Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/mrkkrp/htaglib

Haskell bindings for TagLib, an audio meta-data library
https://github.com/mrkkrp/htaglib

bindings haskell taglib

Last synced: 13 days ago
JSON representation

Haskell bindings for TagLib, an audio meta-data library

Awesome Lists containing this project

README 

        
# HTagLib



[![License BSD3](https://img.shields.io/badge/license-BSD3-brightgreen.svg)](http://opensource.org/licenses/BSD-3-Clause)

[![Hackage](https://img.shields.io/hackage/v/htaglib.svg?style=flat)](https://hackage.haskell.org/package/htaglib)

[![Stackage Nightly](http://stackage.org/package/htaglib/badge/nightly)](http://stackage.org/nightly/package/htaglib)

[![Stackage LTS](http://stackage.org/package/htaglib/badge/lts)](http://stackage.org/lts/package/htaglib)

![CI](https://github.com/mrkkrp/htaglib/workflows/CI/badge.svg?branch=master)



* [Alternatives](#alternatives)

* [A note for FLAC users](#a-note-for-flac-users)

* [Quick start](#quick-start)

    * [Reading meta data](#reading-meta-data)

    * [Writing meta data](#writing-meta-data)

    * [Conclusion](#conclusion)

* [License](#license)



This is Haskell bindings to [TagLib](https://taglib.github.io/), a library

for reading and editing meta-data of several popular audio formats.



It works with the following formats:



* MP3

* FLAC

* MPC

* Speex

* WavPack TrueAudio

* WAV

* AIFF

* MP4

* ASF



This happens in an abstract, uniform way, so you don't need to handle any

low-level details. As a consequence, it's currently not possible to work

with format-specific functionality.



## Alternatives



There is at least two other Haskell bindings to TagLib:



* [`libtagc`](https://hackage.haskell.org/package/libtagc)

* [`taglib`](https://hackage.haskell.org/package/taglib)



Both are low level, without any type safety or higher-level abstractions.



## A note for FLAC users



If you want to work with FLAC, there is a [complete Haskell

binding](https://github.com/mrkkrp/flac) to `libFLAC`—the reference FLAC

implementation. It allows us to work with all FLAC metadata (read and write)

and also provides a Haskell API to the stream encoder and the stream

decoder. Please prefer that package if you don't need to work with other

audio formats.



## Quick start



First, since this is bindings to C-interface of the library, you'll need to

install the library itself. If you're on a Unix-like system, chances are

you'll have it in the official repositories of your distro.



### Reading meta data



Now to the hacking. It's recommended that you define a record representing

meta-data of audio track in your program, like this:



```haskell

module Main (main) where



import Data.Monoid

import Sound.HTagLib

import System.Environment (getArgs)



data AudioTrack = AudioTrack

  { atTitle :: Title,

    atArtist :: Artist,

    atAlbum :: Album,

    atComment :: Comment,

    atGenre :: Genre,

    atYear :: Maybe Year,

    atTrack :: Maybe TrackNumber

  }

  deriving (Show)

```



We use unique types for every component of meta data, so it's more difficult

to use a track title instead of a track artist, for example. String meta

data types have smart constructors, but `Title`, `Artist`, `Album`,

`Comment`, and `Genre` all are instances of `IsString`, so it is enough to

turn on the `OverloadedStrings` language extension to use normal string

literals to create values of these types.



`Year` and `TrackNumber` may be not set or missing, in this case you get

`Nothing`. This is possible with string-based fields too, but in that case

you just get empty strings. `Year` and `TrackNumber` have smart constructors

that make sure that the values are positive (i.e. zero is not allowed).



OK, it's time to read some info. There is `TagGetter` type which is an

applicative functor. You first construct `TagGetter` which will retrieve

entire `AudioTrack` for you using the applicative style:



```haskell

audioTrackGetter :: TagGetter AudioTrack

audioTrackGetter =

  AudioTrack

    <$> titleGetter

    <*> artistGetter

    <*> albumGetter

    <*> commentGetter

    <*> genreGetter

    <*> yearGetter

    <*> trackNumberGetter

```



Perfect, now use `getTags` to read the entire record:



```haskell

main :: IO ()

main = do

  path <- head <$> getArgs

  track <- getTags path audioTrackGetter

  print track

```



For example (alignment is added):



```

$ ./example "/home/mark/music/David Bowie/1977, Low/01 Speed of Life.flac"

AudioTrack

  { atTitle = Title "Speed of Life",

    atArtist = Artist "David Bowie",

    atAlbum = Album "Low",

    atComment = Comment "",

    atGenre = Genre "",

    atYear = Just (Year 1977),

    atTrack = Just (TrackNumber 1)

  }

```



Success! It's also possible to extract audio properties like sample rate,

etc. but it's not shown here for simplicity, consult Haddocks for more

information.



N.B. If you need to extract the duration, TagLib only returns the number of

seconds as an integer. This means that if you want to calculate the total

duration of an album, you'll get a slightly incorrect result. The right

solution is to extract the duration as floating-point number, for that we

recommend the bindings to

`libsndfile`—[`hsndfile`](https://hackage.haskell.org/package/hsndfile) (or

the above-mentioned `flac` package for Haskell if you work with FLAC).



### Writing meta data



`TagSetter` is an instance of `Monoid`. This means that we can set title and

artist of audio track like this:



```haskell

main :: IO ()

main = do

  (path : title : artist : _) <- getArgs

  setTags path Nothing $

    titleSetter (mkTitle title)

      <> artistSetter (mkArtist artist)

  track <- getTags path audioTrackGetter

  print track

```



This code loads a file and changes the “title” and “artist” meta data

fields.



## Contribution



Issues, bugs, and questions may be reported in [the GitHub issue tracker for

this project](https://github.com/mrkkrp/htaglib/issues).



Pull requests are also welcome.



## License



Copyright © 2015–present Mark Karpov



Distributed under BSD 3 clause license.