28

For a long time I've been using a relative clunky technique which involves Audacity with a LAME plugin. This is fine I guess, but the appeal of the Terminal approach is I can be a little finer grained with my [options] and perhaps use more up-to-date binaries.

Furthermore, my MacBook is ageing a little now and if I can get rid of an unnecessary GUI, all the better.

Thanks in advance.

  • 1
    you will actually get points for doing that ;) – Mortimer Feb 24 '11 at 14:35
  • Haha... I've answered the question but it's saying I can't confirm my answer for two days. Sorry. Still figuring out how things work around here. Awesome site. :D – boehj Feb 24 '11 at 15:15
39

Converting a single file without preserving tags

brew install lame
flac --decode --stdout test.flac | lame --preset extreme - test.mp3
  • --decode --stdout = -dc
  • lame - $outfile = input from STDIN
  • --preset extreme = ~245 kbit/s VBR

A shell script that preserves some ID3 tags

#!/bin/bash

for f in "$@"; do
    [[ "$f" != *.flac ]] && continue
    album="$(metaflac --show-tag=album "$f" | sed 's/[^=]*=//')"
    artist="$(metaflac --show-tag=artist "$f" | sed 's/[^=]*=//')"
    date="$(metaflac --show-tag=date "$f" | sed 's/[^=]*=//')"
    title="$(metaflac --show-tag=title "$f" | sed 's/[^=]*=//')"
    year="$(metaflac --show-tag=date "$f" | sed 's/[^=]*=//')"
    genre="$(metaflac --show-tag=genre "$f" | sed 's/[^=]*=//')"
    tracknumber="$(metaflac --show-tag=tracknumber "$f" | sed 's/[^=]*=//')"

    flac --decode --stdout "$f" | lame --preset extreme --add-id3v2 --tt "$title" --ta "$artist" --tl "$album" --ty "$year" --tn "$tracknumber" --tg "$genre" - "${f%.flac}.mp3"
done

To use the script, just save it somewhere like ~/bin/flac2mp3 and make it executable with chmod +x ~/bin/flac2mp3.

This would convert all flac files in your Music folder:

find ~/Music/ -name '*.flac' -exec ~/bin/flac2mp3 {} \;

Or slightly faster, since it only calls flac2mp3 once:

find ~/Music/ -name '*.flac' -print0 | xargs -0 ~/bin/flac2mp3
  • 2
    You should post the answer here, not a reference to the text in the question. IMHO, you should edit both question and answer and move here the conclusion. – lpacheco Feb 24 '11 at 12:19
  • OK, will do. Sorry. – boehj Feb 24 '11 at 15:20
  • 2
    ${file%.flac}.mp3 is awesome! Previously I was using ${x:: ${#x}-3}m4a in order to change the filename of the song from .wav to .m4a. Awesome to see a way that looks quite a bit easier. – Jason Salaz Mar 28 '11 at 18:03
  • 1
    Looks like there is a bug in a Option 3. Possibly because of lame version, but current code don't tell to lame it should use input stream as input file, and also output file is not specified, since stream is used, it is necessary. For me final code is : !/bin/sh file="$1" outfile=${file%.flac}.mp3 eval $(metaflac --export-tags-to - "$file" | sed "s/=\(.*\)/='\1'/") flac -cd "$file" | lame --preset standard \ --add-id3v2 --tt "$TITLE" --ta "$ARTIST" --tl "$ALBUM" \ --ty "$DATE" --tn "$TRACKNUMBER" --tg "$GENRE" \ - "$outfile" – Mehal Feb 28 '12 at 23:17
  • Also it's nice to create a script which does this 'find' stuff ... – Mehal Feb 28 '12 at 23:21
10

ffmpeg would preserve tags (but not cover art) by default.

for f in *.flac; do ffmpeg -i "$f" -aq 1 "${f%flac}mp3"; done

-aq 1 corresponds to -V 1 in lame. -acodec libfaac would convert the files to AAC:

for f in *.flac; do ffmpeg -i "$f" -acodec libfaac -aq 200 "${f%flac}m4a"; done
  • I just did this and it said: ``` Metadata: comment : Cover (front) encoder : Lavc57.107.100 png ``` macOS finder shows the cover art. ffmpeg 3.4.2 from brew. – Habbie 12 hours ago
  • I then realised my ffmpeg was very old. I upgraded it to 4.1.3 with the same result - mp3 files of the same size, with working cover art. – Habbie 11 hours ago
3

i took what you guys had, but then made it run even faster by using xargs to parallelize the jobs.

find <directory> -name '*.flac' -print0 | xargs -0 -P8 -n1  /usr/local/bin/flac2mp3

Then this is the script from above /usr/local/bin/flac2mp3

#!/usr/bin/env bash

for f in "$@"; do
  [[ "$f" != *.flac ]] && continue
  album="$(metaflac --show-tag=album "$f" | sed 's/[^=]*=//')"
  artist="$(metaflac --show-tag=artist "$f" | sed 's/[^=]*=//')"
  date="$(metaflac --show-tag=date "$f" | sed 's/[^=]*=//')"
  title="$(metaflac --show-tag=title "$f" | sed 's/[^=]*=//')"
  year="$(metaflac --show-tag=date "$f" | sed 's/[^=]*=//')"
  genre="$(metaflac --show-tag=genre "$f" | sed 's/[^=]*=//')"
  tracknumber="$(metaflac --show-tag=tracknumber "$f" | sed 's/[^=]*=//')"

  flac --decode --stdout "$f" \ 
         | lame --preset extreme \
                --add-id3v2 \
                 --tt "$title" \
                 --ta "$artist" \
                 --tl "$album" \
                 --ty "$year" \
                 --tn "$tracknumber" \
                 --tg "$genre" \
                 - "${f%.flac}.mp3"
done

and heres some stats for the performance speedup using parallelism.

find <dirOfFlac24s> -name '*.flac -print0 | xargs -0 -P8 -n1 /usr/local/bin/flac2mp320  

0.00s user 0.00s system 60% cpu 0.002 total
115.94s user 1.40s system 359% cpu 32.655 total

time /usr/local/bin/flac2mp320 <dirOfFlac24s>/*.flac
96.63s user 1.46s system 109% cpu 1:29.98 total

you can see it also utilized my CPUs more effectively, i have an intel i7, so 8 is probably the right number of processes.

2

Found this thread while trying to do direct encoding of MP3s from FLAC source files. Boehj’s answer provides a decent scripting option, but I personally prefer to use FFmpeg, so this is the Bash script I came up with to handle this task. Tested and works great in macOS Sierra (10.12.2).

Perquisites: You should have ffmpeg and lame already installed on your Mac. The easiest way to do this is via Homebrew. First make sure you have Homebrew installed like this:

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

Then run this command to install ffmpeg and lame:

brew install ffmpeg lame

Once that is done you are ready to run this script. This script will look for FLAC files in the directory path/to/FLAC/files but that can be changed to simply be . if the FLAC files are in the same directory you are running this script in. When it runs it will create an mp3/ subdirectory where all of the MP3 files will be placed.

find -E "path/to/FLAC/files" -type f -iregex ".*\.(FLAC)$" |\
  while read full_audio_filepath
  do

    # Break up the full audio filepath stuff into different directory and filename components.
    audio_dirname=$(dirname "${full_audio_filepath}");
    audio_basename=$(basename "${full_audio_filepath}");
    audio_filename="${audio_basename%.*}";
    # audio_extension="${audio_basename##*.}";

    # Set the MP3
    mp3_dirpath="${audio_dirname}/mp3";
    mp3_filepath="${mp3_dirpath}/${audio_filename}.mp3";

    # Create the child MP3 directory.
    mkdir -p "${mp3_dirpath}";

    # Get the track metadata.
    mp3_title=$(ffprobe 2> /dev/null -show_format "${full_audio_filepath}" | grep -i TAG:TITLE= | cut -d '=' -f 2- );
    mp3_artist=$(ffprobe 2> /dev/null -show_format "${full_audio_filepath}" | grep -i TAG:ARTIST= | cut -d '=' -f 2- );
    mp3_album=$(ffprobe 2> /dev/null -show_format "${full_audio_filepath}" | grep -i TAG:ALBUM= | cut -d '=' -f 2- );
    mp3_year=$(ffprobe 2> /dev/null -show_format "${full_audio_filepath}" | grep -i TAG:YEAR= | cut -d '=' -f 2- );
    mp3_track=$(ffprobe 2> /dev/null -show_format "${full_audio_filepath}" | grep -i TAG:TRACK= | cut -d '=' -f 2- | sed 's/^0*//' );
    mp3_tracktotal=$(ffprobe 2> /dev/null -show_format "${full_audio_filepath}" | grep -i TAG:TRACKTOTAL= | cut -d '=' -f 2- | sed 's/^0*//' );
    mp3_genre=$(ffprobe 2> /dev/null -show_format "${full_audio_filepath}" | grep -i TAG:GENRE= | cut -d '=' -f 2- );

    # Where the magic happens.
    ffmpeg -y -v quiet -nostdin -i "${full_audio_filepath}" -ar 44100 -sample_fmt s16 -ac 2 -f s16le -acodec pcm_s16le - | \
      lame --quiet --add-id3v2 --pad-id3v2 --tt "${mp3_title}" --ta "${mp3_artist}" --tl "${mp3_album}" --tn "${mp3_track}"/"${mp3_tracktotal}" --tg "${mp3_genre}" -r -m s --lowpass 19.7 -V 3 --vbr-new -q 0 -b 96 --scale 0.99 --athaa-sensitivity 1 - "${mp3_filepath}";

  done

Some notes on things I learned “The Hard Way™” so others can gain from what I did differently in this script compared to others on the Internet.

  • The grep commands for tag parsing (using FFprobe which is installed with FFmpeg) are case insensitive using the -i option to make it grep -i.
  • The following cut command is now limited to dividing the output only based on the first = in a tag name with the -f 2- option which makes the command cut -d '=' -f 2-. For example, Pavement has a song titled “5-4=Unity” and if only the second chunk were selected via cut that title would have been truncated to “5-4”.
  • For track—and total track—numbers I added an extra pipe to sed which gets rid of leading zeros: sed 's/^0*//'.
  • In similar scripts around the Internet, the FFmpeg output is something like -f wav and that would actually compress the FFmpeg output which makes no sense in a pipe setup where LAME is going to re-encode it. Instead the output here is set to -f s16le -acodec pcm_s16le which is basically RAW output; perfect for piping audio to another process like this.
  • To deal with RAW output on the LAME side of the pipe, I had to add the -r option.
  • Also note the --tt, --ta, --tl, --tn and --tg ID3v2 tag options for LAME. When audio is streamed/piped from one process into LAME the the metadata from the source file is lost. One suggested option is to get FFmpeg to save the metadata to a text file by setting the option with -f ffmetadata "[metadata filename here]" and then running FFmpeg again with the something like this: -i "[metadata filename here]" -map_metadata 1 -c:a copy [destination mp3 file] id3v2_version 3 -write_id3v1 1. That works, but note the requirement for a destination file. Seems like FFmpeg only imports metadata when it can copy the file which seems like a very wasteful process. Using FFprobe to get values and then setting them in LAME with --tt, --ta, --tl, --tn and --tg options works better; all the metadata is written in place so duplicate file needs to be generated.

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