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|
package downloader
import (
"io/ioutil"
"os"
"os/exec"
"strconv"
"sync"
"time"
"github.com/mammothbane/thulani-go/wav"
)
// downloader handles a download for a particular song.
type downloader struct {
Url string
StartTime time.Duration
Duration time.Duration
EndTime time.Duration
once sync.Once
done chan struct{}
pb chan *wavBundle
info videoInfo
}
const clipTime = 10 * time.Second
const preloadCount = 5
func newDownload(url string, startTime, dur time.Duration) (*downloader, error) {
vInfo, err := info(url)
if err != nil {
return nil, err
}
if dur == 0 {
dur = vInfo.Duration - startTime
}
dl := &downloader{
Url: url,
StartTime: startTime,
Duration: dur,
EndTime: startTime + dur,
done: make(chan struct{}, 1),
pb: make(chan *wavBundle, preloadCount),
info: *vInfo,
}
go dl.schedule()
return dl, nil
}
func (d *downloader) Stop() {
d.once.Do(func() {
close(d.done)
})
}
func (d *downloader) Start() <-chan []byte {
out := make(chan []byte, 1024)
go func() {
defer close(out)
select {
case <-d.done:
for wavB := range d.pb {
wavB.wav.Stop()
wavB.cleanup()
}
return
default:
}
for wavB := range d.pb {
wavB.wav.Start(out)
select {
case <-d.done:
wavB.wav.Stop()
wavB.cleanup()
case <-wavB.wav.Done:
}
}
}()
return out
}
func (d *downloader) schedule() {
defer close(d.pb)
for i := 0; ; i++ {
select {
case <-d.done:
return
default:
}
clipStart := time.Duration(i)*clipTime + d.StartTime
clipEnd := time.Duration(i+1)*clipTime + d.StartTime
if clipStart >= d.EndTime {
return
}
dur := clipTime
if clipEnd > d.EndTime {
dur = d.EndTime - clipStart
}
wavb, err := d.downloadSegment(clipStart, dur)
if err != nil {
log.Errorf("error setting up download: %q", err)
return
}
select {
case d.pb <- wavb:
case <-d.done:
return
}
}
}
func (d *downloader) downloadSegment(startTime, duration time.Duration) (*wavBundle, error) {
startSecond := int(startTime.Seconds())
args := []string{
"-ss", strconv.Itoa(startSecond),
"-i", d.info.Url.String(),
"-c:a", "pcm_s16le",
"-f", "wav",
"-ar", "48000",
"-ac", "2",
"-vn", "-y",
}
dur := int(duration.Seconds())
if dur > 0 && startTime+duration < d.info.Duration {
args = append(args, "-t", strconv.Itoa(dur))
}
file, err := ioutil.TempFile("", "thulani_")
if err != nil {
return nil, err
}
clearTemp := func() {
if err := file.Close(); err != nil {
log.Errorf("error closing temp file: %q", err)
}
if err := os.Remove(file.Name()); err != nil {
log.Errorf("unable to remove temp file: %q", err)
}
}
args = append(args, file.Name())
dl := exec.Command(`ffmpeg`, args...)
b, err := dl.CombinedOutput()
if err != nil {
clearTemp()
log.Errorf("ffmpeg failed: \n%v", string(b))
return nil, err
}
wv, err := wav.New(file.Name())
if err != nil {
clearTemp()
return nil, err
}
return &wavBundle{wav: wv, cleanup: clearTemp}, err
}
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