ebiten/audio/wav/decode.go
2016-08-02 01:47:25 +09:00

145 lines
3.8 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/audio"
)
// Stream is a decoded audio stream.
type Stream struct {
src audio.ReadSeekCloser
headerSize int64
dataSize int64
}
// Read is implementation of io.Reader's Read.
func (s *Stream) Read(p []byte) (int, error) {
return s.src.Read(p)
}
// Seek is implementation of io.Seeker's Seek.
func (s *Stream) Seek(offset int64, whence int) (int64, error) {
if whence == 0 {
offset += s.headerSize
}
return s.src.Seek(offset, whence)
}
// Read is implementation of io.Closer's Close.
func (s *Stream) Close() error {
return s.src.Close()
}
// Size returns the size of decoded stream in bytes.
func (s *Stream) Size() int64 {
return s.dataSize
}
// Decode decodes WAV (RIFF) data to playable stream.
//
// The format must be 2 channels, 16bit little endian PCM.
// The sample rate must be same as that of audio context.
func Decode(context *audio.Context, src audio.ReadSeekCloser) (*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(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 ")):
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
// TODO: Remove this magic number
if channelNum != 2 {
return nil, fmt.Errorf("wav: channel num must be 2")
}
bitsPerSample := int(buf[14]) | int(buf[15])<<8
// TODO: Remove this magic number
if bitsPerSample != 16 {
return nil, fmt.Errorf("wav: bits per sample must be 16")
}
sampleRate := int64(buf[4]) | int64(buf[5])<<8 | int64(buf[6])<<16 | int64(buf[7])<<24
if int64(context.SampleRate()) != sampleRate {
return nil, fmt.Errorf("wav: sample rate must be %d but %d", context.SampleRate(), 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
}
}
s := &Stream{
src: src,
headerSize: headerSize,
dataSize: dataSize,
}
return s, nil
}