ffmpeg split & convert

split.go

package ffmpeg

import (
	"fmt"
	"os"
	"regexp"
	"strings"

	"github.com/gofrs/uuid"
)

// SplitFile splits file into parts
func SplitFile(filename string, splitBy float64, treshold float64) ([]string, error) {
	format, err := GetFileFormat(filename)
	if err != nil {
		return nil, err
	}

	// Generate split points

	points := splitPoints(format.StartTime, format.Duration, splitBy, treshold)
	if len(points) == 0 {
		// skip splitting by using 1 point greater than duration
		points = append(points, format.Duration+1)
	}
	segments := strings.Trim(strings.Replace(fmt.Sprint(points), " ", ",", -1), "[]")

	// Split file

	outputFile := fmt.Sprintf("%s%s-%%04d.mp4", os.TempDir(), uuid.Must(uuid.NewV4()))
	_, stderr, err := execCmd(
		ffmpeg,
		"-v", "info", // log level
		"-y",           // overwrite files
		"-i", filename, // input filename
		"-f", "segment", "-segment_times", segments, // split points
		"-c:a", "aac", // codec
		"-b:a", "64k", // bitrate
		"-ar", "48000", // sample
		"-map", "0:0", // TODO: map only audio streams from input to output
		"-reset_timestamps", "1", // set start time of every chunk to 0
		"-movflags", "+faststart", // move meta to the beginning
		outputFile, // output file format
	)
	if err != nil {
		if len(stderr) > 0 {
			return nil, fmt.Errorf("ffmpeg: %s", stderr)
		}
		return nil, fmt.Errorf("ffmpeg: %s", err)
	}

	// Collect filenames from output
	matches := splitOutput.FindAllStringSubmatch(string(stderr), -1)

	files := []string{}
	for _, m := range matches {
		files = append(files, m[1])
	}

	if len(files) == 0 {
		return nil, fmt.Errorf("Not output files")
	}

	return files, nil
}

func splitPoints(start float64, stop float64, length float64, treshold float64) (points []float64) {
	for {
		if stop-start <= length+treshold {
			return
		}
		start += length
		points = append(points, start)
	}
}

var splitOutput = regexp.MustCompile("Opening '([^']+)' for writing")