clipper/backend/youtube/youtube.go

235 lines
6.3 KiB
Go

package youtube
import (
"bytes"
"context"
"encoding/json"
"errors"
"fmt"
"io"
"log"
"math"
"os"
"os/exec"
"strconv"
"sync"
"time"
"git.netflux.io/rob/clipper/media"
youtubev2 "github.com/kkdai/youtube/v2"
)
const SizeOfInt16 = 2
const (
rawAudioCodec = "pcm_s16le"
rawAudioFormat = "s16le"
rawAudioSampleRate = 48000
)
const (
thumbnailPrescaleWidth = -1
thumbnailPrescaleHeight = 120
thumbnailWidth = 177 // 16:9
thumbnailHeight = 100 // "
)
// YoutubeClient wraps the youtube.Client client.
type YoutubeClient interface {
GetVideoContext(context.Context, string) (*youtubev2.Video, error)
GetStreamContext(context.Context, *youtubev2.Video, *youtubev2.Format) (io.ReadCloser, int64, error)
}
// Downloader downloads a set of Youtube media for a given video ID, including
// separate audio and video files and a JSON metadata file. Additionally, it
// also renders the downloaded audio file as a raw audio file.
type Downloader struct {
youtubeClient YoutubeClient
}
// NewDownloader returns a new *Downloader.
func NewDownloader(youtubeClient YoutubeClient) *Downloader {
return &Downloader{youtubeClient: youtubeClient}
}
type audioResult struct {
*media.Audio
err error
}
type videoResult struct {
*media.Video
err error
}
// Download downloads the relevant audio and video files for the provided
// Youtube video ID. If successful, a *media.MediaSet struct containing
// metadata about the downloaded items is returned.
func (d *Downloader) Download(ctx context.Context, videoID string) (*media.MediaSet, error) {
var video *youtubev2.Video
video, err := d.youtubeClient.GetVideoContext(ctx, videoID)
if err != nil {
return nil, fmt.Errorf("error fetching video: %v", err)
}
mediaSet := media.NewMediaSet(videoID)
audioResultChan := make(chan audioResult, 1)
videoResultChan := make(chan videoResult, 1)
var wg sync.WaitGroup
wg.Add(2)
go func() {
defer close(audioResultChan)
audio, audioErr := d.downloadAudio(ctx, video, mediaSet.EncodedAudioPath(), mediaSet.RawAudioPath())
result := audioResult{audio, audioErr}
audioResultChan <- result
wg.Done()
}()
go func() {
defer close(videoResultChan)
video, videoErr := d.downloadVideo(ctx, video, mediaSet.VideoPath(), mediaSet.ThumbnailPath())
result := videoResult{video, videoErr}
videoResultChan <- result
wg.Done()
}()
wg.Wait()
audioResult := <-audioResultChan
videoResult := <-videoResultChan
if err = audioResult.err; err != nil {
return nil, fmt.Errorf("error downloading audio: %v", err)
}
if err = videoResult.err; err != nil {
return nil, fmt.Errorf("error downloading video: %v", err)
}
mediaSet.Audio = *audioResult.Audio
mediaSet.Video = *videoResult.Video
metadataFile, err := os.Create(mediaSet.MetadataPath())
if err != nil {
return nil, fmt.Errorf("error opening metadata file: %v", err)
}
if err = json.NewEncoder(metadataFile).Encode(mediaSet); err != nil {
return nil, fmt.Errorf("error encoding metadata: %v", err)
}
if err = metadataFile.Close(); err != nil {
return nil, fmt.Errorf("error writing metadata file: %v", err)
}
log.Println("finished downloading mediaset")
return mediaSet, nil
}
func (d *Downloader) downloadAudio(ctx context.Context, video *youtubev2.Video, outPath, rawOutPath string) (*media.Audio, error) {
if len(video.Formats) == 0 {
return nil, errors.New("error selecting audio format: no format available")
}
format := SortAudio(video.Formats)[0]
log.Printf("selected audio format: %s", FormatDebugString(&format, false))
stream, _, err := d.youtubeClient.GetStreamContext(ctx, video, &format)
if err != nil {
return nil, fmt.Errorf("error fetching audio stream: %v", err)
}
rawAudioFile, err := os.Create(rawOutPath)
if err != nil {
return nil, fmt.Errorf("error creating raw audio file: %v", err)
}
encodedAudioFile, err := os.Create(outPath)
if err != nil {
return nil, fmt.Errorf("error creating encoded audio file: %v", err)
}
streamReader := io.TeeReader(stream, encodedAudioFile)
var errOut bytes.Buffer
cmd := exec.CommandContext(ctx, "ffmpeg", "-i", "-", "-f", rawAudioFormat, "-ar", strconv.Itoa(rawAudioSampleRate), "-acodec", rawAudioCodec, "-")
cmd.Stdin = streamReader
cmd.Stdout = rawAudioFile
cmd.Stderr = &errOut
if err = cmd.Run(); err != nil {
log.Println(errOut.String())
return nil, fmt.Errorf("error processing audio: %v", err)
}
if err = rawAudioFile.Close(); err != nil {
return nil, fmt.Errorf("error writing raw audio file: %v", err)
}
rawAudioFile, err = os.Open(rawOutPath)
if err != nil {
return nil, fmt.Errorf("error opening raw audio file: %v", err)
}
fi, err := rawAudioFile.Stat()
if err != nil {
return nil, fmt.Errorf("error reading raw audio file info: %v", err)
}
numFrames := fi.Size() / int64(SizeOfInt16) / int64(format.AudioChannels)
sampleRate, err := strconv.Atoi(format.AudioSampleRate)
if err != nil {
return nil, fmt.Errorf("invalid samplerate: %s", format.AudioSampleRate)
}
return &media.Audio{
Bytes: fi.Size(),
Channels: format.AudioChannels,
Frames: numFrames,
SampleRate: sampleRate,
}, nil
}
func thumbnailGridSize(msecs int) (int, int) {
secs := msecs / 1000
x := int(math.Floor(math.Sqrt(float64(secs))))
if x*x < secs {
return x + 1, x
}
return x, x
}
func (d *Downloader) downloadVideo(ctx context.Context, video *youtubev2.Video, outPath string, thumbnailOutPath string) (*media.Video, error) {
if len(video.Formats) == 0 {
return nil, errors.New("error selecting audio format: no format available")
}
format := SortVideo(video.Formats)[0]
log.Printf("selected video format: %s", FormatDebugString(&format, false))
durationMsecs, err := strconv.Atoi(format.ApproxDurationMs)
if err != nil {
return nil, fmt.Errorf("could not parse video duration: %s", err)
}
stream, _, err := d.youtubeClient.GetStreamContext(ctx, video, &format)
if err != nil {
return nil, fmt.Errorf("error fetching video stream: %v", err)
}
videoFile, err := os.Create(outPath)
if err != nil {
return nil, fmt.Errorf("error creating video file: %v", err)
}
if _, err = io.Copy(videoFile, stream); err != nil {
return nil, fmt.Errorf("error processing video: %v", err)
}
return &media.Video{
Bytes: format.ContentLength,
ThumbnailWidth: thumbnailWidth,
ThumbnailHeight: thumbnailHeight,
Duration: time.Duration(durationMsecs) * time.Millisecond,
}, nil
}