# flacconv
flacconv is a 100% POSIX and (hopefully) portable[^1] shell script that recursively converts directories of flac files to opus/mp3.

with no flags, it recursively converts flac files in the specified directory (or directories) to opus with a bitrate of 128k, retaining all metadata and not deleting the original flac files

it also has options for you to change the bitrate, use a variable quality for mp3, keep/remove metadata, and parallel processing

## dependencies
- Some implementation of a shell and [POSIX Utilities](https://pubs.opengroup.org/onlinepubs/9699919799/idx/utilities.html) (usually, this is GNU coreutils, which you probably have)
- `mktemp -u` (again, probably have this already)
- `flac` and `metaflac` (usually bundled together)
- `lame` (only if encoding to mp3)
- `opus-tools` (only if encoding to opus)
- [`opustags`](https://github.com/fmang/opustags) (optional, to use the -e option)
- `curl` (optional, for checking for updates)

## usage
```
usage: flacconv [-huvVipe3] [-b BITRATE] [-l LEVEL] [-k KEYS] [-r KEYS] [-j THREADS] [--] <DIRECTORY...>

flacconv recursively converts directories of flac files to opus/mp3
DIRECTORY can be specified multiple times
IF ENCODING TO MP3, -k AND -r WILL NOT WORK. the only metadata that will be kept is the following:
  TITLE, ARTIST, ALBUM, ALBUMARTIST, DATE, GENRE, TRACKNUMBER, COMMENT, and the cover picture
(blame id3. just use opus)

 -h           show script help
 -u           check for updates
 -v           verbose output (messy with multithreading)
 -V           very verbose output (VERY messy, use only for debugging and with like, -j 1)
 -i           ignore script-stopping warnings
 -d           delete original flac files after transcoding
 -3           switch output filetype to mp3
 -b <BITRATE> output bitrate in kbits (default 128)
              this value is variable for opus & CBR for mp3
 -l <LEVEL>   mp3 only: use specified mp3 variable quality (0-9). integer only
              OVERRIDES -b
 -k <KEYS>    keep specified flac metadata KEYS in output file
              keys can be seen using metaflac --export-tags-to=- file.flac
              argument is a comma or pipe-separated list of keys, case-insensitive
              (i.e. -k "artist,title,albumartist,album,date")
              if both -k and -r are not present, all keys are kept.
 -r <KEYS>    remove specified flac metadata KEYS in output file
              option argument is of the same format as -k
              if set to "ALL" (with capitalization), all keys are removed
 -p           remove embedded picture in output files
 -e           remove the "encoder" tag that automatically gets applied with opusenc
              (requires opustags)
 -j <THREADS> use the specified amount of threads for parallel processing
              if omitted, CPU core count will be used
```

## examples
recursively convert a directory of flacs to opus 128k, removing the picture and ENCODER tags for every file

`flacconv -p -e /path/to/dir`

recursively convert the current directory to mp3 320k

`flacconv -b 320 -3 .`

recursively convert current directory to opus 160k, while removing any COMMENT or DESCRIPTION tags

`flacconv -b 160 -r comment,description .`

recursively convert current directory to mp3 v0, removing all pictures

`flacconv -3 -l 0 -p .`

[^1]: tested with dash, bash, and yash (set -o posixly-correct) on linux. further testing encouraged