screencasting

#!/usr/bin/env bash
# Record desktop (or webcam) with microphone audio using ffmpeg.

set -euo pipefail

PIDFILE="${PIDFILE:-/tmp/screencasting.pid}"
video_source=( )
video_encoder=( -c:v libx264 -r 30 )
audio_source=( -f alsa -ac 2 -i default )
audio_encoder=( -c:a aac -b:a 128k )
output_name="$HOME/output_$(date +%Y%m%d%H%M%S).mkv"
webcam_only=false

info() {
    printf 'Usage: %s [-p] [-w] [-o FILE] [-s] [-h]\n' "$0"
    printf '\t-p\tUse PulseAudio input instead of ALSA\n'
    printf '\t-w\tRecord webcam only (/dev/video0)\n'
    printf '\t-o\tSet output file path\n'
    printf '\t-s\tStop active recording\n'
    printf '\t-h\tDisplay this help\n'
}

stop_recording() {
    if [[ -f "$PIDFILE" ]] && kill -0 "$(cat "$PIDFILE")" 2>/dev/null; then
        kill "$(cat "$PIDFILE")"
        rm -f "$PIDFILE"
        echo 'Recording stopped.'
    else
        echo 'No active recording found.' >&2
        return 1
    fi
}

while getopts 'pwo:sh' o; do
    case "$o" in
        p) audio_source=( -f pulse -ac 2 -i default ) ;;
        w) webcam_only=true ;;
        o) output_name=$OPTARG ;;
        s)
            stop_recording
            exit 0
            ;;
        h)
            info
            exit 0
            ;;
        *)
            info
            exit 1
            ;;
    esac
done

command -v ffmpeg >/dev/null 2>&1 || {
    echo 'ffmpeg is required but was not found in PATH.' >&2
    exit 1
}

if $webcam_only; then
    video_source=( -i /dev/video0 )
else
    command -v xdpyinfo >/dev/null 2>&1 || {
        echo 'xdpyinfo is required to capture desktop size.' >&2
        exit 1
    }
    screen_size=$(xdpyinfo | awk '/dimensions/{print $2; exit}')
    video_source=( -f x11grab -s "$screen_size" -i :0.0 )
fi

if [[ -f "$PIDFILE" ]] && kill -0 "$(cat "$PIDFILE")" 2>/dev/null; then
    echo 'A recording session is already running. Use -s to stop it.' >&2
    exit 1
fi

ffmpeg -y -nostdin "${video_source[@]}" "${audio_source[@]}" \
    "${video_encoder[@]}" "${audio_encoder[@]}" "$output_name" >/dev/null 2>&1 &

echo "$!" > "$PIDFILE"
echo "Recording started: $output_name"