Subject: Re: [linux-audio-dev] beat slicer under linux
From: Marek Peteraj (petemar_AT_kiwwi.sk)
Date: Fri Oct 05 2001 - 08:21:15 EEST
On Thu, 2001-10-04 at 09:20, Paul Davis wrote:
> >Slightly off topic either but is there any beat-slicer under linux right now?
> >I wonder how much effort it would take to port such app from windows to
> >linux? There used to be such app under windows, it was freeware, but
> >it's not available anymore...
>
> 1) my experience, as i mentioned before, is that the GUI for complex
> audio+MIDI applications, is at least 2/3 of the code, and at least
> that much of the effort. since its unlikely that xrazor was written
> using any kind of cross-platform toolkit, porting such a beast (if
> the code was available) would be a difficult undertaking.
The GUI is relatively simple...
> the "insides" of such programs are relatively easy to write,
> 2) depending on what you mean by a beat slicer,
i think this document describes in more detail what it does:
The Beat Munging technology allows you to analyze an audio track,
determine its tempo, and find where the beats are.
Based on that preliminary analysis, beat munging lets you loop the track,
modify its tempo, its swing, and even its time signature,
all in real time while listening to the track.
It can analyze and modify any sample that has rhythmic information at the touch of a button.
When you first press the BeatM button, an analysis takes place of the
selected sample. During this analysis, all of the beat transients in the
sample are located by performing a frequency-domain analysis of the
signal. The patented Beat Munging algorithm looks at the energy in
various frequency bands and locates the times where the energy rises
sharply, identifying them as transients. Transients usually correspond
to percussion hits and note attacks, although Beat Munging is not
usually able to detect notes that have a legato attack. Based on the
detected transients, Beat Munging assumes that the tempo is constant for
the duration of the audio track and calculates the tempo in BPM that
best matches the distribution of transients. In addition, Beat Munging
determines where the beats occur, i.e., is able to tap its foot to the
music (and presumably, tap at the right time!).
http://www.emu.com/products/esynthKeys/tutorials.html
Say you have a 4/4 drum sample which goes like:
1 2 3 4
b b beat b bb bb beat
the 'b'-s and 'beat'-s are transients and refered to as regions in
XRazor, the word region has a different meaning here...
You could have sample dumps and MIDI note maps(thats what XRazor
currently does), or the recycle+cubase approach, in which a file would
be created by xrazor containing the tempo/note map and the transients,
the file could be imported into an ardour session - it would show up as
regions positioned according to the tempo/note/bar/beat information
contained in the file and in ardour...So if the above 'bb-beat' had a
calculated tempo of 137BPM and ardour was set to 120, ardour would
automatically reposition the regions to match the current tempo...
i'd very much like
> to add this functionality to ardour. we already have regions,
> and can export regions to audio files.
I think it would be better to have a beat-slicer as a separate app,
because its purpose is also to find loops, and you could prepare your
samples for use in an ardour session...
> a framework for sample dumps and MIDI note maps would be needed.
maybe we could ask the author of XRazor...
Marek
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