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audio/internal/convert: Reuse a buffer cache

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This commit is contained in:
Hajime Hoshi 2021-10-31 19:40:58 +09:00
parent 611cbad5d7
commit 630df60894
1 changed files with 14 additions and 9 deletions
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23
audio/internal/convert/stereo16.go
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@ -22,6 +22,7 @@ type Stereo16 struct {
source io.ReadSeeker
mono bool
eight bool
buf []byte
}
func NewStereo16(source io.ReadSeeker, mono, eight bool) *Stereo16 {
@ -40,15 +41,19 @@ func (s *Stereo16) Read(b []byte) (int, error) {
if s.eight {
l /= 2
}
buf := make([]byte, l)
n, err := s.source.Read(buf)
if cap(s.buf) < l {
s.buf = make([]byte, l)
}
n, err := s.source.Read(s.buf[:l])
if err != nil && err != io.EOF {
return 0, err
}
switch {
case s.mono && s.eight:
for i := 0; i < n; i++ {
v := int16(int(buf[i])*0x101 - (1 << 15))
v := int16(int(s.buf[i])*0x101 - (1 << 15))
b[4*i] = byte(v)
b[4*i+1] = byte(v >> 8)
b[4*i+2] = byte(v)
@ -56,15 +61,15 @@ func (s *Stereo16) Read(b []byte) (int, error) {
}
case s.mono && !s.eight:
for i := 0; i < n/2; i++ {
b[4*i] = buf[2*i]
b[4*i+1] = buf[2*i+1]
b[4*i+2] = buf[2*i]
b[4*i+3] = buf[2*i+1]
b[4*i] = s.buf[2*i]
b[4*i+1] = s.buf[2*i+1]
b[4*i+2] = s.buf[2*i]
b[4*i+3] = s.buf[2*i+1]
}
case !s.mono && s.eight:
for i := 0; i < n/2; i++ {
v0 := int16(int(buf[2*i])*0x101 - (1 << 15))
v1 := int16(int(buf[2*i+1])*0x101 - (1 << 15))
v0 := int16(int(s.buf[2*i])*0x101 - (1 << 15))
v1 := int16(int(s.buf[2*i+1])*0x101 - (1 << 15))
b[4*i] = byte(v0)
b[4*i+1] = byte(v0 >> 8)
b[4*i+2] = byte(v1)