add offset script

2023/video/offset.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+
+set -euo pipefail
+
+function msg {
+    echo "${@}" >&2
+}
+
+function die {
+    msg "${@}"
+    exit 1
+}
+
+if [[ $# -ne 3 ]]; then
+    die "usage: ${0} <input> <output> <offset>"
+fi
+
+input="${1}"
+output="${2}"
+offset="${3}"
+
+if [[ ! -f "${input}" ]]; then
+    die "input file ${input} does not exist"
+fi
+
+if [[ -e "${output}" ]]; then
+    die "output file ${output} already exists"
+fi
+
+ffmpeg -i "${input}" -itsoffset "${offset}" -i "${input}" -map 1:v -map 0:a -c copy "${output}"