Change HomeKit codec from AAC to ELD

cmd/ffmpeg/README.md

@@ -1,3 +1,17 @@
+## FFplay output
+
+[FFplay](https://stackoverflow.com/questions/27778678/what-are-mv-fd-aq-vq-sq-and-f-in-a-video-stream) `7.11 A-V:  0.003 fd=   1 aq=   21KB vq=  321KB sq=    0B f=0/0`:
+
+- `7.11` - master clock, is the time from start of the stream/video
+- `A-V` - av_diff, difference between audio and video timestamps
+- `fd` - frames dropped
+- `aq` - audio queue (0 - no delay)
+- `vq` - video queue (0 - no delay)
+- `sq` - subtitle queue
+- `f` - timestamp error correction rate (Not 100% sure)
+
+`M-V`, `M-A` means video stream only, audio stream only respectively.
+
 ## Devices Windows
 
 ```

pkg/homekit/client.go

@@ -163,7 +163,7 @@ func (c *Client) Start() error {
 		switch track.Codec.Name {
 		case streamer.CodecH264:
 			vs.Track = track
-		case streamer.CodecAAC:
+		case streamer.CodecELD:
 			as.Track = track
 		}
 	}
@@ -233,14 +233,6 @@ func (c *Client) getMedias() []*streamer.Media {
 			Channels: uint16(hkCodec.Parameters.Channels),
 		}
 
-		switch hkCodec.Type {
-		case rtp.AudioCodecType_AAC_ELD:
-			codec.Name = streamer.CodecAAC
-		default:
-			fmt.Printf("unknown codec: %d", hkCodec.Type)
-			continue
-		}
-
 		switch hkCodec.Parameters.Samplerate {
 		case rtp.AudioCodecSampleRate8Khz:
 			codec.ClockRate = 8000
@@ -252,6 +244,16 @@ func (c *Client) getMedias() []*streamer.Media {
 			panic(fmt.Sprintf("unknown clockrate: %d", hkCodec.Parameters.Samplerate))
 		}
 
+		switch hkCodec.Type {
+		case rtp.AudioCodecType_AAC_ELD:
+			codec.Name = streamer.CodecELD
+			// only this value supported by FFmpeg
+			codec.FmtpLine = "profile-level-id=1;mode=AAC-hbr;sizelength=13;indexlength=3;indexdeltalength=3;config=F8EC3000"
+		default:
+			fmt.Printf("unknown codec: %d", hkCodec.Type)
+			continue
+		}
+
 		media := &streamer.Media{
 			Kind: streamer.KindAudio, Direction: streamer.DirectionSendonly,
 			Codecs: []*streamer.Codec{codec},

pkg/streamer/media.go

@@ -33,6 +33,8 @@ const (
 	CodecOpus = "OPUS" // payloadType: 111
 	CodecG722 = "G722"
 	CodecMPA  = "MPA" // payload: 14
+
+	CodecELD = "ELD" // AAC-ELD
 )
 
 const PayloadTypeMP4 byte = 255
@@ -41,7 +43,7 @@ func GetKind(name string) string {
 	switch name {
 	case CodecH264, CodecH265, CodecVP8, CodecVP9, CodecAV1, CodecJPEG:
 		return KindVideo
-	case CodecPCMU, CodecPCMA, CodecAAC, CodecOpus, CodecG722, CodecMPA:
+	case CodecPCMU, CodecPCMA, CodecAAC, CodecOpus, CodecG722, CodecMPA, CodecELD:
 		return KindAudio
 	}
 	return ""
@@ -187,13 +189,19 @@ func MarshalSDP(medias []*Media) ([]byte, error) {
 		}
 
 		codec := media.Codecs[0]
+
+		name := codec.Name
+		if name == CodecELD {
+			name = CodecAAC
+		}
+
 		md := &sdp.MediaDescription{
 			MediaName: sdp.MediaName{
 				Media:  media.Kind,
 				Protos: []string{"RTP", "AVP"},
 			},
 		}
-		md.WithCodec(payloadType, codec.Name, codec.ClockRate, codec.Channels, codec.FmtpLine)
+		md.WithCodec(payloadType, name, codec.ClockRate, codec.Channels, codec.FmtpLine)
 
 		sd.MediaDescriptions = append(sd.MediaDescriptions, md)