How To Use
BpmDj:
the automixer
Introduction
BpmDj contains a small submodule, the automixer, which
enables
you to 'glue' together a set of songs fully automatically. This can be
useful for online radio stations, or to
create
mixes for portable mp3 players. The
process
itself works in about 80% of the times and depends on the correct
availability
of the tempo information. The mixes are created offline and are
created
a bit faster than realtime, so it should be possible to create an XMMS
plugin from this software. If somebidy wants to do this. Please contact
me. The automixer will probably not be further developed because it has
only as sucessrate of 80 % which is good (and also shows why
DJ's are actually usefull :). If this program should become tooo
perfect
we might as well kiss our hobbies goodbye :)
License
If you
use
this software to automatically create online mixes, please have the
decency
to mention the program you used to do so. Also, if you modify the
program and use it for broadcasting (and/or selling) purposes, you
MUST release the modified code ge-GPL-ed.
Preliminary
Observations
Before we explain how you can use
this
feature, we need to point out that good results can only be expected
when
the two songs that needs to be mixed have a
compatible
rythm. For instance blues does not mix very well with techno
the two songs that needs to be mixed have
the same
time signature. For isntance a 3/4 measure cannot be easily mixed with
a 4/4 measure
the two songs have a similar sound spectrum.
If they don't it will be very hard to detect the 'same' bassdrums, or
hihats.
The Automixer Dialog
Box
Selecting The Songs
Start bpmdj. Select some songs in the Songs-tab and add
them
to the queue by pressing right and slecting 'Add To Queue'. If you know
that those songs doesn't have a similar spectrum make sure to insert a
set of transitional songs. You can do this by going to the Queue-tab,
selecting
all the songs, pressing the right mpouse button ans electing 'insert
random
songs'. All the songs in the queue must have a correct tempo
signature.
When you have created a list to your liking you can continue.
Setting the Automixer Options
Now press the 'Fully Automatic Mix' button in the right
bottom
corner of the Queue-tab. The automixer dialog will pop up, as pictured
above. Not all options are enabled yet. In future versions these
will be however. Let's investigate the different options:
Head, % position in file: this
option let
you choose the starting point of a new song. This describes the
position
in the NEW song, not the old.
Process, Normalize Songs: beacuse
not all
songs have equal volumes, you can choose to normalize all songs to
their
peak-level.
Process, Volume Accounting: this
option enables
barely audible beats to be taken into account less. Sometimes (not very
oftezn) this might help in creating a good mix. However, my experience
shows that this not often works as it is supposed to do.
Process, Fine Scan Tempo: sometimes
the tempo-line
of a piece of music drifts. With this option you can make the merger
perform
a new tempo scan, specifically suited to do the mix afterwards. This
takes
some extra time but might be usefull for better results.

Process, Measures To Mix: how many
measures
should the mix itself take
Process, Measures to Slide: over
how many
measures should the best match be found. To explain these two values a
bit more. In the figure above, we see how song A is gradually replcaed
by song B. How long this takes is described by the 'measures to mix'
value.
However, choosing the best position to mix two songs together requires
a certain window to search in. The size of this window (the
pruple
ruler at the bottom) is the 'measures to slide' value.
Process, Measures for Tempo switch.
How much
measure must be spent in tempo switching. This value will be cut if
there
is not enough music present.
Process, Dump raw head/tail and mix:
during
the process, the mergeer programm can dump the head (the X
measures
of the new song), the tail (the Y measures of the old song over which
to
slide) and the mix itself. When the mix has been dumped it is possible
to immiedatelly play only the mix using bplay. Therefer sleect Play
Mixes.
Process, Verbose: dump extra
information about
file-sizes and mix positions. Not very useful, but necessary to help
debugging
the thing.
Other options represnet how the output happens. Normally, one big raw
file
is created by gradually appending new songs to the end of an already
existing
file. When the whole process is complete, this file can be split into
pieces
and encoded again.
Starting the Process
Once the options are selected, you can press 'Ok'. Now a
script
is written to disk, called 'process_mix.sh'. Go to the BpmDj directory
and start this script. In future versions, this will be started
automatically.
Command Line Options
The program used to create the mixes
is called merger. By
typing merger --help you can select all options available in the above
dialog box.
Copyright (c)
Werner
Van Belle December 2001
e-mail:
werner.van.belle@vub.ac.be
Tel: +32 486 68
84
48; Fax: +32 2 629 35 25