ffmpeg subtitles

subtitles

#!/usr/bin/env sh

input="$1"
output="$2"
subtitle_format="$3"
subcommand="$4"
start="$5"
end="$6"

extension() {
	file="$1"; shift
	echo "$file" | grep -o '\.[[:alnum:]_.]*$'
}

temp_dir="$(mktemp -d)" # Note: `mktemp` is not POSIX
temp_input="$temp_dir/input$(extension "$input")"
temp_output="$temp_dir/output$(extension "$output")"
ln -s "$input" "$temp_input"

# Reset positional args
set --

set -- "$@" \
	-i file:"$temp_input"

# Set input opts
if [ -n "$start" ]; then
	set -- "$@" \
		-ss "$start"
fi
if [ -n "$end" ]; then
	set -- "$@" \
		-to "$end"
fi

# Set overlay opts
case "$subtitle_format" in
	text)
		set -- "$@" \
			-vf subtitles="$temp_input:force_style='Fontname=Circe Rounded,Outline=2,Shadow=0,PrimaryColour=&H00FFFFFF,SecondaryColour=&H00FFFFFF,OutlineColour=&H00000000'"

		case "$subcommand" in
		screencap)
			;;
		*)
			set -- "$@" \
				-map 0 \
				-map '-s:0'
			;;
		esac
		;;
	bitmap)
		set -- "$@" \
			-filter_complex '[v:0][s:0]overlay=shortest=1[vs_0]'

		case "$subcommand" in
		screencap)
			set -- "$@" \
				-map '[vs_0]'
			;;
		*)
			set -- "$@" \
				-map 0 \
				-map '-v:0' \
				-map '-s:0' \
				-map '[vs_0]'
			;;
		esac
		;;
esac

set -- "$@" \
	-map_metadata -1

# Set output opts
case "$subcommand" in
	overlay)
		set -- "$@" \
			-c copy \
			-c:v h264 \
			-crf 0 \
			file:"$temp_output"
		;;
	screencap)
		set -- "$@" \
			-frames:v 1 \
			-q:v 1 \
			file:"$temp_output"
		;;
esac

ffmpeg "$@"
exit_code="$?"

mv "$temp_output" "$output"
rm -r "$temp_dir"

exit "$exit_code"