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Ramblings on code, startups, and everything in between

It rained, it snowed, but hey it’s Friday! Grab some beers and snack on some links.

Posted In: Friday Links

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A couple of months ago I was at Firebrand Saints and started wondering how the effects that they run on their videos work. At Firebrand, their main bar has a few flat screen TVs showing cable channels you’d expect but every now and then one of the TVs will start displaying the video through a filter. So as you’re sitting at the bar you’ll notice Sportcenter go from regular video to what looks like Sportcenter put through a pixelated filter. Unfortunately, the fall got a bit busy and I forgot to jot this down but it recently came back to me while watching the Family Guy – Take On Me skit.

So how do you programmatically apply effects to video? After some searching around, it seems like the preferred way to do this is to convert the video to a series of images, apply the effects, and then encode the images back to a video. Since we’re on Linux the weapons of choice for this are libav (ffmpeg fork) and ImageMagick. Additionally, I used youtube-dl to grab some source video from YouTube.

Playing around with manipulating videos and images is pretty CPU intensive so I decided to do this on a c3.xlarge. Once you have a machine up, just run the following to get everything setup:

Now, snag yourself a video from YouTube:

Next, you’ll want to extract the audio and then the individual frames from the video:

And now for the fun part – time to apply some effects to the image! As an fun first pass I ran the “paint” transform across the images. PS. Remember how we launched on that c3.xlarge? Well now we can run the transforms in parallel with xargs:

Finally, you’ll need to encode the images back together into a video format of your choice:

Here’s a clip of the video I ended up with:

So what else can you do with this? Well that’s the awesome part! An image manipulations you can do programmatically (ImageMagick, NodeJS, etc.) you can apply to your video.

Perhaps some Mystery Science Taylor Swift?

Unfortunately this adventure has left me with more questions than answers:

  • How do you apply filters to a video in real time?
  • Would it be possible to integrate this into a rooted (or stock) Chromecast?
  • Could you build something to support user interactivity? Maybe with Canvas/nodeJS?

I’d love any thoughts, input, or ideas!

Posted In: General

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It’s Friday, you did it! To bootstrap your weekend we’ve got some kickass links from the last week.

Posted In: Friday Links

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We’d like to extend congratulations to one of our clients, SoonSpoon, on being acquired by Reserve, a New York-based restaurant reservations application.  Led by one of the co-founders of Uber, Reserve aims to simplify the restaurant reservation process much like Uber did for the taxi industry. You can read more about them in this recent Boston Globe article.

With Priceline recently purchasing OpenTable for a cool $2.5 billion, the online reservation space seems to be gaining momentum and piling up more success stories.  Although we’re sad to see them go, we are excited for the SoonSpoon guys and are glad to have helped them build out their beta product (you may have remembered our blog post from their launch).

SoonSpoon had a great idea and relentlessly executed on it, building a strong community of partner restaurants and users. In the day in age where many try but few succeed it’s always inspiring to see a start-up success story – as Michael Dell once put it, “Ideas are commodity. Execution of them is not.”

Posted In: Launch, Startups

I’m pretty bullish on Bitcoin so a few months ago I set out to build a “pure” Bitcoin related application. Specifically, I was looking to build an application that leveraged the Bitcoin network directly, without using any third party APIs or services. The goal behind avoiding third party services was to explore how difficult using the Bitcoin network directly is and also to embrace Bitcoin’s decentralized nature and not rely on another company to move coins.

Conceptually the way the Bitcoin network works is relatively straightforward. You move coins by creating transactions which are just messages written and cryptographically signed in a specific format and then you listen for transactions which include your addresses to keep your balance up to date. Of course, the devil is in the details and there’s a dauntingly large number of them. For example, Ken Shiriff explains how to craft a transaction by hand in Bitcoins the hard way: Using the raw Bitcoin protocol and it’s no easy read. Given that just crafting transactions involved so much code, I started researching existing open source libraries that facilitate working with Bitcoin.

After doing some research, it looked like the most popular approach to interfacing with the network directly was to run the bitcoind deamon and then make RPC calls to the exposed functions. Objectively, using RPC calls to bitcoind qualifies as a “pure” solution but I still didn’t love it. After a bit more searching, I came across bitcoinj which is a pure Java library for working with Bitcoin.

Unlike bitcoind, bitcoinj is a library so its designed to be embedded in other codebases and it supports simplified payment verification (SPV) which allows it to operate without downloading the entire blockchain, ~25GB as of today. On top of this, its written in Java so it’s easy to use from Scala, something I’d been looking to experiment with.

So what are some key takeaways from using bitcoinj?

  • Test on the TestNet: Although debugging new code with live money would be thrilling. the TestNet allows you to develop against the Bitcoin network without using “live” coins. With bitcoinj, if you instantiate TestNet3Params you’ll connect into the Testnet.
  • TestNet Fountains: Testing is pretty tough without some coins but luckily you can use fountains to grab some. http://faucet.xeno-genesis.com/ worked well for me to grab some coins. Just a heads up, TestNet transactions take awhile to get broadcast and included into the Blockchain so be patient.
  • Extend WalletAppKit: WalletAppKit is a utility class which helps bootstrap everything you need for a SPV wallet and will save you some headaches. I started off trying to hand roll everything and quickly switched over to extending WalletAppKit.
  • Chain API: Since the Chain API can be used on the TestNet it’s useful for testing your own applications. Specifically, Bitcoinj treats sending and receiving coins to “yourself” weirdly so it’s more effective to use Chain to test transactions.
  • Coin.parseCoin: Sorting out how many Satoshis you want to send is surprisingly difficult since sendCoins accepts a Coin object. Luckily, Coin.parseCoin will accept a BTC value and return representative Coin object.
  • Blockchain downloads and wallet start up slow down development: Even in SPV mode, it still takes a non-trivial amount of time to “catch up” if your client hasn’t been running for awhile. On top of that, starting up the wallet takes a few minutes since it has to discover and connect to beers. What this translates to is resuming development after being away for a while is slow and the “edit, compile, test” loop isn’t as tight as usual.
  • It’s real money: This should go without saying but once you’re running on the live Bitcoin network you’re playing with real money so be careful. If your keys get out anyone will be able to move your coins out of your addresses. So be careful what you check in on git and if you’re building something public definitely take a second to lock down your server.

Anyway, this was my first time building something Bitcoin related and it was a positive experience. The project is still private but I’ll definitely share it once it’s released. As always, questions or comments are welcome!

Posted In: Bitcoin

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