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adpcm: naming and documentation

This commit is contained in:
Trek H 2019-05-06 18:02:17 +09:30
parent 0570d7823d
commit 9fadb47902
1 changed files with 10 additions and 10 deletions
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20
codec/adpcm/adpcm.go
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@ -315,12 +315,12 @@ func (e *encoder) Write(inPcm []byte) (int, error) {
// Write takes a slice of bytes of arbitrary length representing adpcm and decodes it into pcm. // 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. // It writes its output to the decoder's dst.
// The number of bytes written out is returned along with any error that occured. // The number of bytes written out is returned along with any error that occured.
func (d *decoder) Write(inAdpcm []byte) (int, error) { func (d *decoder) Write(chunk []byte) (int, error) {
// Initialize decoder with first 4 bytes of the inAdpcm. // Initialize decoder with first 4 bytes of the chunk.
d.est = int16(binary.LittleEndian.Uint16(inAdpcm[:byteDepth])) d.est = int16(binary.LittleEndian.Uint16(chunk[:byteDepth]))
d.index = int16(inAdpcm[byteDepth]) d.index = int16(chunk[byteDepth])
d.step = stepTable[d.index] d.step = stepTable[d.index]
n, err := d.dst.Write(inAdpcm[:byteDepth]) n, err := d.dst.Write(chunk[:byteDepth])
if err != nil { if err != nil {
return n, err return n, err
} }
@ -328,8 +328,8 @@ func (d *decoder) Write(inAdpcm []byte) (int, error) {
// For each byte, seperate it into two nibbles (each nibble is a compressed sample), // 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. // then decode each nibble and output the resulting 16-bit samples.
// If padding flag is true (Adpcm[3]), only decode up until the last byte, then decode that separately. // If padding flag is true (Adpcm[3]), only decode up until the last byte, then decode that separately.
for i := headBytes; i < len(inAdpcm)-int(inAdpcm[3]); i++ { for i := headBytes; i < len(chunk)-int(chunk[3]); i++ {
twoNibs := inAdpcm[i] twoNibs := chunk[i]
nib2 := byte(twoNibs >> 4) nib2 := byte(twoNibs >> 4)
nib1 := byte((nib2 << 4) ^ twoNibs) nib1 := byte((nib2 << 4) ^ twoNibs)
@ -349,8 +349,8 @@ func (d *decoder) Write(inAdpcm []byte) (int, error) {
return n, err return n, err
} }
} }
if inAdpcm[3] == 0x01 { if chunk[3] == 0x01 {
padNib := inAdpcm[len(inAdpcm)-1] padNib := chunk[len(chunk)-1]
samp := make([]byte, byteDepth) samp := make([]byte, byteDepth)
binary.LittleEndian.PutUint16(samp, uint16(d.decodeSample(padNib))) binary.LittleEndian.PutUint16(samp, uint16(d.decodeSample(padNib)))
_n, err := d.dst.Write(samp) _n, err := d.dst.Write(samp)
@ -364,7 +364,7 @@ func (d *decoder) Write(inAdpcm []byte) (int, error) {
// BytesOutput will return the number of adpcm bytes that will be generated for the given pcm data byte size. // BytesOutput will return the number of adpcm bytes that will be generated for the given pcm data byte size.
func BytesOutput(pcm int) int { func BytesOutput(pcm int) int {
// for X pcm bytes, byteDepth (eg. 2 bytes) are left uncompressed, the rest is compressed by a factor of 4 // For X 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. // 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. // Also if there are an even number of samples, there will be half a byte of padding added to the last byte.
if pcm%bytesPerEnc == 0 { if pcm%bytesPerEnc == 0 {