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Motion Interpolation for Glitch Aesthetics using FFmpeg part 0

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As you may have seen in this blog post I made use of FFmpeg’s minterpolate motion interpolation options to make all of the faces morph. There’s quite a few options for minterpolate and many different combinations of options that can be used. i had to consult Wikipedia to figure out exactly what the different motion estimation algorithms were but even with that information I couldn’t visualise how it would change the output. To add to this how I’m using minterpolate isn’t a typical use case.

To make things easier for those wishing to use FFmpeg’s minterpolate to create glitch aesthetics I have compiled 36 videos each showing a different combination of processing options. The source video can be seen below and features two of my favourite things: cats (obtained from here) and rainbows.

I’ve slowed it down so that you can see exactly what’s in the video, but the original can be downloaded here.

The base script used for each video is: 

ffmpeg -i cat_rainbow_original.mp4 -filter:v "setpts=62.5*PTS,minterpolate='fps=25:mb_size=16:search_param=400:vsbmc=0:scd=none:

In part two of March’s Development Update I explained why I set scd to none and search_param to 400. I could have of course documented what happens when all of the processing options are changed but that would result in me having to make hundreds of videos! The options that were changed were the mc_mode (motion compensation mode), me_mode (motion estimation mode), and me (motion estimation algorithm).

Test conditions

These videos were created using FFmpeg 7:4.1.4-1build2, installed from the Ubuntu repositories, on a Dell XPS 15 (2017 edition) with 16GB memory, a i7 processor and an Nvidia GeForce GTK 1050 graphics card, all running on Ubuntu 19.10 using proprietary drivers.

I don’t have a Windows or Mac machine, and haven’t used other Linux distributions so can’t test these scripts in those conditions. If there’s any problems with getting FFmpeg on your machine it’s best that you contact the developers for assistance.

Observations

My first observation is that the esa me_mode takes frikkin ages to complete! Each video using this me_mode took about four hours to process. I did consider killing the script but for completeness I let it run.

Using bilat me_mode produces the most chaotic results by far. Just compare 026_mc_mode=obmc_me_mode=bilat_me=epzs.mp4 to 008_mc_mode=obmc_me_mode=bidir_me=epzs.mp4 and you’ll see what I mean.

For a video of this length nearly all of the scripts (except for those using esa) took between 30 seconds and 1 minute to complete, and that’s on machines with and without a GPU. This is good news if you don’t want to have to carry around a powerhouse laptop all the time.

All of this reminds me a bit of datamoshing. It’s more predictable and controllable, but the noise and melty movement it creates, especially some of the ones using bilat me_mode, remind me of the bloom effect in datamoshing. This could be down to the source material, and I’d be interested to see experiments involving datamoshed videos.

Let’s a go!

With that all said let’s jump into sharing the results. As there’s 36 videos I’ll be splitting it over nine blog posts over nine days, with the last being posted on 28th March 2020. Each will contain the script I used as well as the output video. Links to each part can be found below:

Producing audio for Let’s Never Meet

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For the majority of my career in art I’ve been primarily known for my visual artwork. I’ve dabbled in making noises with my Sonification Studies performances (which may make a comeback at some point) but it’s only since my 2018 performance at databit.me that I’ve regularly made and performed music.

On the performance side I’ve mostly used TidalCycles. You may have seen that I have been doing live streams of my rehearsals.

Outside of live coding I’ve spent most of my time getting to grips with software-based synthesisers and DAWs. When asking for advice on this most people told me to use software like Ableton. What these well-meaning people may not realise is that I exclusively use (Ubuntu) Linux and only open source software. This gives me the freedom that open source grants me but boy does it sometimes cause headaches! Plenty of people use the open source options available to them but this approach is still the road less travelld and so I’ve found myself sometimes asking lots of questions and either not getting a response or getting the response that what I’m trying to achieve is not possible.

And so for the last year or so that I’ve creating workflows that work for me. For this I’ve been using Ardour, which is a pretty good cross-platform DAW. So far I’ve produced soundtracks to two of my artworks, We Are Your Friends and Let’s Never Meet. In this Development Update I’ll go over a little trick I learnt whilst making the soundtrack for Let’s Never Meet.

In short, Let’s Never Meet is about meeting people over the internet. The soundtrack is actually a remix of a an Android alarm ring tone.

It’s not an alarm tone that I use myself but it was ambient enough to work in an outdoor setting for an extended period without getting annoying. Plus using a sample from my phone just somehow felt appropriate, if you know what I mean. After many many many hours of producing my remix sounded a bit like this:

I was really happy with the results but it felt like there was something missing. It was pretty samey throughout and I think there needed to be some kind of buildup or change in pace. To address this I decide to add some percussion. I turned to the glitch sample set that is downloaded when you install TidalCycles. It has a nice percussive quality and definitely sound glitchy and electronic, again in fitting with the digital theme of the piece.

As far as playing these samples I did consider manipulating them in TidalCycles and importing the whole recording file into Ardour, but I also wanted to get better with Ardour so sought a solution within that software. The glitch pack contains eight samples and I needed to be able to load them into Ardour to trigger/play at will. The drumkv1 plugin is the perfect solution to this.

It’s a sampler where you assign samples to midi notes. To play the notes you could use a midi keyboard, send the notes from Pure Data, or basically any software that can send midi. I decided to use the x42 step sequencer to input the midi notes. It’s a very simple step sequencer originally built for the MOD platform but, because it’s an lv2 plugin, it can run in any host that supports it.

Using this sequencer I could easily create an eight-step loop that starts simple builds up with more drums over time.

With the samples assigned to midi notes I just needed a way to press the pads in the step sequencer. I have two physical controllers, a Launchpad X and a MPK Mini. The latter only has two rows of four drum pads. The former is an 8×8 grid but I can’t yet program it properly to work with the software I use (more on that another time). In any case, in looking into how to use the Launchpad X with x42 the plugin’s author, Robin Gareus, told me that it’d never be possible because x42 doesn’t accept midi input 🙁

I accepted that using a software or hardware midi controller was a no go. I would have to use a mouse, which wasn’t ideal but it would work. The plugin’s author did recommend that I look into BSequencer. It appears to accept midi input but with a deadline looming I didn’t want to spend more time on this by learning yet another software.

Using my mouse in Ardour I started to record the input of me playing the step sequence but I noticed the midi notes from x42 weren’t being recorded.

I found this very strange. drumkv1 was blinking to show it was receiving midi but nothing was being recorded. After some research I discovered that it was because Ardour records external midi. When I loaded x42 as a plugin within Ardour it was sending midi internally. To get around this there are two solutions:

I used Carla as a plugin host to load x42 and then sent the midi output to the correct track in Ardour.

Carla showing x42 being connected to Ardour

This worked but I was getting a lot of latency with the input and the notes didn’t align properly. This is probably easy to solve by tuning my system to reduce latency (I already use the realtime kernel), or maybe something that I was doing wrong, but again with a looming deadline I didn’t want to do anything drastic and time consuming.

The second option was to send the output of x42 out into another application and then have that external application send its midi input into Ardour. To do this I loaded a2jmidid, connected the track’s midi output into it, and then connected the output of a2jmidid into the track in Ardour.

Screenshot showing ardour connecting to a2jmidid and back again

When I started up x42 again in Ardour and started clicking on its pads it all worked as expected!

After all of that effort I recorded myself building up the percussion. Here’s the finished track 🙂

I’ve been having a lot of fun making music, so expect more of it from me in the future.

Seamlessly loop Wave Modifier in Blender

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Seamless animation

For the Improviz gifs one of the requirements that Rumblesan set is that the gifs loop seamlessly. That is, one would not be able to tell where the gifs beings and ends. In Blender making an animation seamless is pretty easy. There’s lots of examples out there but for completion here’s my simple take on it.

With the default cube selected press I and then press on Location. This inserts a keyframe for the location (this menu can also be accessed in Object > Animation > Insert Keyframe). On the Timeline at the bottom move the animation 20 frames. Then, move the cube to somewhere else.

Now press I to insert a keyframe for the location. Ta da! You now have an animation! To make it loop we need to repeat the first keyframe. On the Timeline go forward another 20 frames (so you’re now on frame 40). In the Timeline select the first keyframe. Press Shift + D to duplicate it and then move it to frame 40.

Set the end of your animation to be frame 40. Now when you press play (space bar) the animation loops seamlessly!

As an aside if you’re interested in animation check out Eadweard Muybridge. And if you’re into Pure Data check out this tutorial I made in 2017.

Seamlessly loop Wave Modifier

So, that’s one easy way to make a seamless looping animation. However, Rumblesan was more interested in are gifs that warp and morph. This is one example he sent me.

via GIPHY

In Blender one really useful modifier for making these animations is the Wave modifier. In fact, looking through all of the gifs in 2020 by that artist (Vince McKelvie) it looks like he makes extensive use of this modifier. I love how simple it is to get distorted objects without much effort.

The one thing I’ve always found difficult is making the looping of the waves seamless. I haven’t seen many tutorials on achieving this, and those that I have found rely a bit on guesswork, which isn’t ideal. So, I set out to understand this modifier. After a lot of trial and error and “maths” I finally consulted the documentation and started to figure it out! The documentation on this modifier is quite good but here’s my alternative explanation which may help those who think in a similar way to me.

To get your wave lasting a specific duration, first you need to know how long you want your animation to last. For this example I set mine to 50 frames.

You then need to decide on the Width of the waves. The smaller the number the more ripples you’ll have on your object. This value is relative to the object. So, if you set it to 0.10 you’ll have 10 ripples through your object. If you set it to 1 you’ll have one ripple. I’ve set mine to 0.25.

For the Speed you need to do a bit of maths. Copy the value of Width (0.25) and in the Speed argument enter: (0.25*2)/50. Replace 0.25 with whatever value you set for Width and 50 with however long your wave animation lasts before it loops. Another way to represent this would be:

Speed = ($width*2)/$animationlength

The animation loops however the waves don’t affect the whole object. This is because we need to add a negative offset so that the wave starts before the animation is visible. This is where we need more maths! Enter this into the Offset value:

((1/0.25)*50)*-1

The first part, 1/025, is to work out how many times we’d need to repeat the Width before the whole object has ripples throughout it. We multiply by 50 as that is the animation duration. Then, we multiply by -1 to get the inverse, which because the offset. Another way to represent this would be:

Offset = ((1/$width)*$animationlength)*-1

And now the whole object has waves through it and loops seamlessly!

Ta da!

Since I originally made the gifs I have found that there are alternative methods for achieving a wavy object which rely on the displacement node and Displacement modifier or the Lattice or Cast modifier. These solutions have much more documentation but I’m glad I spent the time figuring out the Wave modifier.

Overlaying multiple textures in Blender

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In 2019 I made an internet artwork for Fermynwood’s programme Toggler.

For this work I decided to use a similar aesthetic and process to Visually Similar. I talked a little bit about the process behind Visually Similar in a June’s Development Update. The node tree to overlay each of the transparent textures looked a bit like this.

Click to embiggen

When trying to do the same with the Toggler artwork I came across something weird that meant some textures just weren’t showing. So I decided to ask on Stack Exchange and Reddit why this might be the case.

Click to embiggen

It looks like I wasn’t using the alpha channels properly and didn’t need to use the Add math node, or just needed to use it properly. If were to apply the same process retrospectively to Visually Similar the artwork would look like this.

Curiously several of the textures didn’t show up. I suspect that doing it this “proper” way revealed that I had the order of the nodes incorrect. If I show the work again I’m might edit it so it looks “right”, but in this case the mistakes yielded a more preferable result.

Installing Bcc: at Vivid Projects part 3

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In this final part of this three-part series I’ll be going over installing Xuan Ye‘s work in the Bcc exhibition. This work posed a similar challenge to Scott Benesiinaabandan’s work. I needed to automatically load a web page except this time I needed to allow for user interaction via the mouse and keyboard.

The artwork isn’t online so I’ll again go over the basic premise. A web page is loaded that features a tiled graphic with faded captcha text on top of it. The user is asked to input the text and upon doing so is presented with a new tiled background image and new captcha. This process is repeated until the user decides to stop.

Bcc:

I could have installed this artwork on a Raspberry Pi but thankfully I had access to a spare Leneovo ThinkPad T420 laptop, which negated the need for me to buy a keyboard and screen (#win). The laptop is a refurbished model from 2011 and was running Windows 7 when I got it. It is possibly powerful enough to handle a full installation of Ubuntu but I didn’t want to risk it running slowly so instead I installed Lubuntu, which is basically a lightweight version of Ubuntu.

As I had installed Scott’s work I already knew how to automate the loading of a webpage and how to reopen it should it be closed. The main problem was how to restrict the user and keep the user from deviating from the artwork. Figuring this out became a cat and mouse game and was never 100% solved.

Whilst in kiosk mode in Chromium pretty much all of the keyboard shortcuts can be used. This means that a moderately tech-savvy user could press Ctrl + T to open a new tab, Ctrl + O to open a file, Ctrl + W close the browser tab, Alt + F4/Ctrl + Q to quit the browser or basically any other shortcut to deviate from the artwork. Not ideal!

Bcc:

My first thought was to try and disable these shortcuts within Chromimum. As far as I could tell at the time there wasn’t any option to change keyboard shortcuts. There must be usability or security reasons for this but in this situation it sucks. After a bit of searching I found the Shortkeys extension which allows for remapping of commands from a nice gui 🙂 Only one problem. I tried to remap/disable the Ctrl + T command and got this error.


More information here.

Drats! I tried its suggestion and it still didn’t work. Double drats! Eventually I realised that even if did disable some Chromium-specific shortcuts there were still system-wide ones which would still work. Depending on your operating system Ctrl + Q/W will always close a window or quit a program, as will Alt + F4, Super/Windows + D will show the desktop, and Super/Windows + E/Shift + E will open the Home folder. I needed to disable these system-wide.

LXQT has a gui for editing keyboard shortcuts. Whilst it doesn’t allow for completely removing a shortcut, it does allow a user to remap them.

As you can see from the screenshot above I “disabled” some common shortcuts by making them execute, well, nothing! Actually it runs “;”, but still that has the effect of disabling it. Huzzah! But what about the other keyboard shortcuts, I hear you ask. Well, this is where I rely on the ignorance of the users. Y’see, as much as it is used within Android phones and basically most web servers, Linux/Ubuntu is still used by a relatively small amount of people. Even smaller is the amount of people using Lubuntu or another LXQT-based Linux distribution. And even smaller is the amount that work in the arts, in Birmingham, and would be at Vivid Projects during three weeks in September, and knew how I installed the work, and… I think you get my point.

During the exhibition anyone could have pressed Ctrl + Shift + T to open a terminal, run killall bcc.sh to kill the script that reopens Chromium, undo the shortcut remappings and then played Minecraft. I was just counting on the fact that few would know how to and few would have a reason to. After all there was some really great art on the screens!

After the exhibition was installed Jessica Rose suggested that one simple solution would have been to disable the Ctrl key. It’s extreme but technically it would have worked at stopping users from getting up to mischief. It would have had the negative effect of preventing me, an administrator, from using the computer to, for example, fix any errors. The solution I implemented, whilst not bullet proof, worked.

That’s the end of December’s Development Updates. Installing Bcc was frustrating at times but did push me to think more about how people interact with technology in a gallery installation setting. It’s never just a case of buying expensive hardware and putting it in front of people. There needs to be processes – either hardware or software based – that protect the public and the artwork. It doesn’t help when lots of technology is built to be experienced/used by one user at a time (it’s called a PC (personal computer) for a reason y’all). Change is no doubt to make it more about groups and collaboration but, y’know, it’ll take time.

Installing Bcc: at Vivid Projects part 2

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The next artwork that was challenging to install was Monuments: Psychic Landscapes by Scott Benesiinaabandan.

Bcc:

I won’t be showing the full artwork as all of the artworks were exclusive to Bcc: and it’s up to the artists whether they show it or not. On a visual level the basic premise of the artwork is that the viewer visits a web page which loads an artwork in the form of a Processing sketch. There is a statue in the centre which becomes obscured by lots of abstract shapes over time whilst an ambient soundtrack plays in the background. At whatever point the viewer chooses they can refresh the screen to clear all of the shapes, once again revealing the statue.

On a technical level the artwork isn’t actually that difficult to install. All that needs doing is opening the web page. The difficult part is controlling user interaction.

If you’ve ever been to an exhibition with digital screen-based artworks which allow user interaction via a mouse, keyboard or even touch screen then you’ve probably seen those same screens not functioning as intended. People always find a way to exist the installation and reveal the desktop or, worse yet, launch a different program or website. So, the choice was made very early on to automate the user interaction in this artwork. After all, aside from loading the artwork, the only user interaction needed was to press F5 to refresh the page. How hard could it be?

Well, it’s very hard to do. Displaying the artwork required two main steps:

  • Launch the web page
  • Refresh the artwork after x seconds

Launch a web page

Launching a specific web page on startup is a relatively easy task. Raspbian by default comes bundled with Chromium so I decided to use this browser (more on that later). The Chromium Man Page says that in order to launch a webpage you just need to run chromium-browser http://example.com. Simple! There’s lots of ways to run a command automatically once a Raspberry Pi is turned on but I settled on this answer and placed a script on the Desktop, made it executable (chmod +x script.sh), and in ~/.config/lxsession/LXDE-pi/autostart I added the line @sh /home/pi/Desktop/script_1.sh. At this stage the script simply was:

#!/bin/bash

while true ; do chromium-browse --noerrdialogs --kiosk --app=http://example.com ; done

I’ll break it down in reverse order. --kiosk launches the browser but in full screen and without the address bar and other decorations. A user can still open/close tabs but since there’s no keyboard interaction this doesn’t matter. --noerrdialogs prevents error dialogs from appearing. In my case the one that kept appearing was the Restore Pages dialog that appears if you don’t shut down Chrome properly. Useful in many cases, but since there’s no keyboard I don’t want this appearing.

I wrapped all of this in a while true loop to safeguard against mischievous people who somehow manage to hack their way into the Raspberry Pi (ssh was disabled), or if Chromium shuts down for some reason. It’s basically checking to see if Chromium is open and if it isn’t it launches it. This will become very important for the next step

Refresh a web page

This is surprisingly difficult to achieve! As mentioned before, this piece requires a user to refresh the page at whatever point they desire. As we were automating this we decided that we wanted a refresh every five minutes.

Unfortunately Chromium doesn’t have any options for automatic refreshing of a web page. There are lots of free plugins that offer automatic refreshing. However, at the time that I tried them they all need to be manually activated. I couldn’t just set it and forget it. It could be argued that asking a gallery assistant to press on a button to activate the auto refreshing isn’t too taxing a task. However, automating ensures that it will always definitely be done.

At this point I looked at other browsers. Midori is lightweight enough to be installed on a Raspberry Pi. It has options to launch a web page from the command line and, according to this Stackexchange answer it has had the option since at least 2014 to refresh a web page using the -i or --inactivity-reset= option. However, I tried this and it just wasn’t working. I don’t know why and couldn’t find any bug reports about it.

It was at this point that I unleashed the most inelegant, hacky, don’t-judge-me-on-my-code-judge-me-on-my-results, horrible solution ever. What if instead of refreshing the browser tab I refreshed the browser itself i.e. close and reopen the browser? I already had a while true loop to reopen it if it closed so all I needed was another command or script that would send the killall command to Chromium after a specific amount of time (five minutes). I created another script with this as its contents:

#!/bin/bash

while true ; do sleep 300 ; killall chromium-browser ; done

The sleep command makes the script wait 300 seconds (five minutes) before proceeding onto the next part, which is to kill (close) chromimum-browser. And, by wrapping it in a while-true loop it’ll do this until the end of eternity the exhibition. Since implementing this I noticed a similar answer on the Stackoverflow site which puts both commands in a single file.

And there you have it. To refresh a web page I basically have to kill it every 300 seconds. More violent than it needs to be!

Installing Bcc: at Vivid Projects part 1

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I took a bit of a break from writing the Development Updates. September was pretty busy with Bcc: (more on that below) and then I was completing a commission for Will’s Kitchen/The Shakespeare Birthplace Trust and preparing for my solo exhibition, We Are Your Friends.

With all of that now completed I’m writing a few posts about one project in particular: Bcc:

The Bcc: exhibition opened at Vivid Projects on Friday 6th September. It was a collaboration between Vancouver-based Decoy Magazine and Birmingham-based Vivid Projects. The exhibition featured a curated selection of works from Decoy Magazine’s online art subscription service called Bcc:. The basic premise is that each month you’d get specially commissioned art in your e-mail inbox.

Bcc:

Bcc:

After being part of Bcc: in 2018 I suggested to Lauren Marsden, the Curator and Editor of Decoy Magazine, that it could possibly become an IRL exhibition at Vivid Projects. At the time I was still working there so I worked on getting most things in place to get the exhibition going. Then I left in 2019. Because of my prior involvement in Bcc: and the massive technical challenge involved in installing the work (more on that later) I was asked to produce the exhibition.

Depending on how you look at it the technical aspect of installing the exhibition could be very simple. Most of the works in Bcc: were short movies and animations/gifs, and Vivid Projects has long used the Adafruit Raspberry Pi Video Looper to handle playing videos.

Some works, however, required more attention. There were some works that were interactive websites, some that were animated gifs and some that require additional hardware. Prior to the exhibition this probably didn’t present any problems as the works were viewed by most likely one person on their personal phone or computer. The challenge comes when it’s on a shared computer in a public environment. Additionally, operating the works needs to be as hands off as possible. That is, I didnt want it to be the case that myself or another technician had to be on hand every day to go through complicated procedures to turn on all of the work. They needed to be automatic. With 17 works each needing their own computer/Raspberry Pi there was a lot to prepare. Over the next few posts I’ll take you through some of the works and their technical challenges:

Playing gifs on a raspberry pi

Of the 17 works on show in the exhibition 10 were animated gifs. To stay true to the small nature of animated gifs (don’t get me started on the concept of HD gifs) we decided to display the gifs on the Official Raspberry Pi 7″ Touchscreen Display. This proved to be a really good decision overall. It required that visitors get really close to the works and spend time with a format that can sometimes be a bit throwaway.

Bcc:

As mentioned before, for a long time Vivid Projects has used the Adafruiit Raspberry Pi Video Looper software to play videos. It works (mostly) great with the exception that it doesn’t play animated gifs. The main underlying software, omxplayer, only supports video files. Even the supplied alternative player, hello_video, also only plays video files.

Your immediate though might be to just convert the animated gifs to video files. Whilst this “works” there is always the danger that in converting a file you reduce the quality of it. For an artist like Nicolas Sassoon, who makes pixel-perfect animations that match a specific screen size, this would be unacceptable. So I went on a journey to find a way to play gifs.

The requirements for the software is that it should operate in a similar way to the Adafruit software and play a gif on loop with little or no pause between loops. It should play in the frame buffer (i.e. without needing to load the desktop) and it should make use of the GPU (helps prevent screen tearing). And for a bonus it should be able to play a series of gifs one after the other. Simple, right?

TL;DR: There isn’t a reliable way, I had to convert to a video.

Some of the solutions I saw were saying to use Imagemagick to play the gifs. This wouldn’t work as I would need to launch the desktop. Then, I’d need to script it to go full screen, centre the gif, change the background to black etc.

FBI and FIM don’t support animated gifs, although they are useful if you ever want to play a slideshow of static images.

feh is another image viewer that uses the framebuffer. However, it also doesn’t support animated gifs and, according to this response from the author, this is by design.

This suggested solution of converting to images kinda works but doesn’t take into account if each animation frame has different durations (see this GIMP tutorial for example on how to use it). With that in mind for this to work I would need to get the duration of each frame in each of the 10 gifs, separate the gifs into their individual frames, and then tell feh to play each frame for it’s specified duration. So, this method could work but it would require a lot of work!

This thread on the Raspberry Pi forum did provide a possible solution which I didn’t try but it also pointed me to FBpyGIF, which was certainly the most promising of the solutions. However, a couple of problems prevent me from using it. Still very promising though!

Finally, I tried one of the various GIF Frames that play a folder of animated gifs on loop. Sounds like it works but there’s screen tearing on some fast-moving gifs. I’m guessing this is because it doesn’t have hardware acceleration and/or because it uses Chromium to play the gifs.

Soooooo after all of this I felt a bit defeated and I decided to just convert the animated gifs to videos. I used Handbrake and noticed no loss of quality in the conversion. Even if there was, on a 7-inch screen it’d be quite hard to see. Using the Adafruit player/omxplayer I was initially having some issues with aspect ratio. Even with –aspect-mode set to fill stretch or letterbox, the videos were being stretched to fill the screen. To illustrate take the following video, which is 1024×68/4:3.


(fyi it was made using Natron and this script to add in a timecode)

When play on the screen it is stretched to fill the screen.

The Raspberry Pi touch screen has a resolution of 800 x 480, which is a 5:3 aspect ratio. Most of the videos and animated gifs were HD/16:9 so would be letterboxed by default.

So I had the bright idea of padding each video so that it was exactly 800×480.

Now, the Adafruit player/omxplayer says it can play any video which is H.264 encoded but I’ve had some troubles in the past, so whenever I’m given a video I usually convert it using Handbrake with the Fast 1080p30 preset. These settings have always worked for me but for some reason on this occasion the video was stuttering a lot! What was strange was that the original videos (the animated gifs converted to videos without resizing) played fine. Even after they were run through Handbrake. Why when they were converted to 800×480 size did they stutter?

It was two days before the exhibition opening that I remembered that some time in 2016 I had an issue with omxplayer in that it didn’t play videos if the video didn’t have an audio track. Why? I don’t know. Maybe audio was the problem in this scenario too? It was worth a try and so I decided to disbale the audio track using the -n -1 option. This doesn’t just turn the audio down, it disable encoding of it. And guess what. IT WORKED!

I have absolutely no idea why this worked or why the error ocurred in the first place. Here’s the extra arguments that I included on line 107 of video_looper.ini.

extra_args = --no-osd --audio_fifo 0.01 --video_fifo 0.01 -n -1 --aspect-mode stretch

All of that just to play animated gifs! Now that I had the code perfected copying it to all of the other Raspberry Pi’s was simple. If the aforementioned softwares had animated gif playback by default then this would’ve been solved much quicker but for now it seems the most reliable way to play animated gifs on a loop on a Raspberry Pi is to convert them to video.

What’s happening on Twitter

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The following is compiled from a bunch of Tweets that I made in December 2018. After reading you’ll see why I have to write it here! While it is not directly related with programming or making art, it does help with Getting Things Done, so I decided to include it here.

Like many people I’ve started to remove myself from a lot of social media websites. First was Facebook in 2017. The reason for this is that was really annoyed that it was using nostalgia to manipulate me into staying on the website. In shoving 10 year-old photos into my view through the On This Day feature it was giving me little hits of dopamine by reminding me of the good ol’ times, even if they were 10 years ago with people that, for whatever reason, are no longer part of my life.

One solution to this was to make sure that Facebook only had recent information about me. I started manually deleting anything that was more than 2 year old. I eventually found a Chrome plugin (use at your own risk) that made it easier to do but this process was a chore that ultimately didn’t solve the fact that Facebook was the problem. After about a year I left unannounced. After deleting my account, of course.

My “relationship” with Twitter is a bit different. I’ve always preferred it over Facebook as it isn’t as intrusive, at least not directly. It doesn’t constantly ask you to share who you’re dating, identify your family, upload photos from your night out or tag your friends in everything. Instead it felt like it was more concerned with what was happening at that moment.

Like Facebook, though, I became a bit concerned with how much data about me it was storing. I started using the website in 2008 (Facebook in 2007) and have used it almost daily since then. Over that time I have grown and changed as a person many times over. I don’t want this history to be fully documented and, more importantly, available for anyone to browse through. Whilst the majority of the 40k tweets I accumulated over that period probably consists mostly of cat gifs, memes and the word “lol”, maybe there’s there events that I’d rather not have documented, like Tweets showing friendships and relationships falling apart, embarrassing photos of myself or others on nights out, or even just me saying something that was totally out of order.

I’m glad that I have friends (and enemies) that have called me out on my bullshit and hope that they continue to point out times when I do something wrong. However, I’d rather that the trail of data I leave on these sites that I use every day reflected me as I am now, not who I was 10 or even 20 years ago.

So, I went on a mission to find a way to keep my Tweets current. I needed a tool, or tools, that would automatically delete Tweets older than a certain time period.

A lot has been written about Tweetdelete. However, I don’t want to rely on a third party service. Many people do trust the service, but there’s always risks in using third party services, especially when they have access to a lot of your information. Then there’s the risk that it could one day shut down so I decided that I wanted something that I could deploy myself.

Deploying your own script requires that you register a developer account on Twitter.

Delete tweets is a Python script that let’s you delete tweets and specify a cut off date. However, to run it you need to download your Twitter archive. At the time of writing this can only be done once a month and has to be done manually. So, you could automate the running of the script but there’s still manual intervention required.

This Python script is similar but it lets you specify cutoff date as a number of days, not dates. Still, it requires downloading your Twitter archive manually.

This Ruby script works perfectly! You specify cutoff point in days and then when it is run it deletes any tweets older than that cutoff point. It even has the option to put in the ID of Tweets that you want to save. It only requires a developer account and you don’t need to download your archive.

There’s even a companion script that removes Likes. This doesn’t have any options for date cutoff but in my case it doesn’t matter. Once I’ve liked something once it doesn’t mean that I like it (or anything else that person has posted) forever so I’m not sure why I need to have my likes recorded and archived.

I decided to install both scripts on an always-on Raspberry Pi. Installing them took a bit of time due to it needing to install a bunch of Ruby gems. Once it was installed I set up a cron job to run the script at regular intervals. I have mine set to twice a day and to only keep the last two weeks of tweets. I feel that that is enough time for the tweets/memes to have whatever impact that they’re going to have. After two weeks they’re gone.

All of this effort to manage my experience of using Twitter might not be a solution and instead might be more of a distraction from the fact that the problem is Twitter, and maybe even social media in general. There have been many efforts from individuals to make social media better. On Facebook there is F.B. Purity which helps remove things like adverts, the On This Day feature and other things.

One of my favourite tools that I still use is the Facebook and Twitter Demetricator from Ben Grosser. These desktop-only tools remove mentions of the number of Likes, replies and retweets a post gets so that you can focus on the cat memes important things. These plugins have been getting a lot of attention recently. See Ben’s Instagram for more.

This of course doesn’t solve social media’s problems but just makes my experience of it just that little bit less stressful.

Select objects of similar size in Inkscape

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For the AlgoMech 2019 festival in June I created a new performative drawing piece, A Perfect Circle. The piece is about how we interface with computers that analyse our activities. It consists of a video and accompanying plotter drawings.

Making A Perfect Circle presented me with a few challenges. The make the video element I hacked together a couple of Processing scripts that did basic motion tracking by following a user-specified colour. It would draw these lines, creating new lines (instead of adding to an existing line) at each major turn and giving them a unique colour.

The next stage was to export those drawn lines to SVGs (or PDFs) so that I could export them to Inkscape and then a plotter. Fortunately Processing already has functions for exporting to SVGs. Unfortunately for me if I were to implement this as is suggested in the help file it would export both the drawn line and the background video as a still frame. I produced a very hacky workaround (with help from Ben Neal) which “works” but produces a few unwanted artefacts.

Before I go on I should probably explain what a plotter is as the unwanted artefacts relate to it. For this I will copy from the Wikipedia article on plotters:

The plotter is a computer printer for printing vector graphics. Plotters draw pictures on paper using a pen. In the past, plotters were used in applications such as computer-aided design, as they were able to produce line drawings much faster and of a higher quality than contemporary conventional printers, and small desktop plotters were often used for business graphics.

At home I have a Silhouette Cameo 2 vinyl cutter. When using this great Inkscape plugin I can bypass Silhouette’s proprietary software and send artwork directly to the cutter from Inkscape. Thanks to a pen holder adaptor I can replace the vinyl cutting blades with a pen and turn the vinyl cutter into a plotter 🙂

Back to the Processing sketch. The hacky code that I made produced the desired lines but also it had lots of additional single-node paths/dots at the start of each line.

Removing these wouldn’t be very easy. Using Edit > Select Same > Fill and Stroke or Fill Color or any of the other options wouldn’t work as it would also end up selecting the lines. I then had the bright idea to select objects based on their size. All of the dots had a dimension of 4.057×4.000px, so in theory there would be an option like Edit > Select Same > Size. However, this is not so.

After a discussion on the Inkscape forum I opened a feature request on the Inkscape bug tracker to select objects of similar size. One thing I added to this was the idea of a threshold. Using this you could select objects that were within n% of the size of the selected object. If you’ve ever used GIMP you would have seen a similar function in its fuzzy selection tool This could definitely be useful if you trace bitmaps and it produces a lot of speckles. I also added a mockup to show how it could be applied to other options in the Edit > Select Same menu options.

Anyway, at the moment this exists as a feature request. I think Inkscape is concentrating on delivering version 1.0 of the software so I don’t expect to see this implemented any time soon. As with anything in the land of open source, if you’ve got the skills to do this please contribute!

In the end I used fablabnbg’s Inkscape extension to chain all (or most) of the paths into one big path. This made selecting the dots easier as I could just hide the big path(s) once they were chained together.

After that it was a simple case of sending it to the plotter!

Convert Object texture coordinates to UV in Blender

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Making digital art is quite a lengthy process and even moreso if you’re using non standard processes or making your own software. For awhile I’ve wanted to write about my processes and how I’ve overcome the bugs and problems. In what will hopefully be a regular series of blog posts I’m going to give a bit of insight into this process. In a way it’ll be a tutorial. Let’s go!

For Visually Similar I wanted to texture each 3D model using lots of images found on the internet. Rather than create one single material containing a texture with all of the found images I instead decided I would add a material for each image texture and, using their alpha channels, composite them over each other.

If you’ve ever had to position something accurately on a UV map you’ll know how much of a pain it can be. So fortunately, in the Texture Coordinate node you can use the Object outlet to another object (usually an empty) as the source of its coordinates. This uses the reference object’s local Z direction as its up direction.

So far,so good, except it did not yet work in Blender’s new EEVEE rendering engine. Yes, yes, I know EEVEE is still under development and shouldn’t be used in production etc. Still, after doing a bit of research it looks like this is going to be implemented.

So, I had a rather smrat idea as a workaround. Could I take the UV coordinates generated by the Object oulet whilst using Cycles and paste those into the UV texture options using a Mapping node? Short answer: no. To do this I would need some sort of viewer or analyser node that would show me the data being output from a node. So, I suggested this idea on the Right-Click Select ideas website. A healthy discussion followed and hopefully something will come of it.

In the end I had to resort to baking the texture and then applying that to the 3D model. In doing this I learnt that baking a UV texture on a complex model will take a lifetime, and so I had to do it on a decimated model and then put that on the original, complex model. This, of course, created some unwanted artefacts. *sadface*

Since I originally encountered this problem it has actually been addressed in a Blender update! However, it only works at render time but it’s progress! 🙂

So that is some insight into how I make some of my art. There’s a lot of problem solving, lots of showstopping bugs and lots of workarounds. Somewhere in that process art is made! I’m hoping to do these every month but we’ll see how that goes.