Get metadata and stream info from a flac audio file

get_flac_info.go

package main

import (
	"flag"
	"fmt"
	"log"
	"os"

	"github.com/mewkiz/flac"
	"github.com/mewkiz/flac/meta"
)

// go run get_flac_info.go "/home/guenther/Downloads/[2010] Odd Blood/04 - i remember.flac"
// go run get_flac_info.go "/home/guenther/Downloads/05 - holiday in cambodia (live).flac"

var typeName = map[meta.Type]string{
	meta.TypeVorbisComment: "VORBIS_COMMENT",
}

func main() {
	flag.Parse()
	if flag.NArg() < 1 {
		fmt.Fprintln(os.Stderr, "Exiting, no path(s) supplied")
		os.Exit(1)
	}
	for _, path := range flag.Args() {
		err := list(path)
		if err != nil {
			log.Fatalln(err)
		}
	}
}

func list(path string) error {
	// Open FLAC stream.
	stream, err := flac.ParseFile(path)
	if err != nil {
		return err
	}

	// Get general file info
	// File owner and file creation date are non-cross-platform (but possible)
	// https://stackoverflow.com/questions/20875336/how-can-i-get-a-files-ctime-atime-mtime-and-change-them-using-golang
	fi, err := os.Stat(path)
	if err != nil {
		return err
	}

	listStreamInfo(stream.Info, fi)
	fmt.Printf("---\n")
	listComments(stream.Blocks)

	return nil
}

// listComments prints selected metadata tags present in the flac file
func listComments(bs []*meta.Block) {
	vc := getVorbisComment(bs, false)

	fmt.Printf("album           : %s\n", getTag("ALBUM", vc))
	fmt.Printf("album artist    : %s\n", getTag("ALBUMARTIST", vc))
	fmt.Printf("artist          : %s\n", getTag("ARTIST", vc))
	fmt.Printf("date            : %s\n", getTag("DATE", vc))
	fmt.Printf("discnumber      : %s\n", getTag("DISCNUMBER", vc))
	fmt.Printf("disctotal       : %s\n", getTag("DISCTOTAL", vc))
	fmt.Printf("genre           : %s\n", getTag("GENRE", vc))
	fmt.Printf("title           : %s\n", getTag("TITLE", vc))
	fmt.Printf("tracknumber     : %s\n", getTag("TRACKNUMBER", vc))
	fmt.Printf("totaltracks     : %s\n", getTag("TOTALTRACKS", vc))
}

// getVorbisComment iterates through all the blocks, and returns the one containing the vorbis comment
func getVorbisComment(bs []*meta.Block, print bool) *meta.VorbisComment {
	for _, block := range bs {
		switch body := block.Body.(type) {
		case *meta.VorbisComment:
			if print {
				for _, tag := range body.Tags {
					fmt.Printf(" %s=%s\n", tag[0], tag[1])
				}
			}
			return body
		}
	}
	return nil
}

// getTag iterates through all the tags in a vorbis comment, and returns the specified one
func getTag(t string, vc *meta.VorbisComment) string {
	for _, tag := range vc.Tags {
		if tag[0] == t {
			return tag[1]
		}
	}
	return ""
}

// listStreamInfo prints technical info about the flac file
func listStreamInfo(si *meta.StreamInfo, fi os.FileInfo) {
	fileSize := fi.Size()
	runTime := si.NSamples / uint64(si.SampleRate)
	bitRate := fileSize / 125 / int64(runTime)

	fmt.Printf("file size       : %d bytes\n", fileSize)
	fmt.Printf("file name       : %s\n", fi.Name())
	fmt.Printf("file mode       : %s\n", fi.Mode())
	fmt.Printf("file mod time   : %s\n", fi.ModTime())
	fmt.Printf("run time        : %d seconds\n", runTime)
	fmt.Printf("bit rate        : %d kbps\n", bitRate)
	fmt.Printf("min blocksize   : %d samples\n", si.BlockSizeMin)
	fmt.Printf("max blocksize   : %d samples\n", si.BlockSizeMax)
	fmt.Printf("min framesize   : %d bytes\n", si.FrameSizeMin)
	fmt.Printf("max framesize   : %d bytes\n", si.FrameSizeMax)
	fmt.Printf("sample rate     : %d Hz\n", si.SampleRate)
	fmt.Printf("channels        : %d\n", si.NChannels)
	fmt.Printf("bits per sample : %d\n", si.BitsPerSample)
	fmt.Printf("total samples   : %d\n", si.NSamples)
	fmt.Printf("MD5             : %x\n", si.MD5sum)
}