webrtc: support reading, publishing, proxying LPCM tracks

internal/formatprocessor/generic.go

@@ -20,7 +20,7 @@ func newGeneric(
 	generateRTPPackets bool,
 ) (*formatProcessorGeneric, error) {
 	if generateRTPPackets {
-		return nil, fmt.Errorf("we don't know how to generate RTP packets of format %+v", forma)
+		return nil, fmt.Errorf("we don't know how to generate RTP packets of format %T", forma)
 	}
 
 	return &formatProcessorGeneric{

internal/protocols/webrtc/incoming_track.go

@@ -19,6 +19,11 @@ const (
 	keyFrameInterval = 2 * time.Second
 )
 
+const (
+	mimeTypeMultiopus = "audio/multiopus"
+	mimeTypeL16       = "audio/L16"
+)
+
 var incomingVideoCodecs = []webrtc.RTPCodecParameters{
 	{
 		RTPCodecCapability: webrtc.RTPCodecCapability{
@@ -95,7 +100,7 @@ var incomingVideoCodecs = []webrtc.RTPCodecParameters{
 var incomingAudioCodecs = []webrtc.RTPCodecParameters{
 	{
 		RTPCodecCapability: webrtc.RTPCodecCapability{
-			MimeType:    mimeMultiopus,
+			MimeType:    mimeTypeMultiopus,
 			ClockRate:   48000,
 			Channels:    3,
 			SDPFmtpLine: "channel_mapping=0,2,1;num_streams=2;coupled_streams=1",
@@ -104,7 +109,7 @@ var incomingAudioCodecs = []webrtc.RTPCodecParameters{
 	},
 	{
 		RTPCodecCapability: webrtc.RTPCodecCapability{
-			MimeType:    mimeMultiopus,
+			MimeType:    mimeTypeMultiopus,
 			ClockRate:   48000,
 			Channels:    4,
 			SDPFmtpLine: "channel_mapping=0,1,2,3;num_streams=2;coupled_streams=2",
@@ -113,7 +118,7 @@ var incomingAudioCodecs = []webrtc.RTPCodecParameters{
 	},
 	{
 		RTPCodecCapability: webrtc.RTPCodecCapability{
-			MimeType:    mimeMultiopus,
+			MimeType:    mimeTypeMultiopus,
 			ClockRate:   48000,
 			Channels:    5,
 			SDPFmtpLine: "channel_mapping=0,4,1,2,3;num_streams=3;coupled_streams=2",
@@ -122,7 +127,7 @@ var incomingAudioCodecs = []webrtc.RTPCodecParameters{
 	},
 	{
 		RTPCodecCapability: webrtc.RTPCodecCapability{
-			MimeType:    mimeMultiopus,
+			MimeType:    mimeTypeMultiopus,
 			ClockRate:   48000,
 			Channels:    6,
 			SDPFmtpLine: "channel_mapping=0,4,1,2,3,5;num_streams=4;coupled_streams=2",
@@ -131,7 +136,7 @@ var incomingAudioCodecs = []webrtc.RTPCodecParameters{
 	},
 	{
 		RTPCodecCapability: webrtc.RTPCodecCapability{
-			MimeType:    mimeMultiopus,
+			MimeType:    mimeTypeMultiopus,
 			ClockRate:   48000,
 			Channels:    7,
 			SDPFmtpLine: "channel_mapping=0,4,1,2,3,5,6;num_streams=4;coupled_streams=4",
@@ -140,7 +145,7 @@ var incomingAudioCodecs = []webrtc.RTPCodecParameters{
 	},
 	{
 		RTPCodecCapability: webrtc.RTPCodecCapability{
-			MimeType:    mimeMultiopus,
+			MimeType:    mimeTypeMultiopus,
 			ClockRate:   48000,
 			Channels:    8,
 			SDPFmtpLine: "channel_mapping=0,6,1,4,5,2,3,7;num_streams=5;coupled_streams=4",
@@ -193,6 +198,30 @@ var incomingAudioCodecs = []webrtc.RTPCodecParameters{
 		},
 		PayloadType: 8,
 	},
+	{
+		RTPCodecCapability: webrtc.RTPCodecCapability{
+			MimeType:  mimeTypeL16,
+			ClockRate: 8000,
+			Channels:  2,
+		},
+		PayloadType: 120,
+	},
+	{
+		RTPCodecCapability: webrtc.RTPCodecCapability{
+			MimeType:  mimeTypeL16,
+			ClockRate: 16000,
+			Channels:  2,
+		},
+		PayloadType: 121,
+	},
+	{
+		RTPCodecCapability: webrtc.RTPCodecCapability{
+			MimeType:  mimeTypeL16,
+			ClockRate: 48000,
+			Channels:  2,
+		},
+		PayloadType: 122,
+	},
 }
 
 // IncomingTrack is an incoming track.
@@ -245,7 +274,7 @@ func newIncomingTrack(
 			PacketizationMode: 1,
 		}
 
-	case strings.ToLower(mimeMultiopus):
+	case strings.ToLower(mimeTypeMultiopus):
 		t.format = &format.Opus{
 			PayloadTyp:   uint8(track.PayloadType()),
 			ChannelCount: int(track.Codec().Channels),
@@ -301,6 +330,14 @@ func newIncomingTrack(
 			ChannelCount: int(channels),
 		}
 
+	case strings.ToLower(mimeTypeL16):
+		t.format = &format.LPCM{
+			PayloadTyp:   uint8(track.PayloadType()),
+			BitDepth:     16,
+			SampleRate:   int(track.Codec().ClockRate),
+			ChannelCount: int(track.Codec().Channels),
+		}
+
 	default:
 		return nil, fmt.Errorf("unsupported codec: %+v", track.Codec())
 	}

internal/protocols/webrtc/outgoing_track.go

@@ -8,10 +8,6 @@ import (
 	"github.com/pion/webrtc/v3"
 )
 
-const (
-	mimeMultiopus = "audio/multiopus"
-)
-
 // OutgoingTrack is a WebRTC outgoing track
 type OutgoingTrack struct {
 	Format format.Format
@@ -62,7 +58,7 @@ func (t *OutgoingTrack) codecParameters() (webrtc.RTPCodecParameters, error) {
 		if forma.ChannelCount > 2 {
 			return webrtc.RTPCodecParameters{
 				RTPCodecCapability: webrtc.RTPCodecCapability{
-					MimeType:  mimeMultiopus,
+					MimeType:  mimeTypeMultiopus,
 					ClockRate: 48000,
 					Channels:  uint16(forma.ChannelCount),
 				},
@@ -140,6 +136,28 @@ func (t *OutgoingTrack) codecParameters() (webrtc.RTPCodecParameters, error) {
 			PayloadType: 8,
 		}, nil
 
+	case *format.LPCM:
+		if forma.BitDepth != 16 {
+			return webrtc.RTPCodecParameters{}, fmt.Errorf("unsupported LPCM bit depth: %d", forma.BitDepth)
+		}
+
+		if forma.ClockRate() != 8000 && forma.ClockRate() != 16000 && forma.ClockRate() != 48000 {
+			return webrtc.RTPCodecParameters{}, fmt.Errorf("unsupported clock rate: %d", forma.ClockRate())
+		}
+
+		if forma.ChannelCount != 1 && forma.ChannelCount != 2 {
+			return webrtc.RTPCodecParameters{}, fmt.Errorf("unsupported channel count: %d", forma.ChannelCount)
+		}
+
+		return webrtc.RTPCodecParameters{
+			RTPCodecCapability: webrtc.RTPCodecCapability{
+				MimeType:  mimeTypeL16,
+				ClockRate: uint32(forma.ClockRate()),
+				Channels:  uint16(forma.ChannelCount),
+			},
+			PayloadType: 96,
+		}, nil
+
 	default:
 		return webrtc.RTPCodecParameters{}, fmt.Errorf("unsupported track type: %T", forma)
 	}

internal/protocols/webrtc/peer_connection_test.go

@@ -169,6 +169,51 @@ func TestPeerConnectionPublishRead(t *testing.T) {
 				ChannelCount: 1,
 			},
 		},
+		{
+			"l16 8000 stereo",
+			&format.LPCM{
+				PayloadTyp:   96,
+				BitDepth:     16,
+				SampleRate:   8000,
+				ChannelCount: 2,
+			},
+			&format.LPCM{
+				PayloadTyp:   96,
+				BitDepth:     16,
+				SampleRate:   8000,
+				ChannelCount: 2,
+			},
+		},
+		{
+			"l16 16000 stereo",
+			&format.LPCM{
+				PayloadTyp:   96,
+				BitDepth:     16,
+				SampleRate:   16000,
+				ChannelCount: 2,
+			},
+			&format.LPCM{
+				PayloadTyp:   96,
+				BitDepth:     16,
+				SampleRate:   16000,
+				ChannelCount: 2,
+			},
+		},
+		{
+			"l16 48khz stereo",
+			&format.LPCM{
+				PayloadTyp:   96,
+				BitDepth:     16,
+				SampleRate:   48000,
+				ChannelCount: 2,
+			},
+			&format.LPCM{
+				PayloadTyp:   96,
+				BitDepth:     16,
+				SampleRate:   48000,
+				ChannelCount: 2,
+			},
+		},
 	} {
 		t.Run(ca.name, func(t *testing.T) {
 			pc1 := &PeerConnection{

internal/servers/webrtc/read_index.html

@@ -158,6 +158,24 @@
 	return lines.join('\r\n');
 };
 
+const enableL16 = (section) => {
+	let lines = section.split('\r\n');
+
+	lines[0] += " 120";
+	lines.splice(lines.length - 1, 0, "a=rtpmap:120 L16/8000/2");
+	lines.splice(lines.length - 1, 0, "a=rtcp-fb:120 transport-cc");
+
+	lines[0] += " 121";
+	lines.splice(lines.length - 1, 0, "a=rtpmap:121 L16/16000/2");
+	lines.splice(lines.length - 1, 0, "a=rtcp-fb:121 transport-cc");
+
+	lines[0] += " 122";
+	lines.splice(lines.length - 1, 0, "a=rtpmap:122 L16/48000/2");
+	lines.splice(lines.length - 1, 0, "a=rtcp-fb:122 transport-cc");
+
+	return lines.join('\r\n');
+};
+
 const enableStereoOpus = (section) => {
 	let opusPayloadFormat = '';
 	let lines = section.split('\r\n');
@@ -202,6 +220,10 @@
 				sections[i] = enableMultichannelOpus(sections[i]);
 			}
 
+			if (nonAdvertisedCodecs.includes('L16/48000/2')) {
+				sections[i] = enableL16(sections[i]);
+			}
+
 			break;
 		}
 	}