refactor

internal/mpeg/mpeg.go

@@ -1 +0,0 @@
-package mpeg

main.go

@@ -6,160 +6,12 @@ import (
 	"io"
 	"log"
 	"os"
+
+	"git.netflux.io/rob/avframes/pkg/mpeg"
 )
 
 const fname = "/home/rob/share/home-office/example.mp3"
 
-type (
-	AudioVersionId int
-	Layer          int
-)
-
-type Decoder struct{}
-
-const (
-	AudioVersionMPEG25 AudioVersionId = iota
-	AudioVersionReserved
-	AudioVersionMPEG2
-	AudioVersionMPEG1
-)
-
-const (
-	LayerReserved Layer = iota
-	LayerIII
-	LayerII
-	LayerI
-)
-
-var (
-	bitRates = [5][16]int{
-		{0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, 0},
-		{0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0},
-		{0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 0},
-		{0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0},
-		{0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0},
-	}
-
-	sampleRates = [4][4]int{
-		{11025, 12000, 8000, 0},
-		{0, 0, 0, 0},
-		{22050, 24000, 16000, 0},
-		{44100, 48000, 32000, 0},
-	}
-
-	samplesPerFrame = [4][4]int{
-		{0, 576, 1152, 384},
-		{0, 0, 0, 0},
-		{0, 576, 1152, 384},
-		{0, 1152, 1152, 384},
-	}
-)
-
-type header []byte
-
-func (h header) HasSyncWord() bool {
-	return h[0] == 0xff && h[1]&0xe0 == 0xe0
-}
-
-func (h header) AudioVersionId() AudioVersionId {
-	return AudioVersionId((h[1] >> 3) & 0x3)
-}
-
-func (h header) Layer() Layer {
-	return Layer((h[1] >> 1) & 0x3)
-}
-
-func (h header) IsProtected() bool {
-	return h[1]&1 == 1
-}
-
-func (h header) String() string {
-	return fmt.Sprintf("%08b", h)
-}
-
-func (h header) SamplesPerFrame() int {
-	return samplesPerFrame[h.AudioVersionId()][h.Layer()]
-}
-
-func (h header) SampleRate() int {
-	i := h.AudioVersionId()
-	j := (h[2] >> 2) & 0x3
-	return sampleRates[i][j]
-}
-
-func (h header) PaddingBytes() int {
-	if isPadded := (h[2] >> 1) & 1; isPadded == 0 {
-		return 0
-	}
-	switch h.Layer() {
-	case LayerI:
-		return 4
-	case LayerII, LayerIII:
-		return 1
-	default:
-		return 0
-	}
-}
-
-func (h header) IsValid() bool {
-	if len(h) < 4 {
-		return false
-	}
-	if !h.HasSyncWord() {
-		return false
-	}
-	if h.AudioVersionId() == AudioVersionReserved {
-		return false
-	}
-	if h.Layer() == LayerReserved {
-		return false
-	}
-	if h.BitRate() == 0 {
-		return false
-	}
-	if h.SampleRate() == 0 {
-		return false
-	}
-
-	return true
-}
-
-func (h header) Len() int {
-	// TODO premultiply bitrates?
-	bps := float64(h.SamplesPerFrame()) / 8
-	return int((bps*float64(h.BitRate()*1000))/float64(h.SampleRate()) + float64(h.PaddingBytes()))
-}
-
-func (h header) BitRate() int {
-	// TODO: improve this
-	var j int
-	switch h.AudioVersionId() {
-	case AudioVersionMPEG1:
-		switch h.Layer() {
-		case LayerIII:
-			j = 2
-		case LayerII:
-			j = 1
-		case LayerI:
-			j = 0
-		default:
-			return 0
-		}
-	case AudioVersionReserved:
-		return 0
-	case AudioVersionMPEG2, AudioVersionMPEG25:
-		switch h.Layer() {
-		case LayerIII, LayerII:
-			j = 4
-		case LayerI:
-			j = 3
-		default:
-			return 0
-		}
-	}
-	return bitRates[j][h[2]>>4]
-}
-
 func main() {
 	f, err := os.Open(fname)
 	if err != nil {
@@ -179,7 +31,7 @@ func main() {
 			log.Fatal(err)
 		}
 
-		if h := header(buf); h.IsValid() {
+		if h := mpeg.Header(buf); h.IsValid() {
 			fmt.Printf("Got header: %v, audio version: %d, layer index: %d, bitrate: %d, samplerate: %d, samplesPerFrame: %d, padding: %d, size: %d\n", h, h.AudioVersionId(), h.Layer(), h.BitRate(), h.SampleRate(), h.SamplesPerFrame(), h.PaddingBytes(), h.Len())
 			bufreader.Discard(h.Len() - 4)
 		} else {

pkg/mpeg/mpeg.go

@@ -0,0 +1,153 @@
+package mpeg
+
+import "fmt"
+
+type (
+	AudioVersionId int
+	Layer          int
+)
+
+type Decoder struct{}
+
+const (
+	AudioVersionMPEG25 AudioVersionId = iota
+	AudioVersionReserved
+	AudioVersionMPEG2
+	AudioVersionMPEG1
+)
+
+const (
+	LayerReserved Layer = iota
+	LayerIII
+	LayerII
+	LayerI
+)
+
+var (
+	bitRates = [5][16]int{
+		{0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, 0},
+		{0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0},
+		{0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 0},
+		{0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0},
+		{0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0},
+	}
+
+	sampleRates = [4][4]int{
+		{11025, 12000, 8000, 0},
+		{0, 0, 0, 0},
+		{22050, 24000, 16000, 0},
+		{44100, 48000, 32000, 0},
+	}
+
+	samplesPerFrame = [4][4]int{
+		{0, 576, 1152, 384},
+		{0, 0, 0, 0},
+		{0, 576, 1152, 384},
+		{0, 1152, 1152, 384},
+	}
+)
+
+type Header []byte
+
+func (h Header) HasSyncWord() bool {
+	return h[0] == 0xff && h[1]&0xe0 == 0xe0
+}
+
+func (h Header) AudioVersionId() AudioVersionId {
+	return AudioVersionId((h[1] >> 3) & 0x3)
+}
+
+func (h Header) Layer() Layer {
+	return Layer((h[1] >> 1) & 0x3)
+}
+
+func (h Header) IsProtected() bool {
+	return h[1]&1 == 1
+}
+
+func (h Header) String() string {
+	return fmt.Sprintf("%08b", h)
+}
+
+func (h Header) SamplesPerFrame() int {
+	return samplesPerFrame[h.AudioVersionId()][h.Layer()]
+}
+
+func (h Header) SampleRate() int {
+	i := h.AudioVersionId()
+	j := (h[2] >> 2) & 0x3
+	return sampleRates[i][j]
+}
+
+func (h Header) PaddingBytes() int {
+	if isPadded := (h[2] >> 1) & 1; isPadded == 0 {
+		return 0
+	}
+	switch h.Layer() {
+	case LayerI:
+		return 4
+	case LayerII, LayerIII:
+		return 1
+	default:
+		return 0
+	}
+}
+
+func (h Header) IsValid() bool {
+	if len(h) < 4 {
+		return false
+	}
+	if !h.HasSyncWord() {
+		return false
+	}
+	if h.AudioVersionId() == AudioVersionReserved {
+		return false
+	}
+	if h.Layer() == LayerReserved {
+		return false
+	}
+	if h.BitRate() == 0 {
+		return false
+	}
+	if h.SampleRate() == 0 {
+		return false
+	}
+
+	return true
+}
+
+func (h Header) Len() int {
+	// TODO premultiply bitrates?
+	bps := float64(h.SamplesPerFrame()) / 8
+	return int((bps*float64(h.BitRate()*1000))/float64(h.SampleRate()) + float64(h.PaddingBytes()))
+}
+
+func (h Header) BitRate() int {
+	// TODO: improve this
+	var j int
+	switch h.AudioVersionId() {
+	case AudioVersionMPEG1:
+		switch h.Layer() {
+		case LayerIII:
+			j = 2
+		case LayerII:
+			j = 1
+		case LayerI:
+			j = 0
+		default:
+			return 0
+		}
+	case AudioVersionReserved:
+		return 0
+	case AudioVersionMPEG2, AudioVersionMPEG25:
+		switch h.Layer() {
+		case LayerIII, LayerII:
+			j = 4
+		case LayerI:
+			j = 3
+		default:
+			return 0
+		}
+	}
+	return bitRates[j][h[2]>>4]
+}

pkg/mpeg/mpeg_test.go

@@ -1,8 +1,9 @@
-package main
+package mpeg_test
 
 import (
 	"testing"
 
+	"git.netflux.io/rob/avframes/pkg/mpeg"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -13,7 +14,7 @@ func TestHasSyncWord(t *testing.T) {
 		expResult bool
 	}{
 		{
-			"empty header",
+			"empty mpeg.Header",
 			[]byte{0, 0, 0, 0},
 			false,
 		},
@@ -28,7 +29,7 @@ func TestHasSyncWord(t *testing.T) {
 			true,
 		},
 		{
-			"full header",
+			"full mpeg.Header",
 			[]byte{0xff, 0xff, 0xff, 0xff},
 			true,
 		},
@@ -36,7 +37,7 @@ func TestHasSyncWord(t *testing.T) {
 
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			h := header(tc.bytes)
+			h := mpeg.Header(tc.bytes)
 			assert.Equal(t, tc.expResult, h.HasSyncWord())
 		})
 	}
@@ -44,38 +45,38 @@ func TestHasSyncWord(t *testing.T) {
 
 func TestAudioVersionId(t *testing.T) {
 	bytes := []byte{0xff, 0xe8, 0, 0}
-	h := header(bytes)
+	h := mpeg.Header(bytes)
-	assert.Equal(t, AudioVersionReserved, h.AudioVersionId())
+	assert.Equal(t, mpeg.AudioVersionReserved, h.AudioVersionId())
 
 	bytes = []byte{0xff, 0xf0, 0, 0}
-	h = header(bytes)
+	h = mpeg.Header(bytes)
-	assert.Equal(t, AudioVersionMPEG2, h.AudioVersionId())
+	assert.Equal(t, mpeg.AudioVersionMPEG2, h.AudioVersionId())
 
 	bytes = []byte{0xff, 0xff, 0, 0}
-	h = header(bytes)
+	h = mpeg.Header(bytes)
-	assert.Equal(t, AudioVersionMPEG1, h.AudioVersionId())
+	assert.Equal(t, mpeg.AudioVersionMPEG1, h.AudioVersionId())
 
 	bytes = []byte{0xff, 0xe0, 0, 0}
-	h = header(bytes)
+	h = mpeg.Header(bytes)
-	assert.Equal(t, AudioVersionMPEG25, h.AudioVersionId())
+	assert.Equal(t, mpeg.AudioVersionMPEG25, h.AudioVersionId())
 }
 
 func TestLayer(t *testing.T) {
 	bytes := []byte{0xff, 0xe0, 0, 0}
-	h := header(bytes)
+	h := mpeg.Header(bytes)
-	assert.Equal(t, LayerReserved, h.Layer())
+	assert.Equal(t, mpeg.LayerReserved, h.Layer())
 
 	bytes = []byte{0xff, 0xe2, 0, 0}
-	h = header(bytes)
+	h = mpeg.Header(bytes)
-	assert.Equal(t, LayerIII, h.Layer())
+	assert.Equal(t, mpeg.LayerIII, h.Layer())
 
 	bytes = []byte{0xff, 0xe4, 0, 0}
-	h = header(bytes)
+	h = mpeg.Header(bytes)
-	assert.Equal(t, LayerII, h.Layer())
+	assert.Equal(t, mpeg.LayerII, h.Layer())
 
 	bytes = []byte{0xff, 0xe6, 0, 0}
-	h = header(bytes)
+	h = mpeg.Header(bytes)
-	assert.Equal(t, LayerI, h.Layer())
+	assert.Equal(t, mpeg.LayerI, h.Layer())
 }
 
 func TestPaddingBytes(t *testing.T) {
@@ -118,7 +119,7 @@ func TestPaddingBytes(t *testing.T) {
 
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			h := header(tc.bytes)
+			h := mpeg.Header(tc.bytes)
 			assert.Equal(t, tc.expPadding, h.PaddingBytes())
 		})
 	}
@@ -126,11 +127,11 @@ func TestPaddingBytes(t *testing.T) {
 
 func TestIsProtected(t *testing.T) {
 	bytes := []byte{0xff, 0xe1, 0, 0}
-	h := header(bytes)
+	h := mpeg.Header(bytes)
 	assert.True(t, h.IsProtected())
 
 	bytes = []byte{0xff, 0xe0, 0, 0}
-	h = header(bytes)
+	h = mpeg.Header(bytes)
 	assert.False(t, h.IsProtected())
 }
 
@@ -204,7 +205,7 @@ func TestSamplesPerFrame(t *testing.T) {
 
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			h := header(tc.bytes)
+			h := mpeg.Header(tc.bytes)
 			assert.Equal(t, tc.expSamplesPerFrame, h.SamplesPerFrame())
 		})
 	}
@@ -217,7 +218,7 @@ func TestBitRate(t *testing.T) {
 		expBitRate int
 	}{
 		{
-			"empty header",
+			"empty mpeg.Header",
 			[]byte{0, 0, 0, 0},
 			0,
 		},
@@ -332,7 +333,7 @@ func TestBitRate(t *testing.T) {
 			160,
 		},
 		{
-			"full header",
+			"full mpeg.Header",
 			[]byte{1, 1, 1, 1},
 			0,
 		},
@@ -340,7 +341,7 @@ func TestBitRate(t *testing.T) {
 
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			h := header(tc.bytes)
+			h := mpeg.Header(tc.bytes)
 			assert.Equal(t, tc.expBitRate, h.BitRate())
 		})
 	}
@@ -416,7 +417,7 @@ func TestSampleRate(t *testing.T) {
 
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			h := header(tc.bytes)
+			h := mpeg.Header(tc.bytes)
 			assert.Equal(t, int(tc.expSampleRate), int(h.SampleRate()))
 		})
 	}
@@ -462,7 +463,7 @@ func TestLen(t *testing.T) {
 
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			h := header(tc.bytes)
+			h := mpeg.Header(tc.bytes)
 			assert.Equal(t, tc.expLen, h.Len())
 		})
 	}