Some Useful ffmpeg Incantations

ffmpeg, if you haven’t heard of it, is a free, open source video multitool. I use it for many different things, but just infrequently enough to forget the commands. Thought I’d write a few of them here.

Here’s how to cut a section from a full video, without re-encoding the video. This command crops the first ten seconds and copies that content to a new file:

ffmpeg -i video_full.mp4 -ss 00:00:00 -to 00:10:00 -c copy video_section.mp4

To concatenate multiple clips without re-encoding, you need to create a list. You can type this list in the command window but it’s easier to create a text file with the following format.

file '/path/to/clip1'
file '/path/to/clip2'
file '/path/to/clip3'


ffmpeg -f concat -safe 0 -i vidlist.txt -c copy output

Although it may seem a bit clunky, this is a fast way to trim out unwanted sections of clips without re-encoding. Simply trim out the good section and then concatenate them together.

(I got this example from Elder Geek on Stackoverflow)

Here’s how to convert a video into a sequence of still images:

ffmpeg -i video.flv image%d.jpg

And back:

$ ffmpeg -f image01 -i image%d.jpg video.mp4
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Still dark at the start.

Work in the dark.

Leave in the dark.

Ready for those bright lights.

Hard fights

Long nights

It wasn’t easy

But it was worthwhile.

It wasn’t simple

But it was satisfying.

It wasn’t just me

It was a whole team.

The whole way.

Thanks everyone.

Here’s to outsized ambition.

To clarity

And vision.

Here’s to structure

And systems.

Here’s to family –

And also to friends (who left us this year)

And friends (who left us this year)

I leave you with this.

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RIP Aaron M. Clarke

Aaron Clarke and I met in 2007 at NDSU, during our Ph.D. work. Aaron was immediate. Bright, funny, goofy – and smart as hell. On top of that, he was imaginative and warm – rare in frozen Fargo, North Dakota, where we wintered. It became obvious that Aaron outclassed his classmates. He would become a great scientist.

Aaron had a truly outsized desire to teach. He took me under his wing and explained everything from pre-calc to Fourier transforms (I did not deserve any of it – all pearls before swine). He loved to share (and overshare) his interests, knowledge, and fascination with everything about vision and the brain. We would often joke about “cracking the brain code”.  We would often just joke – Aaron loved to laugh. To know Aaron was to know the sound of his laughter.

Grad school was horrible for me, the ugly stuff started right away. In my first year, the bathroom above my desk broke open and leaked sewage over my books and things. It was Aaron that called – not any of the other students present. He also went out of his way to save my camera from that shitstorm. Here’s that voicemail:

That’s just how Aaron was. He cared and he always showed up (and not just for me). When my tooth was rotting out of my head, and I couldn’t afford to fix it, Aaron was there. When I needed to move equipment out of a flooded basement, Aaron was there. When my elbow was broken and I could no longer afford to live in my cheap apartment, Aaron helped me move.

We went through a lot of shit in grad school; most people do. Aaron, time and again, looked for any opportunity to help. He had a huge heart and really deeply cared for other people. I was sick a lot and had no health insurance – there was a time when I didn’t show up for a few days straight.  Aaron never failed to call:

More than anybody else, Aaron made me feel a welcome part of the vision science community. Aaron enthusiastically introduced me to numerous friends and labmates from around the world. Even since leaving the Dakotas and the vision science community, I have found him famous and infamous among vision scientists, known as a bright and high-energy guy. Hell, even when Minard Hall collapsed on our labs and lives, he seemed unfazed and continued to produce great research.

The guy was unstoppable.

He was also hungry. Man, Aaron could eat. And we were both poor so we shared a lot of food. Someone gave me a broken pizza oven, and I fixed it. We’d go to this grody awful grocery store called Sun Mart (right next to his apartment and walking distance to the lab):

…and buy $1.99 frozen pizzas and dress them up with white vinegar and mealy tomatoes, and bake them in that oven. I remember when he introduced me to information theory and Claude Shannon. And we’d sit there learning about encoding and information transmission over our pizza, working the problems, reading the papers.

Later, I pulled a grill off the curb. A new Asian market had opened up in town, and had a loss leader deal – $5/lb ribeye steaks. We ate a LOT of those. I always let Aaron know when I was going there, and he always wanted some. And we fished in the Red River, too. And ate it for breakfast. From our email about it, Aaron said: “P.S.  We absolutely have to do that again.  It was awesome.” We said that about a lot of the things we did.

You might notice that many of the images in this post are the two of us working together. And that’s because we worked together often. We built book scanning machines, stereo cameras, display alignment systems (Johnny Lee-style), and a bunch of other stuff.  The book scanner in this picture was “Aaron’s Scanner” – I built him this scanner in exchange for PageBuilder, the first DIY Book Scanner software package. Which, of course, he wrote in Matlab. In a weekend. Here’s the original announcement.


Without Aaron, I would not have won the Instructables contest and built a huge community. And I wouldn’t have had so much fun doing it:

Today I sit in my workshop in Los Angeles, California. Workin’ on a Sunday, like Aaron and I used to do. And I have this life and this job in no small part because I met Aaron Clarke – because of his hard work and sharp mind, sure, but also because of the way he shared his time. You see, winning that Instructables contest (and the laser cutter) changed my life and got me out of the Dakotas and that ill-fated grad program. And when it came time to drop out and go, Aaron helped me pack my car, and sent the laser with me.

We both went on to work in vision related fields – myself in display research and development, and Aaron in Turkey doing vision science, and more recently joining Magic Leap. We’d have had a lot to talk about, if I’d ever called.

Aaron passed away in his home Saturday, November 24, 2018. I would say Rest In Peace but that’s ridiculous if you knew the guy, he wouldn’t want me to talk like that.

So, Rock On In Peace, Aaron “The Man” Clarke. You are the man. I miss you terribly. I am so sorry for not reaching out for 4 straight years. Thank you for helping me. I am proud of what we created.

If you have a story or something to share about Aaron, please post it here.

Update: Yuliya S. shared a video (via Eugenie) in which you can hear Aaron laughing and enjoying fireworks – it really brought a smile to my face:



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New project – dancing mic stand for Justin Timberlake

I left Apple last year to start my own prototyping business. I knew I’d find interesting work, but I didn’t know how interesting.

As Vice Chief, I designed and built the dancing mic stand that Justin Timberlake used in his Superbowl performance . The whole thing was a collaboration with choreographer Marty Kudelka, who came up with the original idea.  The public reception has been great — I even got a shoutout in my home town news.


A post shared by Mark Nguyen (@marklashark) on

And after that, I engineered and built a 2.0 version of the dancing mic stand for his Man Of The Woods worldwide tour. It debuted this evening in Toronto – and how!

Of course, the mic stand is only part of the show – I have to give props to JT’s crew, Fireplay, All Access, and TAIT for all they did to make this possible. And of course, all respect to JT for absolutely owning the performance.


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Exit Criteria

I spent two years at a big tech company, and in that time I learned a lot about leadership – both how to inspire people to do their very best (and only that), and how to squander their efforts and spoil their enthusiasm. I will quote the late Steve Jobs. Know I am not endorsing him, just presenting some of his ideas.

Your time is limited, so don’t waste it living someone else’s life. Don’t be trapped by dogma — which is living with the results of other people’s thinking. Don’t let the noise of others’ opinions drown out your own inner voice. And most important, have the courage to follow your heart and intuition. They somehow already know what you truly want to become. Everything else is secondary.

I think if you do something and it turns out pretty good, then you should go do something else wonderful, not dwell on it for too long. Just figure out what’s next.

My favorite things in life don’t cost any money. It’s really clear that the most precious resource we all have is time.

For a while at least, I have my time back. Hello, World.


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Two Thousand Sixteen

We spent 2016 in Silicon Valley. What a fever dream.

Such a bait-and-switch.

What to do but organize. 

Bring all capabilities online,

And get everything on wheels.

It’s a good time to be bright,


and sharp:

It’s a good time to listen,

to purge,

to grow.

This year, I learned that free time is freedom.  My DIY ethos is stronger than ever.

Thank you, friends and family for all the sharp thoughts

and bright ideas.

See you in the future.



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Internet Dan Seems To Be Dead

It does seem that way, though I’m not.

Biche would know; she was in the shop with me when Internet Dan became my identity, calling, and full-time occupation.

Dead is the wrong word. I retired this year – and in the process, I published more than I ever have before. In fact, I said damn near everything I had to say. Twenty two thousand words. Do me a favor and read through it:


Then I gave the DIY Book Scanner project to Jonathon and Scann. It was hard to let go of so much identity. You don’t simply walk away from six years of sweat, blood, and plywood. Or 1700 square feet of productive, self-sufficient space. But here I am with my brother, tearing it

It’s not easy to hand over a business that is making money. Or to risk compromising friendships with die-hard supporters like Scann, Jonathon, jck57, or Johannes. I now know I did the right thing, and I know it because I can see the work taking new forms, making new headway and progress in directions I could never seem to take it. Sometimes you just have to get out of the way.


These 50-odd weeks were heavy learning. And my mind changed a lot. I wanted to post about these things. In no order –

1: I no longer believe in Open Hardware licensing as endorsed by OSHWA. It’s bogus; legally toothless; dangerous to people with good intentions. It’s borderline fraud; copyright cannot protect hardware. Pretending like it does is a pretty big mistake, pushing it on others is inexcusable. I decided to make the book scanner design public domain – I wasn’t about to screw it up like other people who harvest Open Source for profit. I recommend you do the same.

2: Some of the most interesting work is secret; I used to hate secrets, but I now understand they can provide something valuable – a safe space to explore new ideas without a constant chattering peanut gallery. I still believe in radical openness, but not for everything. Secrecy has value. Interestingly, secrecy is also the reason that certain communities (like the intelligence community) can never publicly defend themselves. Sucks to be them, but it’s something to keep in mind when you criticize an organization with no outgoing interface. Or when you join one. Finally, I also learned that secrecy gives people a lot of latitude to lie about what they’ve done. No one can know if you really did it, after all.

3. I can’t do it alone. Radical self-sufficiency is still powerful in me; I still think it is best to Do It Yourself. I want to live in a world of my own making, and I want to make everything in it. And I do this, perhaps more than others.  Years ago, Golan Levin and I were having a conversation about writing image processing software for the DIY Book Scanner. When I said how badly I wanted to write the software, he challenged – “Haven’t you learned anything from your own project?” – meaning that I should rely on others to do what they are good at. To crowdsource something more than enthusiasm. But beyond projects and hardware, I have also learned that life is better with a partner. Whole essays hide behind that sentence.

3. My generation faces two major challenges – the struggle for human rights (these are the rights to gay marriage, to equal pay for women, to equality for all races, to equal access to all that life has to offer) — and the struggle for control of our data and privacy. Right now, we are losing both of these struggles. I honestly and naively thought we were doing better than we were, but that is an absurd position in light of this year’s revelatory authority tantrums (cops continuously killing blacks, the slow-burn of Snowden revelations). I have nothing good to say about this. My generation is way more concerned with where their food notionally comes from than where their data is going. And while there’s a lot of lip service to feminism, racial equality, and gay rights, there’s a lot more actual work going on to legalize marijuana. Actions are the acid test of platitudes. And the approach generally sucks. I like the way Alexis Madrigal framed it:

“Individuals unplugging is not actually an answer to the biggest technological problems of our time just as any individual’s local, organic dietary habits don’t solve global agriculture’s issues”

While our generation may be the most technologically ensconced yet on earth, we’re mostly incompetent in programming and controlling that technology. The most powerful and democratizing lever ever in human hands is barely able to pry us off the couch in the middle of the walled garden. I’m ashamed.


Well, this is my year-end post. Usually these posts are basically big picture-poems; here are some words and images to keep the tradition strong. Sorry that more of these weren’t shared at the time they were created. Time has been tight.

I didn’t think 2015 would be the year I left Los Angeles. I had planned to stay.

I miss you, Towne.

Inside –

and Out.

Miss you Max and Marisa,

Miss you Ali and Pehr. pehr

And Eric and America and Susan and Lanny and Quinn and Sebastian and Slators and Arnars and Schwerts and Imagineers all. And all those family members that died this year. We burned the Christmas tree for you.

Miss you Pho 87, whoa

Miss you Spring for Coffee, there is nothing like you here

Miss you fast, cheap help,

Miss you, morning walks and incoming airplane constellations.

Much of this year was getting my thoughts together – but I’m also learning to organize things-



(power tools)

(air tools)



(paint and tape)




A smaller and more efficient space makes more sense, anyway. Thanks, Rob, for all your Googly help with this:

It’s been good getting our house into order. I always said I never would.

but piece by piece

petal by petal

pin by pin



handDANDANUNITED_1000px_DSC03720-EditWe did it. Goddamn! I got the better deal. By far. Thank you for asking, Dana.

I love our life together. I love our family – the Reetz side:

And the Dana side:

And Stan:

Always maintained I wouldn’t marry. But I’d never met a Dana before. We share words like these:

And do things like this:

and this:coconut

and this:swing

also meals like these.

I hope it’s clear, I’m really not dead – just different. I can’t work from the position I used to; I have to do something new. Fortunately, I have help.

The next few years will be most interesting.

Miss you all. Have a great 2016.


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Anti-Intrusion/Anti-Graffiti Measures


Check out this standpipe. Above it, there is a fire escape which has obviously-painted-over graffiti. On it, there is a mess of thick, black grease, and next to it is a coil of razor and barbed wire.

Hadn’t seen this rather extreme approach to climbers before.

Near my building there are often streetwalkers. They tear the rearview mirrors from vehicles, presumably to check makeup/freshen up. After several losses, one of my neighbors applied axle grease to the back of his mirrors. The interesting thing, in my mind, is that it’s not the slipperiness, it’s about and cleanliness and appearance. For someone who lives on the street, a sink and special soap for heavy grease is hard to find. For a community that is visually oriented and fashion conscious like graf artists, something that spoils a new set of Converse may be a better defense than something that threatens life and limb.

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Struggling to pay rent. GoPro to the rescue.

Like any reasonable person, my landlord wants a check shoved under an unmarked door in the basement. Problem is, at night an on the weekends, the door leading to the basement is locked. I am so motivated to pay my landlord that I jammed a credit card into the door to try to open it. Anyone who has tried this “trick” knows that 9 times out of 10 you just break off the damned card and the door remains locked.

As it turns out, Dana was just sponsored by GoPro, so I have around 7 metric shit-tons of GoPro garbage in my workshop. The lexan-like material that they use in their packaging felt flexible enough to be a good shim.

2015-01-01 17.19.47

Dimensions unimportant. Big enough so you can grab on with two hands.
2015-01-01 17.08.42

2015-01-01 17.04.45

Start high above the latch and work down. Use force.
2015-01-01 17.05.16

2015-01-01 17.05.29

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2014 Ends and Pieces

2014 in three sentences:

  • Designing, manufacturing, promoting, and documenting new book scanners consumed every waking minute.
  • In spite of a great 4-year run, I lost my enthusiasm for my professional work as an Imagineer and Disney Researcher, so I moved on.
  • I pushed myself harder than ever before, and paid for it and got paid for it.

That’s what it was, this is what it felt and looked like.

Waking up in Los Angeles.

In Fargo.

On a beach somewhere, rocket propellant night-light.

At a fire with my brothers.shed

In a tent on the grass.

That’s how these things start.silence

Friends get involved – the best ones.

It always looks bad.

It always starts hard. If just one person knew better than you, you could ask.

Most of the time, you just have to build it. Answer with your prototypes.

You gotta do it again and again and again, I highly recommend robots.

Yeah, it always looks bad. Even with your fanciest math. StartsLike5

Before it starts to cohere. StartsLike6

Before first light. StartsLike11

If you do it right, you might get some other things out of it, too. StartsLike19

Bigger things. StartsLike12

Good ideas get better. StartsLike16r

If you can find them, the best friends have their own ideas. StartsLike7

Their own agendas and intelligence.js valerian pierre scanner sculpture

They embody good ideas getting better. StartsLike8

Challenged, invigorated, expanded — like they were yours to begin with.

When things feel strong, repeat.


Repeat. StartsLike15

Revise. Revise

Repeat. repeat

Revise. reviserepeat

Repeat. repeat2

Revise. reviserepeatreviserepeat

Repeat, I’m beat. There’s no end to this, but a year’s gone by.
Ending here – always gotta keep in mind that fast feedback is the most important result of working this way. The mistake is to confuse motion with progress. It’s time for me to fix on what I’ve learned, take it in, and correct course, again.

To everyone who showed up, everyone who supported, who delivered on time, who didn’t over-promise, who taught me new things: thank you.

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Affordable Affordances

I use a bicycle wrench to tighten the collet on my CNC router. It has 32mm and 30mm box-end openings – 30mm fits the nut on my collet. About half the time, I put the wrong side on the collet and feel a mild pang of annoyance. This is a failure of the tool markings (low contrast and low discriminability between end sizes) and a failure on my part because I should have fixed it the first time it happened.

An obvious solution would be to just cut the useless end off. Reducing the functionality of tools isn’t my first line of offense, so for years I’ve just suffered this minor frustration. Anyone who’s worked in a shop long enough knows that these tiny annoyances add up over time and make things less fun and mistakes more frequent. Today, it finally annoyed me enough to think of a proper lazy fix. By gaff-taping over the far end, I created a grippy surface and a visually obvious orientation for the wrench.



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DIYBookscanner on Exhibit in Paris

vanni foldout scanner sculpture on exhibit

Pierre Vanni dialed up the foldout scanner an order of magnitude. The gorgeous monster is part of Pierre’s exhibit Google Raconte at Les Arts Décoratifs in Paris.

Thanks to him (right) and his accomplices JS (left) and Valerian.

js valerian pierre scanner sculpture

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Two Thousand Thirteen Seconds B-Sides and Rarities

Consider this my 2013 photo essay; it started as an experiment in taking a one-second video every day and ended up a pretty and personal thing. I only removed work-related videos; there are pieces of around 460 videos in this compilation. Everything is shown roughly in order from January to December. The music is mine and it’s unfinished demo material.

Special thanks to Dana, Eric, Matti, Scann, Stan, Jillian, Greg, Testa, Dolce, Tox, Pehr, and all those unmentioned.

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The Making Of Skull Face 2013


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Every Year, I Draw A Skull On My Face With Eyeliner Pencil (2013)

2013: Reetz2013Skull









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Vote With Your Wallet

voteWhether you mean to or not.

Los Angeles, California, 2011.

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Inevitability and Proximity

I keep hearing “It will happen” or “It’s gonna happen”, referring to inevitability in a social context.  These predictions are likely to be correct, if only because things are set up badly – in a negligent way, even – and no corrective action is being taken.gasoline

Los Angeles, California, 2013.

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Recently Hauled A Bit Of Foam


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Sewing Kit

I made a sewing kit for Dana, who is on the road with JT. It’s a 3D printed, laser cut box with a wide assortment of garment repair and management stuff jammed inside.
2013-10-19 16.46.16

Here, it is pictured with the lid and topmost components removed. 2013-10-19 16.49.01

Here you can see the full contents, which I will come back and detail someday. I’m particularly proud of the thread spools. I printed tiny caps for them that converted them into storage containers for pins, bra-clips, seam rippers, buttons, etc.
2013-10-19 16.52.44

You may notice a lack of scissors. A scissors was unnecessary because Dana already has one in her Leatherman Wave.

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Egress Axe

2013-10-20 08.59.31

I was impressed to see the glow-in-the-dark grab handle, and doubly impressed to see a handy fire-axe available for chopping out of a locked freezer cabinet.

So impressed, in fact, that I was apparently unable to take a focused photograph.

Smart’N’Final, Los Angeles, CA.

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