, clockrate uint32) *RTPCodec {
	c := NewRTPCodec(RTPCodecTypeVideo,
		VP9,
		clockrate,
		0,
		"",
		payloadType,
		nil) // pion/webrtc#755
	return c
}

// NewRTPH264Codec is a helper to create an H264 codec
func NewRTPH264Codec(payloadType uint8, clockrate uint32) *RTPCodec {
	c := NewRTPCodec(RTPCodecTypeVideo,
		H264,
		clockrate,
		0,
		"level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42001f",
		payloadType,
		&codecs.H264Payloader{})
	return c
}

// RTPCodecType determines the type of a codec
type RTPCodecType int

const (

	// RTPCodecTypeAudio indicates this is an audio codec
	RTPCodecTypeAudio RTPCodecType = iota + 1

	// RTPCodecTypeVideo indicates this is a video codec
	RTPCodecTypeVideo
)

func (t RTPCodecType) String() string {
	switch t {
	case RTPCodecTypeAudio:
		return "audio"
	case RTPCodecTypeVideo:
		return "video"
	default:
		return ErrUnknownType.Error()
	}
}

// NewRTPCodecType creates a RTPCodecType from a string
func NewRTPCodecType(r string) RTPCodecType {
	switch {
	case strings.EqualFold(r, "audio"):
		return RTPCodecTypeAudio
	case strings.EqualFold(r, "video"):
		return RTPCodecTypeVideo
	default:
		return RTPCodecType(0)
	}
}

// RTPCodec represents a codec supported by the PeerConnection
type RTPCodec struct {
	RTPCodecCapability
	Type        RTPCodecType
	Name        string
	PayloadType uint8
	Payloader   rtp.Payloader
}

// NewRTPCodec is used to define a new codec
func NewRTPCodec(
	codecType RTPCodecType,
	name string,
	clockrate uint32,
	channels uint16,
	fmtp string,
	payloadType uint8,
	payloader rtp.Payloader,
) *RTPCodec {
	return &RTPCodec{
		RTPCodecCapability: RTPCodecCapability{
			MimeType:    codecType.String() + "/" + name,
			ClockRate:   clockrate,
			Channels:    channels,
			SDPFmtpLine: fmtp,
		},
		PayloadType: payloadType,
		Payloader:   payloader,
		Type:        codecType,
		Name:        name,
	}
}

// RTPCodecCapability provides information about codec capabilities.
type RTPCodecCapability struct {
	MimeType     string
	ClockRate    uint32
	Channels     uint16
	SDPFmtpLine  string
	RTCPFeedback []RTCPFeedback
}

// RTPHeaderExtensionCapability is used to define a RFC5285 RTP header extension supported by the codec.
type RTPHeaderExtensionCapability struct {
	URI string
}

// RTPCapabilities represents the capabilities of a transceiver
type RTPCapabilities struct {
	Codecs           []RTPCodecCapability
	HeaderExtensions []RTPHeaderExtensionCapability
}