From b0f46bc919080ff2c358c056306451b4e8a7e76c Mon Sep 17 00:00:00 2001
From: Alex X <alexey.khit@gmail.com>
Date: Sun, 14 Dec 2025 17:17:52 +0300
Subject: [PATCH] Fix backchannel audio for xiaomi isa.camera.hlc6

---
 pkg/xiaomi/backchannel.go | 28 +++++++++++++++++++++-------
 pkg/xiaomi/producer.go    |  2 ++
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/pkg/xiaomi/backchannel.go b/pkg/xiaomi/backchannel.go
index 3e1b0f4c..0c4cefc4 100644
--- a/pkg/xiaomi/backchannel.go
+++ b/pkg/xiaomi/backchannel.go
@@ -4,12 +4,11 @@ import (
 	"time"
 
 	"github.com/AlexxIT/go2rtc/pkg/core"
+	"github.com/AlexxIT/go2rtc/pkg/pcm"
 	"github.com/AlexxIT/go2rtc/pkg/xiaomi/miss"
 	"github.com/pion/rtp"
 )
 
-const size8bit40ms = 8000 * 0.040
-
 func (p *Producer) AddTrack(media *core.Media, _ *core.Codec, track *core.Receiver) error {
 	if err := p.client.SpeakerStart(); err != nil {
 		return err
@@ -23,11 +22,26 @@ func (p *Producer) AddTrack(media *core.Media, _ *core.Codec, track *core.Receiv
 	case core.CodecPCMA:
 		var buf []byte
 
-		sender.Handler = func(pkt *rtp.Packet) {
-			buf = append(buf, pkt.Payload...)
-			for len(buf) >= size8bit40ms {
-				_ = p.client.WriteAudio(miss.CodecPCMA, buf[:size8bit40ms])
-				buf = buf[size8bit40ms:]
+		if p.model == "isa.camera.hlc6" {
+			dst := &core.Codec{Name: core.CodecPCML, ClockRate: 8000}
+			transcode := pcm.Transcode(dst, track.Codec)
+
+			sender.Handler = func(pkt *rtp.Packet) {
+				buf = append(buf, transcode(pkt.Payload)...)
+				const size = 2 * 8000 * 0.040 // 16bit 40ms
+				for len(buf) >= size {
+					_ = p.client.WriteAudio(miss.CodecPCM, buf[:size])
+					buf = buf[size:]
+				}
+			}
+		} else {
+			sender.Handler = func(pkt *rtp.Packet) {
+				buf = append(buf, pkt.Payload...)
+				const size = 8000 * 0.040 // 8bit 40 ms
+				for len(buf) >= size {
+					_ = p.client.WriteAudio(miss.CodecPCMA, buf[:size])
+					buf = buf[size:]
+				}
 			}
 		}
 	case core.CodecOpus:
diff --git a/pkg/xiaomi/producer.go b/pkg/xiaomi/producer.go
index 6a7537e4..f9164d0b 100644
--- a/pkg/xiaomi/producer.go
+++ b/pkg/xiaomi/producer.go
@@ -16,6 +16,7 @@ import (
 type Producer struct {
 	core.Connection
 	client *miss.Client
+	model  string
 }
 
 func Dial(rawURL string) (core.Producer, error) {
@@ -60,6 +61,7 @@ func Dial(rawURL string) (core.Producer, error) {
 			Transport:  client,
 		},
 		client: client,
+		model:  query.Get("model"),
 	}, nil
 }