thumbnail/video.go

package thumbnail

import (
	"bytes"
	"fmt"
	"io"
	"os/exec"
)

func (this *Thumbnailer) RenderScaledFfmpeg(absPath string) ([]byte, error) {

	scaleCmd := fmt.Sprintf(
		`thumbnail,scale='if(gt(a,%d/%d),%d,-1)':'if(gt(a,%d/%d),-1,%d)'`,
		this.height, this.width, this.height,
		this.height, this.width, this.width,
	)

	// BUG(): always produces ASPECT_SVELTE shape - need to re-pad for ASPECT_PADDED

	var vcodec string
	switch this.ofmt {
	case OUTPUT_JPG:
		vcodec = "mjpeg" // yes really
	case OUTPUT_PNG_CRUSH:
		vcodec = "png"
	default:
		return nil, ErrInvalidOption
	}

	cmd := exec.Command(
		"ffmpeg",
		"-loglevel", "0",
		"-an",
		"-i", absPath,
		"-vf", scaleCmd,
		"-frames:v", "1",
		"-f", "image2pipe",
		"-c:v", vcodec,
		"-",
	)

	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return nil, err
	}

	err = cmd.Start()
	if err != nil {
		return nil, err
	}

	out := bytes.Buffer{}
	_, err = io.Copy(&out, stdout)
	if err != nil {
		return nil, err
	}

	err = cmd.Wait()
	if err != nil {
		return nil, err
	}

	return out.Bytes(), nil
}