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especially a short one.

To see a World in a grain of sand,

And Heaven in a wild flower,

Hold Infinity in the palm of your hand

And Eternity in an hour.

— William Blake

The video was created with a custom-made kinetic typography system that emulates a low-fi terminal display. The system is controlled by a plain-text configuration file that defines scenes and timings—there is no GUI. There is also no post-processing of any kind, such as After Effects. Everything that you see in the final video was generated programatically. The creation process took about a month.

This page describes this system's design in detail. Fair warning: it gets into the weeds quite a bit.

The original music score for Aleph 2 is 6 minutes and 34 seconds in length.

The score tempo is 118 bpm (1.967 beats per second, 0.082 beats per frame). There are 194.1 measures in the video (29.5 measures per minute, 0.492 measures per second, 0.020 measures per frame).

The video format is 24 fps, so the track comprises 9,473 frames (1440 frames per minute, 48.814 frames per measure, 12.203 frames per beat, 3.051 frames per 16th note).

The typography uses the Classic Console font, expanded by me to include set theory characters such as `\aleph`, `\mathbb{N}`, `\mathbb{R}`, `\notin`, `\varnothing` and so on.

The video is 16:9 and each frame is rendered at 1,920 × 1,080. Text is set on a grid of 192 columns and 83 rows (maximum of 15,936 characters per frame).

The entire video is first initialized as an `(x,y,z)` matrix of size 192 × 83 × 9,473 (150,961,728 elements). The `z` dimension is the time dimension and each matrix slice (e.g. `x,y,1`) corresponds to a given frame.

The video is then built up from a series of scenes. Briefly, this process is single-threaded and takes about 30 minutes and during this time the matrix is populated with text characters. As the scenes are built up, each element in the matrix stays blank or has a colored character assigned to it. Periodically, effects are added such as random glitches. All elements are synchronized to the tempo of the score and transitions can be triggered from drum score midi files. For example, in parts, the background for each frame flashes to the kick and snare. I get into the detail of this below.

Once the matrix has been fully populated, each frame is output to a PNG file (e.g. 000000.png ... 009472.png). Below you can see 10 frames in the range 2490–2499 from the Bijection 2 section of the video at 1:42.

The frames were then stitched into a PNG movie in 24-bit RGB color space using ffmpeg.

ffmpeg -thread_queue_size 32 -r 24 -y -i "frames/aleph/%06d.png" $offset $seek -i wav/aleph.wav -pix_fmt rgb24 -avoid_negative_ts make_zero -shortest -r 24 -c:v png -f mov aleph.mov

The .mov file is then converted into DXV format used by the Resolume VJ software that Max Cooper uses in his shows to control the displays.

If you watch the video on YouTube, please know that the YouTube temporal and chroma compression *greatly* reduces the quality of the original 24-bit RGB master, which was used for the Barbican Hall performance. The YouTube compression bleaches out the vibrant red, which really pops out in the master version, and blurs frames during fast strobing, which neuters parts of the video that are designed to be overwhelming, such as the drop transition to 24 fps strobing during the natural number power set.

Here is Max's original direction for the video's narrative and art style.

I want to show ever growing lists of numbers, then split the lists somehow (left/right of screen) and show how you can pair subsets of Aleph 0 / integers with themselves, then show how Cantor's diagonal argument can be used to pair the fractions with the natural numbers, then show his other diagonal argument for proving the reals are greater than Aleph 0, then show the process (very roughly and with maximum artistic licence if necessary) of taking the power set of infinite sets to create larger infinities to get up to Aleph 1, Aleph 2, and maybe further if the system allows. In the end it should just be complete text/number chaos on screen along with the intense chaos of the audio.

We'd have to be very careful to avoid any Matrix reference visually! ... but that low-fi / command line style would be suitable I think.

In terms of animation, the technical requirements were relatively simple. Everything would be rendered with a fixed-width font with no anti-aliasing and the color palette would be very limited (e.g. black, grey, white and a red for emphasis). Nothing other than characters would be drawn (no lines, circles or other geometrical shapes) and there would be no gradients. Basically, very lo-fi and 8-bit.

Despite the fact that I've never made any kind of animation before, I thought that these requirements could be relatively easy to achieve. After all, if worse came to worst, I told myself that I could always generate the video frame-by-frame.

However, it quickly became obvious that traditional keyframe systems could not be easily used to tell our story. Tools like Adobe After effects rely on interpolation between keyframes. But in our video every frame is essentially a keyframe. This meant that any kind of interpolation between scene points would have to be programmed—while After Effects makes it easy to move things around on the screen, it requires scripting to generate content based on lists of numbers, set elements, and so on. And since I have no experience in After Effects, I thought it would be faster to code my own system than to learn After Effects' expression language to (possibly) later discover that what I wanted to do was either hard or practically impossible for me to achieve within our time frame (a month).

I knew that I was reasonably good at prototyping and generating custom visualizations, so it felt safer to create something from scratch.

The final version of the system, which is very much a prototype, is about 6,000 lines of Perl. The Aleph 2 video is built out from about 2,000 lines of plain-text configuration that defines scenes, timings and effects.

It took about a week to figure out how to design the system. As we were building out the video, I iterated between creating the story and creating the system to tell the story. This was iterative and felt very much like trying to simultaneously building and flying a plane.

At times, the entire process would crash down on me because some tiny tweak fundamentally changed how everything worked.

For example, one extremely nagging aspect of the code that I patched only half-way through the entire process had to do with how time was specified. From the start, I made use of measure:beat:16note notation, such as for scene starts and ends (e.g. 2:2 to 4:1 meant a scene started on measure 2 beat 2 and stopped at measure 4 beat 1).

This notation used 1-indexing (e.g. 1:1:1 is the first 16th note of the score). 0-indexing would have been unintuitive because musically one counts beats as 1, 2, 3, 4 and not 0, 1, 2, 3. Importantly, I wanted the way we referred to timings in conversation (e.g. on the "and of 2" of the 4th measure) to be directly reflected in the code.

All this made sense until I needed a notation to express duration. When I started using 1:1 to indicate a duration of 1 measure and 1 beat, I had to reconcile the difference between 1:1 as a point in time and as a duration—the former specified the beginning of the interval (e.g. frame=0) and the latter the end (frame=61). It also took me forever to decide whether the duration of 5 beats should be expressed as 1:2 (e.g. end is start of beat 2) or 1:1 (e.g. end is end of beat 1).

The fact that the video frame rate is 24 fps made things even more complicated. At this frame rate, there are 3.051 frames per 16th note. This meant that any duration of 1 frame (which happens during fast strobing) couldn't be expressed by the integer notation of measure:note:16note. I didn't want to have to write 0:0:0.3278, which seemed a tedious way of saying "1 frame". Furthermore, because frames didn't neatly match up to 16th note boundaries, quite a lot of time is spent checking that timing definitions don't suffer from rounding issues.

In the final video, you'll see the measure timer in the upper right corner. The : between the measure and beat flashes as a red + on the beat (118 bpm). Next to the measure timestamp you'll see a min:sec:frame timestamp and hexadecimal readout of the frame number.

Discover Cantor's transfinite numbers through my music video for the Aleph 2 track of Max Cooper's Yearning for the Infinite (album page, event page).

I discuss the math behind the video and the system I built to create the video.

*Everything we see hides another thing, we always want to see what is hidden by what we see.
—Rene Magritte*

A Hidden Markov Model extends a Markov chain to have hidden states. Hidden states are used to model aspects of the system that cannot be directly observed and themselves form a Markov chain and each state may emit one or more observed values.

Hidden states in HMMs do not have to have meaning—they can be used to account for measurement errors, compress multi-modal observational data, or to detect unobservable events.

In this column, we extend the cell growth model from our Markov Chain column to include two hidden states: normal and sedentary.

We show how to calculate forward probabilities that can predict the most likely path through the HMM given an observed sequence.

Grewal, J., Krzywinski, M. & Altman, N. (2019) Points of significance: Hidden Markov Models. *Nature Methods* **16**:795–796.

Altman, N. & Krzywinski, M. (2019) Points of significance: Markov Chains. *Nature Methods* **16**:663–664.

My cover design for Hola Mundo by Hannah Fry. Published by Blackie Books.

Curious how the design was created? Read the full details.

*You can look back there to explain things,
but the explanation disappears.
You'll never find it there.
Things are not explained by the past.
They're explained by what happens now.
—Alan Watts*

A Markov chain is a probabilistic model that is used to model how a system changes over time as a series of transitions between states. Each transition is assigned a probability that defines the chance of the system changing from one state to another.

Together with the states, these transitions probabilities define a stochastic model with the Markov property: transition probabilities only depend on the current state—the future is independent of the past if the present is known.

Once the transition probabilities are defined in matrix form, it is easy to predict the distribution of future states of the system. We cover concepts of aperiodicity, irreducibility, limiting and stationary distributions and absorption.

This column is the first part of a series and pairs particularly well with Alan Watts and Blond:ish.

Grewal, J., Krzywinski, M. & Altman, N. (2019) Points of significance: Markov Chains. *Nature Methods* **16**:663–664.

*Places to go and nobody to see.*

Exquisitely detailed maps of places on the Moon, comets and asteroids in the Solar System and stars, deep-sky objects and exoplanets in the northern and southern sky. All maps are zoomable.

Quantile regression explores the effect of one or more predictors on quantiles of the response. It can answer questions such as "What is the weight of 90% of individuals of a given height?"

Unlike in traditional mean regression methods, no assumptions about the distribution of the response are required, which makes it practical, robust and amenable to skewed distributions.

Quantile regression is also very useful when extremes are interesting or when the response variance varies with the predictors.

Das, K., Krzywinski, M. & Altman, N. (2019) Points of significance: Quantile regression. *Nature Methods* **16**:451–452.

Altman, N. & Krzywinski, M. (2015) Points of significance: Simple linear regression. *Nature Methods* **12**:999–1000.