navidrome/core/ffmpeg/ffmpeg.go

package ffmpeg

import (
	"context"
	"errors"
	"fmt"
	"io"
	"os"
	"os/exec"
	"strconv"
	"strings"
	"sync"

	"github.com/navidrome/navidrome/conf"
	"github.com/navidrome/navidrome/log"
)

type FFmpeg interface {
	Transcode(ctx context.Context, command, path string, maxBitRate, offset int) (io.ReadCloser, error)
	ExtractImage(ctx context.Context, path string) (io.ReadCloser, error)
	ConvertToWAV(ctx context.Context, path string) (io.ReadCloser, error)
	ConvertToFLAC(ctx context.Context, path string) (io.ReadCloser, error)
	Probe(ctx context.Context, files []string) (string, error)
	CmdPath() (string, error)
}

func New() FFmpeg {
	return &ffmpeg{}
}

const (
	extractImageCmd = "ffmpeg -i %s -an -vcodec copy -f image2pipe -"
	probeCmd        = "ffmpeg %s -f ffmetadata"
	createWavCmd    = "ffmpeg -i %s -c:a pcm_s16le -f wav -"
	createFLACCmd   = "ffmpeg -i %s -f flac -"
)

type ffmpeg struct{}

func (e *ffmpeg) Transcode(ctx context.Context, command, path string, maxBitRate, offset int) (io.ReadCloser, error) {
	if _, err := ffmpegCmd(); err != nil {
		return nil, err
	}
	args := createFFmpegCommand(command, path, maxBitRate, offset)
	return e.start(ctx, args)
}

func (e *ffmpeg) ExtractImage(ctx context.Context, path string) (io.ReadCloser, error) {
	if _, err := ffmpegCmd(); err != nil {
		return nil, err
	}
	args := createFFmpegCommand(extractImageCmd, path, 0, 0)
	return e.start(ctx, args)
}

func (e *ffmpeg) ConvertToWAV(ctx context.Context, path string) (io.ReadCloser, error) {
	args := createFFmpegCommand(createWavCmd, path, 0, 0)
	return e.start(ctx, args)
}

func (e *ffmpeg) ConvertToFLAC(ctx context.Context, path string) (io.ReadCloser, error) {
	args := createFFmpegCommand(createFLACCmd, path, 0, 0)
	return e.start(ctx, args)
}

func (e *ffmpeg) Probe(ctx context.Context, files []string) (string, error) {
	if _, err := ffmpegCmd(); err != nil {
		return "", err
	}
	args := createProbeCommand(probeCmd, files)
	log.Trace(ctx, "Executing ffmpeg command", "args", args)
	cmd := exec.CommandContext(ctx, args[0], args[1:]...) // #nosec
	output, _ := cmd.CombinedOutput()
	return string(output), nil
}

func (e *ffmpeg) CmdPath() (string, error) {
	return ffmpegCmd()
}

func (e *ffmpeg) start(ctx context.Context, args []string) (io.ReadCloser, error) {
	log.Trace(ctx, "Executing ffmpeg command", "cmd", args)
	j := &ffCmd{args: args}
	j.PipeReader, j.out = io.Pipe()
	err := j.start()
	if err != nil {
		return nil, err
	}
	go j.wait()
	return j, nil
}

type ffCmd struct {
	*io.PipeReader
	out  *io.PipeWriter
	args []string
	cmd  *exec.Cmd
}

func (j *ffCmd) start() error {
	cmd := exec.Command(j.args[0], j.args[1:]...) // #nosec
	cmd.Stdout = j.out
	if log.CurrentLevel() >= log.LevelTrace {
		cmd.Stderr = os.Stderr
	} else {
		cmd.Stderr = io.Discard
	}
	j.cmd = cmd

	if err := cmd.Start(); err != nil {
		return fmt.Errorf("starting cmd: %w", err)
	}
	return nil
}

func (j *ffCmd) wait() {
	if err := j.cmd.Wait(); err != nil {
		var exitErr *exec.ExitError
		if errors.As(err, &exitErr) {
			_ = j.out.CloseWithError(fmt.Errorf("%s exited with non-zero status code: %d", j.args[0], exitErr.ExitCode()))
		} else {
			_ = j.out.CloseWithError(fmt.Errorf("waiting %s cmd: %w", j.args[0], err))
		}
		return
	}
	_ = j.out.Close()
}

// Path will always be an absolute path
func createFFmpegCommand(cmd, path string, maxBitRate, offset int) []string {
	split := strings.Split(fixCmd(cmd), " ")
	var parts []string

	for _, s := range split {
		if strings.Contains(s, "%s") {
			s = strings.ReplaceAll(s, "%s", path)
			parts = append(parts, s)
			if offset > 0 && !strings.Contains(cmd, "%t") {
				parts = append(parts, "-ss", strconv.Itoa(offset))
			}
		} else {
			s = strings.ReplaceAll(s, "%t", strconv.Itoa(offset))
			s = strings.ReplaceAll(s, "%b", strconv.Itoa(maxBitRate))
			parts = append(parts, s)
		}
	}

	return parts
}

func createProbeCommand(cmd string, inputs []string) []string {
	split := strings.Split(fixCmd(cmd), " ")
	var args []string

	for _, s := range split {
		if s == "%s" {
			for _, inp := range inputs {
				args = append(args, "-i", inp)
			}
		} else {
			args = append(args, s)
		}
	}
	return args
}

func fixCmd(cmd string) string {
	split := strings.Split(cmd, " ")
	var result []string
	cmdPath, _ := ffmpegCmd()
	for _, s := range split {
		if s == "ffmpeg" || s == "ffmpeg.exe" {
			result = append(result, cmdPath)
		} else {
			result = append(result, s)
		}
	}
	return strings.Join(result, " ")
}

func ffmpegCmd() (string, error) {
	ffOnce.Do(func() {
		if conf.Server.FFmpegPath != "" {
			ffmpegPath = conf.Server.FFmpegPath
			ffmpegPath, ffmpegErr = exec.LookPath(ffmpegPath)
		} else {
			ffmpegPath, ffmpegErr = exec.LookPath("ffmpeg")
			if errors.Is(ffmpegErr, exec.ErrDot) {
				log.Trace("ffmpeg found in current folder '.'")
				ffmpegPath, ffmpegErr = exec.LookPath("./ffmpeg")
			}
		}
		if ffmpegErr == nil {
			log.Info("Found ffmpeg", "path", ffmpegPath)
			return
		}
	})
	return ffmpegPath, ffmpegErr
}

var (
	ffOnce     sync.Once
	ffmpegPath string
	ffmpegErr  error
)