alsa: unexported ringbuffer chunksize

Chunksize can be calculated without needing an ALSA device instance.

Added a DataSize function to pcm package for calculating size of pcm data given relevant attributes.

Removed ChunkSize from config revid config struct.

Changed NewByteLexer to accept an in rather than a pointer.

cmd/audio-netsender/main.go

@@ -151,9 +151,9 @@ func main() {
 		Data:   ab.Data,
 	}
 
-	recSize := (((len(ac.pb.Data) / ac.dev.BufferFormat().Channels) * ac.channels) / ac.dev.BufferFormat().Rate) * ac.rate
+	cs := pcm.DataSize(ac.parameters.rate, ac.parameters.channels, ac.parameters.bits, float64(ac.parameters.period), 0)
 	rbLen := rbDuration / ac.period
-	ac.rb = ring.NewBuffer(rbLen, recSize, rbTimeout)
+	ac.rb = ring.NewBuffer(rbLen, cs, rbTimeout)
 
 	go ac.input()
 

codec/codecutil/lex.go

@@ -32,12 +32,15 @@ import (
 
 // ByteLexer is used to lex bytes using a buffer size which is configured upon construction.
 type ByteLexer struct {
-	bufSize *int
+	bufSize int
 }
 
 // NewByteLexer returns a pointer to a ByteLexer with the given buffer size.
-func NewByteLexer(bufSize *int) *ByteLexer {
-	return &ByteLexer{bufSize: bufSize}
+func NewByteLexer(s int) (*ByteLexer, error) {
+	if s <= 0 {
+		return nil, fmt.Errorf("invalid buffer size: %v", s)
+	}
+	return &ByteLexer{bufSize: s}, nil
 }
 
 // zeroTicks can be used to create an instant ticker.
@@ -48,15 +51,8 @@ func init() {
 	close(zeroTicks)
 }
 
-// Lex reads *l.bufSize bytes from src and writes them to dst every d seconds.
+// Lex reads l.bufSize bytes from src and writes them to dst every d seconds.
 func (l *ByteLexer) Lex(dst io.Writer, src io.Reader, d time.Duration) error {
-	if l.bufSize == nil {
-		return fmt.Errorf("buffer size has not been set")
-	}
-	bufSize := *l.bufSize
-	if bufSize <= 0 {
-		return fmt.Errorf("invalid buffer size: %v", bufSize)
-	}
 	if d < 0 {
 		return fmt.Errorf("invalid delay: %v", d)
 	}
@@ -69,7 +65,7 @@ func (l *ByteLexer) Lex(dst io.Writer, src io.Reader, d time.Duration) error {
 		defer ticker.Stop()
 	}
 
-	buf := make([]byte, bufSize)
+	buf := make([]byte, l.bufSize)
 	for {
 		<-ticker.C
 		off, err := src.Read(buf)

codec/codecutil/lex_test.go

@@ -51,8 +51,15 @@ func TestByteLexer(t *testing.T) {
 	for i, tt := range lexTests {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
 			dst := bytes.NewBuffer([]byte{})
-			l := NewByteLexer(&tt.n)
-			err := l.Lex(dst, bytes.NewReader(tt.data), tt.t)
+			l, err := NewByteLexer(tt.n)
+			if err != nil {
+				if tt.isValid {
+					t.Errorf("unexpected error: %v", err)
+				} else {
+					t.Skip()
+				}
+			}
+			err = l.Lex(dst, bytes.NewReader(tt.data), tt.t)
 			if err != nil && err != io.EOF {
 				if tt.isValid {
 					t.Errorf("unexpected error: %v", err)

codec/pcm/pcm.go

@@ -32,6 +32,8 @@ import (
 	"encoding/binary"
 	"fmt"
 
+	"bitbucket.org/ausocean/av/codec/adpcm"
+	"bitbucket.org/ausocean/av/codec/codecutil"
 	"github.com/pkg/errors"
 )
 
@@ -65,6 +67,15 @@ type Buffer struct {
 	Data   []byte
 }
 
+// DataSize takes audio attributes describing audio data and returns the size of that data.
+func DataSize(rate, channels, bitDepth int, period float64, codec uint8) int {
+	s := int(float64(channels) * float64(rate) * float64(bitDepth/8) * period)
+	if codec == codecutil.ADPCM {
+		s = adpcm.EncBytes(s)
+	}
+	return s
+}
+
 // Resample takes Buffer c and resamples the pcm audio data to 'rate' Hz and returns a Buffer with the resampled data.
 // Notes:
 // 	- Currently only downsampling is implemented and c's rate must be divisible by 'rate' or an error will occur.

device/alsa/alsa.go

@@ -63,15 +63,14 @@ const (
 
 // An ALSA device holds everything we need to know about the audio input stream and implements io.Reader and device.AVDevice.
 type ALSA struct {
-	l         Logger        // Logger for device's routines to log to.
-	mode      uint8         // Operating mode, either running, paused, or stopped.
-	mu        sync.Mutex    // Provides synchronisation when changing modes concurrently.
-	title     string        // Name of audio title, or empty for the default title.
-	dev       *yalsa.Device // ALSA device's Audio input device.
-	pb        pcm.Buffer    // Buffer to contain the direct audio from ALSA.
-	rb        *ring.Buffer  // Ring buffer to contain processed audio ready to be read.
-	chunkSize int           // This is the number of bytes that will be stored in rb at a time.
-	Config                  // Configuration parameters for this device.
+	l      Logger        // Logger for device's routines to log to.
+	mode   uint8         // Operating mode, either running, paused, or stopped.
+	mu     sync.Mutex    // Provides synchronisation when changing modes concurrently.
+	title  string        // Name of audio title, or empty for the default title.
+	dev    *yalsa.Device // ALSA device's Audio input device.
+	pb     pcm.Buffer    // Buffer to contain the direct audio from ALSA.
+	rb     *ring.Buffer  // Ring buffer to contain processed audio ready to be read.
+	Config               // Configuration parameters for this device.
 }
 
 // Config provides parameters used by the ALSA device.
@@ -93,7 +92,7 @@ type Logger interface {
 // OpenError is used to determine whether an error has originated from attempting to open a device.
 type OpenError error
 
-// NewALSA initializes and returns an ALSA device which has its logger set as the given logger.
+// New initializes and returns an ALSA device which has its logger set as the given logger.
 func New(l Logger) *ALSA { return &ALSA{l: l} }
 
 // Set will take a Config struct, check the validity of the relevant fields
@@ -149,24 +148,9 @@ func (d *ALSA) Set(c config.Config) error {
 		Data:   ab.Data,
 	}
 
-	// Account for channel conversion.
-	chunkSize := float64(len(d.pb.Data) / d.dev.BufferFormat().Channels * d.Channels)
-
-	// Account for resampling.
-	chunkSize = (chunkSize / float64(d.dev.BufferFormat().Rate)) * float64(d.SampleRate)
-	if chunkSize < 1 {
-		return errors.New("given Config parameters are too small")
-	}
-
-	// Account for codec conversion.
-	if d.Codec == codecutil.ADPCM {
-		d.chunkSize = adpcm.EncBytes(int(chunkSize))
-	} else {
-		d.chunkSize = int(chunkSize)
-	}
-
 	// Create ring buffer with appropriate chunk size.
-	d.rb = ring.NewBuffer(rbLen, d.chunkSize, rbTimeout)
+	cs := pcm.DataSize(d.SampleRate, d.Channels, d.BitDepth, d.RecPeriod, 0)
+	d.rb = ring.NewBuffer(rbLen, cs, rbTimeout)
 
 	// Start device in paused mode.
 	d.mode = paused
@@ -206,11 +190,6 @@ func (d *ALSA) Stop() error {
 	return nil
 }
 
-// ChunkSize returns the number of bytes written to the ringbuffer per d.RecPeriod.
-func (d *ALSA) ChunkSize() int {
-	return d.chunkSize
-}
-
 // validate checks if Config parameters are valid and returns an error if they are not.
 func validate(c *Config) error {
 	if c.SampleRate <= 0 {

device/alsa/alsa_test.go

@@ -32,6 +32,7 @@ import (
 	"time"
 
 	"bitbucket.org/ausocean/av/codec/codecutil"
+	"bitbucket.org/ausocean/av/codec/pcm"
 	"bitbucket.org/ausocean/av/revid/config"
 	"bitbucket.org/ausocean/utils/logger"
 )
@@ -63,8 +64,8 @@ func TestDevice(t *testing.T) {
 	if err != nil {
 		t.Error(err)
 	}
-	chunkSize := ai.ChunkSize()
-	lexer := codecutil.NewByteLexer(&chunkSize)
+	cs := pcm.DataSize(c.SampleRate, c.Channels, c.BitDepth, c.RecPeriod, c.InputCodec)
+	lexer, err := codecutil.NewByteLexer(cs)
 	go lexer.Lex(ioutil.Discard, ai, time.Duration(c.RecPeriod*float64(time.Second)))
 	time.Sleep(time.Duration(c.RecPeriod*float64(time.Second)) * time.Duration(n))
 	ai.Stop()

revid/config/config.go

@@ -237,7 +237,6 @@ type Config struct {
 	RecPeriod  float64 // How many seconds to record at a time.
 	Channels   int     // Number of audio channels, 1 for mono, 2 for stereo.
 	BitDepth   int     // Sample bit depth.
-	ChunkSize  int     // ChunkSize is the size of the chunks in the audio.Device's ringbuffer.
 
 	RTPAddress     string // RTPAddress defines the RTP output destination.
 	BurstPeriod    uint   // BurstPeriod defines the revid burst period in seconds.

revid/revid.go

@@ -42,6 +42,7 @@ import (
 	"bitbucket.org/ausocean/av/codec/h264"
 	"bitbucket.org/ausocean/av/codec/h265"
 	"bitbucket.org/ausocean/av/codec/mjpeg"
+	"bitbucket.org/ausocean/av/codec/pcm"
 	"bitbucket.org/ausocean/av/container/flv"
 	"bitbucket.org/ausocean/av/container/mts"
 	"bitbucket.org/ausocean/av/device"
@@ -363,8 +364,13 @@ func (r *Revid) setupPipeline(mtsEnc func(dst io.WriteCloser, rate float64) (io.
 		}
 
 		r.input = alsa.New(r.cfg.Logger)
-		cs := r.input.(*alsa.ALSA).ChunkSize()
-		r.lexTo = codecutil.NewByteLexer(&cs).Lex
+
+		l, err := codecutil.NewByteLexer(pcm.DataSize(r.cfg.SampleRate, r.cfg.Channels, r.cfg.BitDepth, r.cfg.RecPeriod, r.cfg.InputCodec))
+		if err != nil {
+			return err
+		}
+		r.lexTo = l.Lex
+
 	}
 
 	// Configure the input device. We know that defaults are set, so no need to