4 files changed, 44 insertions, 3 deletions

diff --git a/Makefile b/Makefile
index 0ddaac3..efd898a 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@ MAKEFLAGS+=-j3
 dev: watch server
 
 webring:
-        ruby bin/webring.py
+        ruby bin/webring.rb
 
 watch:
         jekyll b --watch
diff --git a/_includes/webring.html b/_includes/webring.html
index 2ef29b8..7eb5332 100644
--- a/_includes/webring.html
+++ b/_includes/webring.html
@@ -43,10 +43,10 @@
         <div>For over 10 years now, I run two self-built NAS (Network Storage) devices which serve media (currently via Jellyfin) and run daily backups of all my PCs and servers. In this article, I describe my goals, which hardware I picked for my new build (and why) and how I set it up. Design Goals I use my network storage device...</div>
       </li>
       <li>
-        <a href="https://utcc.utoronto.ca/~cks/space/blog/tech/FirewallsAndMACs" target="_blank" rel="noopener">Network firewalls and Ethernet addresses</a>
+        <a href="https://utcc.utoronto.ca/~cks/space/blog/sysadmin/OurVaryingPhysicalSecurityLevels" target="_blank" rel="noopener">Our varying levels of what you could charitably call &#39;physical security&#39;</a>
         —
         <a href="https://utcc.utoronto.ca/~cks/space/blog/" target="_blank" rel="noopener">Chris&#39;s Wiki :: blog</a>
-        <div>Over on the Fediverse I mentioned that on some networks we authorize machines by controlling what Ethernet addresses ('MACs') get what IP addresses. In response, I was asked a very good question about why not have the firewall work by Ethernet address instead of IP. A starting answer is that firewalls have traditionall...</div>
+        <div>As I mentioned way back when I discussed how rogue wireless access points are a bigger risk at universities, one of the unusual things about universities is that we usually don't have anywhere near as much physical security as, say, a typical company does. This is because in practice most university buildings are open ...</div>
       </li>
       <li>
         <a href="https://szymonkaliski.com/writing/2023-10-02-building-a-diy-pen-plotter/" target="_blank" rel="noopener">Building a DIY Pen Plotter</a>
diff --git a/_posts/2023-11-04-using-ffmpeg-to-combine-video-side-by-side.md b/_posts/2023-11-04-using-ffmpeg-to-combine-video-side-by-side.md
new file mode 100644
index 0000000..23d14b7
--- /dev/null
+++ b/_posts/2023-11-04-using-ffmpeg-to-combine-video-side-by-side.md
@@ -0,0 +1,41 @@
+---
+title: "Using ffmpeg to combine videos side by side"
+permalink: /using-ffmpeg-to-combine-video-side-by-side.html
+date: 2023-11-04T09:04:28+02:00
+layout: post
+type: note
+draft: false
+---
+
+I had a 4 webm videos (each 492x451) that I wanted to combine to be played side
+by side and I tried [iMovie](https://support.apple.com/imovie) and
+[Kdenlive](https://kdenlive.org/) and failed to do it in an easy way. I needed
+this for Github readme file so it also needed to be a GIF.
+
+The following is the [ffmpeg](https://ffmpeg.org/) version of it.
+
+```sh
+ffmpeg -y \
+  -i 01.webm \
+  -i 02.webm \
+  -i 03.webm \
+  -i 04.webm \
+  -filter_complex "\
+        [0:v] trim=duration=8, setpts=PTS-STARTPTS, scale=492x451, fps=6 [a0]; \
+        [1:v] trim=duration=8, setpts=PTS-STARTPTS, scale=492x451, fps=6 [a1]; \
+        [2:v] trim=duration=8, setpts=PTS-STARTPTS, scale=492x451, fps=6 [a2]; \
+        [3:v] trim=duration=8, setpts=PTS-STARTPTS, scale=492x451, fps=6 [a3]; \
+        [a0][a1][a2][a3] xstack=inputs=4:layout=0_0|w0_0|w0+w1_0|w0+w1+w2_0, scale=1000:-1 [v]" \
+  -map "[v]" \
+  -crf 23 \
+  -preset veryfast \
+  trigraphs.gif
+```
+
+- This will produce `trigraphs.gif` that is also scaled to max 1000px in width
+  (refer to `scale=1000:-1`).
+- The important part for 4x1 stack is `xstack=inputs=4:layout=0_0|w0_0|w0+w1_0|w0+w1+w2_0`.
+- This will also cap frame rate to 6 (refer to `fps=6`) since that is enough and
+  this makes playback of GIFs smoother in a browser.
+
+![Result](./assets/notes/trigraphs.gif)
diff --git a/assets/notes/trigraphs.gif b/assets/notes/trigraphs.gif
new file mode 100644
index 0000000..f579b9d
--- /dev/null
+++ b/assets/notes/trigraphs.gif