Reverse-Engineering Xkcd's 'Frequency'

I am trying to apply the Chinese remainder theorem to solve the time required for all of the events to occur simultaneously. I am ignoring the GIF timing bug.<p><pre><code> 1. Normalize times to integers. 2. Assume congruence at x = t mod (t+1). 3. Solve congruence system. 4. Denormalize result. </code></pre> Python solution: <a href="http://ideone.com/Wh2SR6" rel="nofollow">http:&#x2F;&#x2F;ideone.com&#x2F;Wh2SR6</a> Solution perspective: <a href="http://www.wolframalpha.com/input/?i=3541760026837707223455613087881588712157229686722179240978118057837619969343910617190906282246617252766842304240193875476480000000000+seconds" rel="nofollow">http:&#x2F;&#x2F;www.wolframalpha.com&#x2F;input&#x2F;?i=35417600268377072234556...</a>

Not super related to the content, but I love the &quot;Show Code&quot; button at the bottom of the article. So often sites either show code inline and break up my reading, or just dump the whole thing into a github repo, which loses context. That button is awesome, because I can read the whole thing to understand the problem, then review the code the next time through with better context.<p>Awesome!

For anyone wondering how to dump gif loop time.<p><pre><code> curl -s http:&#x2F;&#x2F;imgs.xkcd.com&#x2F;comics&#x2F;frequency&#x2F;turnsignal1.gif | giftext | grep DelayTime | cut -d&#x27;:&#x27; -f 2 | awk &#x27;{s+=$1} END {print s&#x2F;100}&#x27; </code></pre> The results seem to correspond with authors table.

There are some really clever people in this world.<p>One to make it.<p>One to take it apart.

I can&#x27;t imagine a better followup to an xkcd strip. Bravo.

Awesome, this is one of my favorite XKCDs. I&#x27;ve been mulling over a plan in my mind to make a physical version of it, looking similar to a deep picture frame or display case. It would use white acrylic with the text somehow printed or transferred on, backlit by white LEDs (maybe incandescent lamps would look nicer?). Each cell would be separated by thin black wood or plastic strips. It should be pretty easy to control the whole thing with an arduino, and I think it would make an awesome wall display.

What I found interesting was the format of the gifs themselves. They were mostly or completely uncompressed, totaling 8MB. I can only think of one possible reason to do this, which would be to take advantage of HTTP compression to go inter-frame instead of using the builtin intra-frame that gifs have (.5MB vs 4MB). But HTTP compression was turned off too.

There&#x27;s more analysis here than reverse engineering. Nice work still.

I&#x27;m still trying to understand where the frequency is stored? Is it a value that can be embedded into the gif?

Didn&#x27;t get the &quot;A european resident has their first kiss&quot; though. Wouldn&#x27;t it make more sense to divide the frequency by two and state &quot;Two european residents have their first kiss&quot;?

To me the most interesting thing in this article were the urls of the inlined images, &lt;img src=&quot;data:image&#x2F;png;base64,...&gt; I had no idea you could do that.

Does anyone know the answer to the &quot;turn signal problem&quot; he poses? Why does the beat frequency he observes match what he calculated?

I&#x27;m completely distracted by the fact that this was #1331.<p>Surely he must have something truly epic saved up for 1337.<p>Right? Anyone?

This page is hard crashing Safari latest on my MBP 2013. Anyone else experiencing this?

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