On Sat, May 3, 2008 at 11:04 AM, Mark Knecht <markknecht@xxxxxxxxx> wrote:
>
> On Sat, May 3, 2008 at 7:12 AM, Rui Nuno Capela <rncbc@xxxxxxxxx> wrote:
> >
> > Pieter Palmers wrote:
> >
> > > Rui Nuno Capela wrote:
> > >
> > > > Mark Knecht wrote:
> > > >
> > > > > On Fri, May 2, 2008 at 12:21 PM, Rui Nuno Capela <rncbc@xxxxxxxxx>
> > wrote:
> > > > >
> > > >
> > >
> > > [...]
> > >
> > >
> > > >
> > > > > As for edge dragging, in Acid this allows you to play a portion of a
> > > > > loop. If I place a loop in a session the tempo is adjusted
> > > > > automatically and I hear the whole loop. If I drag the left edge to
> > > > > the right I lose the front part of the loop. If I drag the right edge
> > > > > to the left I lose the last part of the loop. There are ways to drag
> > > > > the loop to an out-of-sync point if you want but I don't use it much,
> > > > > really only for beat slicing where they have better tools in the
> > > > > editor.
> > > > >
> > > > >
> > > >
> > > > when you import (or drop) a new audio file into the qtractor time-line,
> > it's always assumed that the new clip is in tempo with the current session.
> > if you find it is not the case, you can trim and/or (time-)stretch the clip
> > until you see fit. take a tour:
> > > >
> > >
> > > [...]
> > >
> > > As far as I can remember, the "automagic-ness" of ACID relies on some sort
> > of extra metadata. I think it was embedded in the WAV file, but it might
> > have been somewhere else.
> > >
> > > The point is, if there is such metadata in a clip (e.g. wav), why no use
> > it? Have an option like "strech clip according to tempo metadata" or the
> > likes. If I remember your LAC presentation correctly, all resampling is done
> > "on-the-fly" (modulo some cacheing) so isn't is simply initializing the
> > 'stretch factor' to a proper value?
> > >
> > > 2cents for the masses,
> > >
> > >
> >
> > that's a good point indeed. i do remember that Mark has aslo referred to me
> > about the meta-data acid do stuff into wavs, but i'm afraid i've lost the
> > hint at the bottomless qtractor todo list ;)
> >
> > question that occurs to me atm. might be: does libsndfile have the means to
> > read or access that meta-data ?
> >
> > as said, implicitly, i don't nor ever used acid, but it might be of some
> > help if someone would hand out one of the acid-stuffed wavs for me to try?
> >
> > cheers
> > --
> > rncbc aka Rui Nuno Capela
> > rncbc@xxxxxxxxx
> >
>
> Short answer, yes, sort of...
>
> I don't remember what app it is and I'm not in Linux at the moment but
> I think it might be sndfileinfo has the ability to read a lot of the
> meta-data. Problem was whomever I worked on this with 5 years ago (I
> think it was Erik in those days but please don't let my bad memory
> tarnish his reputation) ran out of time/interest and only got part of
> the work done. Fortunately what he did get done was apparently
> accurate so at least it's a good start. I do see that libsndfile lists
> reading loop data as added in Nov., 2004 but I know I worked on it
> earlier than that.
>
> Anyway, when you find the right app and you download a few 'Acidized'
> loops from the ACIDPlanet site for free you'll find that the info
> tells you not only tempo & key but it also gives the author, library
> name and probably most interesting, trimming information. Apparently
> many Acid loops have a bit of a leader and trailer in the file. It's
> my suspicion that the loop author suggests where to start and stop
> playing, thus synchronizing the loop's natural beats with the measure
> bars in the session. A few samples before and after thus allow for
> some automatic fade-in/fade-out, etc., without everything being so
> abrupt. That's all guessing on my part though.
>
> I think the important issue here is that not ever Acid loop has
> exactly the right number of samples to equal tempo. Doing some
> calculations:
>
> 60 BPM is 1 beat/sec. Assuming a 4/4 time signature and a 1 measure
> loop then the loop's sound be 4 seconds long. 4 seconds of 44.1KHz
> audio would suggest 176,400 16-bit samples. (Per channel) When you
> look at the actual length it may be 178,000 or 180,000 with trim
> information to suggest where to play from and to.
>
> The issue (I think) is that if you just played the whole loop, from
> first sample to last, then the playback wouldn't be identical to the
> way the loop author hears it on a system that honors this start/end
> data. Close, but not identical.
>
> Hope this helps, and again, all credit to those who build these wonderful toys.
>
> Cheers,
> Mark
>
Here's a couple of examples of sndfile-info looking at Acid loops. The
first is a drum loop, the second a promo I got off of AcidPlanet this
morning. There are certainly tempo problems with both of these as
neither loop is 120BP natively but remember it was a work in progress
where progress stopped and not that anyone said the work was done...
- Mark
mark@lightning ~/Desktop/My Data/Music/072 BPM (Slow Groove) $
sndfile-info Fill1.wav
Version : libsndfile-1.0.17
========================================
File : Fill1.wav
Length : 441654
RIFF : 441646
WAVE
fmt : 16
Format : 0x1 => WAVE_FORMAT_PCM
Channels : 2
Sample Rate : 44100
Block Align : 6
Bit Width : 24
Bytes/sec : 264600
data : 440934
acid : 24
Flags : 0x0000 (Loop,RootNoteInvalid,StretchOff,RAMBased,??Off)
Root note : 0x3C
???? : 0xFFFF8000
???? : 0.000000
Beats : 2
Meter : 4/4
Tempo : 120.000008
strc : 636
End
----------------------------------------
Sample Rate : 44100
Frames : 73489
Channels : 2
Format : 0x00010003
Sections : 1
Seekable : TRUE
Duration : 00:00:01.666
Signal Max : 7.23123e+06 (-1.29 dB)
mark@lightning ~/Desktop/My Data/Music/072 BPM (Slow Groove) $
mark@lightning ~/Desktop/My Data/Music/Painting After Hours $
sndfile-info AFTERHOURS\ EDM\ pahPROMO\ 01.wav
Version : libsndfile-1.0.17
========================================
File : AFTERHOURS EDM pahPROMO 01.wav
Length : 2619310
RIFF : 2619302
WAVE
fmt : 16
Format : 0x1 => WAVE_FORMAT_PCM
Channels : 2
Sample Rate : 44100
Block Align : 4
Bit Width : 16
Bytes/sec : 176400
data : 2605292
acid : 24
Flags : 0x0002 (Loop,RootNoteValid,StretchOff,RAMBased,??Off)
Root note : 0x36
???? : 0xFFFF8000
???? : 0.000000
Beats : 32
Meter : 4/4
Tempo : 120.000000
strc : 4636
*** str2 : 20 (unknown marker)
*** bmrk : 7024 (unknown marker)
*** dtbt : 520 (unknown marker)
LIST : 82
INFO
*** MRAT : 4
ICOP : (c) 2008 Sony Creative Software Inc. All rights reserved.
*** mudp : 1612 (unknown marker)
End
----------------------------------------
Sample Rate : 44100
Frames : 651323
Channels : 2
Format : 0x00010002
Sections : 1
Seekable : TRUE
Duration : 00:00:14.769
Signal Max : 32735 (-0.01 dB)
mark@lightning ~/Desktop/My Data/Music/Painting After Hours $
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