VBR in path_formats / queries / inline plugin

[JOJ0]

Is it possible to find out whether an MP3 file is VBR-encoded? I'd like to extend an inline plugin item_field to also return 1 if the MP3 file was encoded with VBR:

item_fields:
    ...
    ...
    quality: |
        if format == 'FLAC':
            return 1
        else:
            if bitrate > 200000:
                return 1
        return 0

I tried the encoder var already but that often does not contain anything.

I'm also up for any other ideas to find out whether the files are of a certain quality.

[JOJ0]

Using mutagen-inspect, I find this information in my files:

- MPEG 1 layer 3, 170297 bps (VBR, LAME 3.93.0+, --preset standard), 44100 Hz, 2 chn, 312.91 seconds (audio/mp3)

Is it possible to access the information in the first brackets (...) from beets?

[JOJ0]

I just found out that I can access a field called bitrate_mode that contains the VBR information:

$ beet info -i bitrate_mode united future good luck
/remote/data/music-library/DowntempoTriphopDubAcidjazz/United Future Organization - 1999 -  Bon Voyage/01 - United Future Organization - Bon Voyage - Good Luck Shore (1999).mp3
bitrate_mode: VBR

Unfortunately my extended inline plugin function does not work. Why?

    quality: |
        if format == 'FLAC':
            return 1
        elif bitrate > 255000:
            return 1
        elif 'VBR' in bitrate_mode:
            return 1
        return 0

I also tried to access this field with beet ls, but no luck:

$ ls -f '$bitrate_mode' united future good luck

$

It looks like the field is empty. If the variablename would be wrong the result would look like this:

$ beet ls -f '$bitratemode' united future good luck 
$ $bitratemode

Why? Any hints? Or bug? Or missing feature?

Cheers in advance!

[JOJ0]

Found a partly solution but not the root cause:

The bitrate_mode field often is empty in my collection (Total in lib about 2500):

$ beet ls bitrate_mode::'^$' format:mp3 | wc -l
1527

Trying to update from the files into the beets db:

beet update -F bitrate_mode bitrate_mode::'^$' format:mp3

results in: some files contain the information and beets lib is updated:

...
Rockers Hi‐Fi - Rockers to Rockers - 08 - Look for a Spark (1995/GB) [524 102-2]  f:MP3-119k a:02-12/MusicBrainz |Dub, Ska, Reggae, Downtempo
  bitrate_mode:  -> VBR
Asian Dub Foundation - Rafi’s Revenge - 01 - Naxalite (1998/GB) [FFRR / 556 006-2]  f:MP3-225k a:02-06/MusicBrainz |Dub, Ska, Reggae
  bitrate_mode:  -> VBR
Asian Dub Foundation - Rafi’s Revenge - 02 - Buzzin’ (1998/GB) [FFRR / 556 006-2]  f:MP3-251k a:02-06/MusicBrainz |Dub, Ska, Reggae
  bitrate_mode:  -> VBR
Asian Dub Foundation - Rafi’s Revenge - 03 - Black White (1998/GB) [FFRR / 556 006-2]  f:MP3-228k a:02-06/MusicBrainz |Dub, Ska, Reggae
  bitrate_mode:  -> VBR
...

Some files don't seem to contain the information and bitrate_mode stays empty.

It's unclear why those files that contain it, haven't been updated on beets import. Not sure if this is of interest to anyone but if it is: Could this be a bug? Or is there certain situation when it is expected behaviour that bitrate_mode is not written to the lib/database on import?

After beet update run was through only a few bitrate_mode fields could be filled (~50):

$ beet ls bitrate_mode::'^$' format:mp3 | wc -l             
1466

[RollingStar]

I've seen people use the heuristic of "is the bitrate 160, 192, 256, 128" etc. kbps and if not, assume VBR.

[JOJ0]

Thanks for this nice suggestion @RollingStar

For now I came to the conclusion, well rather an assumption that CBR or VBR information might have been written by encoders already, and I suppose writing CBR is not always done, but VBR is written, since is "something special" an encoder might want to mention. Could be bollocks but for now seems to work out :-)

FWIW, these are my current inline fields:

    quality: |
        # print(dir(bitrate_mode))
        # print(bitrate_mode)
        if format == 'FLAC':
            return 1
        elif bitrate >= 193000:
            return 1
        elif bitrate_mode == 'VBR':
            return 1
        return 0
    fmt_format: |
        f = 'f:'
        f += f'{format}'
        if format == 'MP3':
            f+= '-' + str(bitrate)[:3] + 'k'
        f += 'VBR' if bitrate_mode == 'VBR' else ''
        f += 'CBR' if bitrate_mode == 'CBR' else ''
        return f