Add 'l' hotkey for quickly listening into the incoming audio stream

README.md

@@ -141,6 +141,14 @@ disabled and the contents of the second line of the status bar will be written
 as new console log lines. This is also the case if a Unix/VT100 terminal is
 not available.
 
+### Hotkeys
+
+Currently the only supported hotkey is `l` (listen), which toggles audio
+stream playback to the default sound device. This is useful for quickly
+listening into the audio stream coming from the server (the transceiver).
+Note that audio will be played to the previously created virtual sound card
+regardless of this setting.
+
 ## Authors
 
 - Norbert Varga HA2NON [nonoo@nonoo.hu](mailto:nonoo@nonoo.hu)

audio-linux.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"github.com/akosmarton/papipes"
+	"github.com/mesilliac/pulse-simple"
 )
 
 const audioSampleRate = 48000
@@ -19,6 +20,8 @@ const audioFrameSize = 1920 // 20ms
 const maxPlayBufferSize = audioFrameSize * 5
 
 type audioStruct struct {
+	devName string
+
 	source papipes.Source
 	sink   papipes.Sink
 
@@ -33,14 +36,58 @@ type audioStruct struct {
 	mutex   sync.Mutex
 	playBuf *bytes.Buffer
 	canPlay chan bool
+
+	togglePlaybackToDefaultSoundcardChan chan bool
+	defaultSoundCardStream               *pulse.Stream
 }
 
 var audio audioStruct
 
+func (a *audioStruct) togglePlaybackToDefaultSoundcard() {
+	if a.defaultSoundCardStream == nil {
+		log.Print("turned on audio playback")
+		ss := pulse.SampleSpec{Format: pulse.SAMPLE_S16LE, Rate: 48000, Channels: 1}
+		a.defaultSoundCardStream, _ = pulse.Playback("kappanhang", a.devName, &ss)
+	} else {
+		_ = a.defaultSoundCardStream.Drain()
+		a.defaultSoundCardStream.Free()
+		a.defaultSoundCardStream = nil
+		log.Print("turned off audio playback")
+	}
+}
+
+func (a *audioStruct) playToVirtualSoundcard(d []byte) {
+	for len(d) > 0 {
+		written, err := a.source.Write(d)
+		if err != nil {
+			if _, ok := err.(*os.PathError); !ok {
+				reportError(err)
+			}
+			break
+		}
+		d = d[written:]
+	}
+}
+
+func (a *audioStruct) playToDefaultSoundcard(d []byte) {
+	for len(d) > 0 {
+		written, err := a.defaultSoundCardStream.Write(d)
+		if err != nil {
+			if _, ok := err.(*os.PathError); !ok {
+				reportError(err)
+			}
+			break
+		}
+		d = d[written:]
+	}
+}
+
 func (a *audioStruct) playLoop(deinitNeededChan, deinitFinishedChan chan bool) {
 	for {
 		select {
 		case <-a.canPlay:
+		case <-a.togglePlaybackToDefaultSoundcardChan:
+			a.togglePlaybackToDefaultSoundcard()
 		case <-deinitNeededChan:
 			deinitFinishedChan <- true
 			return
@@ -65,19 +112,9 @@ func (a *audioStruct) playLoop(deinitNeededChan, deinitFinishedChan chan bool) {
 				break
 			}
 
-			for {
+			a.playToVirtualSoundcard(d[:bytesToWrite])
-				written, err := a.source.Write(d)
+			if a.defaultSoundCardStream != nil {
-				if err != nil {
+				a.playToDefaultSoundcard(d[:bytesToWrite])
-					if _, ok := err.(*os.PathError); !ok {
-						reportError(err)
-					}
-					break
-				}
-				bytesToWrite -= written
-				if bytesToWrite == 0 {
-					break
-				}
-				d = d[written:]
 			}
 		}
 	}
@@ -175,16 +212,17 @@ func (a *audioStruct) loop() {
 // We only init the audio once, with the first device name we acquire, so apps using the virtual sound card
 // won't have issues with the interface going down while the app is running.
 func (a *audioStruct) initIfNeeded(devName string) error {
+	a.devName = devName
 	bufferSizeInBits := (audioSampleRate * audioSampleBytes * 8) / 1000 * pulseAudioBufferLength.Milliseconds()
 
 	if !a.source.IsOpen() {
-		a.source.Name = "kappanhang-" + devName
+		a.source.Name = "kappanhang-" + a.devName
-		a.source.Filename = "/tmp/kappanhang-" + devName + ".source"
+		a.source.Filename = "/tmp/kappanhang-" + a.devName + ".source"
 		a.source.Rate = audioSampleRate
 		a.source.Format = "s16le"
 		a.source.Channels = 1
 		a.source.SetProperty("device.buffering.buffer_size", bufferSizeInBits)
-		a.source.SetProperty("device.description", "kappanhang: "+devName)
+		a.source.SetProperty("device.description", "kappanhang: "+a.devName)
 
 		// Cleanup previous pipes.
 		sources, err := papipes.GetActiveSources()
@@ -202,14 +240,14 @@ func (a *audioStruct) initIfNeeded(devName string) error {
 	}
 
 	if !a.sink.IsOpen() {
-		a.sink.Name = "kappanhang-" + devName
+		a.sink.Name = "kappanhang-" + a.devName
-		a.sink.Filename = "/tmp/kappanhang-" + devName + ".sink"
+		a.sink.Filename = "/tmp/kappanhang-" + a.devName + ".sink"
 		a.sink.Rate = audioSampleRate
 		a.sink.Format = "s16le"
 		a.sink.Channels = 1
 		a.sink.UseSystemClockForTiming = true
 		a.sink.SetProperty("device.buffering.buffer_size", bufferSizeInBits)
-		a.sink.SetProperty("device.description", "kappanhang: "+devName)
+		a.sink.SetProperty("device.description", "kappanhang: "+a.devName)
 
 		// Cleanup previous pipes.
 		sinks, err := papipes.GetActiveSinks()
@@ -233,6 +271,7 @@ func (a *audioStruct) initIfNeeded(devName string) error {
 		a.play = make(chan []byte)
 		a.canPlay = make(chan bool)
 		a.rec = make(chan []byte)
+		a.togglePlaybackToDefaultSoundcardChan = make(chan bool)
 		a.deinitNeededChan = make(chan bool)
 		a.deinitFinishedChan = make(chan bool)
 		go a.loop()

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/fatih/color v1.9.0
 	github.com/google/goterm v0.0.0-20200907032337-555d40f16ae2
 	github.com/mattn/go-isatty v0.0.11
+	github.com/mesilliac/pulse-simple v0.0.0-20170506101341-75ac54e19fdf
 	github.com/pborman/getopt v1.1.0
 	go.uber.org/multierr v1.6.0 // indirect
 	go.uber.org/zap v1.16.0

go.sum

@@ -21,6 +21,8 @@ github.com/mattn/go-colorable v0.1.4/go.mod h1:U0ppj6V5qS13XJ6of8GYAs25YV2eR4EVc
 github.com/mattn/go-isatty v0.0.8/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
 github.com/mattn/go-isatty v0.0.11 h1:FxPOTFNqGkuDUGi3H/qkUbQO4ZiBa2brKq5r0l8TGeM=
 github.com/mattn/go-isatty v0.0.11/go.mod h1:PhnuNfih5lzO57/f3n+odYbM4JtupLOxQOAqxQCu2WE=
+github.com/mesilliac/pulse-simple v0.0.0-20170506101341-75ac54e19fdf h1:Zkc2mThKEz8uIFMN5S9Vde4F075QqonswrYWngsjq0g=
+github.com/mesilliac/pulse-simple v0.0.0-20170506101341-75ac54e19fdf/go.mod h1:w/UDU7AYzhUNZpb9TmWkrEFVu1+yA8jn++5871x9hWc=
 github.com/pborman/getopt v1.1.0 h1:eJ3aFZroQqq0bWmraivjQNt6Dmm5M0h2JcDW38/Azb0=
 github.com/pborman/getopt v1.1.0/go.mod h1:FxXoW1Re00sQG/+KIkuSqRL/LwQgSkv7uyac+STFsbk=
 github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=

keyboard.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"os"
+	"os/exec"
+)
+
+type keyboardStruct struct {
+}
+
+var keyboard keyboardStruct
+
+func (s *keyboardStruct) loop() {
+	var b []byte = make([]byte, 1)
+	for {
+		n, err := os.Stdin.Read(b)
+		if n > 0 && err == nil {
+			if b[0] == 'l' {
+				if audio.togglePlaybackToDefaultSoundcardChan != nil {
+					// Non-blocking send to channel.
+					select {
+					case audio.togglePlaybackToDefaultSoundcardChan <- true:
+					default:
+					}
+				}
+			}
+		}
+	}
+}
+
+func (s *keyboardStruct) init() {
+	if err := exec.Command("stty", "-F", "/dev/tty", "cbreak", "min", "1").Run(); err != nil {
+		log.Error("can't disable input buffering")
+	}
+	if err := exec.Command("stty", "-F", "/dev/tty", "-echo").Run(); err != nil {
+		log.Error("can't disable displaying entered characters")
+	}
+
+	go s.loop()
+}
+
+func (s *keyboardStruct) deinit() {
+	_ = exec.Command("stty", "-F", "/dev/tty", "echo").Run()
+}

main.go

@@ -99,6 +99,8 @@ func main() {
 	osSignal := make(chan os.Signal, 1)
 	signal.Notify(osSignal, os.Interrupt, syscall.SIGTERM)
 
+	keyboard.init()
+
 	var shouldExit bool
 	var exitCode int
 	for !shouldExit {
@@ -120,6 +122,7 @@ func main() {
 	audio.deinit()
 	serialTCPSrv.deinit()
 	serialPort.deinit()
+	keyboard.deinit()
 
 	log.Print("exiting")
 	os.Exit(exitCode)