func newStereoSine(freqL, freqR, sampleRate float64) *stereoSine {
	s := &stereoSine{nil, freqL / sampleRate, 0, freqR / sampleRate, 0}
	var err error
	s.Stream, err = portaudio.OpenDefaultStream(0, 2, sampleRate, 0, s.processAudio)
	chk(err)
	return s
}

// NewSequencer creates and returns a pointer to a New Sequencer.
// Returns an error if there is one encountered
// During initializing portaudio, or the default stream
func NewSequencer() (*Sequencer, error) {
	err := portaudio.Initialize()
	if err != nil {
		return nil, err
	}

	s := &Sequencer{
		Timer: NewTimer(),
		Bar:   0,
		Beat:  0,
	}

	stream, err := portaudio.OpenDefaultStream(
		InputChannels,
		OutputChannels,
		float64(SampleRate),
		portaudio.FramesPerBufferUnspecified,
		s.ProcessAudio,
	)

	if err != nil {
		return nil, err
	}

	s.Stream = stream

	return s, nil
}

func (o *PortAudioOutput) Start(op OutputParams) error {
	var err error
	o.start.Do(func() {
		o.op = op
		MakeRecycleChannel(op)
		if o.stream == nil {
			o.stream, err = portaudio.OpenDefaultStream(0, o.channels, op.SampleRate, op.BufferSize, o)
			if err != nil {
				logger.Println("portaudio output creation failed", err)
				return
			}
		}
		err = o.stream.Start()
		if err != nil {
			logger.Println("portaudio output start failed", err)
			return
		}
		err = o.inputs[0].Start(op)
		if err != nil {
			logger.Println("input 0 start failed", err)
			o.stream.Stop()
			return
		}
		logger.Printf("portaudio Start %T %p", o.inputs[0], o.inputs[0])
		o.stop = new(sync.Once)
	})
	return err
}

func main() {
	flag.Parse()

	sequencer := NewSequencer()

	for _, file := range flag.Args() {
		pattern, err := drum.DecodeFile(file)
		if err != nil {
			log.Fatal(err)
		}
		if err := sequencer.Add(pattern); err != nil {
			log.Fatal(err)
		}
		log.Print(pattern.String())
	}

	portaudio.Initialize()
	defer portaudio.Terminate()
	stream, err := portaudio.OpenDefaultStream(0, 2, 44100, 0, func(o []int32) {
		sequencer.Read(o)
	})
	if err != nil {
		log.Fatal(err)
	}
	defer stream.Close()
	stream.Start()
	defer stream.Stop()

	sequencer.Start()

	for {
		time.Sleep(time.Second)
	}
}

func main() {
	sampleRate := 44100
	blockSize := 205 * sampleRate / 8000
	window := blockSize / 4
	dt := dtmf.NewStandard(sampleRate, blockSize)
	lastKey := -1
	keyCount := 0
	samples := make([]float32, blockSize)

	if err := portaudio.Initialize(); err != nil {
		log.Fatalf("Initialize: %+v", err)
	}
	defer func() {
		if err := portaudio.Terminate(); err != nil {
			log.Fatalf("Terminate: %+v", err)
		}
	}()
	inputBuf := make([]float32, window)
	stream, err := portaudio.OpenDefaultStream(1, 0, float64(sampleRate), len(inputBuf), inputBuf)
	if err != nil {
		log.Fatalf("OpenDefaultStream: %+v", err)
	}
	defer stream.Close()
	if err := stream.Start(); err != nil {
		log.Fatalf("Start: %+v", err)
	}
	defer stream.Stop()

	fmt.Printf("%+v\n", stream.Info())

	sig := make(chan os.Signal, 1)
	signal.Notify(sig, os.Interrupt, os.Kill)
	for {
		if err := stream.Read(); err != nil {
			log.Fatalf("Read: %+v", err)
		}

		copy(samples, samples[window:])
		copy(samples[len(samples)-len(inputBuf):], inputBuf)

		if k, t := dt.Feed(samples); k == lastKey && t > 0.0 {
			keyCount++
			if keyCount == 10 {
				fmt.Printf("%c", dtmf.Keypad[k])
			}
		} else {
			lastKey = k
			keyCount = 0
		}

		select {
		case <-sig:
			fmt.Println()
			return
		default:
		}
	}
}

// Runs the sampler, commencing output to an audio device.
func (s *Sampler) Run() error {
	portaudio.Initialize()
	var err error
	s.stream, err = portaudio.OpenDefaultStream(0, 2, 44100, 0, s.processAudio)
	if err != nil {
		return err
	}
	return s.stream.Start()
}

// Play will play the given pattern.
// It will generate different sounds for each instrument
// every time it is called. For simplification, those sounds
// are just sine waves.
func (p *Pattern) Play(playingTime time.Duration) error {
	// Initialize portaudio
	portaudio.Initialize()
	defer portaudio.Terminate()

	stream, err := portaudio.OpenDefaultStream(0, 1, sampleRate, 0, processAudio)
	if err != nil {
		return errors.New("could not open default stream")
	}
	defer stream.Close()

	// Create random tone map
	toneMap = make(map[byte]*tone)
	rand.Seed(time.Now().Unix())
	for i := range p.instruments {
		var err error
		toneMap[i], err = newTone(rand.Float64()*600+300, sampleRate)
		if err != nil {
			return fmt.Errorf("could not create tone for instrument %v", i)
		}
	}

	stream.Start()
	defer stream.Stop()

	// Signal for stopping
	timeOut := time.After(playingTime)

	timePerStep := time.Duration(60/p.header.BPM*1000) * time.Millisecond
	ticker := time.NewTicker(timePerStep)
	currentStep := 0

	// Play!
	for _ = range ticker.C {
		for i, instrument := range p.instruments {
			if instrument.Pattern[currentStep] == 0 {
				toneMap[i].playing = false
			} else {
				toneMap[i].playing = true
			}
		}

		currentStep++
		if currentStep > 15 {
			currentStep = 0
		}

		select {
		case <-timeOut:
			ticker.Stop()
			return nil
		default:
		}
	}

	return nil
}

func newStereoSine(freqL, freqR, sampleRate float64) *stereoSine {
	s := &stereoSine{nil,
		// timestep, phase, pan
		freqL / sampleRate, 0, -1,
		freqR / sampleRate, 0, 1,
		0, 0, make(chan bool)}
	var err error
	s.Stream, err = portaudio.OpenDefaultStream(0, 2, sampleRate, 0, s.processAudio)
	chk(err)
	return s
}

func (a *app) OnInit() {
	var err error
	a.r, err = os.Open(*in)
	if err != nil {
		log.Fatalf("Unable to open file '%s': %s", *in, err)
	}
	var wm webm.WebM
	a.reader, err = webm.Parse(a.r, &wm)
	if err != nil {
		log.Fatal("Unable to parse file: ", err)
	}
	a.duration = wm.GetDuration()
	var vtrack *webm.TrackEntry
	if !*justaudio {
		vtrack = wm.FindFirstVideoTrack()
	}
	var vstream *webm.Stream
	if vtrack != nil {
		vstream = webm.NewStream(vtrack)
		a.fduration = vtrack.GetDefaultDuration()
		a.vchan = vstream.VideoChannel()
	}
	var atrack *webm.TrackEntry
	if !*justvideo {
		atrack = wm.FindFirstAudioTrack()
	}
	var astream *webm.Stream
	if atrack != nil {
		astream = webm.NewStream(atrack)
	}
	splitter := webm.NewSplitter(a.reader.Chan)
	splitter.Split(astream, vstream)

	a.steps = uint(0xffffffff)
	a.img = <-a.vchan
	a.pimg = a.img

	chk := func(err error) {
		if err != nil {
			panic(err)
		}
	}
	if atrack != nil {
		channels := int(atrack.Audio.Channels)
		a.aw = &AudioWriter{ch: astream.AudioChannel(),
			channels: channels, active: true}
		a.pastream, err = portaudio.OpenDefaultStream(0, channels,
			atrack.Audio.SamplingFrequency, 0, a.aw)
		chk(err)
		chk(a.pastream.Start())
	}
}

func main() {
	chk := func(err error) {
		if err != nil {
			panic(err)
		}
	}
	stream, err := portaudio.OpenDefaultStream(0, 2, sampleRate, 0, newStereoSine(256, 320, sampleRate))
	chk(err)
	defer stream.Close()
	chk(stream.Start())
	time.Sleep(2 * time.Second)
	chk(stream.Stop())
}

func main() {
	chk := func(err error) {
		if err != nil {
			panic(err)
		}
	}
	stream, err := portaudio.OpenDefaultStream(0, 1, 44100, 128, noiseGenerator{})
	chk(err)
	defer stream.Close()
	chk(stream.Start())
	time.Sleep(1e9)
	chk(stream.Stop())
}

func main() {
	chk := func(err error) {
		if err != nil {
			panic(err)
		}
	}
	bufferSize := 4096
	stream, err := portaudio.OpenDefaultStream(1, 1, 44100, bufferSize, &echoer{make([]float32, bufferSize)})
	chk(err)
	defer stream.Close()
	chk(stream.Start())
	time.Sleep(4e9)
	chk(stream.Stop())
}

func (s *sound) Play() error {
	chans := len(s.sample())
	str, err := portaudio.OpenDefaultStream(0, chans, s.sampleRate, 0, s.processAudio)
	if err != nil {
		return err
	}
	if err = str.Start(); err != nil {
		return err
	}

	<-s.quit
	if err := str.Stop(); err != nil {
		return err
	}
	return str.Close()
}

// InitAudio starts up PortAudio, creates a stream and
// returns a pointer to an Audio struct, or an error.
func InitAudio() (*Audio, error) {
	a := Audio{
		tracks: make([]*Track, 0),
	}
	err := portaudio.Initialize()
	if err != nil {
		return nil, err
	}
	stream, err := portaudio.OpenDefaultStream(
		0, 2, float64(44100), 0, a.playCallback,
	)
	if err != nil {
		return nil, err
	}
	a.stream = stream
	a.stream.Start()
	return &a, nil
}

func (m *mixer) mix(signalChan chan SoundGen) {
	var err error
	m.Stream, err = portaudio.OpenDefaultStream(0, 2, sampleRate, 0, m.processAudio)
	chk(err)
	defer m.Close()
	chk(m.Start())
	defer m.Stop()
	for s := range signalChan {
		if len(m.signals) > 5 {
			//go func() { fmt.Println("yar!") }() // s m.signals[0]) { s.SilentStop() }
			go func(m *mixer) {
				fmt.Println("SILENCIO!")
				// m.signals[0].SilentStop()
				m.signals = m.signals[1:]
			}(m) // s m.signals[0]) { s.SilentStop() }
		}
		m.signals = append(m.signals, s)
	}
}

func (e *Engine) Start() error {
	stream, err := portaudio.OpenDefaultStream(0, 1, waveHz, nSamples, e.processAudio)
	if err != nil {
		return err
	}
	errc := make(chan error)
	go func() {
		err = stream.Start()
		errc <- err
		if err != nil {
			return
		}
		<-e.done
		err = stream.Stop()
		if err == nil {
			err = stream.Close()
		}
		e.done <- err
	}()
	return <-errc
}

func (pa *portAudio) player() {
	out := make([]int16, 2048*2)

	stream, err := portaudio.OpenDefaultStream(
		0,
		2,     // audio.format.Channels,
		44100, // float64(audio.format.SampleRate),
		len(out),
		&out,
	)
	if err != nil {
		panic(err)
	}
	defer stream.Close()

	stream.Start()
	defer stream.Stop()

	for {
		// Decode the incoming data which is expected to be 2 channels and
		// delivered as int16 in []byte, hence we need to convert it.

		select {
		case audio := <-pa.buffer:
			if len(audio.frames) != 2048*2*2 {
				// panic("unexpected")
				// don't know if it's a panic or track just ended
				break
			}

			j := 0
			for i := 0; i < len(audio.frames); i += 2 {
				out[j] = int16(audio.frames[i]) | int16(audio.frames[i+1])<<8
				j++
			}

			stream.Write()
		}
	}
}

func NewPort(sampleRate, channels int) (Output, error) {
	// todo: fix race condition
	if portInitCount == 0 {
		portaudio.Initialize()
	}
	portInitCount++

	p := port{
		ch: make(chan []float32),
	}
	var err error
	p.st, err = portaudio.OpenDefaultStream(0, channels, float64(sampleRate), 1024, p.Fetch)
	if err != nil {
		p.Dispose()
		return nil, err
	}
	if err := p.st.Start(); err != nil {
		p.Dispose()
		return nil, err
	}
	return &p, nil
}

func newMixer() (*mixer, error) {
	m := &mixer{
		stream:   nil,
		gain:     0.1, // TODO make mutable
		incoming: make(chan (<-chan []float32)),
		audio:    make(chan chan []float32),
		quit:     make(chan chan struct{}),
	}

	stream, err := portaudio.OpenDefaultStream(iChan, oChan, sRate, bufSz, m)
	if err != nil {
		return nil, err
	}
	if err := stream.Start(); err != nil {
		return nil, err
	}
	log.Printf("mixer: stream started")
	m.stream = stream

	go m.loop()
	return m, nil
}

// Play is a blocking call which initializes the audio subsystem. It should
// be called on a separate goroutine. Calling Stop will trigger Play to
// return.
func (m *Mixer) Play() {
	const (
		ICHAN = 1
		OCHAN = 1
	)
	m.mtx.Lock()
	defer m.mtx.Unlock()
	m.on = true
	stream, err := portaudio.OpenDefaultStream(ICHAN, OCHAN, SRATE, BUFSZ, m)
	if err != nil {
		panic(fmt.Sprintf("open: %s", err))
	}
	defer stream.Close()
	if err = stream.Start(); err != nil {
		panic(fmt.Sprintf("start: %s", err))
	}
	m.cnd.Wait()
	if err = stream.Stop(); err != nil {
		panic(fmt.Sprintf("stop: %s", err))
	}
	m.on = false
	m.cnd.Broadcast()
}