subsonic-tui/vendor/github.com/gopxl/beep/mp3/decode.go

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// Package mp3 implements audio data decoding in MP3 format.
package mp3
import (
"fmt"
"io"
"github.com/gopxl/beep"
gomp3 "github.com/hajimehoshi/go-mp3"
"github.com/pkg/errors"
)
const (
gomp3NumChannels = 2
gomp3Precision = 2
gomp3BytesPerFrame = gomp3NumChannels * gomp3Precision
)
// Decode takes a ReadCloser containing audio data in MP3 format and returns a StreamSeekCloser,
// which streams that audio. The Seek method will panic if rc is not io.Seeker.
//
// Do not close the supplied ReadSeekCloser, instead, use the Close method of the returned
// StreamSeekCloser when you want to release the resources.
func Decode(rc io.ReadCloser) (s beep.StreamSeekCloser, format beep.Format, err error) {
defer func() {
if err != nil {
err = errors.Wrap(err, "mp3")
}
}()
d, err := gomp3.NewDecoder(rc)
if err != nil {
return nil, beep.Format{}, err
}
format = beep.Format{
SampleRate: beep.SampleRate(d.SampleRate()),
NumChannels: gomp3NumChannels,
Precision: gomp3Precision,
}
return &decoder{rc, d, format, 0, nil}, format, nil
}
type decoder struct {
closer io.Closer
d *gomp3.Decoder
f beep.Format
pos int
err error
}
func (d *decoder) Stream(samples [][2]float64) (n int, ok bool) {
if d.err != nil {
return 0, false
}
var tmp [gomp3BytesPerFrame]byte
for i := range samples {
dn, err := d.d.Read(tmp[:])
if dn == len(tmp) {
samples[i], _ = d.f.DecodeSigned(tmp[:])
d.pos += dn
n++
ok = true
}
if err == io.EOF {
break
}
if err != nil {
d.err = errors.Wrap(err, "mp3")
break
}
}
return n, ok
}
func (d *decoder) Err() error {
return d.err
}
func (d *decoder) Len() int {
return int(d.d.Length()) / gomp3BytesPerFrame
}
func (d *decoder) Position() int {
return d.pos / gomp3BytesPerFrame
}
func (d *decoder) Seek(p int) error {
if p < 0 || d.Len() < p {
return fmt.Errorf("mp3: seek position %v out of range [%v, %v]", p, 0, d.Len())
}
_, err := d.d.Seek(int64(p)*gomp3BytesPerFrame, io.SeekStart)
if err != nil {
return errors.Wrap(err, "mp3")
}
d.pos = p * gomp3BytesPerFrame
return nil
}
func (d *decoder) Close() error {
err := d.closer.Close()
if err != nil {
return errors.Wrap(err, "mp3")
}
return nil
}