add post on screencasting

Makefile

@@ -6,6 +6,7 @@ update:
 
 serve: clean update
 	bundler exec jekyll serve --incremental
+	xdg-open http://127.0.0.1:4000
 
 web: clean update
 	# Update website: "afrendeiro.github.io"

_posts/2024-04-10-screencasting-on-ubuntu-ffmpeg-ftw.md

@@ -0,0 +1,80 @@
+---
+layout: post
+title: "Screencasting on Ubuntu - ffmpeg FTW!"
+description: "Screencasting on Ubuntu - ffmpeg FTW!"
+category: notebook
+tags: [video, ubuntu, screencast]
+---
+{% include JB/setup %}
+
+
+Sometimes I have to create recordings of a presentation beforehand for recruiting people (PhD program) or conferences.
+
+I've used Zoom previously for this, but it was not very good.
+
+Here's my little guide for creating high-quality screencast recordings on an Ubuntu Linux laptop.
+
+It uses utilities like `guvcview`, `xprop`, `xdpyinfo`, and (of course) `ffmpeg` to customize and optimize the recording process.
+
+The process is roughly like this:
+ - Have a little window on your screen showing your camera always on top of any window (`guvcview`)
+ - Record whole screen with `ffmpeg` (raw mkv full resolution)
+ - Edit (trim) and convert to mp4 for sharing
+
+`recordmydesktop` at first seemed like a good option but [it has a bug which ruined my recording :/](https://github.com/Enselic/recordmydesktop/issues/23).
+
+## My setup (`guvcview`, `ffmpeg`)
+
+### Display own video on screen
+`guvcview` provides a very minimal camera window that is ideal for screencasts.
+Run `guvcview` to get your own camera on the screen, select "Always on top" on its window, drag to corner.
+
+#### Hide gnome top bar of guvcview window
+`guvcview` uses the native window manager (gnome in Ubuntu) and this still has decorations (top bar window). Use `xprop` to temporarily remove the gnome top bar window:
+Click on window to hide:
+```bash
+xprop -format _MOTIF_WM_HINTS 32c -set _MOTIF_WM_HINTS 2
+```
+Specify window name beforehand:
+```bash
+xprop -name 'Your window name' -format _MOTIF_WM_HINTS 32c -set _MOTIF_WM_HINTS 2
+```
+
+### Query display dimensions (for ffmpeg)
+```bash
+xdpyinfo | grep dimensions
+```
+Note: `xrandr | grep '*' ` does not work correctly in high dpi screens.
+
+### Record desktop with `ffmpeg`, edit and convert with ffmpeg
+```bash
+RESOLUTION=5120x3200  # laptop screen
+RESOLUTION=6144x3456  # external display
+ffmpeg -f x11grab -framerate 30 -video_size $RESOLUTION -i $DISPLAY -f pulse -ac 2 -i default -c:v libx264 -preset ultrafast -crf 0 -c:a aac -strict experimental -b:a 128k output.mkv
+```
+This will output a massive video file in full quality (~4Gb per 10 min).
+
+Downsample to 1080p and convert to mp4:
+```bash
+ffmpeg -i output.mkv -vf "scale=1920:-1" -c:v libx264 -preset slow -crf 22 -c:a aac output.mp4
+```
+
+Trim first 5 seconds re-encoding (better to re-encode otherwise it may not match a keyframe) - should've been done already from the mkv but forgot!
+```bash
+ffmpeg -ss 5 -i output.mp4 -c:v libx264 -preset fast -crf 22 -c:a aac -strict experimental output.trimmed.mp4
+```
+
+## Alternative: `recordmydesktop` (not recommended!)
+
+```bash
+recordmydesktop --no-frame --fps 30 --v_quality 22 --s_quality 10
+```
+
+Beware of this issue: https://github.com/Enselic/recordmydesktop/issues/23
+Last time it meant my recording was unusable - none of the solutions online worked!
+
+Trim the top and bottom 160 pixels
+```bash
+recordmydesktop --no-frame --fps 30 --v_quality 22 --s_quality 10 --width 5120 --height 3040 -y 160
+```
+

index.md

@@ -1688,7 +1688,7 @@ description: "My personal website"
     </div>
     <br>
     <div class="col-sm-12" style="margin-bottom: 30px;">
-        <p>Last updated on 2024-04-08.</p>
+        <p>Last updated on 2024-04-11.</p>
     </div>
     <br>
 </div>