micolous · January 15, 2020 11:44 · Jan 15, 2020 · Jan 15, 2020 · Jan 14, 2020 · Jan 14, 2020
diff --git a/glitch.sh b/glitch.sh
@@ -18,8 +18,8 @@
 #
 # If you wonder "what is xrandr?" -- it's a command-line tool for Xorg (graphics/display server)
 # that lets you adjust display settings.  It's a very powerful tool with a lot of options; but
-# most Linux desktop environments' display settings dialog are good enough to enable a second
-# display in mirroring or extending modes. :)
+# most Linux desktop environments' display settings dialog make it very easy to "just" enable
+# a second display in mirroring or extending modes. :)
 #
 ######
 #

diff --git a/glitch.sh b/glitch.sh
@@ -1,20 +1,43 @@
 #!/bin/bash
-# "Does anyone know how to use xrandr" glitch slides using FFMPEG. #lca2020
+# "Does anyone know how to use xrandr" glitch slides using ffmpeg. #lca2020
 # Author: Michael Farrell <[email protected]>
 # License: BSD-2-Clause or CC-0 (your choice).
 #
-# Create the "normal" title slide segment from PNG, running for 7 seconds
+######
+#
+# For linux.conf.au in Gold Coast, Ruan (@xfxf) asked me to make a simple "smoosh / defrag"
+# slide that would be displayed as a holding slide between talks.  I made some others with some
+# AV team "in-jokes"... :)
+#
+# On the third day of the conference (2020-01-15), the video generated by this script was shown
+# on-screen: https://twitter.com/glasnt/status/1217220463924928513
+#
+# This uses a title slide, "lca2020-xrandr-720p.png", which is displayed normally for 7 seconds,
+# then "glitches" for 2 seconds, and then returns to normal for 7 seconds. It is intended to be
+# run in a loop.
+#
+# If you wonder "what is xrandr?" -- it's a command-line tool for Xorg (graphics/display server)
+# that lets you adjust display settings.  It's a very powerful tool with a lot of options; but
+# most Linux desktop environments' display settings dialog are good enough to enable a second
+# display in mirroring or extending modes. :)
+#
+######
+#
+# Create the "normal" title slide segment from PNG, running for 7 seconds (xrandr-regular-7s.ts)
 ffmpeg -loop 1 -i lca2020-xrandr-720p.png -t 7 \
   -codec:v mpeg2video -b:v 5000k xrandr-regular-7s.ts
 
-# Create the "glitched" title slide segment from PNG, running for 2 seconds
+# Create the "glitched" title slide segment from PNG, running for 2 seconds (xrandr-broken-2s.ts)
 # This adds noise every 1000 bytes of the (video) bitstream:
 # Docs: https://ffmpeg.org/ffmpeg-bitstream-filters.html#noise
 ffmpeg -loop 1 -i lca2020-xrandr-720p.png -t 2 \
   -codec:v mpeg2video -bsf:v noise=1000 -b:v 5000k xrandr-broken-2s.ts
 
-# Stitch the files back together, and re-encode.
+# Stitch the files back together, and re-encode (xrandr-partial.ts)
 # We need to re-encode because the behaviour of glitched bitstream is unpredictable between players.
 ffmpeg -f concat -safe 0 \
   -i <(for f in xrandr-regular-7s.ts xrandr-broken-2s.ts xrandr-regular-7s.ts; do echo "file '$PWD/$f'"; done) \
   -b:v 5000k xrandr-partial.ts
+
+# That file was called "partial" because my first version of this was _entirely_ glitched.
+# But that was just unreadable. :)
diff --git a/glitch.sh b/glitch.sh
@@ -8,7 +8,7 @@ ffmpeg -loop 1 -i lca2020-xrandr-720p.png -t 7 \
   -codec:v mpeg2video -b:v 5000k xrandr-regular-7s.ts
 
 # Create the "glitched" title slide segment from PNG, running for 2 seconds
-# This adds noise every 1000 bytes of the bitstream:
+# This adds noise every 1000 bytes of the (video) bitstream:
 # Docs: https://ffmpeg.org/ffmpeg-bitstream-filters.html#noise
 ffmpeg -loop 1 -i lca2020-xrandr-720p.png -t 2 \
   -codec:v mpeg2video -bsf:v noise=1000 -b:v 5000k xrandr-broken-2s.ts

diff --git a/glitch.sh b/glitch.sh
@@ -8,7 +8,8 @@ ffmpeg -loop 1 -i lca2020-xrandr-720p.png -t 7 \
   -codec:v mpeg2video -b:v 5000k xrandr-regular-7s.ts
 
 # Create the "glitched" title slide segment from PNG, running for 2 seconds
-# This adds noise every 1000 bytes of the bitstream.
+# This adds noise every 1000 bytes of the bitstream:
+# Docs: https://ffmpeg.org/ffmpeg-bitstream-filters.html#noise
 ffmpeg -loop 1 -i lca2020-xrandr-720p.png -t 2 \
   -codec:v mpeg2video -bsf:v noise=1000 -b:v 5000k xrandr-broken-2s.ts
 

diff --git a/glitch.sh b/glitch.sh
@@ -4,16 +4,16 @@
 # License: BSD-2-Clause or CC-0 (your choice).
 #
 # Create the "normal" title slide segment from PNG, running for 7 seconds
-ffmpeg -y -loop 1 -i lca2020-xrandr-720p.png -t 7 \
+ffmpeg -loop 1 -i lca2020-xrandr-720p.png -t 7 \
   -codec:v mpeg2video -b:v 5000k xrandr-regular-7s.ts
 
 # Create the "glitched" title slide segment from PNG, running for 2 seconds
 # This adds noise every 1000 bytes of the bitstream.
-ffmpeg -y -loop 1 -i lca2020-xrandr-720p.png -t 2 \
+ffmpeg -loop 1 -i lca2020-xrandr-720p.png -t 2 \
   -codec:v mpeg2video -bsf:v noise=1000 -b:v 5000k xrandr-broken-2s.ts
 
 # Stitch the files back together, and re-encode.
 # We need to re-encode because the behaviour of glitched bitstream is unpredictable between players.
-ffmpeg -y -f concat -safe 0 \
+ffmpeg -f concat -safe 0 \
   -i <(for f in xrandr-regular-7s.ts xrandr-broken-2s.ts xrandr-regular-7s.ts; do echo "file '$PWD/$f'"; done) \
   -b:v 5000k xrandr-partial.ts
diff --git a/glitch.sh b/glitch.sh
@@ -1,4 +1,8 @@
 #!/bin/bash
+# "Does anyone know how to use xrandr" glitch slides using FFMPEG. #lca2020
+# Author: Michael Farrell <[email protected]>
+# License: BSD-2-Clause or CC-0 (your choice).
+#
 # Create the "normal" title slide segment from PNG, running for 7 seconds
 ffmpeg -y -loop 1 -i lca2020-xrandr-720p.png -t 7 \
   -codec:v mpeg2video -b:v 5000k xrandr-regular-7s.ts

diff --git a/glitch.sh b/glitch.sh
@@ -0,0 +1,15 @@
+#!/bin/bash
+# Create the "normal" title slide segment from PNG, running for 7 seconds
+ffmpeg -y -loop 1 -i lca2020-xrandr-720p.png -t 7 \
+  -codec:v mpeg2video -b:v 5000k xrandr-regular-7s.ts
+
+# Create the "glitched" title slide segment from PNG, running for 2 seconds
+# This adds noise every 1000 bytes of the bitstream.
+ffmpeg -y -loop 1 -i lca2020-xrandr-720p.png -t 2 \
+  -codec:v mpeg2video -bsf:v noise=1000 -b:v 5000k xrandr-broken-2s.ts
+
+# Stitch the files back together, and re-encode.
+# We need to re-encode because the behaviour of glitched bitstream is unpredictable between players.
+ffmpeg -y -f concat -safe 0 \
+  -i <(for f in xrandr-regular-7s.ts xrandr-broken-2s.ts xrandr-regular-7s.ts; do echo "file '$PWD/$f'"; done) \
+  -b:v 5000k xrandr-partial.ts
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