Looks like bpm operator is broken

[rrolla]

Describe the bug
BPM operator https://www.liquidsoap.info/doc-2.1.3/reference.html#bpm always return 0., looks like with some version upgrade this is broken

To Reproduce

musicSource = playlist(id="musicSource", "/mnt/test/bpm")

musicSourceBpm = bpm(id="bpm", musicSource)

def detectBpm()
    metadata = musicSource.last_metadata() ?? []
    title = "#{metadata['artist']} - #{metadata['title']}"
    bpm = musicSourceBpm.bpm()
    bpmWithTitle = "BPM: #{string_of(int_of_float(bpm))} #{title}"
    print(bpmWithTitle)
end

def startDetectBpm()
    thread.run(delay=20.0, (fun() -> begin detectBpm() {} end))
end

def onMetadataHandler(metadata)
    startDetectBpm()
end

musicSource.on_metadata(onMetadataHandler)

returns

BPM: 0 Dj Gollum × Empyre One - Supernova (Original Mix)

Expected behavior
after calling detectBpm it should return BPM instead of 0

Version details

• OS: Debian
• Version 2.1.3

Also checked plugins on liquidsoap installation, looks ok:

liquidsoap --list-plugins | grep bpm
 + bpm
  Detect the BPM (number of beats per minute). The returned source has a method `bpm`, which can be called to compute it.
   + bpm
 ?bpm : float?, ?ms : int?, ?hz : float?,
   set timing. (default: 2, possible values: 0 (bpm), 1 (ms), 2 (hz))
  + bpm
 ?bpm : float?, ?ms : int?, ?hz : float?,
   set timing. (default: 2, possible values: 0 (bpm), 1 (ms), 2 (hz))
  + bpm
liquidsoap --list-plugins | grep soundtouch
 + soundtouch

Install method
Via deb package 2.1.3-debian-bullseye-1_amd64.deb

Other issue
If I call bpm directly on musicSource instead add to new variable musicSourceBpm
eg

musicSourceBpm = bpm(id="bpm", musicSource)
# instead musicSourceBpm = bpm(id="bpm", musicSource)

the metadata is stripped out from musicSource

[toots]

Hi,

Is the source connected to an output? You need to be actively pulling data from it to generate stats. At the very lease you should add:

output.dummy(musicSourceBpm)

I just confirmed that the operator is at least working on main and added a regression test for it. Please re-open if you still see an issue in your own version with an output added.

[rrolla]

Hi,

Is the source connected to an output? You need to be actively pulling data from it to generate stats. At the very lease you should add:

output.dummy(musicSourceBpm)

I just confirmed that the operator is at least working on main and added a regression test for it. Please re-open if you still see an issue in your own version with an output added.

Hey @toots yes that source is connected to output, glad that you added tests, so you will suggest to try on Rolling Release 2.1.x?

[toots]

Confirmed also working on 2.1.x. The reported BPM is 60., which is what the metronome source is set to.

[toots]

Could be that the BPM algorithm is failing on your content, tho. It will for instance report 0. on a sine waveform or noise source.