Subject: Re: [linux-audio-user] Resampling loop libraries
From: Mark Knecht (markknecht_AT_attbi.com)
Date: Sat Apr 26 2003 - 17:11:29 EEST
On Sat, 2003-04-26 at 04:14, Frank Barknecht wrote:
> Hallo,
> Mark Knecht hat gesagt: // Mark Knecht wrote:
>
> > Sox looks interesting. Quite a lot of capabilities there also.
> >
> > Maybe I need to do something to take advantage of the 'Acidized'
> > feature of the loops also? Acid loops have tempo and root note info in
> > the files. It would be nice to somehow be able to use that to get a
> > better result.
>
> In my understanding (which may well be much out of date) the Acid-info
> is just meta-data to let Acid show things like bpm and such quckly.
> So it's useless for time stretching or shifting (I use these terms
> interchangably, which is technically not correct, I guess)
>
Frank,
I had heard the same thing, but ran into some interesting things when
I imported a few specific Acid loops into Pro Tools.
If you are familiar with Acid, then you know that as you extend the
loop across a track in Acid, when you go beyond the 'end' of the loop,
then Acid repeats the loop.
However, when I take some of these loops into Pro Tools, I find that
the loop is longer than what Acid shows. Essentially, the loop is not
'trimmed' to the length that Acid is showing. Now, Acid also supports
'One Shots', which have nothing to do with tempo, so I think the
meta-data is tied up with all of that also. I suspect that this
meta-data must inform Acid which part of the loop file to use.
Also, 'tempo' must be related to how many audio samples are in a
loop, correct? A 1 measure loop at 144BPM would have fewer samples than
a 1 measure loop at 91BPM. Granted, if all loops were trimmed to a known
length, then tempo could be calculated, but some loops are 4 measures,
while others are 16, so there are difficulties without knowing how long
the loop is supposed to be musically.
The last thing about tempo, and really the one that seems to cause
the most problems with the audio, is that it is difficult in Acid to mix
loops that were recorded at radically different tempos. If I combine a
144BMP loop with a 91BMP loop, and the song is at 94BPM, Acid does a
fine job of adjusting the 91BMP loop to the new tempo, but it does a far
worse job of adjusting the 144BPM loop. (This applies to pitch shifting
also. It's pretty good over about 5-6 half steps, but goes pretty sour
much beyond that.
Anyway, I was hoping there are some ideas or experiences out there
that could do a better job than Acid does on the fly.
Thanks,
Mark
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