123 lines
2.5 KiB
Go
123 lines
2.5 KiB
Go
package main
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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"io"
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"log"
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"os"
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"os/exec"
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"strconv"
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"github.com/kkdai/youtube/v2"
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)
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const (
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ItagM4AAudio = 140
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SizeOfInt16 = 2
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DefaultAudioCodec = "pcm_s16le"
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DefaultFormat = "s16le"
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DefaultSampleRate = 44100
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)
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type byteToIntConverter struct {
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callback func(p []uint16)
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buf []uint16
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}
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func (w byteToIntConverter) Write(p []byte) (int, error) {
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if len(p)%2 != 0 {
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panic("need to handle odd number of bytes")
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}
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// grow the internal buffer if necessary:
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exp := len(p) / SizeOfInt16
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if len(w.buf) < exp {
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w.buf = append(w.buf, make([]uint16, exp)...)
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}
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for i := 0; i < len(p); i += SizeOfInt16 {
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w.buf[i/2] = binary.LittleEndian.Uint16(p[i : i+SizeOfInt16])
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}
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w.callback(w.buf)
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return len(p), nil
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}
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type AudioDownloader struct {
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videoID string
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ytClient youtube.Client
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}
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func NewAudioDownloader(videoID string) *AudioDownloader {
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return &AudioDownloader{videoID: videoID}
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}
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func (d *AudioDownloader) ReadInts(fn func(p []uint16)) error {
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cachePath := fmt.Sprintf("cache/%s.raw", d.videoID)
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var reader io.Reader
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fetch := true
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if _, err := os.Stat(cachePath); err == nil {
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if fptr, err := os.Open(cachePath); err == nil {
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defer fptr.Close()
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reader = fptr
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fetch = false
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} else {
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log.Printf("warning: error opening cache file: %v", err)
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}
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}
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if fetch {
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log.Println("fetching audio stream from youtube...")
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video, err := d.ytClient.GetVideo(d.videoID)
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if err != nil {
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return fmt.Errorf("error fetching video: %v", err)
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}
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format := video.Formats.FindByItag(ItagM4AAudio)
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stream, _, err := d.ytClient.GetStream(video, format)
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if err != nil {
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return fmt.Errorf("error fetching stream: %v", err)
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}
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cacheFile, err := os.Create(cachePath)
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if err != nil {
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return fmt.Errorf("error creating cache file: %v", err)
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}
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reader = io.TeeReader(stream, cacheFile)
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}
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var errOut bytes.Buffer
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cmd := exec.Command("ffmpeg", "-i", "-", "-f", DefaultFormat, "-ar", strconv.Itoa(DefaultSampleRate), "-acodec", DefaultAudioCodec, "-")
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cmd.Stdin = reader
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cmd.Stdout = byteToIntConverter{callback: fn}
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cmd.Stderr = &errOut
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if err := cmd.Run(); err != nil {
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log.Println(errOut.String())
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return fmt.Errorf("error calling ffmpeg: %v", err)
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}
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return nil
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}
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func main() {
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videoID := "s_oJYdRlrv0"
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downloader := NewAudioDownloader(videoID)
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err := downloader.ReadInts(func(p []uint16) {
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// log.Printf("ints = %+v", p[0:16])
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})
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if err != nil {
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log.Fatalf("error calling downloader: %v", err)
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}
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log.Println("done")
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}
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