Accept Windows surround audio on Mini 2

station/README.md

@@ -88,7 +88,7 @@ mount -o remount,ro /
 CGO_ENABLED=0 GOOS=linux GOARCH=arm64 go build -trimpath -ldflags='-s -w' -o scream-receiver ./cmd/scream-receiver
 ```
 
-Скопируй бинарник на станцию в `/data/opt/alice-backend` и запусти из этого каталога. Укажи адрес станции и адрес Windows. Приёмник работает с запущенным PulseAudio, принимает моно или стерео PCM в пакетах Scream и воспроизводит их через вход `music`. На этот вход действуют Room EQ и приглушение на время разговора.
+Скопируй бинарник на станцию в `/data/opt/alice-backend` и запусти из этого каталога. Укажи адрес станции и адрес Windows. Приёмник работает с запущенным PulseAudio, принимает до восьми каналов PCM в пакетах Scream и сводит их в PulseAudio и воспроизводит их через вход `music`. На этот вход действуют Room EQ и приглушение на время разговора.
 
 ```sh
 ./scream-receiver -listen 192.168.1.135:4010 -source 192.168.1.170

station/cmd/scream-receiver/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"encoding/binary"
 	"errors"
 	"flag"
 	"log"
@@ -10,6 +11,7 @@ import (
 	"os/exec"
 	"os/signal"
 	"strconv"
+	"strings"
 	"syscall"
 	"time"
 )
@@ -21,13 +23,48 @@ const (
 )
 
 type format struct {
-	rate     int
-	channels byte
-	sample   string
+	rate       int
+	channels   byte
+	sample     string
+	channelMap string
+}
+
+// Windows sends channels in ascending order of the speaker mask bits.
+var speakerPositions = [...]string{
+	"front-left", "front-right", "front-center", "lfe",
+	"rear-left", "rear-right", "front-left-of-center", "front-right-of-center",
+	"rear-center", "side-left", "side-right", "top-center",
+	"top-front-left", "top-front-center", "top-front-right", "top-rear-left",
+}
+
+func channelMap(channels byte, mask uint16) string {
+	if channels == 1 {
+		return "mono"
+	}
+	if channels == 2 {
+		return "front-left,front-right"
+	}
+	positions := make([]string, 0, channels)
+	for bit, position := range speakerPositions {
+		if mask&(1<<bit) != 0 {
+			positions = append(positions, position)
+		}
+	}
+	if len(positions) == int(channels) {
+		return strings.Join(positions, ",")
+	}
+	// Some endpoints omit the speaker mask. Use the conventional surround order.
+	if channels == 6 {
+		return "front-left,front-right,front-center,lfe,rear-left,rear-right"
+	}
+	if channels == 8 {
+		return "front-left,front-right,front-center,lfe,rear-left,rear-right,side-left,side-right"
+	}
+	return ""
 }
 
 func packetFormat(packet []byte) (format, bool) {
-	if len(packet) != packetBytes || packet[2] < 1 || packet[2] > 2 {
+	if len(packet) != packetBytes || packet[2] < 1 || packet[2] > 8 {
 		return format{}, false
 	}
 	rate := 48000
@@ -49,7 +86,11 @@ func packetFormat(packet []byte) (format, bool) {
 	default:
 		return format{}, false
 	}
-	return format{rate * multiple, packet[2], sample}, true
+	if (packetBytes-headerBytes)%(int(packet[2])*int(packet[1]/8)) != 0 {
+		return format{}, false
+	}
+	layout := channelMap(packet[2], binary.BigEndian.Uint16(packet[3:5]))
+	return format{rate * multiple, packet[2], sample, layout}, layout != ""
 }
 
 const pulse = "/data/opt/alice-backend/spotify"
@@ -63,7 +104,8 @@ type playback struct {
 func startPlayback(f format, latency int) (*playback, error) {
 	cmd := exec.Command(pulse+"/run", pulse+"/bin/pacat", "--playback", "--raw",
 		"--device=music", "--format="+f.sample, "--rate="+strconv.Itoa(f.rate),
-		"--channels="+strconv.Itoa(int(f.channels)), "--latency-msec="+strconv.Itoa(latency),
+		"--channels="+strconv.Itoa(int(f.channels)), "--channel-map="+f.channelMap,
+		"--latency-msec="+strconv.Itoa(latency),
 		"--client-name=PC Audio", "--stream-name=Scream")
 	cmd.Env = append(os.Environ(), "PULSE_SERVER=unix:/tmp/alice-pulse/native",
 		"PULSE_RUNTIME_PATH=/tmp/alice-pulse", "PULSE_COOKIE=/tmp/alice-pulse/cookie")
@@ -103,6 +145,7 @@ func receive(conn *net.UDPConn, peer netip.Addr, latency int) error {
 	packet := make([]byte, packetBytes+1)
 	var lastSeen time.Time
 	var retryAfter time.Time
+	var lastRejected time.Time
 	for {
 		if current != nil {
 			if err := conn.SetReadDeadline(lastSeen.Add(idleTimeout)); err != nil {
@@ -126,6 +169,10 @@ func receive(conn *net.UDPConn, peer netip.Addr, latency int) error {
 		}
 		f, valid := packetFormat(packet[:n])
 		if !valid {
+			if time.Since(lastRejected) >= 30*time.Second {
+				log.Printf("unsupported Scream packet from %s: %d bytes, header %x", peer, n, packet[:min(n, headerBytes)])
+				lastRejected = time.Now()
+			}
 			continue
 		}
 		lastSeen = time.Now()