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vorbis.go
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/
vorbis.go
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// Copyright 2015 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 vorbis provides Ogg/Vorbis decoder.
package vorbis
import (
"fmt"
"io"
"github.com/jfreymuth/oggvorbis"
"github.com/hajimehoshi/ebiten/v2/audio"
"github.com/hajimehoshi/ebiten/v2/audio/internal/convert"
)
// Stream is a decoded audio stream.
type Stream struct {
decoded io.ReadSeeker
size int64
}
// Read is implementation of io.Reader's Read.
func (s *Stream) Read(p []byte) (int, error) {
return s.decoded.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.decoded.Seek(offset, whence)
}
// Length returns the size of decoded stream in bytes.
func (s *Stream) Length() int64 {
return s.size
}
type decoder interface {
Read([]float32) (int, error)
SetPosition(int64) error
Length() int64
Channels() int
SampleRate() int
}
type decoded struct {
totalBytes int
posInBytes int
decoder decoder
decoderr io.Reader
}
func (d *decoded) Read(b []byte) (int, error) {
if d.decoderr == nil {
d.decoderr = convert.NewReaderFromFloat32Reader(d.decoder)
}
l := d.totalBytes - d.posInBytes
if l > len(b) {
l = len(b)
}
if l < 0 {
return 0, io.EOF
}
retry:
n, err := d.decoderr.Read(b[:l])
if err != nil && err != io.EOF {
return 0, err
}
if n == 0 && l > 0 && err != io.EOF {
// When l is too small, decoder's Read might return 0 for a while. Let's retry.
goto retry
}
d.posInBytes += n
if d.posInBytes == d.totalBytes || err == io.EOF {
return n, io.EOF
}
return n, nil
}
func (d *decoded) Seek(offset int64, whence int) (int64, error) {
next := int64(0)
switch whence {
case io.SeekStart:
next = offset
case io.SeekCurrent:
next = int64(d.posInBytes) + offset
case io.SeekEnd:
next = int64(d.totalBytes) + offset
}
// pos should be always even
next = next / 2 * 2
d.posInBytes = int(next)
d.decoder.SetPosition(next / int64(d.decoder.Channels()) / 2)
d.decoderr = nil
return next, nil
}
func (d *decoded) Length() int64 {
return int64(d.totalBytes)
}
// decode accepts an ogg stream and returns a decorded stream.
func decode(in io.ReadSeeker) (*decoded, int, int, error) {
r, err := oggvorbis.NewReader(in)
if err != nil {
return nil, 0, 0, err
}
d := &decoded{
// TODO: r.Length() returns 0 when the format is unknown.
// Should we check that?
totalBytes: int(r.Length()) * r.Channels() * 2, // 2 means 16bit per sample.
posInBytes: 0,
decoder: r,
}
if _, err := d.Read(make([]byte, 65536)); err != nil && err != io.EOF {
return nil, 0, 0, err
}
if _, err := d.Seek(0, io.SeekStart); err != nil {
return nil, 0, 0, err
}
return d, r.Channels(), r.SampleRate(), nil
}
// Decode decodes Ogg/Vorbis data to playable stream.
//
// 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) {
decoded, channelNum, sampleRate, err := decode(src)
if err != nil {
return nil, err
}
if channelNum != 1 && channelNum != 2 {
return nil, fmt.Errorf("vorbis: number of channels must be 1 or 2 but was %d", channelNum)
}
var s io.ReadSeeker = decoded
size := decoded.Length()
if channelNum == 1 {
s = convert.NewStereo16(s, true, false)
size *= 2
}
if sampleRate != context.SampleRate() {
r := convert.NewResampling(s, size, sampleRate, context.SampleRate())
s = r
size = r.Length()
}
stream := &Stream{decoded: s, size: size}
return stream, nil
}