adpcmgo: encodeblock function added

cmd/adpcmgo/cmd/encode/encode.go

@@ -1,22 +1,38 @@
 package main
 
 import (
+	"flag"
 	"fmt"
 	"io/ioutil"
 
-	"github.com/bovarysme/adpcm"
+	"bitbucket.org/ausocean/av/cmd/adpcmgo"
 )
 
-// WIP
 func main() {
+	var inPath string
+	flag.StringVar(&inPath, "path", "test.pcm", "file path of input data")
+	flag.Parse()
 	//read pcm
 	pcm, err := ioutil.ReadFile(inPath)
 	if err != nil {
 		panic(err)
 	}
+
 	//encode adpcm
 	var comp []byte
-	adpcm.Encode(pcm, &comp)
+	start := 0
+	for i := 0; i < len(pcm); i++ {
+		if i%1010 == 1009 {
+			block := pcm[start : i+1]
+			encBlock, err := adpcmgo.EncodeBlock(block)
+			if err != nil {
+				//todo: use correct logging of error
+				panic(err)
+			}
+			comp = append(comp, encBlock...)
+			start = i + 1
+		}
+	}
 	// save adpcm to file
 	adpcmPath := "out.adpcm"
 	err = ioutil.WriteFile(adpcmPath, comp, 0644)

cmd/adpcmgo/codec.go

@@ -1,18 +1,19 @@
 package adpcmgo
 
 import (
+	"encoding/binary"
 	"fmt"
 	"math"
 )
 
 // table of index changes
-var indexTable = []int{
+var indexTable = []int16{
 	-1, -1, -1, -1, 2, 4, 6, 8,
 	-1, -1, -1, -1, 2, 4, 6, 8,
 }
 
 // quantize step size table
-var stepTable = []int{
+var stepTable = []int16{
 	7, 8, 9, 10, 11, 12, 13, 14,
 	16, 17, 19, 21, 23, 25, 28, 31,
 	34, 37, 41, 45, 50, 55, 60, 66,
@@ -28,25 +29,24 @@ var stepTable = []int{
 }
 
 var (
-	encPred  = 0
-	encIndex = 0
-	encStep  = 7
-	decPred  = 0
-	decIndex = 0
-	decStep  = 7
+	encPred  int16
+	encIndex int16
+	decPred  int16
+	decIndex int16
+	decStep  int16 = 7
 )
 
 // EncodeSample takes a single 16 bit PCM sample and
 // returns a byte of which the last 4 bits are an encoded ADPCM nibble
-func EncodeSample(sample int) byte {
+func EncodeSample(sample int16) byte {
 
 	// find difference from predicted sample
 	delta := sample - encPred
 
 	// set sign bit and find absolute value of difference
-	var newSample byte
+	var nibble byte
 	if delta < 0 {
-		newSample = 8
+		nibble = 8
 		delta = -delta
 	}
 
@@ -57,7 +57,7 @@ func EncodeSample(sample int) byte {
 	// quantize delta down to four bits
 	for i := 0; i < 3; i++ {
 		if delta > step {
-			newSample |= mask
+			nibble |= mask
 			delta -= step
 			diff += step
 		}
@@ -66,72 +66,110 @@ func EncodeSample(sample int) byte {
 	}
 
 	// adjust predicted sample based on calculated difference
-	if newSample&8 != 0 {
+	if nibble&8 != 0 {
 		encPred -= diff
 	} else {
 		encPred += diff
 	}
 
 	// check for underflow and overflow
-	fmt.Print("max, min: ", math.MaxInt16)
-	fmt.Println(math.MinInt16)
 	if encPred < math.MinInt16 {
 		encPred = math.MinInt16
 	} else if encPred > math.MaxInt16 {
 		encPred = math.MaxInt16
 	}
 
-	encIndex += indexTable[newSample&7]
+	encIndex += indexTable[nibble&7]
 
 	// check for underflow and overflow
 	if encIndex < 0 {
 		encIndex = 0
-	} else if encIndex > len(stepTable)-1 {
-		encIndex = len(stepTable) - 1
+	} else if encIndex > int16(len(stepTable)-1) {
+		encIndex = int16(len(stepTable) - 1)
 	}
 
-	return newSample
+	return nibble
 }
 
 // DecodeSample takes a byte, the last 4 bits of which contain a single
-// 4 bit ADPCM value/sample, and returns a 16 bit decoded PCM sample
-func DecodeSample(nibble byte) int {
+// 4 bit ADPCM nibble, and returns a 16 bit decoded PCM sample
+func DecodeSample(nibble byte) int16 {
 
-	diff := 0
+	// compute predicted sample estimate (decPred):
 
+	// calculate difference
+	var diff int16
 	if nibble&4 != 0 {
 		diff += decStep
 	}
-
 	if nibble&2 != 0 {
 		diff += decStep >> 1
 	}
-
 	if nibble&1 != 0 {
 		diff += decStep >> 2
 	}
-
 	diff += decStep >> 3
-
+	// account for sign bit
 	if nibble&8 != 0 {
 		diff = -diff
 	}
-
+	// adjust predicted sample based on calculated difference
 	decPred += diff
 
+	// check for overflow and underflow
 	if decPred > math.MaxInt16 {
 		decPred = math.MaxInt16
 	} else if decPred < math.MinInt16 {
 		decPred = math.MinInt16
 	}
 
+	// compute new step size:
+
+	// adjust index into step size lookup table using nibble
 	decIndex += indexTable[nibble]
+	// check for overflow and underflow
 	if decIndex < 0 {
 		decIndex = 0
-	} else if decIndex > len(stepTable)-1 {
-		decIndex = len(stepTable) - 1
+	} else if decIndex > int16(len(stepTable)-1) {
+		decIndex = int16(len(stepTable) - 1)
 	}
+	// find new quantizer step size
 	decStep = stepTable[decIndex]
 
 	return decPred
 }
+
+func calcHead(sample []byte) []byte {
+	fmt.Println(sample[0], sample[1])
+	intSample := int16(binary.LittleEndian.Uint16(sample))
+
+	fmt.Println("before enc", intSample)
+
+	EncodeSample(intSample)
+	head := sample
+
+	fmt.Println(encIndex)
+
+	head = append(head, byte(uint16(encIndex)))
+	head = append(head, byte(0x00))
+	return head
+}
+
+func EncodeBlock(block []byte) ([]byte, error) {
+	if len(block) != 1010 {
+		return nil, fmt.Errorf("unsupported block size. Given: %v, expected: 1010, ie. 505 16-bit PCM samples", len(block))
+	}
+
+	result := calcHead(block[0:2])
+
+	for i := 2; i < len(block); i++ {
+		if (i+1)%4 == 0 {
+			sample2 := EncodeSample(int16(binary.LittleEndian.Uint16(block[i-1 : i+1])))
+			sample := EncodeSample(int16(binary.LittleEndian.Uint16(block[i+1 : i+3])))
+			result = append(result, byte((sample<<4)|sample2))
+
+		}
+	}
+
+	return result, nil
+}