Allow specifying the number of input channels

examples/record/main.go

@@ -23,7 +23,7 @@ func main() {
 	}
 	defer microphone.Terminate()
 
-	stream, format, err := microphone.OpenDefaultStream(44100)
+	stream, format, err := microphone.OpenDefaultStream(44100, 2)
 	if err != nil {
 		log.Fatal(err)
 	}

go.mod

@@ -3,7 +3,7 @@ module github.com/MarkKremer/microphone
 go 1.12
 
 require (
-	github.com/faiface/beep v1.0.1
+	github.com/faiface/beep v1.0.2
 	github.com/gordonklaus/portaudio v0.0.0-20180817120803-00e7307ccd93
 	github.com/pkg/errors v0.8.1
 	github.com/stretchr/testify v1.3.0

go.sum

@@ -2,6 +2,8 @@ github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/faiface/beep v1.0.1 h1:SYTt7Bpt0C9KgeLkyNzTTuW9o3D3lTyAPAwCr5EQjO4=
 github.com/faiface/beep v1.0.1/go.mod h1:1yLb5yRdHMsovYYWVqYLioXkVuziCSITW1oarTeduQM=
+github.com/faiface/beep v1.0.2 h1:UB5DiRNmA4erfUYnHbgU4UB6DlBOrsdEFRtcc8sCkdQ=
+github.com/faiface/beep v1.0.2/go.mod h1:1yLb5yRdHMsovYYWVqYLioXkVuziCSITW1oarTeduQM=
 github.com/gdamore/encoding v1.0.0/go.mod h1:alR0ol34c49FCSBLjhosxzcPHQbf2trDkoo5dl+VrEg=
 github.com/gdamore/tcell v1.1.1/go.mod h1:K1udHkiR3cOtlpKG5tZPD5XxrF7v2y7lDq7Whcj+xkQ=
 github.com/gopherjs/gopherjs v0.0.0-20180628210949-0892b62f0d9f/go.mod h1:wJfORRmW1u3UXTncJ5qlYoELFm8eSnnEO6hX4iZ3EWY=

microphone.go

@@ -3,10 +3,15 @@
 package microphone
 
 import (
+	"errors"
 	"github.com/faiface/beep"
 	"github.com/gordonklaus/portaudio"
 )
 
+var (
+	invalidAmountOfInputChannelsError = errors.New("invalid amount of inputChannels specified. microphone.OpenDefaultStream func expects exactly 2 or 1")
+)
+
 // Init initializes internal datastructures of PortAudio and
 // the host APIs for use.
 //
@@ -38,12 +43,19 @@ func Terminate() error {
 const bufferSize = 512
 
 // OpenDefaultStream opens the default input stream.
-func OpenDefaultStream(sampleRate beep.SampleRate) (s *Streamer, format beep.Format, err error) {
+func OpenDefaultStream(sampleRate beep.SampleRate, inputChannels int) (s *Streamer, format beep.Format, err error) {
+	if inputChannels > 2 || inputChannels == 0 {
+		return nil, beep.Format{}, invalidAmountOfInputChannelsError
+	}
+
 	s = &Streamer{}
-	s.buffer = make([][]float32, 2)
-	s.buffer[0] = make([]float32, bufferSize)
-	s.buffer[1] = make([]float32, bufferSize)
-	s.stream, err = portaudio.OpenDefaultStream(2, 0, float64(sampleRate), bufferSize, s.buffer)
+	s.buffer = make([][]float32, inputChannels)
+
+	for i := range s.buffer {
+		s.buffer[i] = make([]float32, bufferSize)
+	}
+
+	s.stream, err = portaudio.OpenDefaultStream(inputChannels, 0, float64(sampleRate), bufferSize, s.buffer)
 	if err != nil {
 		return nil, beep.Format{}, err
 	}
@@ -52,7 +64,7 @@ func OpenDefaultStream(sampleRate beep.SampleRate) (s *Streamer, format beep.For
 	s.pos = bufferSize
 	format = beep.Format{
 		SampleRate:  sampleRate,
-		NumChannels: 2,
+		NumChannels: inputChannels,
 		// NOTE(m): I couldn't find how to obtain the actual precision
 		// from the microphone. 3 bytes is the highest precision
 		// supported by the beep library for saving WAV files.
@@ -106,8 +118,7 @@ func (s *Streamer) Stream(samples [][2]float64) (int, bool) {
 
 	var i int
 	for i = 0; i < n; i++ {
-		samples[i][0] = float64(s.buffer[0][s.pos+i])
-		samples[i][1] = float64(s.buffer[1][s.pos+i])
+		samples[i] = convertBufferIntoSamples(s.buffer, s.pos+i)
 	}
 
 	if n == len(samples) {
@@ -128,8 +139,7 @@ func (s *Streamer) Stream(samples [][2]float64) (int, bool) {
 		}
 
 		for i = 0; i < m; i++ {
-			samples[n+i][0] = float64(s.buffer[0][i])
-			samples[n+i][1] = float64(s.buffer[1][i])
+			samples[n+i] = convertBufferIntoSamples(s.buffer, i)
 		}
 
 		n += m
@@ -150,3 +160,19 @@ func (s *Streamer) Err() error {
 func (s *Streamer) Close() error {
 	return s.stream.Close()
 }
+
+func convertBufferIntoSamples(buffer [][]float32, bufferPos int) [2]float64 {
+	var samples [2]float64
+
+	if len(buffer) > 1 {
+		samples[0] = float64(buffer[0][bufferPos])
+		samples[1] = float64(buffer[1][bufferPos])
+
+		return samples
+	}
+
+	samples[0] = float64(buffer[0][bufferPos])
+	samples[1] = float64(buffer[0][bufferPos])
+
+	return samples
+}

microphone_test.go

@@ -25,7 +25,7 @@ func ExampleOpenDefaultStream_recordWav() {
 	}
 	defer Terminate()
 
-	stream, format, err := OpenDefaultStream(44100)
+	stream, format, err := OpenDefaultStream(44100, 1)
 	if err != nil {
 		log.Fatal(err)
 	}