mp3-duration | Replaced usage of failure with thiserror for error

mp3 files comes (optionnaly) with metadata called "ID3 tags" :

ID3 is a de facto standard for metadata in MP3 files

• The ID3v1 tag occupies 128 bytes, beginning with the string TAG 128 bytes from the end of the file.
  
• The Enhanced tag is 227 bytes long, and placed before the ID3v1 tag.

The enhanced tag contains the start-time and end-time fields as the last 6 + 6 bytes of the tag formated like mmm:ss. So it gives you the duration of the song.

The solution would be to download the 355 last bytes of the file and check if the enhanced tag (TAG+) is present, then look for the last 12 bytes of the enhanced tag.

Nowdays, we're mostly using ID3v2 which allows us to embed up to 256MB of informations :

ID3v2 tag is composed of frames. Each frame represents an information. Max frame size is 16MB. Max tag size is 256MB.

The frame you're interested in is the TLEN frame, which represent the length of the song.

But there is no guarantee that any mp3 file will have an ID3v2 tag or that the TLEN frame will be stored in its ID3v2 tag.

/!\ /!\ /!\
If the mp3 file does not contains metadata, the only solution is the one you already came up with : estimating the duration with the mp3-duration module.

If the server accepts Range Request, then we just have to tell him the bytes we want !

ID3v1