From 975a43d39276bd61ef3ed0f9c2eb1adb66b5e60d Mon Sep 17 00:00:00 2001
From: Oliver Eiber <oeiber@sysob.com>
Date: Thu, 31 Jul 2025 21:07:45 +0200
Subject: [PATCH] reduce audio delay by lowering buffer size

---
 pkg/doorbird/backchannel.go | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/pkg/doorbird/backchannel.go b/pkg/doorbird/backchannel.go
index 5e5e8834..dc66ee0e 100644
--- a/pkg/doorbird/backchannel.go
+++ b/pkg/doorbird/backchannel.go
@@ -15,6 +15,14 @@ import (
 	"github.com/pion/rtp"
 )
 
+const (
+	AudioMixerInterval    = 10 * time.Millisecond
+	AudioChannelBuffer    = 10
+	OutputChannelBuffer   = 10
+	SenderCleanupInterval = 5 * time.Second
+	SenderTimeoutDuration = 5 * time.Second
+)
+
 var (
 	cltMu  sync.Mutex
 	cltMap = make(map[string]*Client)
@@ -31,7 +39,7 @@ type AudioMixer struct {
 func NewAudioMixer() *AudioMixer {
 	return &AudioMixer{
 		streams: make(map[string]chan []byte),
-		output:  make(chan []byte, 100),
+		output:  make(chan []byte, OutputChannelBuffer),
 	}
 }
 
@@ -50,7 +58,7 @@ func (m *AudioMixer) AddStream(id string) chan []byte {
 		go m.mixLoop()
 	}
 
-	stream := make(chan []byte, 100)
+	stream := make(chan []byte, AudioChannelBuffer)
 	m.streams[id] = stream
 	return stream
 }
@@ -66,7 +74,7 @@ func (m *AudioMixer) RemoveStream(id string) {
 }
 
 func (m *AudioMixer) mixLoop() {
-	ticker := time.NewTicker(20 * time.Millisecond)
+	ticker := time.NewTicker(AudioMixerInterval)
 	defer ticker.Stop()
 
 	for range ticker.C {
@@ -164,7 +172,6 @@ func Dial(rawURL string) (*Client, error) {
 	cltMu.Lock()
 	defer cltMu.Unlock()
 
-	// Check if we already have a client for this URL
 	if existingClient, exists := cltMap[rawURL]; exists && existingClient.conn != nil {
 		return existingClient, nil
 	}
@@ -235,7 +242,6 @@ func Dial(rawURL string) (*Client, error) {
 		senderStats: make(map[*core.Sender]time.Time),
 	}
 
-	// Store the client in the map
 	cltMap[rawURL] = client
 
 	return client, nil
@@ -269,7 +275,6 @@ func (c *Client) AddTrack(media *core.Media, codec *core.Codec, track *core.Rece
 				c.senderStats[sender] = time.Now()
 				c.mu.Unlock()
 			default:
-				// Channel is full, skip this packet
 			}
 		}
 	}
@@ -281,7 +286,6 @@ func (c *Client) AddTrack(media *core.Media, codec *core.Codec, track *core.Rece
 		go func() {
 			defer func() {
 				if r := recover(); r != nil {
-					// Recover from any panics when mixer is closed
 				}
 			}()
 
@@ -295,7 +299,6 @@ func (c *Client) AddTrack(media *core.Media, codec *core.Codec, track *core.Rece
 					if n, err := conn.Write(mixedData); err == nil {
 						c.Send += n
 					} else {
-						// Connection failed, break out of loop
 						break
 					}
 				}
@@ -314,7 +317,7 @@ func (c *Client) Start() error {
 	}
 
 	go func() {
-		ticker := time.NewTicker(5 * time.Second)
+		ticker := time.NewTicker(SenderCleanupInterval)
 		defer ticker.Stop()
 		for range ticker.C {
 			c.cleanupOrphanedSenders()
@@ -323,12 +326,10 @@ func (c *Client) Start() error {
 
 	buf := make([]byte, 1)
 	for {
-		// Set read deadline to detect connection issues
 		_ = c.conn.SetReadDeadline(time.Now().Add(30 * time.Second))
 		_, err := c.conn.Read(buf)
 		if err != nil {
 			c.cleanup()
-			// Remove this client from the global map
 			cltMu.Lock()
 			delete(cltMap, c.URL)
 			cltMu.Unlock()
@@ -360,7 +361,6 @@ func (c *Client) cleanup() {
 		c.mixer.mu.Unlock()
 	}
 
-	// Close all senders
 	for _, sender := range c.Senders {
 		sender.Close()
 	}
@@ -369,7 +369,6 @@ func (c *Client) cleanup() {
 	c.trackMap = make(map[*core.Sender]string)
 	c.senderStats = make(map[*core.Sender]time.Time)
 
-	// Remove from global map
 	cltMu.Lock()
 	delete(cltMap, c.URL)
 	cltMu.Unlock()
@@ -385,7 +384,7 @@ func (c *Client) cleanupOrphanedSenders() {
 
 	for i, sender := range c.Senders {
 		lastActivity, exists := c.senderStats[sender]
-		if sender.State() == "closed" || !exists || now.Sub(lastActivity) >= 5*time.Second {
+		if sender.State() == "closed" || !exists || now.Sub(lastActivity) >= SenderTimeoutDuration {
 			if trackID, exists := c.trackMap[sender]; exists {
 				c.mixer.RemoveStream(trackID)
 				delete(c.trackMap, sender)