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adpcm: fixing offset error

This commit is contained in:
Trek H 2019-04-26 23:54:05 +09:30
parent c089980175
commit b412b75fc6
1 changed files with 6 additions and 8 deletions
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14
codec/adpcm/adpcm.go
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@ -315,10 +315,11 @@ func (e *encoder) Write(inPcm []byte) (int, error) {
if err != nil {
return n, err
}
for i := 3; i < pcmLen; i += 4 {
nib1 := e.encodeSample(int16(binary.LittleEndian.Uint16(inPcm[i-1 : i+1])))
nib2 := e.encodeSample(int16(binary.LittleEndian.Uint16(inPcm[i+1 : i+3])))
// 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.
// TODO: make all hard coded numbers variables so that other bitrates and compression ratios can be used.
for i := 5; i < pcmLen; i += 4 {
nib1 := e.encodeSample(int16(binary.LittleEndian.Uint16(inPcm[i-3 : i-1])))
nib2 := e.encodeSample(int16(binary.LittleEndian.Uint16(inPcm[i-1 : i+1])))
err = e.dest.WriteByte(byte((nib2 << 4) | nib1))
if err != nil {
return n, err
@ -335,7 +336,6 @@ func (e *encoder) Write(inPcm []byte) (int, error) {
}
n++
}
return n, nil
}
@ -343,7 +343,6 @@ func (e *encoder) Write(inPcm []byte) (int, error) {
// 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) {
// Initialize decoder with first 4 bytes of the inAdpcm.
d.pred = int16(binary.LittleEndian.Uint16(inAdpcm[0:2]))
d.index = int16(inAdpcm[2])
@ -387,11 +386,10 @@ func (d *decoder) Write(inAdpcm []byte) (int, error) {
return n, err
}
}
return n, nil
}
// BytesOutput will return the number of adpcm bytes that will be generated for the given pcm data
// BytesOutput will return the number of adpcm bytes that will be generated for the given pcm data byte size.
func BytesOutput(pcm int) int {
// for X pcm bytes, 2 bytes are left uncompressed, the rest is compressed by a factor of 4
// and a start index and padding byte are added.