From a9e7a73cc8e0a25d21226f00f606703feb83b932 Mon Sep 17 00:00:00 2001
From: Alex X <alexey.khit@gmail.com>
Date: Tue, 28 May 2024 14:01:42 +0300
Subject: [PATCH] Add video bitrate setting for HomeKit source

---
 internal/homekit/homekit.go | 32 ++++++++++++++++++++++++++++++--
 pkg/hap/camera/stream.go    | 13 ++++++++++---
 pkg/homekit/client.go       |  4 +++-
 3 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/internal/homekit/homekit.go b/internal/homekit/homekit.go
index bfe3e971..743aeab9 100644
--- a/internal/homekit/homekit.go
+++ b/internal/homekit/homekit.go
@@ -133,12 +133,19 @@ func Init() {
 var log zerolog.Logger
 var servers map[string]*server
 
-func streamHandler(url string) (core.Producer, error) {
+func streamHandler(rawURL string) (core.Producer, error) {
 	if srtp.Server == nil {
 		return nil, errors.New("homekit: can't work without SRTP server")
 	}
 
-	return homekit.Dial(url, srtp.Server)
+	rawURL, rawQuery, _ := strings.Cut(rawURL, "#")
+	client, err := homekit.Dial(rawURL, srtp.Server)
+	if client != nil && rawQuery != "" {
+		query := streams.ParseQuery(rawQuery)
+		client.Bitrate = parseBitrate(query.Get("bitrate"))
+	}
+
+	return client, err
 }
 
 func hapPairSetup(w http.ResponseWriter, r *http.Request) {
@@ -199,3 +206,24 @@ func findHomeKitURL(stream *streams.Stream) string {
 
 	return ""
 }
+
+func parseBitrate(s string) int {
+	n := len(s)
+	if n == 0 {
+		return 0
+	}
+
+	var k int
+	switch n--; s[n] {
+	case 'K':
+		k = 1024
+		s = s[:n]
+	case 'M':
+		k = 1024 * 1024
+		s = s[:n]
+	default:
+		k = 1
+	}
+
+	return k * core.Atoi(s)
+}
diff --git a/pkg/hap/camera/stream.go b/pkg/hap/camera/stream.go
index b2ef0d9f..23d53c39 100644
--- a/pkg/hap/camera/stream.go
+++ b/pkg/hap/camera/stream.go
@@ -15,7 +15,8 @@ type Stream struct {
 }
 
 func NewStream(
-	client *hap.Client, videoCodec *VideoCodec, audioCodec *AudioCodec, videoSession, audioSession *srtp.Session,
+	client *hap.Client, videoCodec *VideoCodec, audioCodec *AudioCodec,
+	videoSession, audioSession *srtp.Session, bitrate int,
 ) (*Stream, error) {
 	stream := &Stream{
 		id:     core.RandString(16, 0),
@@ -30,11 +31,17 @@ func NewStream(
 		return nil, err
 	}
 
+	if bitrate != 0 {
+		bitrate /= 1024 // convert bps to kbps
+	} else {
+		bitrate = 4096 // default kbps for general FullHD camera
+	}
+
 	videoCodec.RTPParams = []RTPParams{
 		{
 			PayloadType:  99,
 			SSRC:         videoSession.Local.SSRC,
-			MaxBitrate:   299,
+			MaxBitrate:   uint16(bitrate), // iPhone query 299Kbps, iPad/AppleTV query 802Kbps
 			RTCPInterval: 0.5,
 			MaxMTU:       []uint16{1378},
 		},
@@ -43,7 +50,7 @@ func NewStream(
 		{
 			PayloadType:  110,
 			SSRC:         audioSession.Local.SSRC,
-			MaxBitrate:   24,
+			MaxBitrate:   24, // any iDevice query 24Kbps (this is OK for 16KHz and 1 channel)
 			RTCPInterval: 5,
 
 			ComfortNoisePayloadType: []uint8{13},
diff --git a/pkg/homekit/client.go b/pkg/homekit/client.go
index c61acea6..133499d3 100644
--- a/pkg/homekit/client.go
+++ b/pkg/homekit/client.go
@@ -28,6 +28,8 @@ type Client struct {
 	audioSession *srtp.Session
 
 	stream *camera.Stream
+
+	Bitrate int // in bits/s
 }
 
 func Dial(rawURL string, server *srtp.Server) (*Client, error) {
@@ -132,7 +134,7 @@ func (c *Client) Start() error {
 	c.audioSession = &srtp.Session{Local: c.srtpEndpoint()}
 
 	var err error
-	c.stream, err = camera.NewStream(c.hap, videoCodec, audioCodec, c.videoSession, c.audioSession)
+	c.stream, err = camera.NewStream(c.hap, videoCodec, audioCodec, c.videoSession, c.audioSession, c.Bitrate)
 	if err != nil {
 		return err
 	}