ebiten/audio/wav/decode.go

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// Copyright 2016 Hajime Hoshi
//
// 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.
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// Package wav provides WAV (RIFF) decoder.
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package wav
import (
"bytes"
"fmt"
"io"
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"github.com/hajimehoshi/ebiten/v2/audio"
"github.com/hajimehoshi/ebiten/v2/audio/internal/convert"
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)
const (
bitDepthInBytesInt16 = 2
)
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// Stream is a decoded audio stream.
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type Stream struct {
inner io.ReadSeeker
size int64
sampleRate int
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}
// Read is implementation of io.Reader's Read.
func (s *Stream) Read(p []byte) (int, error) {
return s.inner.Read(p)
}
// Seek is implementation of io.Seeker's Seek.
//
// Note that Seek can take long since decoding is a relatively heavy task.
//
// If the underlying source is not an io.Seeker, Seek panics.
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func (s *Stream) Seek(offset int64, whence int) (int64, error) {
return s.inner.Seek(offset, whence)
}
// Length returns the size of decoded stream in bytes.
func (s *Stream) Length() int64 {
return s.size
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}
// SampleRate returns the sample rate of the decoded stream.
func (s *Stream) SampleRate() int {
return s.sampleRate
}
// DecodeWithoutResampling decodes WAV (RIFF) data to playable stream.
//
// The format must be 1 or 2 channels, 8bit or 16bit little endian PCM.
// The format is converted into 2 channels and 16bit.
//
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// DecodeWithoutSampleRate returns error when decoding fails or IO error happens.
//
// The returned Stream's Seek is available only when src is an io.Seeker.
//
// A Stream doesn't close src even if src implements io.Closer.
// Closing the source is src owner's responsibility.
func DecodeWithoutResampling(src io.Reader) (*Stream, error) {
s, err := decode(src)
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if err != nil {
return nil, err
}
return s, nil
}
// DecodeWithSampleRate decodes WAV (RIFF) data to playable stream.
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//
// The format must be 1 or 2 channels, 8bit or 16bit little endian PCM.
// The format is converted into 2 channels and 16bit.
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//
// DecodeWithSampleRate returns error when decoding fails or IO error happens.
//
// DecodeWithSampleRate automatically resamples the stream to fit with sampleRate if necessary.
//
// The returned Stream's Seek is available only when src is an io.Seeker.
//
// A Stream doesn't close src even if src implements io.Closer.
// Closing the source is src owner's responsibility.
//
// Resampling can be a very heavy task. Stream has a cache for resampling, but the size is limited.
// Do not expect that Stream has a resampling cache even after whole data is played.
func DecodeWithSampleRate(sampleRate int, src io.Reader) (*Stream, error) {
s, err := decode(src)
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if err != nil {
return nil, err
}
if sampleRate == s.sampleRate {
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return s, nil
}
r := convert.NewResampling(s.inner, s.size, s.sampleRate, sampleRate, bitDepthInBytesInt16)
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return &Stream{
inner: r,
size: r.Length(),
sampleRate: sampleRate,
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}, nil
}
func decode(src io.Reader) (*Stream, error) {
buf := make([]byte, 12)
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n, err := io.ReadFull(src, buf)
if n != len(buf) {
return nil, fmt.Errorf("wav: invalid header")
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}
if err != nil {
return nil, err
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}
if !bytes.Equal(buf[0:4], []byte("RIFF")) {
return nil, fmt.Errorf("wav: invalid header: 'RIFF' not found")
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}
if !bytes.Equal(buf[8:12], []byte("WAVE")) {
return nil, fmt.Errorf("wav: invalid header: 'WAVE' not found")
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}
// Read chunks
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var dataSize int64
headerSize := int64(len(buf))
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var mono bool
var bitsPerSample int
var sampleRate int
chunks:
for {
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var buf [8]byte
n, err := io.ReadFull(src, buf[:])
if n != len(buf) {
return nil, fmt.Errorf("wav: invalid header")
}
if err != nil {
return nil, err
}
headerSize += 8
size := int64(buf[4]) | int64(buf[5])<<8 | int64(buf[6])<<16 | int64(buf[7])<<24
switch {
case bytes.Equal(buf[0:4], []byte("fmt ")):
// Size of 'fmt' header is usually 16, but can be more than 16.
if size < 16 {
return nil, fmt.Errorf("wav: invalid header: maybe non-PCM file?")
}
buf := make([]byte, size)
n, err := io.ReadFull(src, buf)
if n != len(buf) {
return nil, fmt.Errorf("wav: invalid header")
}
if err != nil {
return nil, err
}
format := int(buf[0]) | int(buf[1])<<8
if format != 1 {
return nil, fmt.Errorf("wav: format must be linear PCM")
}
channelCount := int(buf[2]) | int(buf[3])<<8
switch channelCount {
case 1:
mono = true
case 2:
mono = false
default:
return nil, fmt.Errorf("wav: number of channels must be 1 or 2 but was %d", channelCount)
}
bitsPerSample = int(buf[14]) | int(buf[15])<<8
if bitsPerSample != 8 && bitsPerSample != 16 {
return nil, fmt.Errorf("wav: bits per sample must be 8 or 16 but was %d", bitsPerSample)
}
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sampleRate = int(buf[4]) | int(buf[5])<<8 | int(buf[6])<<16 | int(buf[7])<<24
headerSize += size
case bytes.Equal(buf[0:4], []byte("data")):
dataSize = size
break chunks
default:
buf := make([]byte, size)
n, err := io.ReadFull(src, buf)
if n != len(buf) {
return nil, fmt.Errorf("wav: invalid header")
}
if err != nil {
return nil, err
}
headerSize += size
}
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}
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var s io.ReadSeeker = newSectionReader(src, headerSize, dataSize)
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if mono || bitsPerSample != 16 {
s = convert.NewStereo16(s, mono, bitsPerSample != 16)
if mono {
dataSize *= 2
}
if bitsPerSample != 16 {
dataSize *= 2
}
}
return &Stream{
inner: s,
size: dataSize,
sampleRate: sampleRate,
}, nil
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}
// Decode decodes WAV (RIFF) data to playable stream.
//
// The format must be 1 or 2 channels, 8bit or 16bit little endian PCM.
// The format is converted into 2 channels and 16bit.
//
// Decode returns error when decoding fails or IO error happens.
//
// Decode automatically resamples the stream to fit with the audio context if necessary.
//
// The returned Stream's Seek is available only when src is an io.Seeker.
//
// A Stream doesn't close src even if src implements io.Closer.
// Closing the source is src owner's responsibility.
//
// Deprecated: as of v2.1. Use DecodeWithSampleRate instead.
func Decode(context *audio.Context, src io.Reader) (*Stream, error) {
return DecodeWithSampleRate(context.SampleRate(), src)
}