[Bug 751457] bpmdetect: it's just crazy

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=751457

Dustin Spicuzza <dustin at virtualroadside.com> changed:

           What    |Removed                     |Added
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                 CC|                            |dustin at virtualroadside.com

--- Comment #5 from Dustin Spicuzza <dustin at virtualroadside.com> ---
I just implemented something to use the bpmdetect plugin in python:

https://gist.github.com/virtuald/c30032a5b8cdacd1a6c0

For a given file, I get the following output:

BPM: [30.310665130615234, 101.57039642333984, 50.529014587402344,
34.0688591003418, 50.531585693359375, 30.80596160888672, 32.05588912963867,
34.01376724243164, 154.14556884765625, 34.32243347167969, 103.87847900390625,
154.23440551757812, 34.306034088134766, 154.53562927246094, 38.48063659667969,
154.63739013671875, 38.483619689941406, 154.60488891601562, 38.50436019897461,
154.60694885253906, 38.50547409057617, 154.2655792236328, 38.618038177490234,
154.63363647460938, 38.62126159667969, 154.69009399414062, 152.59304809570312,
38.71311569213867, 151.76808166503906, 51.883724212646484, 152.06051635742188,
51.83548355102539, 151.66751098632812, 38.665931701660156, 151.60060119628906,
152.7415313720703, 51.886207580566406, 153.15924072265625, 51.88606643676758,
153.16085815429688, 38.81463623046875, 36.11669921875, 62.634368896484375,
77.99734497070312, 187.94322204589844, 189.19671630859375, 38.08533477783203]

Lots of noise here. Lucky for us, the bpmdetect plugin uses an external library
(soundtouch) to do the calculation, and has a utility program that outputs BPM.
So, I convert the same file to wav, and then run "soundstretch output.wav -bpm"
to see what I get:

Detected BPM rate 157.7

>From this result, I suspect what the real problem is that the soundtouch
library expects to get the whole file, whereas GStreamer is calling getBpm()
every time transform_ip() is called (eg, when a new buffer comes in). Is there
a way to force the bpmdetect plugin to process the entire file, as opposed to
just a few buffers here and there?

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