Quick notes on livestreaming to YouTube with FFmpeg on a Lenovo X230T

| video, youtube, streaming, ffmpeg, yay-emacs

[2024-01-05 Fri]: Updated scripts

Text from the sketch

Quick thoughts on livestreaming


  • work out loud
  • share tips
  • share more
  • spark conversations
  • (also get questions about things)

Doable with ffmpeg on my X230T:

  • streaming from my laptop
  • lapel mic + system audio,
  • second screen for monitoring

Ideas for next time:

  • Overall notes in Emacs with outline, org-timer timestamped notes; capture to this file
  • Elisp to start/stop the stream → find old code
  • Use the Yeti? Better sound
  • tee to a local recording
  • grab screenshot from SuperNote mirror?

Live streaming info density:

  • High: Emacs News review, package/workflow demo
  • Narrating a blog post to make it a video
  • Categorizing Emacs News, exploring packages
  • Low: Figuring things out

YouTube can do closed captions for livestreams, although accuracy is low. Videos take a while to be ready to download.

Experimenting with working out loud

I wanted to write a report on EmacsConf 2023 so that we could share it with speakers, volunteers, participants, donors, related organizations like the Free Software Foundation, and other communities. I experimented with livestreaming via YouTube while I worked on the conference highlights.

It's a little over an hour long and probably very boring, but it was nice of people to drop by and say hello.

The main parts are:

  • 0:00: reading through other conference reports for inspiration
  • 6:54: writing an overview of the talks
  • 13:10: adding quotes for specific talks
  • 25:00: writing about the overall conference
  • 32:00: squeezing in more highlights
  • 49:00: fiddling with the formatting and the export

It mostly worked out, aside from a brief moment of "uhhh, I'm looking at our private conf.org file on stream". Fortunately, the e-mail addresses that were showed were the public ones.

Technical details


  • I set up environment variables and screen resolution:

      # From pacmd list-sources | egrep '^\s+name'
      LAPEL=alsa_input.usb-Jieli_Technology_USB_Composite_Device_433035383239312E-00.mono-fallback #
      # MIC=$LAPEL
      # AUDIO_WEIGHTS="1 1"
      AUDIO_WEIGHTS="0.5 0.5"
      SCREEN=LVDS-1  # from xrandr
      xrandr --output $SCREEN --mode 1280x720
  • I switch to a larger size and a light theme. I also turn consult previews off to minimize the risk of leaking data through buffer previews.
    my-emacsconf-prepare-for-screenshots: Set the resolution, change to a light theme, and make the text bigger.
    (defun my-emacsconf-prepare-for-screenshots ()
      (shell-command "xrandr --output LVDS-1 --mode 1280x720")
      (modus-themes-load-theme 'modus-operandi)
      (set-face-attribute 'default nil :height 170)


ffmpeg -f x11grab -video_size $SIZE -i :0.0$OFFSET -y /tmp/test.png; display /tmp/test.png
ffmpeg -f pulse -i $MIC -f pulse -i $SYSTEM -filter_complex amix=inputs=2:weights=$AUDIO_WEIGHTS:duration=longest:normalize=0 -y /tmp/test.mp3; mpv /tmp/test.mp3
DATE=$(date "+%Y-%m-%d-%H-%M-%S")
ffmpeg -f x11grab -framerate 30 -video_size $SIZE -i :0.0$OFFSET -f pulse -i $MIC -f pulse -i $SYSTEM -filter_complex "amix=inputs=2:weights=$AUDIO_WEIGHTS:duration=longest:normalize=0" -c:v libx264 -preset fast -maxrate 690k -bufsize 2000k -g 60 -vf format=yuv420p -c:a aac -b:a 96k -y -flags +global_header "/home/sacha/recordings/$DATE.flv" -f flv


DATE=$(date "+%Y-%m-%d-%H-%M-%S")
ffmpeg -f x11grab -framerate 30 -video_size $SIZE -i :0.0$OFFSET -f pulse -i $MIC -f pulse -i $SYSTEM -filter_complex "amix=inputs=2:weights=$AUDIO_WEIGHTS:duration=longest:normalize=0[audio]" -c:v libx264 -preset fast -maxrate 690k -bufsize 2000k -g 60 -vf format=yuv420p -c:a aac -b:a 96k -y -f tee -map 0:v -map '[audio]' -flags +global_header  "/home/sacha/recordings/$DATE.flv|[f=flv]rtmp://a.rtmp.youtube.com/live2/$YOUTUBE_KEY"

To restore my previous setup:

my-emacsconf-back-to-normal: Go back to a more regular setup.
(defun my-emacsconf-back-to-normal ()
  (shell-command "xrandr --output LVDS-1 --mode 1366x768")
  (modus-themes-load-theme 'modus-vivendi)
  (set-face-attribute 'default nil :height 115)
  (keycast-mode -1))

Ideas for next steps

I can think of a few workflow tweaks that might be fun:

  • a stream notes buffer on the right side of the screen for context information, timestamped notes to make editing/review easier (maybe using org-timer), etc. I experimented with some streaming-related code in my config, so I can dust that off and see what that's like. I also want to have an org-capture template for it so that I can add notes from anywhere.
  • a quick way to add a screenshot from my Supernote to my Org files

I think I'll try going through an informal presentation or Emacs News as my next livestream experiment, since that's probably higher information density.

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