Screencast to file through gstreamer, using resolution of screen

gst_screencast.sh

#!/bin/bash

set -euo pipefail

# Record the screen into an h264 encoded MP4.
# Determing video resolution from the screen being recorded.
#
# Required gst-launch and xrandr.
#
# Based on https://stackoverflow.com/a/33822024/92049
# and https://stackoverflow.com/a/44686527/92049

if [ $# != 1 ]; then
  echo "Usage: $(basename $0) OUTFILE"
  exit 2
fi
outfile="$1"

# Append .mp4 to outfile, if required.
if [[ ! "$outfile" =~ .mp4$ ]]; then
    outfile="${outfile}.mp4"
fi

# Determine resolution using xrandr.
resxy=$(xrandr | grep '\*' | awk '{print $1}')
resx=$(echo "$resxy" | cut -d 'x' -f1)
resy=$(echo "$resxy" | cut -d 'x' -f2)

echo
echo "screen resolution: ${resx}x${resy}"
echo "video resolution:${resx}x${resy}"
echo "writting video to ${outfile}"
echo "ctrl+c to stop recording"

gst-launch-1.0 --quiet ximagesrc use-damage=0 \
  ! video/x-raw,framerate=30/1 \
  ! videoscale method=0 \
  ! video/x-raw,width="$resx",height="$resy" \
  ! videoconvert \
  ! x264enc \
  ! filesink location="$outfile"