audio/mp3, audio/vorbis, audio/wav: add DecodeWithoutResampling

Updates #2055

audio/mp3/decode.go

@@ -57,7 +57,27 @@ func (s *Stream) Length() int64 {
 	return s.orig.Length()
 }
 
-// DecodeWithSampleRate decodes MP3 source and returns a decoded stream.
+// DecodeWithoutResampling decodes an MP3 source and returns a decoded stream.
+//
+// DecodeWithoutResampling 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) {
+	d, err := mp3.NewDecoder(src)
+	if err != nil {
+		return nil, err
+	}
+	s := &Stream{
+		orig:       d,
+		resampling: nil,
+	}
+	return s, nil
+}
+
+// DecodeWithSampleRate decodes an MP3 source and returns a decoded stream.
 //
 // DecodeWithSampleRate returns error when decoding fails or IO error happens.
 //

audio/vorbis/vorbis.go

@@ -139,6 +139,35 @@ func decode(in io.Reader) (*decoded, int, int, error) {
 	return d, r.Channels(), r.SampleRate(), nil
 }
 
+// DecodeWithoutResampling decodes Ogg/Vorbis data to playable stream.
+//
+// DecodeWithoutResampling 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) {
+	decoded, channelNum, _, 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
+	}
+	stream := &Stream{
+		decoded: s,
+		size:    size,
+	}
+	return stream, nil
+}
+
 // DecodeWithSampleRate decodes Ogg/Vorbis data to playable stream.
 //
 // DecodeWithSampleRate returns error when decoding fails or IO error happens.

audio/wav/decode.go

@@ -102,6 +102,21 @@ func (s *stream) Seek(offset int64, whence int) (int64, error) {
 	return n - s.headerSize, nil
 }
 
+// DecodeWithSampleRate 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.
+//
+// DecodeWithSampleRate 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) {
+	return decode(src, nil)
+}
+
 // DecodeWithSampleRate decodes WAV (RIFF) data to playable stream.
 //
 // The format must be 1 or 2 channels, 8bit or 16bit little endian PCM.
@@ -116,6 +131,10 @@ func (s *stream) Seek(offset int64, whence int) (int64, error) {
 // A Stream doesn't close src even if src implements io.Closer.
 // Closing the source is src owner's responsibility.
 func DecodeWithSampleRate(sampleRate int, src io.Reader) (*Stream, error) {
+	return decode(src, &sampleRate)
+}
+
+func decode(src io.Reader, sampleRate *int) (*Stream, error) {
 	buf := make([]byte, 12)
 	n, err := io.ReadFull(src, buf)
 	if n != len(buf) {
@@ -182,9 +201,9 @@ chunks:
 				return nil, fmt.Errorf("wav: bits per sample must be 8 or 16 but was %d", bitsPerSample)
 			}
 			origSampleRate := int64(buf[4]) | int64(buf[5])<<8 | int64(buf[6])<<16 | int64(buf[7])<<24
-			if int64(sampleRate) != origSampleRate {
+			if sampleRate != nil && int64(*sampleRate) != origSampleRate {
 				sampleRateFrom = int(origSampleRate)
-				sampleRateTo = sampleRate
+				sampleRateTo = *sampleRate
 			}
 			headerSize += size
 		case bytes.Equal(buf[0:4], []byte("data")):

examples/audio/main.go

@@ -134,13 +134,13 @@ func NewPlayer(game *Game, audioContext *audio.Context, musicType musicType) (*P
 	switch musicType {
 	case typeOgg:
 		var err error
-		s, err = vorbis.Decode(audioContext, bytes.NewReader(raudio.Ragtime_ogg))
+		s, err = vorbis.DecodeWithoutResampling(bytes.NewReader(raudio.Ragtime_ogg))
 		if err != nil {
 			return nil, err
 		}
 	case typeMP3:
 		var err error
-		s, err = mp3.Decode(audioContext, bytes.NewReader(raudio.Ragtime_mp3))
+		s, err = mp3.DecodeWithoutResampling(bytes.NewReader(raudio.Ragtime_mp3))
 		if err != nil {
 			return nil, err
 		}
@@ -174,7 +174,7 @@ func NewPlayer(game *Game, audioContext *audio.Context, musicType musicType) (*P
 
 	player.audioPlayer.Play()
 	go func() {
-		s, err := wav.Decode(audioContext, bytes.NewReader(raudio.Jab_wav))
+		s, err := wav.DecodeWithSampleRate(sampleRate, bytes.NewReader(raudio.Jab_wav))
 		if err != nil {
 			log.Fatal(err)
 			return

examples/audioinfiniteloop/main.go

@@ -56,7 +56,7 @@ func (g *Game) Update() error {
 
 	// Decode an Ogg file.
 	// oggS is a decoded io.ReadCloser and io.Seeker.
-	oggS, err := vorbis.Decode(g.audioContext, bytes.NewReader(raudio.Ragtime_ogg))
+	oggS, err := vorbis.DecodeWithoutResampling(bytes.NewReader(raudio.Ragtime_ogg))
 	if err != nil {
 		return err
 	}

examples/audiopanning/main.go

@@ -70,7 +70,7 @@ func (g *Game) initAudio() {
 
 	// Decode an Ogg file.
 	// oggS is a decoded io.ReadCloser and io.Seeker.
-	oggS, err := vorbis.Decode(g.audioContext, bytes.NewReader(raudio.Ragtime_ogg))
+	oggS, err := vorbis.DecodeWithoutResampling(bytes.NewReader(raudio.Ragtime_ogg))
 	if err != nil {
 		log.Fatal(err)
 	}

examples/flappy/main.go

@@ -179,7 +179,7 @@ func (g *Game) init() {
 		g.audioContext = audio.NewContext(48000)
 	}
 
-	jumpD, err := vorbis.DecodeWithSampleRate(48000, bytes.NewReader(raudio.Jump_ogg))
+	jumpD, err := vorbis.DecodeWithoutResampling(bytes.NewReader(raudio.Jump_ogg))
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -188,7 +188,7 @@ func (g *Game) init() {
 		log.Fatal(err)
 	}
 
-	jabD, err := wav.DecodeWithSampleRate(48000, bytes.NewReader(raudio.Jab_wav))
+	jabD, err := wav.DecodeWithoutResampling(bytes.NewReader(raudio.Jab_wav))
 	if err != nil {
 		log.Fatal(err)
 	}

examples/wav/main.go

@@ -58,11 +58,11 @@ func NewGame() (*Game, error) {
 	//         return err
 	//     }
 	//
-	//     d, err := wav.Decode(g.audioContext, f)
+	//     d, err := wav.DecodeWithoutResampling(f)
 	//     ...
 
 	// Decode wav-formatted data and retrieve decoded PCM stream.
-	d, err := wav.Decode(g.audioContext, bytes.NewReader(raudio.Jab_wav))
+	d, err := wav.DecodeWithoutResampling(bytes.NewReader(raudio.Jab_wav))
 	if err != nil {
 		return nil, err
 	}