lofty-rs/README.md

# audiotags

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This crate makes it easier to parse tags/metadata in audio files of different file types.

This crate aims to provide a unified trait for parsers and writers of different audio file formats. This means that you can parse tags in mp3 and m4a files with a single function: `audiotags::from_path()` and get fields by directly calling `.album()`, `.artist()` on its result. Without this crate, you would otherwise need to learn different APIs in **id3**, **mp4ameta** etc. in order to parse metadata in different file formats.

## Example

(Due to copyright restrictions I cannot upload the actual audio files here)

```rust
use audiotags::Tag;
fn main() {
    const MP3: &'static str = "a.mp3";
    let mut tags = Tag::default().read_from_path(MP3).unwrap();
    // without this crate you would call id3::Tag::read_from_path()
    println!("Title: {:?}", tags.title());
    println!("Artist: {:?}", tags.artist());
    tags.set_album_artist("CINDERELLA PROJECT");
    let album = tags.album().unwrap();
    println!("Album title and artist: {:?}", (album.title, album.artist));
    println!("Track: {:?}", tags.track());
    tags.write_to_path(MP3).unwrap();
    // Title: Some("お願い！シンデレラ")
    // Artist: Some("高垣楓、城ヶ崎美嘉、小日向美穂、十時愛梨、川島瑞樹、日野茜、輿水幸子、佐久間まゆ、白坂小梅")
    // Album title and artist: ("THE IDOLM@STER CINDERELLA GIRLS ANIMATION PROJECT 01 Star!!", Some("CINDERELLA PROJECT"))
    // Track: (Some(2), Some(4))
    const M4A: &'static str = "b.m4a";
    let mut tags = Tag::default().read_from_path(M4A).unwrap();
    // without this crate you would call mp4ameta::Tag::read_from_path()
    println!("Title: {:?}", tags.title());
    println!("Artist: {:?}", tags.artist());
    let album = tags.album().unwrap();
    println!("Album title and artist: {:?}", (album.title, album.artist));
    tags.set_total_tracks(4);
    println!("Track: {:?}", tags.track());
    tags.write_to_path(M4A).unwrap();
    // Title: Some("ふわふわ時間")
    // Artist: Some("桜高軽音部 [平沢唯・秋山澪・田井中律・琴吹紬(CV:豊崎愛生、日笠陽子、佐藤聡美、寿美菜子)]")
    // Album title and artist: ("ふわふわ時間", Some("桜高軽音部 [平沢唯・秋山澪・田井中律・琴吹紬(CV:豊崎愛生、日笠陽子、佐藤聡美、寿美菜子)]"))
    // Track: (Some(1), Some(4))
    const FLAC: &'static str = "c.flac";
    let mut tags = Tag::default().read_from_path(FLAC).unwrap();
    // without this crate you would call metaflac::Tag::read_from_path()
    println!("Title: {:?}", tags.title());
    println!("Artist: {:?}", tags.artist());
    let album = tags.album().unwrap();
    println!("Album title and artist: {:?}", (album.title, album.artist));
    tags.set_year(2017);
    println!("Year: {:?}", tags.year());
    tags.write_to_path(FLAC).unwrap();
    // Title: Some("意味/無/ジュニーク・ニコール")
    // Artist: Some("岡部啓一")
    // Album title and artist: ("NieR:Automata Original Soundtrack", Some("SQUARE ENIX"))
    // Year: Some(2017)
}
```

You can convert between different tag types:

```rust
use audiotags::{convert, AudioTagIo, Mp4Tag, Tag, TagType};

fn main() {
    // we have an mp3 and an m4a file
    const MP3_FILE: &'static str = "assets/a.mp3";
    const M4A_FILE: &'static str = "assets/a.m4a";
    // read tag from the mp3 file. Using `default()` so that the type of tag is guessed from the file extension
    let mut mp3tag = Tag::default().read_from_path(MP3_FILE).unwrap();
    // set the title
    mp3tag.set_title("title from mp3 file");
    // we can convert it to an mp4 tag and save it to an m4a file.
    let mut mp4tag = convert_tag!(mp3tag, Mp4Tag);
    mp4tag.write_to_path(M4A_FILE).unwrap();

    // reload the tag from the m4a file; this time specifying the tag type (you can also use `default()`)
    let mp4tag_reload = Tag::with_tag_type(TagType::Mp4)
        .read_from_path(M4A_FILE)
        .unwrap();
    // the tag originated from an mp3 file is successfully written to an m4a file!
    assert_eq!(mp4tag_reload.title(), Some("title from mp3 file"));
}
```

## Supported Formats

| File Fomat    | Metadata Format       | backend                                                     |
| ------------- | --------------------- | ----------------------------------------------------------- |
| `mp3`         | id3v2.4               | [**id3**](https://github.com/polyfloyd/rust-id3)            |
| `m4a/mp4/...` | MPEG-4 audio metadata | [**mp4ameta**](https://github.com/Saecki/rust-mp4ameta)     |
| `flac`        | Vorbis comment        | [**metaflac**](https://github.com/jameshurst/rust-metaflac) |

## Supported Methods

```rust
pub trait AudioTagIo {
    fn title(&self) -> Option<&str>;
    fn set_title(&mut self, title: &str);
    fn remove_title(&mut self);
    fn artist(&self) -> Option<&str>;
    fn remove_artist(&mut self);
    fn set_artist(&mut self, artist: &str);
    fn year(&self) -> Option<i32>;
    fn set_year(&mut self, year: i32);
    fn remove_year(&mut self);
    fn album(&self) -> Option<Album> {
        self.album_title().map(|title| Album {
            title: title.to_owned(),
            artist: self.album_artist().map(|x| x.to_owned()),
            cover: self.album_cover(),
        })
    }
    fn remove_album(&mut self) {
        self.remove_album_title();
        self.remove_album_artist();
        self.remove_album_cover();
    }
    fn album_title(&self) -> Option<&str>;
    fn remove_album_title(&mut self);
    fn album_artist(&self) -> Option<&str>;
    fn remove_album_artist(&mut self);
    fn album_cover(&self) -> Option<Picture>;
    fn remove_album_cover(&mut self);
    fn set_album(&mut self, album: Album) {
        self.set_album_title(&album.title);
        if let Some(artist) = album.artist {
            self.set_album_artist(&artist)
        } else {
            self.remove_album_artist()
        }
        if let Some(pic) = album.cover {
            self.set_album_cover(pic)
        } else {
            self.remove_album_cover()
        }
    }
    fn set_album_title(&mut self, v: &str);
    fn set_album_artist(&mut self, v: &str);
    fn set_album_cover(&mut self, cover: Picture);
    fn track(&self) -> (Option<u16>, Option<u16>) {
        (self.track_number(), self.total_tracks())
    }
    fn set_track(&mut self, track: (u16, u16)) {
        self.set_track_number(track.0);
        self.set_total_tracks(track.1);
    }
    fn remove_track(&mut self) {
        self.remove_track_number();
        self.remove_total_tracks();
    }
    fn track_number(&self) -> Option<u16>;
    fn set_track_number(&mut self, track_number: u16);
    fn remove_track_number(&mut self);
    fn total_tracks(&self) -> Option<u16>;
    fn set_total_tracks(&mut self, total_track: u16);
    fn remove_total_tracks(&mut self);
    fn disc(&self) -> (Option<u16>, Option<u16>) {
        (self.disc_number(), self.total_discs())
    }
    fn set_disc(&mut self, disc: (u16, u16)) {
        self.set_disc_number(disc.0);
        self.set_total_discs(disc.1);
    }
    fn remove_disc(&mut self) {
        self.remove_disc_number();
        self.remove_total_discs();
    }
    fn disc_number(&self) -> Option<u16>;
    fn set_disc_number(&mut self, disc_number: u16);
    fn remove_disc_number(&mut self);
    fn total_discs(&self) -> Option<u16>;
    fn set_total_discs(&mut self, total_discs: u16);
    fn remove_total_discs(&mut self);
    fn write_to(&mut self, file: &mut File) -> Result<(), BoxedError>;
    // cannot use impl AsRef<Path>
    fn write_to_path(&mut self, path: &str) -> Result<(), BoxedError>;
}
```