Add support pcm_s16le audio

pkg/core/README.md

@@ -0,0 +1,40 @@
+## PCM
+
+**RTSP**
+
+- PayloadType=10 - L16/44100/2 - Linear PCM 16-bit big endian
+- PayloadType=11 - L16/44100/1 - Linear PCM 16-bit big endian
+
+https://en.wikipedia.org/wiki/RTP_payload_formats
+
+**Apple QuickTime**
+
+- `raw` - 16-bit data is stored in little endian format
+- `twos` - 16-bit data is stored in big endian format
+- `sowt` - 16-bit data is stored in little endian format
+- `in24` - denotes 24-bit, big endian
+- `in32` - denotes 32-bit, big endian
+- `fl32` - denotes 32-bit floating point PCM
+- `fl64` - denotes 64-bit floating point PCM
+- `alaw` - denotes A-law logarithmic PCM
+- `ulaw` - denotes mu-law logarithmic PCM
+
+https://wiki.multimedia.cx/index.php/PCM
+
+**FFmpeg RTSP**
+
+```
+pcm_s16be, 44100 Hz, stereo => 10
+pcm_s16be, 48000 Hz, stereo => 96 L16/48000/2
+pcm_s16be, 44100 Hz, mono   => 11
+
+pcm_s16le, 48000 Hz, stereo => 96 (b=AS:1536)
+pcm_s16le, 44100 Hz, stereo => 96 (b=AS:1411)
+pcm_s16le, 16000 Hz, stereo => 96 (b=AS:512)
+pcm_s16le, 8000 Hz, stereo  => 96 (b=AS:256)
+
+pcm_s16le, 48000 Hz, mono   => 96 (b=AS:768)
+pcm_s16le, 44100 Hz, mono   => 96 (b=AS:705)
+pcm_s16le, 16000 Hz, mono   => 96 (b=AS:256)
+pcm_s16le, 8000 Hz, mono    => 96 (b=AS:128)
+```

pkg/core/codec.go

@@ -3,10 +3,11 @@ package core
 import (
 	"encoding/base64"
 	"fmt"
-	"github.com/pion/sdp/v3"
 	"strconv"
 	"strings"
 	"unicode"
+
+	"github.com/pion/sdp/v3"
 )
 
 type Codec struct {
@@ -112,6 +113,42 @@ func UnmarshalCodec(md *sdp.MediaDescription, payloadType string) *Codec {
 		case "26":
 			c.Name = CodecJPEG
 			c.ClockRate = 90000
+		case "96", "97", "98":
+			if len(md.Bandwidth) == 0 {
+				c.Name = payloadType
+				break
+			}
+
+			// FFmpeg + RTSP + pcm_s16le = doesn't pass info about codec name and params
+			// so try to guess the codec based on bitrate
+			// https://github.com/AlexxIT/go2rtc/issues/523
+			switch md.Bandwidth[0].Bandwidth {
+			case 128:
+				c.ClockRate = 8000
+			case 256:
+				c.ClockRate = 16000
+			case 384:
+				c.ClockRate = 24000
+			case 512:
+				c.ClockRate = 32000
+			case 705:
+				c.ClockRate = 44100
+			case 768:
+				c.ClockRate = 48000
+			case 1411:
+				// default Windows DShow
+				c.ClockRate = 44100
+				c.Channels = 2
+			case 1536:
+				// default Linux ALSA
+				c.ClockRate = 48000
+				c.Channels = 2
+			default:
+				c.Name = payloadType
+				break
+			}
+
+			c.Name = CodecPCML
 		default:
 			c.Name = payloadType
 		}

pkg/core/core.go

@@ -25,7 +25,9 @@ const (
 	CodecOpus = "OPUS" // payloadType: 111
 	CodecG722 = "G722"
 	CodecMP3  = "MPA" // payload: 14, aka MPEG-1 Layer III
-	CodecPCM  = "L16" // Linear PCM
+	CodecPCM  = "L16" // Linear PCM (big endian)
+
+	CodecPCML = "PCML" // Linear PCM (little endian)
 
 	CodecELD  = "ELD" // AAC-ELD
 	CodecFLAC = "FLAC"

pkg/core/media.go

@@ -3,8 +3,9 @@ package core
 import (
 	"encoding/json"
 	"fmt"
-	"github.com/pion/sdp/v3"
 	"strings"
+
+	"github.com/pion/sdp/v3"
 )
 
 // Media take best from:
@@ -93,7 +94,7 @@ func GetKind(name string) string {
 	switch name {
 	case CodecH264, CodecH265, CodecVP8, CodecVP9, CodecAV1, CodecJPEG:
 		return KindVideo
-	case CodecPCMU, CodecPCMA, CodecAAC, CodecOpus, CodecG722, CodecMP3, CodecPCM, CodecELD, CodecFLAC:
+	case CodecPCMU, CodecPCMA, CodecAAC, CodecOpus, CodecG722, CodecMP3, CodecPCM, CodecPCML, CodecELD, CodecFLAC:
 		return KindAudio
 	}
 	return ""