>> Hi. How are all of you doing? How
was lunch? So I heard that there was no
vegetarian protein at lunch. I also
observed this myself. If you are still
feeling hungry, because of that, we have
leftovers from yesterday still. So
there's a bunch of grilled tofu, and
please -- absolutely feel free to go
grab one. There's also extras in the
fridge that's labeled don't go into it.
So just go into it and take that out, if
this applies to you. And please,
absolutely feel free to grab that. We're
going to get started here shortly. Do I
have any other announcements? I forget.
Anything, Julia? Okay. Cool. So we have
three talks, and then we're going to
have a 15 minute break and then we're
going to have two talks, and then we're
going to eat ice cream. Pretty great. So
first up, we're going to hear from Rafik
Draoui, and he's going to talk about
making music with floppy drives, and an
exercise in yak shaving. Two of my
favorite things.

(applause)

 >> Hello!

 >> Hello!

 >> It works! Hello, everyone. I'm
Rafik. I'm going to speak about floppy
drive music and my adventure yak shaving
my way to other projects from there. So
if you're not familiar with the term yak
shaving, that's one definition. Any
seemingly pointless activity which is
actually necessary to solve a problem
which solves a problem which, several
levels of recursion later, solves the
real problem you're working on. So you
have a project, and in order to do it,
you do something else, and by the end of
the day, you're mucking around with
config files and writing scripts, and
someone asks you: "You're supposed to work on that project"
What does it look like I'm doing? And... Yeah.
Usually you want to minimize yak
shaving.

So you want to minimize that. At worst it's time
wasting or at best, productive
procrastination. But... It can be a good
thing if you just want to learn things.
If you want to move on to other projects
and keep the excitement of programming
alive. So... One of my projects was
making music with floppy drives. So how
does that even work? So sound -- someone
mentioned yesterday -- just air moving
at some frequency, and every sound has a
frequency, so middle A would be 440
hertz, for example. And this is a floppy
drive. With the top removed. And where
the arrow points, it's the head. This is
what reads the data. This moves back and forth. So
you only have to... to make sound of that,
you just have to make the motor move at
the right frequency, and you'll hear
something that sounds kind of like the
note it's supposed to sound like. And
what you do is that... This is the back,
with some pins, and you send the right
voltage, to the right pin at the right
time, then the motor will move. So I
used an Arduino to do that. Turns out
you only need three of these pins to
control the motor. And basically you
just... The song is like a list of pairs. It's a
note, play that note for that many
seconds, play that note for that many
seconds, and so on. But Arduino doesn't
have much memory. Doesn't have an OS or
any file system. So kind of the only way
to do it is to put some bytes in memory.
Like, have some bytecode, and... This is
like Mary had a little lamb. So this
is... Like, the first few lines, the
length of the song, and hold note 64 for
that many milliseconds, and so on and so
on. Needless to say, this is not very
user friendly. If I think about some
other song I want to play, I would have
to sit down and try to encode it like
that. It doesn't work.

So I thought... There's all this music
around. Maybe I can use some other
format and convert it to that. So
there's MIDI files, MIDI protocol,
standard protocol for describing music,
if you were on the internet, 15 years ago,
the background music on some web pages,
mostly MIDI files playing. So they're
all over. I said I'm going to write the
program. Somehow I wrote it in C. Today
I would make a different choice,
probably. But this is an example with
the many, many lines of code. And this
works pretty good. It's all right.

But there were so many edge cases that I
didn't get. And if I think about a song,
I have to find that song. I'm not a
musician. I cannot just take a keyboard
and play my songs. So I needed to do
something else. So yeah, I cannot play
music, but I know how to whistle. I can
whistle a sound or two. So I thought...
Maybe I can just record myself whistling
a tune and have a program -- extract the
melody from it and then convert it. So
this is my next thing. So how does it
work?

There's a thing called discrete Fourier
transform. It's amazing. Just take a
signal, and then you can convert between
time and frequencies. So it's easier with an image. On
the left, it's like a signal. Some sound
you can see -- it's like a lower --
mountains, lower frequency, and a higher one. And when you
put it through the machine of the
Fourier transform, you get what's on the
right. You see the dominant frequency.
The lower one, that's dominant, and the
other one. And so I know the frequency.
As you remember, a note is just a frequency,
so I can just take my recording and run
it through the Fourier transform and
gets the notes. At least, that's the
main idea.

So start with some waveform. Split it
into windows, like a tenth of a second or
as small as you want to go, and you run the Fourier transform
on all these windows. And you get the dominant frequency,
the note. By the way, the algorithm
to do that is called a fast Fourier
transform. One of the most amazing
algorithms of the 20th century. Ties up
lots of computer science fun: Dynamic Programming, recursion,
takings something that -- it's naively, n square complexity, but it
goes to n log n. So check it out.

And then this frequency -- you kind of
normalize them -- forgot to mention that MIDI
files, every note is a number from 0 to
127. So if this is a standard for the music
industry, maybe I should do that as
well. So I kind of round up or down all
the notes. And then you can aggregate...
Like, consecutive notes. And then you
get a list of pairs, which is pretty
close to what we want. Play note 62 for
four units of time. And so on. And this
is not quite perfect.

The output... It's very noisy. So
there's... Like, this is the one, the third one,
it only lasts for one. And you
might think that it might be an error.
Maybe it's really 64, but by going from
the higher note to the other one,
it's... It just picks up... My whistle
was out of tune, maybe. So you might
want to... Or maybe you want to... It's
too fast, and you want to make it
slower, so maybe you want to double the
duration of all the notes.

But this is a pretty cool simple data
structure. List of pairs. So we can just
filter it. Pass some functions and
compose them. So as long as it takes a
list of pairs and outputs a list of
pairs, you can compose these functions.
So I guess the filter is that -- you
know, for example, drop the short notes
and double the duration, and you use
whatever functions you need to get to
whatever you want. And then finally you
just... You can emit it to the back end,
the MIDI file, a floppy, or to json,
because you can.

And yeah. So this works. And, I mean,
it's way better than encoding by hand
already. So... But it's not... You know,
sometimes there's a note that's a bit...
It's a bit out of tune. And you just...
It would be so easy... It's a graphical
interface. Just click on it and move it
up a bit. And it would be it. But with
these functions, you need to... You
know. So I thought maybe I could do a
graphical interface.

And I didn't know anything about, like,
canvas or HTML 5 stuff. By the way I didn't
know anything about any of these things
before as well. So that's an early kind
of screenshot of how it kind of looked.
No drag and drop yet. We have to click
and press a button so it moves. But
basically I used some library, and I
customized it a lot to do what I wanted,
and when things didn't really work out
properly, I tried to... You know, just
do some random calls like -- `canvas.renderAll()`
and it "worked". So I was like... Oh, it's
fine. And now I'm... I got to a point
where I'm... I'm really stuck. Like,
I've kind of dug myself into a hole
with all these careless hacks and
"fixes", so I cannot reproduce a minimal
example to get help or to debug. So
that's where I'm at now. It's a bit of
anticlimax. But... Yeah.

So it still hasn't been... You know,
I've got lots of plans for this... I
want a whole orchestra. I want to maybe
make it interactive, and have all these
ideas, and I'm nowhere close. I've just
been doing all these other things
instead. But it's... I think it's a
really cool thing that I did that,
because I learned lots of new things. I
was at PyCon, and I learned things like
-- iPython notebook, or do some things
with graphics, and I've been told that
karaoke file editors are MIDI. Maybe I
can do karaoke floppy drives. So I'm
stuck for now, but if you have any
ideas, I'm happy to get some help. 30
seconds. So... Yeah. So... Do stuff that
you don't know about, and just keep on
going. And it's on GitHub. It's called a
flopkestra. It's not quite an orchestra
yet. Because Arduino -- it can't process
in Arduino. Gazouilli is my process to extract.
It's a pun in French. You can ask me
later. And there's a video there. A
small teaser. And check it out.

(applause)