MP3 tags missing song duration metadata (TLEN)

[davidgrisham]

I've been using Beets for a long time and am now building my own music player, so I'm getting into parsing my library that has been entirely tagged with Beets. When parsing the id3v2.4 tags from my MP3 files, I'm noticing that there's no TLEN field specifying the duration of the song. I was able to parse the duration from my M4A files via the mvhd atom, and was surprised to find no such information in the MP3 files.

I've seen that, in cases where this information isn't in the metadata, the best way to get the duration of a song in an MP3 file is to parse the entire file. I'd really like to avoid this - is there a way to have Beets write the TLEN field? The only indication I've seen that this did happen at some point was here: #3815

Here's a sample song:

$ mid3v2 -l /home/grish/media/music/library/danny_brown/2023_11-quaranta/1_01-quaranta.mp3
IDv2 tag info for /home/grish/media/music/library/danny_brown/2023_11-quaranta/1_01-quaranta.mp3
APIC=cover front,  (image/png, 10923822 bytes)
TALB=Quaranta
TBPM=0
TCMP=0
TCOM=Daniel Dewan Sewell
TCON=Rap
TDOR=2023-11-17
TDRC=2023-11-17
TIPL=[unrepresentable data]
TIT2=Quaranta
TLAN=eng
TMED=CD
TPE1=Danny Brown
TPE2=Danny Brown
TPOS=1/1
TPUB=Warp
TRCK=1/11
TSOP=Brown, Danny
TSRC=GBBPW2300140
TXXX=ALBUMARTISTSORT=Brown, Danny
TXXX=Album Artist Credit=Danny Brown
TXXX=Artist Credit=Danny Brown
TXXX=CATALOGNUMBER=WARPCD328
TXXX=MusicBrainz Album Artist Id=960afc67-9c21-46dd-9c7f-ff2b509e3150
TXXX=MusicBrainz Album Id=534cddc0-781d-4f56-b61b-08dc62a4a0ea
TXXX=MusicBrainz Album Release Country=GB
TXXX=MusicBrainz Album Status=Official
TXXX=MusicBrainz Album Type=a / l / b / u / m
TXXX=MusicBrainz Artist Id=960afc67-9c21-46dd-9c7f-ff2b509e3150
TXXX=MusicBrainz Release Group Id=6d016b33-9434-4aad-ae31-ec24ad13c845
TXXX=MusicBrainz Release Track Id=204e32b8-2827-49a9-abbd-7540c93a6f13
TXXX=Script=Latn
UFID=http://musicbrainz.org=b'0a8e2d56-b236-4f32-b26d-97c533b03689'
USLT==XXX=

And my beets config:

library       : /home/grish/.config/beets/library.blb
directory     : /home/grish/media/music/library
original_date : yes

import:
    write              : yes
    copy               : no
    move               : yes
    incremental        : no
    timid              : no
    detail             : yes
    per_disc_numbering : yes
    asciify_paths      : yes
    threaded           : yes
    # duplicate_action   : remove

ui:
    color : yes
    colors:
        action: cyan

match:
    ignored  : missing_tracks unmatched_tracks
    preferred:
        media         : ['CD', 'Digital Media|File']
        # original_year : yes
        #countries     : ['US', 'GB|UK']

item_fields:
# artist_custom: u'{}'.format(albumartist.lower())
    album_custom: |
        prefix = u'0' if month < 10 else u''
        smart_month = u'' if (month == '00') else u'_{p}{m}'.format(p=prefix, m=month)
        return u'{y}{m}-{al}'.format(y=year, m=smart_month, al=album.lower())
    track_custom: |
        prefix = u'0' if track < 10 else u''
        smart_track = u'{p}{tr}'.format(p=prefix, tr=track)
        return u'{d}_{tr}-{ti}'.format(d=disc, tr=smart_track, ti=title.lower())

paths:
    default              : %lower{$albumartist}/$album_custom/$track_custom
    singleton            : %lower{$albumartist}/$album_custom/$track_custom
    comp                 : etc/compilations/$album_custom/$track_custom
    albumtype:soundtrack : etc/soundtracks/$album_custom/$track_custom

replace:
    '[\\/]'               : '_'
    '^\.'                 : '_'
    'ñ'                   : 'n'
    '[\x00-\x1f]'         : '_'
    '[<>:"\*\|]'          : '_'
    '[\[\]()&,…\?¿’‘“”≤]' : ''
    '[潘•]'               : ''
    '[‐–‒]'               : '-'
    '[öóðø]'              : 'o'
    '[áåàâä]'             : 'a'
    'ü'                   : 'u'
    '[íï]'                : 'i'
    '[éèê]'               : 'e'
    '[ýÿ]'                : 'y'
    'æ'                   : 'ae'
    '\$'                  : 's'
    '\.$'                 : ''
    '\s+$'                : ''
    "['’!.]"              : ''
    '^\s+'                : ''
    '[\s_]{2,}'           : '_'
    '\s'                  : '_'

plugins: inline fetchart scrub lastgenre ftintitle play info edit web ipfs embedart
fetchart:
    minwidth: 600
    sources: coverart itunes amazon albumart google wikipedia
ftintitle:
    format: (feat. {0})