dndmusicbot/ffmpeg/ffmpeg.go

package ffmpeg

import (
	"bytes"
	"context"
	"os"
	"os/exec"
	"strconv"
	"time"
)

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

func NewFFmpeg(uri string, sampleRate int, channels int) (ff *FFmpeg, err error) {
	ff = new(FFmpeg)
	ctx, cancel := context.WithCancel(context.Background())
	ff.Cancel = cancel

	ff.Cmd = exec.CommandContext(
		ctx,
		"ffmpeg",
		"-i", uri,
		"-f", "s16le",
		"-v", "error",
		//"-stats",
		"-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, 128*1024))
	ff.Cmd.Stdout = ff.Out

	return
}

func (ff *FFmpeg) Start() error {
	ff.Started = true
	err := ff.Cmd.Start()
	go func() {
		if err != nil {
			ff.err <- ff.Cmd.Wait()
		}
	}()

	return err
}

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