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audio/internal/convert: Optimization for seeking

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This commit is contained in:
Hajime Hoshi 2017-06-26 02:18:11 +09:00
parent 3be2b2516f
commit e3176f6693
1 changed files with 69 additions and 29 deletions
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98
audio/internal/convert/resampling.go
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@ -29,25 +29,29 @@ func sinc(x float64) float64 {
} }
type Resampling struct { type Resampling struct {
source audio.ReadSeekCloser source audio.ReadSeekCloser
size int64 size int64
from int from int
to int to int
pos int64 pos int64
srcPos int64 srcBlock int64
srcCacheL []float64 srcBufL map[int64][]float64
srcCacheR []float64 srcBufR map[int64][]float64
lruBlock []int64
} }
const resamplingBufferSize = 4096
func NewResampling(source audio.ReadSeekCloser, size int64, from, to int) *Resampling { func NewResampling(source audio.ReadSeekCloser, size int64, from, to int) *Resampling {
r := &Resampling{ r := &Resampling{
source: source, source: source,
size: size, size: size,
from: from, from: from,
to: to, to: to,
srcBlock: -1,
srcBufL: map[int64][]float64{},
srcBufR: map[int64][]float64{},
} }
r.srcCacheL = make([]float64, r.size/4)
r.srcCacheR = make([]float64, r.size/4)
return r return r
} }
@ -61,27 +65,63 @@ func (r *Resampling) src(i int) (float64, float64, error) {
if i < 0 { if i < 0 {
return 0, 0, nil return 0, 0, nil
} }
if len(r.srcCacheL) <= i { if r.Size()/4 <= int64(i) {
return 0, 0, nil return 0, 0, nil
} }
pos := int(r.srcPos) / 4 nextPos := int64(i) / resamplingBufferSize
if pos <= i { if _, ok := r.srcBufL[nextPos]; !ok {
buf := make([]uint8, 4096) if r.srcBlock+1 != nextPos {
n, err := r.source.Read(buf) if _, err := r.source.Seek(nextPos*resamplingBufferSize*4, io.SeekStart); err != nil {
if err != nil && err != io.EOF { return 0, 0, err
return 0, 0, err }
} }
n = n / 4 * 4 buf := make([]uint8, resamplingBufferSize*4)
buf = buf[:n] c := 0
for c < len(buf) {
n, err := r.source.Read(buf[c:])
c += n
if err != nil {
if err == io.EOF {
break
}
return 0, 0, err
}
}
buf = buf[:c]
sl := make([]float64, resamplingBufferSize)
sr := make([]float64, resamplingBufferSize)
for i := 0; i < len(buf)/4; i++ { for i := 0; i < len(buf)/4; i++ {
srcL := float64(int16(buf[4*i])|(int16(buf[4*i+1])<<8)) / (1<<15 - 1) sl[i] = float64(int16(buf[4*i])|(int16(buf[4*i+1])<<8)) / (1<<15 - 1)
srcR := float64(int16(buf[4*i+2])|(int16(buf[4*i+3])<<8)) / (1<<15 - 1) sr[i] = float64(int16(buf[4*i+2])|(int16(buf[4*i+3])<<8)) / (1<<15 - 1)
r.srcCacheL[pos+i] = srcL
r.srcCacheR[pos+i] = srcR
} }
r.srcPos += int64(n) r.srcBlock = nextPos
r.srcBufL[r.srcBlock] = sl
r.srcBufR[r.srcBlock] = sr
// To keep srcBufL/R not too big, let's remove the least used buffers.
if len(r.lruBlock) >= 4 {
p := r.lruBlock[0]
delete(r.srcBufL, p)
delete(r.srcBufR, p)
r.lruBlock = r.lruBlock[1:]
}
r.lruBlock = append(r.lruBlock, r.srcBlock)
} else {
r.srcBlock = nextPos
idx := -1
for i, p := range r.lruBlock {
if p == r.srcBlock {
idx = i
break
}
}
if idx == -1 {
panic("not reach")
}
r.lruBlock = append(r.lruBlock[:idx], r.lruBlock[idx+1:]...)
r.lruBlock = append(r.lruBlock, r.srcBlock)
} }
return r.srcCacheL[i], r.srcCacheR[i], nil ii := i % resamplingBufferSize
return r.srcBufL[r.srcBlock][ii], r.srcBufR[r.srcBlock][ii], nil
} }
func (r *Resampling) at(t int64) (float64, float64, error) { func (r *Resampling) at(t int64) (float64, float64, error) {