ebiten/audio/loop.go

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// Copyright 2017 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package audio
import (
"fmt"
"io"
"math"
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)
// InfiniteLoop represents a looped stream which never ends.
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type InfiniteLoop struct {
src io.ReadSeeker
lstart int64
llength int64
pos int64
bitDepthInBytes int
bytesPerSample int
// extra is the remainder in the case when the read byte sizes are not multiple of the bit depth.
extra []byte
// afterLoop is data after the loop.
afterLoop []byte
// blending represents whether the loop start and afterLoop are blended or not.
blending bool
noBlendForTesting bool
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}
// NewInfiniteLoop creates a new infinite loop stream with a source stream and length in bytes.
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//
// src is a signed 16bit integer little endian stream, 2 channels (stereo).
//
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// If the loop's total length is exactly the same as src's length, you might hear noises around the loop joint.
// This noise can be heard especially when src is decoded from a lossy compression format like Ogg/Vorbis and MP3.
// In this case, try to add more (about 0.1[s]) data to src after the loop end.
// If src has data after the loop end, an InfiniteLoop uses part of the data to blend with the loop start
// to make the loop joint smooth.
func NewInfiniteLoop(src io.ReadSeeker, length int64) *InfiniteLoop {
return newInfiniteLoopWithIntro(src, 0, length, bitDepthInBytesInt16)
}
// NewInfiniteLoopF32 creates a new infinite loop stream with a source stream and length in bytes.
//
// src is a 32bit float little endian stream, 2 channels (stereo).
//
// If the loop's total length is exactly the same as src's length, you might hear noises around the loop joint.
// This noise can be heard especially when src is decoded from a lossy compression format like Ogg/Vorbis and MP3.
// In this case, try to add more (about 0.1[s]) data to src after the loop end.
// If src has data after the loop end, an InfiniteLoop uses part of the data to blend with the loop start
// to make the loop joint smooth.
func NewInfiniteLoopF32(src io.ReadSeeker, length int64) *InfiniteLoop {
return newInfiniteLoopWithIntro(src, 0, length, bitDepthInBytesFloat32)
}
// NewInfiniteLoopWithIntro creates a new infinite loop stream with an intro part.
// NewInfiniteLoopWithIntro accepts a source stream src, introLength in bytes and loopLength in bytes.
//
// src is a signed 16bit integer little endian stream, 2 channels (stereo).
//
// If the loop's total length is exactly the same as src's length, you might hear noises around the loop joint.
// This noise can be heard especially when src is decoded from a lossy compression format like Ogg/Vorbis and MP3.
// In this case, try to add more (about 0.1[s]) data to src after the loop end.
// If src has data after the loop end, an InfiniteLoop uses part of the data to blend with the loop start
// to make the loop joint smooth.
func NewInfiniteLoopWithIntro(src io.ReadSeeker, introLength int64, loopLength int64) *InfiniteLoop {
return newInfiniteLoopWithIntro(src, introLength, loopLength, bitDepthInBytesInt16)
}
// NewInfiniteLoopWithIntroF32 creates a new infinite loop stream with an intro part.
// NewInfiniteLoopWithIntroF32 accepts a source stream src, introLength in bytes and loopLength in bytes.
//
// src is a 32bit float little endian stream, 2 channels (stereo).
//
// If the loop's total length is exactly the same as src's length, you might hear noises around the loop joint.
// This noise can be heard especially when src is decoded from a lossy compression format like Ogg/Vorbis and MP3.
// In this case, try to add more (about 0.1[s]) data to src after the loop end.
// If src has data after the loop end, an InfiniteLoop uses part of the data to blend with the loop start
// to make the loop joint smooth.
func NewInfiniteLoopWithIntroF32(src io.ReadSeeker, introLength int64, loopLength int64) *InfiniteLoop {
return newInfiniteLoopWithIntro(src, introLength, loopLength, bitDepthInBytesFloat32)
}
func newInfiniteLoopWithIntro(src io.ReadSeeker, introLength int64, loopLength int64, bitDepthInBytes int) *InfiniteLoop {
bytesPerSample := bitDepthInBytes * channelCount
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return &InfiniteLoop{
src: src,
lstart: introLength / int64(bytesPerSample) * int64(bytesPerSample),
llength: loopLength / int64(bytesPerSample) * int64(bytesPerSample),
pos: -1,
bitDepthInBytes: bitDepthInBytes,
bytesPerSample: bytesPerSample,
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}
}
func (i *InfiniteLoop) length() int64 {
return i.lstart + i.llength
}
func (i *InfiniteLoop) ensurePos() error {
if i.pos >= 0 {
return nil
}
pos, err := i.src.Seek(0, io.SeekCurrent)
if err != nil {
return err
}
if pos >= i.length() {
return fmt.Errorf("audio: stream position must be less than the specified length")
}
i.pos = pos
return nil
}
func (i *InfiniteLoop) blendRate(pos int64) float32 {
if pos < i.lstart {
return 0
}
if pos >= i.lstart+int64(len(i.afterLoop)) {
return 0
}
p := (pos - i.lstart) / int64(i.bytesPerSample)
l := len(i.afterLoop) / i.bytesPerSample
return 1 - float32(p)/float32(l)
}
// Read is implementation of ReadSeeker's Read.
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func (i *InfiniteLoop) Read(b []byte) (int, error) {
if err := i.ensurePos(); err != nil {
return 0, err
}
if i.pos+int64(len(b)) > i.length() {
b = b[:i.length()-i.pos]
}
extralen := len(i.extra)
copy(b, i.extra)
i.extra = i.extra[:0]
n, err := i.src.Read(b[extralen:])
n += extralen
i.pos += int64(n)
if i.pos > i.length() {
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panic(fmt.Sprintf("audio: position must be <= length but not at (*InfiniteLoop).Read: pos: %d, length: %d", i.pos, i.length()))
}
// Save the remainder part to extra. This will be used at the next Read.
if rem := n % i.bitDepthInBytes; rem != 0 {
i.extra = append(i.extra, b[n-rem:n]...)
b = b[:n-rem]
n = n - rem
}
// Blend afterLoop and the loop start to reduce noises (#1888).
// Ideally, afterLoop and the loop start should be identical, but they can have very slight differences.
if !i.noBlendForTesting && i.blending && i.pos >= i.lstart && i.pos-int64(n) < i.lstart+int64(len(i.afterLoop)) {
if n%i.bitDepthInBytes != 0 {
panic(fmt.Sprintf("audio: n must be a multiple of bit depth %d [bytes] but not: %d", i.bitDepthInBytes, n))
}
for idx := 0; idx < n/i.bitDepthInBytes; idx++ {
abspos := i.pos - int64(n) + int64(idx)*int64(i.bitDepthInBytes)
rate := i.blendRate(abspos)
if rate == 0 {
continue
}
relpos := abspos - i.lstart
switch i.bitDepthInBytes {
case 2:
afterLoop := int16(i.afterLoop[relpos]) | (int16(i.afterLoop[relpos+1]) << 8)
orig := int16(b[2*idx]) | (int16(b[2*idx+1]) << 8)
newVal := int16(float32(afterLoop)*rate + float32(orig)*(1-rate))
b[2*idx] = byte(newVal)
b[2*idx+1] = byte(newVal >> 8)
case 4:
afterLoop := math.Float32frombits(uint32(i.afterLoop[relpos]) | (uint32(i.afterLoop[relpos+1]) << 8) | (uint32(i.afterLoop[relpos+2]) << 16) | (uint32(i.afterLoop[relpos+3]) << 24))
orig := math.Float32frombits(uint32(b[4*idx]) | (uint32(b[4*idx+1]) << 8) | (uint32(b[4*idx+2]) << 16) | (uint32(b[4*idx+3]) << 24))
newVal := float32(afterLoop*rate + orig*(1-rate))
newValBits := math.Float32bits(newVal)
b[4*idx] = byte(newValBits)
b[4*idx+1] = byte(newValBits >> 8)
b[4*idx+2] = byte(newValBits >> 16)
b[4*idx+3] = byte(newValBits >> 24)
default:
panic("not reached")
}
}
}
if err != nil && err != io.EOF {
return 0, err
}
// Read the afterLoop part if necessary.
if i.pos == i.length() && err == nil {
if i.afterLoop == nil {
buflen := int64(256 * i.bytesPerSample)
if buflen > i.length() {
buflen = i.length()
}
buf := make([]byte, buflen)
pos := 0
for pos < len(buf) {
n, err := i.src.Read(buf[pos:])
if err != nil && err != io.EOF {
return 0, err
}
pos += n
if err == io.EOF {
break
}
}
i.afterLoop = buf[:pos]
}
if len(i.afterLoop) > 0 {
i.blending = true
}
}
if i.pos == i.length() || err == io.EOF {
// Ignore the new position returned by Seek since the source position might not be match with the position
// managed by this.
if _, err := i.src.Seek(i.lstart, io.SeekStart); err != nil {
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return 0, err
}
i.pos = i.lstart
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}
return n, nil
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}
// Seek is implementation of ReadSeeker's Seek.
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func (i *InfiniteLoop) Seek(offset int64, whence int) (int64, error) {
i.blending = false
if err := i.ensurePos(); err != nil {
return 0, err
}
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next := int64(0)
switch whence {
case io.SeekStart:
next = offset
case io.SeekCurrent:
next = i.pos + offset
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case io.SeekEnd:
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return 0, fmt.Errorf("audio: whence must be io.SeekStart or io.SeekCurrent for InfiniteLoop")
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}
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if next < 0 {
return 0, fmt.Errorf("audio: position must >= 0")
}
if next > i.lstart {
next = ((next - i.lstart) % i.llength) + i.lstart
}
// Ignore the new position returned by Seek since the source position might not be match with the position
// managed by this.
if _, err := i.src.Seek(next, io.SeekStart); err != nil {
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return 0, err
}
i.pos = next
return i.pos, nil
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}