ebiten/audio/wav/decode.go

218 lines
5.6 KiB
Go

// 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.
// Package wav provides WAV (RIFF) decoder.
package wav
import (
"bytes"
"fmt"
"io"
"github.com/hajimehoshi/ebiten/v2/audio"
"github.com/hajimehoshi/ebiten/v2/audio/internal/convert"
)
// Stream is a decoded audio stream.
type Stream struct {
inner io.ReadSeeker
size int64
}
// 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.
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
}
type stream struct {
src io.ReadSeeker
headerSize int64
dataSize int64
remaining int64
}
// Read is implementation of io.Reader's Read.
func (s *stream) Read(p []byte) (int, error) {
if s.remaining <= 0 {
return 0, io.EOF
}
if s.remaining < int64(len(p)) {
p = p[0:s.remaining]
}
n, err := s.src.Read(p)
s.remaining -= int64(n)
return n, err
}
// Seek is implementation of io.Seeker's Seek.
func (s *stream) Seek(offset int64, whence int) (int64, error) {
switch whence {
case io.SeekStart:
offset = offset + s.headerSize
case io.SeekCurrent:
case io.SeekEnd:
offset = s.headerSize + s.dataSize + offset
whence = io.SeekStart
}
n, err := s.src.Seek(offset, whence)
if err != nil {
return 0, err
}
if n-s.headerSize < 0 {
return 0, fmt.Errorf("wav: invalid offset")
}
s.remaining = s.dataSize - (n - s.headerSize)
// There could be a tail in wav file.
if s.remaining < 0 {
s.remaining = 0
return s.dataSize, nil
}
return n - s.headerSize, nil
}
// 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.
//
// A Stream doesn't close src even if src implements io.Closer.
// Closing the source is src owner's responsibility.
func Decode(context *audio.Context, src io.ReadSeeker) (*Stream, error) {
buf := make([]byte, 12)
n, err := io.ReadFull(src, buf)
if n != len(buf) {
return nil, fmt.Errorf("wav: invalid header")
}
if err != nil {
return nil, err
}
if !bytes.Equal(buf[0:4], []byte("RIFF")) {
return nil, fmt.Errorf("wav: invalid header: 'RIFF' not found")
}
if !bytes.Equal(buf[8:12], []byte("WAVE")) {
return nil, fmt.Errorf("wav: invalid header: 'WAVE' not found")
}
// Read chunks
dataSize := int64(0)
headerSize := int64(len(buf))
sampleRateFrom := 0
sampleRateTo := 0
mono := false
bitsPerSample := 0
chunks:
for {
buf := make([]byte, 8)
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")
}
channelNum := int(buf[2]) | int(buf[3])<<8
switch channelNum {
case 1:
mono = true
case 2:
mono = false
default:
return nil, fmt.Errorf("wav: channel num must be 1 or 2 but was %d", channelNum)
}
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)
}
sampleRate := int64(buf[4]) | int64(buf[5])<<8 | int64(buf[6])<<16 | int64(buf[7])<<24
if int64(context.SampleRate()) != sampleRate {
sampleRateFrom = int(sampleRate)
sampleRateTo = context.SampleRate()
}
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
}
}
var s io.ReadSeeker = &stream{
src: src,
headerSize: headerSize,
dataSize: dataSize,
remaining: dataSize,
}
if mono || bitsPerSample != 16 {
s = convert.NewStereo16(s, mono, bitsPerSample != 16)
if mono {
dataSize *= 2
}
if bitsPerSample != 16 {
dataSize *= 2
}
}
if sampleRateFrom != sampleRateTo {
r := convert.NewResampling(s, dataSize, sampleRateFrom, sampleRateTo)
s = r
dataSize = r.Length()
}
ss := &Stream{inner: s, size: dataSize}
return ss, nil
}