ADPCM: Improved comment consistancy.

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

@@ -46,14 +46,14 @@ func main() {
 	flag.StringVar(&outPath, "out", "decoded.pcm", "file path of output data")
 	flag.Parse()
 
-	// read adpcm
+	// Read adpcm.
 	comp, err := ioutil.ReadFile(inPath)
 	if err != nil {
 		log.Fatal(err)
 	}
 	fmt.Println("Read", len(comp), "bytes from file", inPath)
 
-	// decode adpcm
+	// Decode adpcm.
 	inBSize := 256
 	numBlocks := 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
@@ -67,7 +67,7 @@ func main() {
 		}
 	}
 
-	// save pcm to file
+	// Save pcm to file.
 	err = ioutil.WriteFile(outPath, decoded.Bytes(), 0644)
 	if err != nil {
 		log.Fatal(err)

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

@@ -46,17 +46,17 @@ func main() {
 	flag.StringVar(&adpcmPath, "out", "encoded.adpcm", "file path of output")
 	flag.Parse()
 
-	//read pcm
+	// Read pcm.
 	pcm, err := ioutil.ReadFile(inPath)
 	if err != nil {
 		log.Fatal(err)
 	}
 	fmt.Println("Read", len(pcm), "bytes from file", inPath)
 
-	//encode adpcm
+	// Encode adpcm.
 	inBSize := 1010
 	numBlocks := len(pcm) / inBSize
-	outBSize := int(float64(inBSize)/4 + 3.5) // compression is 4:1 and 3.5 bytes of info are added to each block
+	outBSize := int(float64(inBSize)/4 + 3.5) // Compression is 4:1 and 3.5 bytes of info are added to each block.
 	comp := bytes.NewBuffer(make([]byte, 0, outBSize*numBlocks))
 	enc := adpcm.NewEncoder(comp)
 	for i := 0; i < numBlocks; i++ {
@@ -67,7 +67,7 @@ func main() {
 		}
 	}
 
-	// save adpcm to file
+	// Save adpcm to file.
 	err = ioutil.WriteFile(adpcmPath, comp.Bytes(), 0644)
 	if err != nil {
 		log.Fatal(err)

stream/adpcm/adpcm.go

@@ -57,13 +57,13 @@ type Decoder struct {
 	step  int16
 }
 
-// table of index changes (see spec)
+// Table of index changes (see spec).
 var indexTable = []int16{
 	-1, -1, -1, -1, 2, 4, 6, 8,
 	-1, -1, -1, -1, 2, 4, 6, 8,
 }
 
-// quantize step size table (see spec)
+// Quantize step size table (see spec).
 var stepTable = []int16{
 	7, 8, 9, 10, 11, 12, 13, 14,
 	16, 17, 19, 21, 23, 25, 28, 31,
@@ -97,12 +97,12 @@ func NewDecoder(dst *bytes.Buffer) *Decoder {
 }
 
 // encodeSample takes a single 16 bit PCM sample and
-// returns a byte of which the last 4 bits are an encoded ADPCM nibble
+// returns a byte of which the last 4 bits are an encoded ADPCM nibble.
 func (e *Encoder) encodeSample(sample int16) byte {
-	// find difference of actual sample from encoder's prediction
+	// Find difference of actual sample from encoder's prediction.
 	delta := sample - e.pred
 
-	// create and set sign bit for nibble and find absolute value of difference
+	// Create and set sign bit for nibble and find absolute value of difference.
 	var nib byte
 	if delta < 0 {
 		nib = 8
@@ -123,7 +123,7 @@ func (e *Encoder) encodeSample(sample int16) byte {
 		step >>= 1
 	}
 
-	// adjust predicted sample based on calculated difference
+	// Adjust predicted sample based on calculated difference.
 	if nib&8 != 0 {
 		e.pred -= diff
 	} else {
@@ -131,7 +131,7 @@ func (e *Encoder) encodeSample(sample int16) byte {
 	}
 
 	e.index += indexTable[nib&7]
-	// check for underflow and overflow
+	// Check for underflow and overflow.
 	if e.index < 0 {
 		e.index = 0
 	} else if e.index > int16(len(stepTable)-1) {
@@ -142,9 +142,9 @@ func (e *Encoder) encodeSample(sample int16) byte {
 }
 
 // decodeSample takes a byte, the last 4 bits of which contain a single
-// 4 bit ADPCM nibble, and returns a 16 bit decoded PCM sample
+// 4 bit ADPCM nibble, and returns a 16 bit decoded PCM sample.
 func (d *Decoder) decodeSample(nibble byte) int16 {
-	// calculate difference
+	// Calculate difference.
 	var diff int16
 	if nibble&4 != 0 {
 		diff += d.step
@@ -157,34 +157,34 @@ func (d *Decoder) decodeSample(nibble byte) int16 {
 	}
 	diff += d.step >> 3
 
-	// account for sign bit
+	// Account for sign bit.
 	if nibble&8 != 0 {
 		diff = -diff
 	}
 
-	// adjust predicted sample based on calculated difference
+	// Adjust predicted sample based on calculated difference.
 	d.pred += diff
 
-	// adjust index into step size lookup table using nibble
+	// Adjust index into step size lookup table using nibble.
 	d.index += indexTable[nibble]
 
-	// check for overflow and underflow
+	// Check for overflow and underflow.
 	if d.index < 0 {
 		d.index = 0
 	} else if d.index > int16(len(stepTable)-1) {
 		d.index = int16(len(stepTable) - 1)
 	}
 
-	// find new quantizer step size
+	// Find new quantizer step size.
 	d.step = stepTable[d.index]
 
 	return d.pred
 }
 
 // calcHead sets the state for the encoder by running the first sample through
-// the encoder, and writing the first sample
+// the encoder, and writing the first sample.
 func (e *Encoder) calcHead(sample []byte) error {
-	// check that we are given 1 16-bit sample (2 bytes)
+	// Check that we are given 1 16-bit sample (2 bytes).
 	sampSize := 2
 	if len(sample) != sampSize {
 		return fmt.Errorf("length of given byte array is: %v, expected: %v", len(sample), sampSize)
@@ -202,10 +202,10 @@ func (e *Encoder) calcHead(sample []byte) error {
 
 // EncodeBlock takes a slice of 1010 bytes (505 16-bit PCM samples).
 // It outputs encoded (compressed) bytes (each byte containing two ADPCM nibbles) to the encoder's dest writer.
-// note: nibbles are output in little endian order, eg. n1n0 n3n2 n5n4...
-// note: first 4 bytes are for initializing the decoder before decoding a block.
-// 		- first two bytes contain the first 16-bit sample uncompressed,
-// 		- third byte is the decoder's starting index for the block, the fourth is padding and ignored
+// Note: nibbles are output in little endian order, eg. n1n0 n3n2 n5n4...
+// Note: first 4 bytes are for initializing the decoder before decoding a block.
+// 		- First two bytes contain the first 16-bit sample uncompressed.
+// 		- Third byte is the decoder's starting index for the block, the fourth is padding and ignored.
 func (e *Encoder) EncodeBlock(block []byte) error {
 	bSize := 1010
 	if len(block) != bSize {
@@ -234,14 +234,14 @@ func (d *Decoder) DecodeBlock(block []byte) error {
 		return fmt.Errorf("unsupported block size. Given: %v, expected: %v", len(block), bSize)
 	}
 
-	// initialize decoder with first 4 bytes of the block
+	// Initialize decoder with first 4 bytes of the block.
 	d.pred = int16(binary.LittleEndian.Uint16(block[0:2]))
 	d.index = int16(block[2])
 	d.step = stepTable[d.index]
 	d.dest.Write(block[0:2])
 
-	// for each byte, seperate it into two nibbles (each nibble is a compressed sample),
-	// then decode each nibble and output the resulting 16-bit samples
+	// For each byte, seperate it into two nibbles (each nibble is a compressed sample),
+	// then decode each nibble and output the resulting 16-bit samples.
 	for i := 4; i < bSize; i++ {
 		twoNibs := block[i]
 		nib2 := byte(twoNibs >> 4)

stream/adpcm/adpcm_test.go

@@ -37,13 +37,13 @@ import (
 // TestEncodeBlock will read PCM data, encode it in blocks and generate ADPCM
 // then compare the result with expected ADPCM.
 func TestEncodeBlock(t *testing.T) {
-	//read input pcm
+	// Read input pcm.
 	pcm, err := ioutil.ReadFile("../../../test/test-data/av/input/raw-voice.pcm")
 	if err != nil {
 		t.Errorf("Unable to read input PCM file: %v", err)
 	}
 
-	//encode adpcm
+	// Encode adpcm.
 	inBSize := 1010
 	numBlocks := len(pcm) / inBSize
 	outBSize := int(float64(inBSize)/4 + 3.5) // compression is 4:1 and 3.5 bytes of info are added to each block
@@ -57,7 +57,7 @@ func TestEncodeBlock(t *testing.T) {
 		}
 	}
 
-	//read expected adpcm file
+	// Read expected adpcm file.
 	exp, err := ioutil.ReadFile("../../../test/test-data/av/output/encoded-voice.adpcm")
 	if err != nil {
 		t.Errorf("Unable to read expected ADPCM file: %v", err)
@@ -71,13 +71,13 @@ func TestEncodeBlock(t *testing.T) {
 // TestDecodeBlock will read encoded ADPCM, decode it in blocks and then compare the
 // resulting PCM with the expected decoded PCM.
 func TestDecodeBlock(t *testing.T) {
-	//read adpcm
+	// Read adpcm.
 	comp, err := ioutil.ReadFile("../../../test/test-data/av/input/encoded-voice.adpcm")
 	if err != nil {
 		t.Errorf("Unable to read input ADPCM file: %v", err)
 	}
 
-	//decode adpcm
+	// Decode adpcm.
 	inBSize := 256
 	numBlocks := 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
@@ -91,7 +91,7 @@ func TestDecodeBlock(t *testing.T) {
 		}
 	}
 
-	//read expected pcm file
+	// Read expected pcm file.
 	exp, err := ioutil.ReadFile("../../../test/test-data/av/output/decoded-voice.pcm")
 	if err != nil {
 		t.Errorf("Unable to read expected PCM file: %v", err)