ffmpeg: scale up or down the duration of the given video

scale-duration

#!/usr/bin/env bash
#
# Scale up or down the duration of the given video
# The final video will be in the mp4 format
#
# Usage:
#   scale-duration <video-path> <desired-duration>
#
# Options:
#   video-path        The video to scale
#   desired-duration  In secods, the final duration fo the video
#
# Example:
#   `scale-duration '/fake/path/video.mov' '10'`
#   This will scale the video to 10 seconds in a
#   new file called: '/fake/path/video.mov.mp4'
#

failure() {
	local message=$1

	echo -e "\033[31m✖\033[0m $message" 1>&2
}

success() {
	local message=$1

	echo -e "\033[32m✓\033[0m $message" 1>&2
}

main() {
	local desired_duration=$2
	local log_path="$(mktemp -t "$$")"
	local video_path=$1

	if [ -z "$video_path" ]; then
		failure 'No ‘video-path’ was given'

		return 1
	fi

	if [ ! -r "$video_path" ]; then
		failure 'Unable to read the given ‘video-path’'

		return 1
	fi

	if [ -z "$desired_duration" ]; then
		failure 'No ‘desired-duration’ was given'

		return 1
	fi

	if [[ ! "$desired_duration" =~ "^[0-9]+(\.[0-9]+)?$|^0?\.[0-9]+$" ]]; then
		failure '‘desired-duration’ must be an integer or float'

		return 1
	fi

	local current_duration=$(ffprobe -i "$video_path" 2>&1 -show_format -v quiet | grep duration | cut -d '=' -f 2)
	local ratio=$(bc -l <<< "$desired_duration / $current_duration")
	local video_folder=$(dirname "$video_path")
	local video_name=$(basename "$video_path")

	ffmpeg -i "$video_path" -filter:v "setpts=$ratio*PTS" "${video_path}.mp4" &> "$log_path"
	local exit_code=$?

	if [ "$exit_code" = 0 ]; then
		echo -e "\033[32m✓\033[0m $video_name"
		rm -f "$log_path"

		return 0
	fi

	echo -e "\033[31m✖\033[0m $video_name"
	cat "$log_path" 1>&2
	rm -f "$log_path"

	return 1
}

main "$@"