ADPCM: Simplified for loops for creating and encoding/decoding blocks

cmd/adpcm/decode-pcm/decode-pcm.go

@@ -31,6 +31,7 @@ import (
 	"flag"
 	"fmt"
 	"io/ioutil"
+	"log"
 
 	"bitbucket.org/ausocean/av/stream/adpcm"
 )
@@ -47,7 +48,7 @@ func main() {
 	// read adpcm
 	comp, err := ioutil.ReadFile(inPath)
 	if err != nil {
-		panic(err)
+		log.Fatal(err)
 	}
 	fmt.Println("Read", len(comp), "bytes from file", inPath)
 
@@ -56,20 +57,19 @@ func main() {
 	numBlocks := int(len(comp) / inBSize)
 	outBSize := 2 + (inBSize-4)*4 // 2 bytes are copied, 2 are used as block header info, the remaining bytes are decompressed 1:4
 	decoded := make([]byte, 0, outBSize*numBlocks)
-	for i, start := inBSize-1, 0; i < len(comp); i += inBSize {
-		block := comp[start : i+1]
+	for i := 0; i < numBlocks; i++ {
+		block := comp[inBSize*i : inBSize*(i+1)]
 		decBlock, err := adpcm.DecodeBlock(block)
 		if err != nil {
-			panic(err)
+			log.Fatal(err)
 		}
 		decoded = append(decoded, decBlock...)
-		start = i + 1
 	}
 
 	// save pcm to file
 	err = ioutil.WriteFile(outPath, decoded, 0644)
 	if err != nil {
-		panic(err)
+		log.Fatal(err)
 	}
 	fmt.Println("Decoded and wrote", len(decoded), "bytes to file", outPath)
 }

cmd/adpcm/encode-pcm/encode-pcm.go

@@ -31,6 +31,7 @@ import (
 	"flag"
 	"fmt"
 	"io/ioutil"
+	"log"
 
 	"bitbucket.org/ausocean/av/stream/adpcm"
 )
@@ -47,7 +48,7 @@ func main() {
 	//read pcm
 	pcm, err := ioutil.ReadFile(inPath)
 	if err != nil {
-		panic(err)
+		log.Fatal(err)
 	}
 	fmt.Println("Read", len(pcm), "bytes from file", inPath)
 
@@ -56,20 +57,19 @@ func main() {
 	numBlocks := int(len(pcm) / inBSize)
 	outBSize := int(float32(inBSize/4) + float32(3.5)) // compression is 4:1 and 3.5 bytes of info are added to each block
 	comp := make([]byte, 0, outBSize*numBlocks)
-	for i, start := inBSize-1, 0; i < len(pcm); i += inBSize {
-		block := pcm[start : i+1]
+	for i := 0; i < numBlocks; i++ {
+		block := pcm[inBSize*i : inBSize*(i+1)]
 		encBlock, err := adpcm.EncodeBlock(block)
 		if err != nil {
-			panic(err)
+			log.Fatal(err)
 		}
 		comp = append(comp, encBlock...)
-		start = i + 1
 	}
 
 	// save adpcm to file
 	err = ioutil.WriteFile(adpcmPath, comp, 0644)
 	if err != nil {
-		panic(err)
+		log.Fatal(err)
 	}
 	fmt.Println("Encoded and wrote", len(comp), "bytes to file", adpcmPath)
 }

stream/adpcm/adpcm.go

@@ -184,7 +184,7 @@ func calcHead(sample []byte) ([]byte, error) {
 	intSample := int16(binary.LittleEndian.Uint16(sample))
 	encodeSample(intSample)
 
-	head := make([]byte, 2)
+	head := make([]byte, 2, 4)
 	head[0] = sample[0]
 	head[1] = sample[1]
 

stream/adpcm/adpcm_test.go

@@ -30,7 +30,10 @@ package adpcm
 import (
 	"bytes"
 	"io/ioutil"
+	"log"
 	"testing"
+
+	"bitbucket.org/ausocean/av/stream/adpcm"
 )
 
 // TestEncodeBlock will read PCM data, encode it in blocks and generate ADPCM
@@ -47,15 +50,13 @@ func TestEncodeBlock(t *testing.T) {
 	numBlocks := int(len(pcm) / inBSize)
 	outBSize := int(float32(inBSize/4) + float32(3.5)) // compression is 4:1 and 3.5 bytes of info are added to each block
 	comp := make([]byte, 0, outBSize*numBlocks)
-	for i, start := inBSize-1, 0; i < len(pcm); i += inBSize {
-		block := pcm[start : i+1]
-
-		encBlock, err := EncodeBlock(block)
+	for i := 0; i < numBlocks; i++ {
+		block := pcm[inBSize*i : inBSize*(i+1)]
+		encBlock, err := adpcm.EncodeBlock(block)
 		if err != nil {
-			t.Errorf("Unable to encode block: %v", err)
+			log.Fatal(err)
 		}
 		comp = append(comp, encBlock...)
-		start = i + 1
 	}
 
 	//read expected adpcm file
@@ -83,14 +84,13 @@ func TestDecodeBlock(t *testing.T) {
 	numBlocks := int(len(comp) / inBSize)
 	outBSize := 2 + (inBSize-4)*4 // 2 bytes are copied, 2 are used as block header info, the remaining bytes are decompressed 1:4
 	decoded := make([]byte, 0, outBSize*numBlocks)
-	for i, start := inBSize-1, 0; i < len(comp); i += inBSize {
-		block := comp[start : i+1]
-		decBlock, err := DecodeBlock(block)
+	for i := 0; i < numBlocks; i++ {
+		block := comp[inBSize*i : inBSize*(i+1)]
+		decBlock, err := adpcm.DecodeBlock(block)
 		if err != nil {
-			t.Errorf("Unable to decode block: %v", err)
+			log.Fatal(err)
 		}
 		decoded = append(decoded, decBlock...)
-		start = i + 1
 	}
 
 	//read expected pcm file