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Merge branch 'master' into comment-config

This commit is contained in:
Saxon 2019-06-06 12:49:52 +09:30
parent 061b015297 0da410166f
commit 947147b9fd
7 changed files with 220 additions and 206 deletions
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386
codec/adpcm/adpcm.go
View File

@ -2,9 +2,6 @@
NAME
adpcm.go
DESCRIPTION
adpcm.go contains functions for encoding/compressing pcm into adpcm and decoding/decompressing back to pcm.
AUTHOR
Trek Hopton <trek@ausocean.org>
@ -30,40 +27,25 @@ LICENSE
Reference algorithms for ADPCM compression and decompression are in part 6.
*/
// Package adpcm provides functions to transcode between PCM and ADPCM.
package adpcm
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"math"
)
// encoder is used to encode to ADPCM from PCM data.
// pred and index hold state that persists between calls to encodeSample and calcHead.
// dest is the output buffer that implements io.writer and io.bytewriter, ie. where the encoded ADPCM data is written to.
type encoder struct {
dest *bytes.Buffer
pred int16
index int16
}
// decoder is used to decode from ADPCM to PCM data.
// pred, index, and step hold state that persists between calls to decodeSample.
// dest is the output buffer that implements io.writer and io.bytewriter, ie. where the decoded PCM data is written to.
type decoder struct {
dest *bytes.Buffer
pred int16
index int16
step int16
}
// PcmBS is the size of the blocks that an encoder uses.
// 'encodeBlock' will encode PcmBS bytes at a time and the output will be AdpcmBS bytes long.
const PcmBS = 1010
// AdpcmBS is the size of the blocks that a decoder uses.
// 'decodeBlock' will decode AdpcmBS bytes at a time and the output will be PcmBS bytes long.
const AdpcmBS = 256
const (
byteDepth = 2 // We are working with 16-bit samples. TODO(Trek): make configurable.
initSamps = 2 // Number of samples used to initialise the encoder.
initBytes = initSamps * byteDepth
headBytes = 4 // Number of bytes in the header of ADPCM.
samplesPerEnc = 2 // Number of sample encoded at a time eg. 2 16-bit samples get encoded into 1 byte.
bytesPerEnc = samplesPerEnc * byteDepth
compFact = 4 // In general ADPCM compresses by a factor of 4.
)
// Table of index changes (see spec).
var indexTable = []int16{
@ -87,28 +69,35 @@ var stepTable = []int16{
32767,
}
// NewEncoder retuns a new ADPCM encoder.
func NewEncoder(dst *bytes.Buffer) *encoder {
e := encoder{
dest: dst,
}
return &e
// Encoder is used to encode to ADPCM from PCM data.
type Encoder struct {
// dst is the destination for ADPCM-encoded data.
dst io.Writer
est int16 // Estimation of sample based on quantised ADPCM nibble.
idx int16 // Index to step used for estimation.
}
// NewDecoder retuns a new ADPCM decoder.
func NewDecoder(dst *bytes.Buffer) *decoder {
d := decoder{
step: stepTable[0],
dest: dst,
}
return &d
// Decoder is used to decode from ADPCM to PCM data.
type Decoder struct {
// dst is the destination for PCM-encoded data.
dst io.Writer
est int16 // Estimation of sample based on quantised ADPCM nibble.
idx int16 // Index to step used for estimation.
step int16
}
// NewEncoder retuns a new ADPCM Encoder.
func NewEncoder(dst io.Writer) *Encoder {
return &Encoder{dst: dst}
}
// encodeSample takes a single 16 bit PCM sample and
// 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.
delta := sample - e.pred
func (e *Encoder) encodeSample(sample int16) byte {
// Find difference between the sample and the previous estimation.
delta := capAdd16(sample, -e.est)
// Create and set sign bit for nibble and find absolute value of difference.
var nib byte
@ -117,217 +106,250 @@ func (e *encoder) encodeSample(sample int16) byte {
delta = -delta
}
step := stepTable[e.index]
step := stepTable[e.idx]
diff := step >> 3
var mask byte = 4
for i := 0; i < 3; i++ {
if delta > step {
nib |= mask
delta -= step
diff += step
delta = capAdd16(delta, -step)
diff = capAdd16(diff, step)
}
mask >>= 1
step >>= 1
}
// Adjust predicted sample based on calculated difference.
if nib&8 != 0 {
e.pred -= diff
} else {
e.pred += diff
diff = -diff
}
e.index += indexTable[nib&7]
// Adjust estimated sample based on calculated difference.
e.est = capAdd16(e.est, diff)
e.idx += indexTable[nib&7]
// Check for underflow and overflow.
if e.index < 0 {
e.index = 0
} else if e.index > int16(len(stepTable)-1) {
e.index = int16(len(stepTable) - 1)
if e.idx < 0 {
e.idx = 0
} else if e.idx > int16(len(stepTable)-1) {
e.idx = int16(len(stepTable) - 1)
}
return nib
}
// calcHead sets the state for the Encoder by running the first sample through
// the Encoder, and writing the first sample to the Encoder's io.Writer (dst).
// It returns the number of bytes written to the Encoder's destination and the first error encountered.
func (e *Encoder) calcHead(sample []byte, pad bool) (int, error) {
// Check that we are given 1 sample.
if len(sample) != byteDepth {
return 0, fmt.Errorf("length of given byte array is: %v, expected: %v", len(sample), byteDepth)
}
n, err := e.dst.Write(sample)
if err != nil {
return n, err
}
_n, err := e.dst.Write([]byte{byte(int16(e.idx))})
if err != nil {
return n, err
}
n += _n
if pad {
_n, err = e.dst.Write([]byte{0x01})
} else {
_n, err = e.dst.Write([]byte{0x00})
}
n += _n
if err != nil {
return n, err
}
return n, nil
}
// init initializes the Encoder's estimation to the first uncompressed sample and the index to
// point to a suitable quantizer step size.
// The suitable step size is the closest step size in the stepTable to half the absolute difference of the first two samples.
func (e *Encoder) init(samples []byte) {
int1 := int16(binary.LittleEndian.Uint16(samples[:byteDepth]))
int2 := int16(binary.LittleEndian.Uint16(samples[byteDepth:initBytes]))
e.est = int1
halfDiff := math.Abs(math.Abs(float64(int1)) - math.Abs(float64(int2))/2)
closest := math.Abs(float64(stepTable[0]) - halfDiff)
var cInd int16
for i, step := range stepTable {
if math.Abs(float64(step)-halfDiff) < closest {
closest = math.Abs(float64(step) - halfDiff)
cInd = int16(i)
}
}
e.idx = cInd
}
// Write takes a slice of bytes of arbitrary length representing pcm and encodes it into adpcm.
// It writes its output to the Encoder's dst.
// The number of bytes written out is returned along with any error that occured.
func (e *Encoder) Write(b []byte) (int, error) {
// Check that pcm has enough data to initialize Decoder.
pcmLen := len(b)
if pcmLen < initBytes {
return 0, fmt.Errorf("length of given byte array must be >= %v", initBytes)
}
// Determine if there will be a byte that won't contain two full nibbles and will need padding.
pad := false
if (pcmLen-byteDepth)%bytesPerEnc != 0 {
pad = true
}
e.init(b[:initBytes])
n, err := e.calcHead(b[:byteDepth], pad)
if err != nil {
return n, err
}
// Skip the first sample and start at the end of the first two samples, then every two samples encode them into a byte of adpcm.
for i := byteDepth; i+bytesPerEnc-1 < pcmLen; i += bytesPerEnc {
nib1 := e.encodeSample(int16(binary.LittleEndian.Uint16(b[i : i+byteDepth])))
nib2 := e.encodeSample(int16(binary.LittleEndian.Uint16(b[i+byteDepth : i+bytesPerEnc])))
_n, err := e.dst.Write([]byte{byte((nib2 << 4) | nib1)})
n += _n
if err != nil {
return n, err
}
}
// If we've reached the end of the pcm data and there's a sample left over,
// compress it to a nibble and leave the first half of the byte padded with 0s.
if pad {
nib := e.encodeSample(int16(binary.LittleEndian.Uint16(b[pcmLen-byteDepth : pcmLen])))
_n, err := e.dst.Write([]byte{nib})
n += _n
if err != nil {
return n, err
}
}
return n, nil
}
// NewDecoder retuns a new ADPCM Decoder.
func NewDecoder(dst io.Writer) *Decoder {
return &Decoder{dst: dst}
}
// 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.
func (d *decoder) decodeSample(nibble byte) int16 {
func (d *Decoder) decodeSample(nibble byte) int16 {
// Calculate difference.
var diff int16
if nibble&4 != 0 {
diff += d.step
diff = capAdd16(diff, d.step)
}
if nibble&2 != 0 {
diff += d.step >> 1
diff = capAdd16(diff, d.step>>1)
}
if nibble&1 != 0 {
diff += d.step >> 2
diff = capAdd16(diff, d.step>>2)
}
diff += d.step >> 3
diff = capAdd16(diff, d.step>>3)
// Account for sign bit.
if nibble&8 != 0 {
diff = -diff
}
// Adjust predicted sample based on calculated difference.
d.pred += diff
// Adjust estimated sample based on calculated difference.
d.est = capAdd16(d.est, diff)
// Adjust index into step size lookup table using nibble.
d.index += indexTable[nibble]
d.idx += indexTable[nibble]
// 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)
if d.idx < 0 {
d.idx = 0
} else if d.idx > int16(len(stepTable)-1) {
d.idx = int16(len(stepTable) - 1)
}
// Find new quantizer step size.
d.step = stepTable[d.index]
d.step = stepTable[d.idx]
return d.pred
return d.est
}
// calcHead sets the state for the encoder by running the first sample through
// the encoder, and writing the first sample to the encoder's io.Writer (dest).
// It returns the number of bytes written to the encoder's io.Writer (dest) along with any errors.
func (e *encoder) calcHead(sample []byte) (int, error) {
// Check that we are given 1 16-bit sample (2 bytes).
const sampSize = 2
if len(sample) != sampSize {
return 0, fmt.Errorf("length of given byte array is: %v, expected: %v", len(sample), sampSize)
}
intSample := int16(binary.LittleEndian.Uint16(sample))
e.encodeSample(intSample)
n, err := e.dest.Write(sample)
if err != nil {
return n, err
}
err = e.dest.WriteByte(byte(uint16(e.index)))
if err != nil {
return n, err
}
n++
err = e.dest.WriteByte(byte(0x00))
if err != nil {
return n, err
}
n++
return n, nil
}
// encodeBlock takes a slice of 1010 bytes (505 16-bit PCM samples).
// It writes encoded (compressed) bytes (each byte containing two ADPCM nibbles) to the encoder's io.Writer (dest).
// The number of bytes written is returned along with any errors.
// 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) (int, error) {
if len(block) != PcmBS {
return 0, fmt.Errorf("unsupported block size. Given: %v, expected: %v, ie. 505 16-bit PCM samples", len(block), PcmBS)
}
n, err := e.calcHead(block[0:2])
if err != nil {
return n, err
}
for i := 3; i < PcmBS; i += 4 {
nib1 := e.encodeSample(int16(binary.LittleEndian.Uint16(block[i-1 : i+1])))
nib2 := e.encodeSample(int16(binary.LittleEndian.Uint16(block[i+1 : i+3])))
err = e.dest.WriteByte(byte((nib2 << 4) | nib1))
if err != nil {
return n, err
}
n++
}
return n, nil
}
// decodeBlock takes a slice of 256 bytes, each byte after the first 4 should contain two ADPCM encoded nibbles.
// It writes the resulting decoded (decompressed) 16-bit PCM samples to the decoder's io.Writer (dest).
// The number of bytes written is returned along with any errors.
func (d *decoder) decodeBlock(block []byte) (int, error) {
if len(block) != AdpcmBS {
return 0, fmt.Errorf("unsupported block size. Given: %v, expected: %v", len(block), AdpcmBS)
}
// 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]
n, err := d.dest.Write(block[0:2])
// Write takes a slice of bytes of arbitrary length representing adpcm and decodes it into pcm.
// It writes its output to the Decoder's dst.
// The number of bytes written out is returned along with any error that occured.
func (d *Decoder) Write(b []byte) (int, error) {
// Initialize Decoder with first 4 bytes of b.
d.est = int16(binary.LittleEndian.Uint16(b[:byteDepth]))
d.idx = int16(b[byteDepth])
d.step = stepTable[d.idx]
n, err := d.dst.Write(b[:byteDepth])
if err != nil {
return n, err
}
// 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 < AdpcmBS; i++ {
twoNibs := block[i]
// If padding flag is true (Adpcm[3]), only decode up until the last byte, then decode that separately.
for i := headBytes; i < len(b)-int(b[3]); i++ {
twoNibs := b[i]
nib2 := byte(twoNibs >> 4)
nib1 := byte((nib2 << 4) ^ twoNibs)
firstBytes := make([]byte, 2)
firstBytes := make([]byte, byteDepth)
binary.LittleEndian.PutUint16(firstBytes, uint16(d.decodeSample(nib1)))
_n, err := d.dest.Write(firstBytes)
_n, err := d.dst.Write(firstBytes)
n += _n
if err != nil {
return n, err
}
secondBytes := make([]byte, 2)
secondBytes := make([]byte, byteDepth)
binary.LittleEndian.PutUint16(secondBytes, uint16(d.decodeSample(nib2)))
_n, err = d.dest.Write(secondBytes)
_n, err = d.dst.Write(secondBytes)
n += _n
if err != nil {
return n, err
}
}
return n, nil
}
// Write takes a slice of bytes of arbitrary length representing pcm and encodes in into adpcm.
// It writes its output to the encoder's dest.
// The number of bytes written out is returned along with any error that occured.
func (e *encoder) Write(inPcm []byte) (int, error) {
numBlocks := len(inPcm) / PcmBS
n := 0
for i := 0; i < numBlocks; i++ {
block := inPcm[PcmBS*i : PcmBS*(i+1)]
_n, err := e.encodeBlock(block)
if b[3] == 0x01 {
padNib := b[len(b)-1]
samp := make([]byte, byteDepth)
binary.LittleEndian.PutUint16(samp, uint16(d.decodeSample(padNib)))
_n, err := d.dst.Write(samp)
n += _n
if err != nil {
return n, err
}
}
return n, nil
}
// Write takes a slice of bytes of arbitrary length representing adpcm and decodes in into pcm.
// It writes its output to the decoder's dest.
// The number of bytes written out is returned along with any error that occured.
func (d *decoder) Write(inAdpcm []byte) (int, error) {
numBlocks := len(inAdpcm) / AdpcmBS
n := 0
for i := 0; i < numBlocks; i++ {
block := inAdpcm[AdpcmBS*i : AdpcmBS*(i+1)]
_n, err := d.decodeBlock(block)
n += _n
if err != nil {
return n, err
}
// capAdd16 adds two int16s together and caps at max/min int16 instead of overflowing
func capAdd16(a, b int16) int16 {
c := int32(a) + int32(b)
switch {
case c < math.MinInt16:
return math.MinInt16
case c > math.MaxInt16:
return math.MaxInt16
default:
return int16(c)
}
return n, nil
}
// EncBytes will return the number of adpcm bytes that will be generated when encoding the given amount of pcm bytes (n).
func EncBytes(n int) int {
// For 'n' pcm bytes, 1 sample is left uncompressed, the rest is compressed by a factor of 4
// and a start index and padding-flag byte are added.
// Also if there are an even number of samples, there will be half a byte of padding added to the last byte.
if n%bytesPerEnc == 0 {
return (n-byteDepth)/compFact + headBytes + 1
}
return (n-byteDepth)/compFact + headBytes
}

14
codec/adpcm/adpcm_test.go
View File

@ -37,14 +37,13 @@ import (
// then compare the result with expected ADPCM.
func TestEncodeBlock(t *testing.T) {
// Read input pcm.
pcm, err := ioutil.ReadFile("../../../test/test-data/av/input/raw-voice.pcm")
pcm, err := ioutil.ReadFile("../../../test/test-data/av/input/original_8kHz_adpcm_test.pcm")
if err != nil {
t.Errorf("Unable to read input PCM file: %v", err)
}
// Encode adpcm.
numBlocks := len(pcm) / PcmBS
comp := bytes.NewBuffer(make([]byte, 0, AdpcmBS*numBlocks))
comp := bytes.NewBuffer(make([]byte, 0, EncBytes(len(pcm))))
enc := NewEncoder(comp)
_, err = enc.Write(pcm)
if err != nil {
@ -52,7 +51,7 @@ func TestEncodeBlock(t *testing.T) {
}
// Read expected adpcm file.
exp, err := ioutil.ReadFile("../../../test/test-data/av/output/encoded-voice.adpcm")
exp, err := ioutil.ReadFile("../../../test/test-data/av/output/encoded_8kHz_adpcm_test.adpcm")
if err != nil {
t.Errorf("Unable to read expected ADPCM file: %v", err)
}
@ -66,14 +65,13 @@ func TestEncodeBlock(t *testing.T) {
// resulting PCM with the expected decoded PCM.
func TestDecodeBlock(t *testing.T) {
// Read adpcm.
comp, err := ioutil.ReadFile("../../../test/test-data/av/input/encoded-voice.adpcm")
comp, err := ioutil.ReadFile("../../../test/test-data/av/input/encoded_8kHz_adpcm_test.adpcm")
if err != nil {
t.Errorf("Unable to read input ADPCM file: %v", err)
}
// Decode adpcm.
numBlocks := len(comp) / AdpcmBS
decoded := bytes.NewBuffer(make([]byte, 0, PcmBS*numBlocks))
decoded := bytes.NewBuffer(make([]byte, 0, len(comp)*4))
dec := NewDecoder(decoded)
_, err = dec.Write(comp)
if err != nil {
@ -81,7 +79,7 @@ func TestDecodeBlock(t *testing.T) {
}
// Read expected pcm file.
exp, err := ioutil.ReadFile("../../../test/test-data/av/output/decoded-voice.pcm")
exp, err := ioutil.ReadFile("../../../test/test-data/av/output/decoded_8kHz_adpcm_test.pcm")
if err != nil {
t.Errorf("Unable to read expected PCM file: %v", err)
}

2
codec/pcm/pcm.go
View File

@ -24,6 +24,8 @@ LICENSE
You should have received a copy of the GNU General Public License in gpl.txt.
If not, see [GNU licenses](http://www.gnu.org/licenses).
*/
// Package pcm provides functions for processing and converting pcm audio.
package pcm
import (

7
exp/adpcm/decode-pcm/decode-pcm.go
View File

@ -2,9 +2,6 @@
NAME
decode-pcm.go
DESCRIPTION
decode-pcm.go is a program for decoding/decompressing an adpcm file to a pcm file.
AUTHOR
Trek Hopton <trek@ausocean.org>
@ -25,6 +22,7 @@ LICENSE
If not, see [GNU licenses](http://www.gnu.org/licenses).
*/
// decode-pcm is a command-line program for decoding/decompressing an adpcm file to a pcm file.
package main
import (
@ -54,8 +52,7 @@ func main() {
fmt.Println("Read", len(comp), "bytes from file", inPath)
// Decode adpcm.
numBlocks := len(comp) / adpcm.AdpcmBS
decoded := bytes.NewBuffer(make([]byte, 0, adpcm.PcmBS*numBlocks))
decoded := bytes.NewBuffer(make([]byte, 0, len(comp)*4))
dec := adpcm.NewDecoder(decoded)
_, err = dec.Write(comp)
if err != nil {

7
exp/adpcm/encode-pcm/encode-pcm.go
View File

@ -2,9 +2,6 @@
NAME
encode-pcm.go
DESCRIPTION
encode-pcm.go is a program for encoding/compressing a pcm file to an adpcm file.
AUTHOR
Trek Hopton <trek@ausocean.org>
@ -25,6 +22,7 @@ LICENSE
If not, see [GNU licenses](http://www.gnu.org/licenses).
*/
// encode-pcm is a command-line program for encoding/compressing a pcm file to an adpcm file.
package main
import (
@ -54,8 +52,7 @@ func main() {
fmt.Println("Read", len(pcm), "bytes from file", inPath)
// Encode adpcm.
numBlocks := len(pcm) / adpcm.PcmBS
comp := bytes.NewBuffer(make([]byte, 0, adpcm.AdpcmBS*numBlocks))
comp := bytes.NewBuffer(make([]byte, 0, adpcm.EncBytes(len(pcm))))
enc := adpcm.NewEncoder(comp)
_, err = enc.Write(pcm)
if err != nil {

5
exp/pcm/resample/resample.go
View File

@ -2,9 +2,6 @@
NAME
resample.go
DESCRIPTION
resample.go is a program for resampling a pcm file.
AUTHOR
Trek Hopton <trek@ausocean.org>
@ -24,6 +21,8 @@ LICENSE
You should have received a copy of the GNU General Public License in gpl.txt.
If not, see [GNU licenses](http://www.gnu.org/licenses).
*/
// resample is a command-line program for resampling a pcm file.
package main
import (

5
exp/pcm/stereo-to-mono/stereo-to-mono.go
View File

@ -2,9 +2,6 @@
NAME
stereo-to-mono.go
DESCRIPTION
stereo-to-mono.go is a program for converting a mono pcm file to a stereo pcm file.
AUTHOR
Trek Hopton <trek@ausocean.org>
@ -24,6 +21,8 @@ LICENSE
You should have received a copy of the GNU General Public License in gpl.txt.
If not, see [GNU licenses](http://www.gnu.org/licenses).
*/
// stereo-to-mono is a command-line program for converting a mono pcm file to a stereo pcm file.
package main
import (