dndmusicbot/ffmpeg/ffmpeg.go

package ffmpeg

import (
	"bytes"
	"context"
	"log"
	"os"
	"os/exec"
	"strconv"
	"sync"
	"time"

	"dndmusicbot/ytdl"
)

type FFmpeg struct {
	Out          *bytes.Buffer
	Cmd          *exec.Cmd
	Started      bool
	Cancel       context.CancelFunc
	Len          time.Duration
	Title        string
	Channel      string
	PMutex       *sync.RWMutex
	ProcessState *os.ProcessState
	err          chan error
	fb           chan bool
}

func NewFFmpeg(uri string, sampleRate int, channels int) (ff *FFmpeg, err error) {
	var yt *ytdl.YTdl
	for {
		yt, err = ytdl.NewYTdl(uri)
		if err != nil {
			log.Println("Something went wrong, trying again.", err)
			continue
		}
		if yt.Url != "" {
			break
		}

		log.Println("Something went wrong, trying again.")
		time.Sleep(500 * time.Millisecond)
	}

RETRY:
	ff = new(FFmpeg)
	ff.PMutex = &sync.RWMutex{}
	ff.Len = yt.Len
	ff.Title = yt.Title
	ff.Channel = yt.Channel
	ctx, cancel := context.WithCancel(context.Background())
	ff.Cancel = cancel

	ff.Cmd = exec.CommandContext(
		ctx,
		"ffmpeg",
		"-xerror",
		"-i", yt.Url,
		"-f", "s16le",
		"-v", "error",
		// "-stats",
		//"-progress", "pipe:2",
		"-ar", strconv.Itoa(sampleRate),
		"-ac", strconv.Itoa(channels),
		"-af", "loudnorm=I=-16:LRA=11:TP=-1.5",
		"pipe:1",
	)

	ff.Cmd.Stderr = os.Stdin

	// FFmpeg requires a certain buffer size to start writing. This seems to be enough?
	// This will grow big enough to fit the whole song.
	ff.Out = bytes.NewBuffer(make([]byte, 43920))
	ff.Cmd.Stdout = ff.Out

	exitctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()

	go func() {
		ff.Cmd.Start()
		ff.err <- ff.Cmd.Wait()
	}()

	select {
	case <-exitctx.Done():
		ff.Started = true
	case <-ff.err:
		log.Println("ffmpeg exited early, retry...")
		goto RETRY
	}

	return
}

func (ff *FFmpeg) Close() error {
	ff.Cancel()
	return nil
}