jmatthewturner/transcode.sh

## transcode.sh
#!/bin/bash

# This script uses ffmpeg to transcode video files into one of a few formats suitable for
# editing in either DaVinci Resolve or Lightworks on a Linux machine. It's purpose is to
# simplify my life and relieve me from having to look up and enter the same very long
# command over and over.
#
# If run with argument "all", the script will prompt for a directory containing video files, and
# transcode all video files in the directory into the selected format. If run with a file as an
# argument, it will transcode only that file, and will provide the additional option of
# selecting a specific range to encode.
#
# It uses a modified version of Dave Miller's excellent ask.sh script, which can be found here:
# https://gist.github.com/davejamesmiller/1965569
#
# To modify ask.sh, simply change line 23 to read
# echo -n -e "$1 [$prompt] "
#
# (Adding the -e flag enables support for escape sequences, which allows
# the colored text formatting.)
#
# It also uses my own colors.sh script, which defines a list of colors
# for text formatting:
# https://gist.github.com/jmatthewturner/2aeee120aa112fd51b000e13579c2654
#
# To run, just make sure that transcode.sh (this script), ask.sh and colors.sh
# are in the same directory. (Everything is done with absolute paths, so it doesn't
# matter where they are.)
#
# Written by jmatthewturner
# https://github.com/jmatthewturner
# https://www.youtube.com/jmatthewturner/
#
# https://gist.github.com/jmatthewturner/6b7034d13f4027f73c7982ecadf006ec
#

. ~/Scripts/ask.sh         # https://gist.github.com/davejamesmiller/1965569
. ~/Scripts/colors.sh      # https://gist.github.com/jmatthewturner/2aeee120aa112fd51b000e13579c2654

################ DEFINITIONS ###################

# CONSTANTS
#
FILE_TYPES='*.MTS *.mov *.mp4 *.mkv *.avi *.m4v'                # Types of video files to transcode.
DEFAULT_TRANSCODE_DIRECTORY="${HOME}/Dragon_of_the_Black_Pool/" # Default directory for transcoded
                                                                # files. You might want to change
                                                                # this to your media drive.

# FFMPEG constants. These are the ffmpeg options that do not change in response to user input.
#
# OPTIONS:
# -loglevel quiet = suppress all output
# -acodec pcm_16le = audio codec: 16bit PCM wave
# -ar 48000 = audio sample rate: 48k
# -r 24000/1001 = framerate: 23.976
OPTIONS=' -loglevel quiet -acodec pcm_s16le -ar 48000 -r 24000/1001 '

# The PADDING option keeps the input video the same size, but adds blue padding to fill out
# a 1920x1080 frame. DNxHD requires this option for certain video sizes, so it is forced for DNxHD.
PADDING=' -vf pad=1920:1080:(ow-iw)/2:(oh-ih)/2:color=blue '

# Variable definitions
#
file_name="${1}"            		# Full path and name of file to be transcoded.
input_file_name=$( basename "${1}" )	# Name of the file to be transcoded.
input_path_name=$( dirname "${1}" )     # Path of the file to be transcoded.
current_dir="$( pwd )"  		# Current working directory.
source_directory=""     		# Source directory for input files.
task=""                 		# Are we transcoding one file, or all video files in a directory?
padding_option=""       		# User's choice of blue padding. Default is none.
pixel_format=""         		# Pixel format is determined based on codec choice.

################# FUNCTIONS ################

explain_usage()
{
	echo
	echo -e ${LIGHTYELLOW}"Usage:${RESET}"
	echo
	echo "./transcode.sh = View this message."
	echo "./transcode.sh all = transcode all vdeo files in current directory"
	echo "./transcode.sh [filename] = transcode a section of [filename]"
	echo
	echo -e "${LIGHTYELLOW}Known issues:${RESET} Transcoding from ProRes to DNxHD may fail."
	echo
	exit 1
}

# Determine whether we're transcoding an entire directory or just one file.
#
determine_task()
{
	if [[ ${file_name} == "" ]]
	then
		explain_usage
	elif [[ ${file_name} == 'all' ]]
	then
		task="transcode_all"
	elif [[ -f "${file_name}" ]]
	then
		task="transcode_one"
	else
		echo
		echo "There is no file ${file_name}."
		explain_usage
	fi
}

# Prompt user for target directory to store transcoded files.
#
prompt_for_target_dir()
{
	echo
	echo -e "${LIGHTYELLOW}Target directory:${RESET}"
	if [[ ${task} == "transcode_all" ]]
	then
        	read -e -i "${source_directory}" target_dir
 	elif [[ ${task} == "transcode_one" ]]
    	then
        	read -e -i "${input_path_name}" target_dir
    	else exit 1
    	fi
}

# Create the target directory if it does not exist.
#
create_target_dir()
{
    	if [[ ! -e "${target_dir}" ]]
    	then
            mkdir ${target_dir}
    	fi
}

# Prompt for a prefix to add to the file name(s).
#
prompt_for_prefix()
{
	echo -e "\n${LIGHTYELLOW}Prefix: (leave blank if none):${RESET}"
        read prefix
}

prompt_for_padding()
{
    	echo -e "\nSelecting the padding option will output a 1920x1080 file, regardless"
    	echo -e "of input file size. The video will reamin the same size, and a blue"
    	echo -e "padding will be added to fill out the remaining pixels of the 1920x1080 frame."
    	echo -e "\nDNxHD will have the padding option selected regardless of your choice.\n"
    	if ask "${LIGHTYELLOW}Select padding option?${RESET}" N
    	then
        	padding_option="${PADDING}"
    	fi
}

# Prompt user for codec.
#
prompt_for_codec()
{
    	echo -e "\n${LIGHTYELLOW}Export Codec?${RESET}"
    	echo -e "1: DNxHD 36Mbps"
    	echo -e "2: ProRes Proxy (45Mbps 422)"
    	echo -e "3: ProRes LT (102 Mbps 422)"
    	echo -e "4: ProRes Standard (147 Mbps 422)"
    	echo -e "5: ProRes HQ (220 Mbps 422)"
    	echo -e "6: ProRes 4444 (330 Mbps 4444)"
    	echo -e "7: ProRes 4444XQ (500 Mbps 4444)"
    	echo -e "8: H.264"
    	echo -e "9: H.265 / HEVC"
    	echo
    	echo -e -n "${LIGHTYELLOW}>${RESET}"
    	read codec_choice

    	# Set some options based on codec_choice.
    	case ${codec_choice} in
        	"1")
        	    codec=' -vcodec dnxhd -b:v 36M -vf pad=1920:1080:(ow-iw)/2:(oh-ih)/2:color=blue '
        	    codec_formatted='DNxHD-36Mbs-23.976'
        	    pixel_format=' -pix_fmt yuv422p '
        	    ;;
        	"2")
        	    codec=' -vcodec prores_ks -profile:v 0 '
        	    codec_formatted='ProRes-Proxy-23.976'
        	    pixel_format=' -pix_fmt yuv422p10le '
        	    ;;
        	"3")
        	    codec=' -vcodec prores_ks -profile:v 1 '
        	    codec_formatted='ProRes-LT-23.976'
        	    pixel_format=' -pix_fmt yuv422p10le '
        	    ;;
        	"4")
        	    codec=' -vcodec prores_ks -profile:v 2 '
        	    codec_formatted='ProRes-Standard-23.976'
        	    pixel_format=' -pix_fmt yuv422p10le '
        	    ;;
        	"5")
        	    codec=' -vcodec prores_ks -profile:v 3 '
        	    codec_formatted='ProRes-HQ-23.976'
        	    pixel_format=' -pix_fmt yuv422p10le '
        	    ;;
        	"6")
        	    codec=' -vcodec prores_ks -profile:v 4 '
        	    codec_formatted='ProRes-4444-23.976'
        	    pixel_format=' -pix_fmt yuv422p10le '
        	    ;;
        	"7")
        	    codec=' -vcodec prores_ks -profile:v 5 '
        	    codec_formatted='ProRes-4444HQ-23.976'
        	    pixel_format=' -pix_fmt yuv422p10le '
        	    ;;
        	"8")
        	    codec=' -vcodec h264 '
        	    codec_formatted='H.264-23.976'
        	    ;;
        	"9")
        	    codec=' -vcodec libx265 '
        	    codec_formatted='H.265-HEVC-(libx)-23.976'
        		    ;;
        	*)
        	    echo -e "\nPlease choose 1-9."
        	    echo
        	    prompt_for_codec   # Poor man's while loop.
        	    ;;
    	esac
}

# Prompt user for source directory only if 'transcode all' was used.
#
prompt_for_source_directory()
{
    	if [[ ${task} == "transcode_all" ]]
    	then
    	    echo -e "\n${LIGHTYELLOW}Source directory for video files:${RESET}"
    	    read -e -i ${DEFAULT_TRANSCODE_DIRECTORY} source_directory
    	fi
}

# Transcode all video files in a supplied directory. Identifies files that match the
# types stored in FILE_TYPES.
#
# I'm just going to say it: I couldn't figure out how to get a directory listing
# directly into an array. My workaround is to put the directory listing into a temp file
# file first, and then move it from the temp file into an array. I'm not proud.
#
transcode_all()
{
    tmp_video_list=$( mktemp ) || exit 1    # Temporary file to store identified video files.
                                            # If mktemp fails for any reason, exit with an error.
    local -a video_files                    # Array to store identified video files.

    # For loop identifies all the files in the source directory that match FILE_TYPES
    # and stores them in tmp_video_list.
    for i in ${FILE_TYPES}
    do
        ls 2> /dev/null 1>> "${tmp_video_list}" "${source_directory}"${i}
    done

    # While loop reads tmp_video_list and adds each line to array variable video_files[].
    while IFS= read -r line
    do
        video_files+=("${line}")
    done < "${tmp_video_list}"

    rm ${tmp_video_list}    # Remove the temp file.

    # Display the list of files to be transcoded for the user.
    echo -e "\n${LIGHTYELLOW}Found ${#video_files[@]} files:${RESET}"
    for ((i = 0; i < ${#video_files[@]}; i++))
    do
        echo -e ${LIGHTYELLOW}$((i+1)).${RESET}$( basename "${video_files[$i]}" )
    done
    echo

    # Display a final confirmation of the target directory.
    echo -e "${LIGHTYELLOW}Transcoding to:${RESET}"
    echo -e "${target_dir}\n"

    # Transcode each file contained in array variable video_files[].
    if ask "${LIGHTYELLOW}Proceed?${RESET}" Y
    then
        echo
        for ((i = 0; i < ${#video_files[@]}; i++))
        do
            # Assign input_file-name for code readability.
            input_file_name=$( basename "${video_files[$i]}" )

            # Display the current file for the user.
            echo -e "${LIGHTYELLOW}Transcoding ${RESET}${input_file_name}..."

            # Transcode the current file.
            ffmpeg -i "${video_files[$i]}" ${codec} ${OPTIONS} ${padding_option} \
                        "${target_dir}${prefix}-${input_file_name%.*}-${codec_formatted}-PCM16b48k.mov"
        done
    else echo -e "Exiting.\n"
    fi
}

# Transcode a single file provided as an argument to the script.
# Prompt for optional filename prefix, start time and duration to encode.
#
transcode_one()
{
	echo -e "\n${LIGHTYELLOW}Transcoding${RESET}"
	echo -e "${LIGHTRED}${input_file_name}${RESET}"
	echo -e "${LIGHTYELLOW}to${RESET}"
	echo -e "${input_path_name}"

	# Prompt user for encoding start time.
	echo -e -n "\n${LIGHTYELLOW}Enter start time in the format HH:MM:SS "
    	echo -e "(leave empty for beginning):${RESET}"
	read start

	# Check if start value is empty. If not, set the start option.
	if [[  ! -z ${start} ]]
    	then
    	    start=" -ss ${start} "
    	fi

    	# Prompt user for encoding length.
	echo -e -n "${LIGHTYELLOW}Enter encode length in the format HH:MM:SS "
	echo -e "(leave empty for entire video):${RESET}"
	read length

    	# Check if length value is empty. If not, set the length option.
	if [[  ! -z ${length} ]]
    	then
        	length=" -t ${length} "
   	fi

	# Display a message for the user and transcode the file.
	echo -e "${LIGHTYELLOW}Transcoding${RESET} ${LIGHTRED}${input_file_name}${LIGHTYELLOW}...${RESET}"
	ffmpeg ${start} ${length} -i "${file_name}" \
            ${codec} ${OPTIONS} ${pixel_format} ${padding_option} \
            "${target_dir}/${prefix}-${input_file_name%.*}-${codec_formatted}-PCM16b48k.mov"
	echo -e -n "\n${target_dir}/${LIGHTRED}${prefix}${input_file_name%.*}-${codec_formatted}-"
	echo -e "PCM16b48k.mov${LIGHTYELLOW} done.${RESET}"
}

############## MAIN ROUTINE ###############

# Configure some options.
#
determine_task                          # Use command line argument to determine which task to execute.
prompt_for_codec                        # Prompt user for codec.
prompt_for_prefix	                # Prompt user for prefix for transcoded files.
prompt_for_padding                      # Ask user if padding is desired.
prompt_for_source_directory             # Prompt user for source directory if transcode all is used.
prompt_for_target_dir                   # Prompt user for destination directory.
create_target_dir		        # Confirm destination directory exists, create if necessary.

# Execute transcoding job.
#
${task}                                 # Executes either transcode_one() or transcode_all().
exit 0                                  # Exit successfully.

#
# Written by jmatthewturner
# https://github.com/jmatthewturner
# https://www.youtube.com/jmatthewturner/
#
# https://gist.github.com/jmatthewturner/6b7034d13f4027f73c7982ecadf006ec
#
	#!/bin/bash

	# This script uses ffmpeg to transcode video files into one of a few formats suitable for
	# editing in either DaVinci Resolve or Lightworks on a Linux machine. It's purpose is to
	# simplify my life and relieve me from having to look up and enter the same very long
	# command over and over.
	#
	# If run with argument "all", the script will prompt for a directory containing video files, and
	# transcode all video files in the directory into the selected format. If run with a file as an
	# argument, it will transcode only that file, and will provide the additional option of
	# selecting a specific range to encode.
	#
	# It uses a modified version of Dave Miller's excellent ask.sh script, which can be found here:
	# https://gist.github.com/davejamesmiller/1965569
	#
	# To modify ask.sh, simply change line 23 to read
	# echo -n -e "$1 [$prompt] "
	#
	# (Adding the -e flag enables support for escape sequences, which allows
	# the colored text formatting.)
	#
	# It also uses my own colors.sh script, which defines a list of colors
	# for text formatting:
	# https://gist.github.com/jmatthewturner/2aeee120aa112fd51b000e13579c2654
	#
	# To run, just make sure that transcode.sh (this script), ask.sh and colors.sh
	# are in the same directory. (Everything is done with absolute paths, so it doesn't
	# matter where they are.)
	#
	# Written by jmatthewturner
	# https://github.com/jmatthewturner
	# https://www.youtube.com/jmatthewturner/
	#
	# https://gist.github.com/jmatthewturner/6b7034d13f4027f73c7982ecadf006ec
	#

	. ~/Scripts/ask.sh # https://gist.github.com/davejamesmiller/1965569
	. ~/Scripts/colors.sh # https://gist.github.com/jmatthewturner/2aeee120aa112fd51b000e13579c2654

	################ DEFINITIONS ###################

	# CONSTANTS
	#
	FILE_TYPES='.MTS .mov .mp4 .mkv .avi .m4v' # Types of video files to transcode.
	DEFAULT_TRANSCODE_DIRECTORY="${HOME}/Dragon_of_the_Black_Pool/" # Default directory for transcoded
	# files. You might want to change
	# this to your media drive.

	# FFMPEG constants. These are the ffmpeg options that do not change in response to user input.
	#
	# OPTIONS:
	# -loglevel quiet = suppress all output
	# -acodec pcm_16le = audio codec: 16bit PCM wave
	# -ar 48000 = audio sample rate: 48k
	# -r 24000/1001 = framerate: 23.976
	OPTIONS=' -loglevel quiet -acodec pcm_s16le -ar 48000 -r 24000/1001 '

	# The PADDING option keeps the input video the same size, but adds blue padding to fill out
	# a 1920x1080 frame. DNxHD requires this option for certain video sizes, so it is forced for DNxHD.
	PADDING=' -vf pad=1920:1080:(ow-iw)/2:(oh-ih)/2:color=blue '

	# Variable definitions
	#
	file_name="${1}" # Full path and name of file to be transcoded.
	input_file_name=$( basename "${1}" ) # Name of the file to be transcoded.
	input_path_name=$( dirname "${1}" ) # Path of the file to be transcoded.
	current_dir="$( pwd )" # Current working directory.
	source_directory="" # Source directory for input files.
	task="" # Are we transcoding one file, or all video files in a directory?
	padding_option="" # User's choice of blue padding. Default is none.
	pixel_format="" # Pixel format is determined based on codec choice.

	################# FUNCTIONS ################

	explain_usage()
	{
	echo
	echo -e ${LIGHTYELLOW}"Usage:${RESET}"
	echo
	echo "./transcode.sh = View this message."
	echo "./transcode.sh all = transcode all vdeo files in current directory"
	echo "./transcode.sh [filename] = transcode a section of [filename]"
	echo
	echo -e "${LIGHTYELLOW}Known issues:${RESET} Transcoding from ProRes to DNxHD may fail."
	echo
	exit 1
	}

	# Determine whether we're transcoding an entire directory or just one file.
	#
	determine_task()
	{
	if [[ ${file_name} == "" ]]
	then
	explain_usage
	elif [[ ${file_name} == 'all' ]]
	then
	task="transcode_all"
	elif [[ -f "${file_name}" ]]
	then
	task="transcode_one"
	else
	echo
	echo "There is no file ${file_name}."
	explain_usage
	fi
	}

	# Prompt user for target directory to store transcoded files.
	#
	prompt_for_target_dir()
	{
	echo
	echo -e "${LIGHTYELLOW}Target directory:${RESET}"
	if [[ ${task} == "transcode_all" ]]
	then
	read -e -i "${source_directory}" target_dir
	elif [[ ${task} == "transcode_one" ]]
	then
	read -e -i "${input_path_name}" target_dir
	else exit 1
	fi
	}

	# Create the target directory if it does not exist.
	#
	create_target_dir()
	{
	if [[ ! -e "${target_dir}" ]]
	then
	mkdir ${target_dir}
	fi
	}

	# Prompt for a prefix to add to the file name(s).
	#
	prompt_for_prefix()
	{
	echo -e "\n${LIGHTYELLOW}Prefix: (leave blank if none):${RESET}"
	read prefix
	}

	prompt_for_padding()
	{
	echo -e "\nSelecting the padding option will output a 1920x1080 file, regardless"
	echo -e "of input file size. The video will reamin the same size, and a blue"
	echo -e "padding will be added to fill out the remaining pixels of the 1920x1080 frame."
	echo -e "\nDNxHD will have the padding option selected regardless of your choice.\n"
	if ask "${LIGHTYELLOW}Select padding option?${RESET}" N
	then
	padding_option="${PADDING}"
	fi
	}

	# Prompt user for codec.
	#
	prompt_for_codec()
	{
	echo -e "\n${LIGHTYELLOW}Export Codec?${RESET}"
	echo -e "1: DNxHD 36Mbps"
	echo -e "2: ProRes Proxy (45Mbps 422)"
	echo -e "3: ProRes LT (102 Mbps 422)"
	echo -e "4: ProRes Standard (147 Mbps 422)"
	echo -e "5: ProRes HQ (220 Mbps 422)"
	echo -e "6: ProRes 4444 (330 Mbps 4444)"
	echo -e "7: ProRes 4444XQ (500 Mbps 4444)"
	echo -e "8: H.264"
	echo -e "9: H.265 / HEVC"
	echo
	echo -e -n "${LIGHTYELLOW}>${RESET}"
	read codec_choice

	# Set some options based on codec_choice.
	case ${codec_choice} in
	"1")
	codec=' -vcodec dnxhd -b:v 36M -vf pad=1920:1080:(ow-iw)/2:(oh-ih)/2:color=blue '
	codec_formatted='DNxHD-36Mbs-23.976'
	pixel_format=' -pix_fmt yuv422p '
	;;
	"2")
	codec=' -vcodec prores_ks -profile:v 0 '
	codec_formatted='ProRes-Proxy-23.976'
	pixel_format=' -pix_fmt yuv422p10le '
	;;
	"3")
	codec=' -vcodec prores_ks -profile:v 1 '
	codec_formatted='ProRes-LT-23.976'
	pixel_format=' -pix_fmt yuv422p10le '
	;;
	"4")
	codec=' -vcodec prores_ks -profile:v 2 '
	codec_formatted='ProRes-Standard-23.976'
	pixel_format=' -pix_fmt yuv422p10le '
	;;
	"5")
	codec=' -vcodec prores_ks -profile:v 3 '
	codec_formatted='ProRes-HQ-23.976'
	pixel_format=' -pix_fmt yuv422p10le '
	;;
	"6")
	codec=' -vcodec prores_ks -profile:v 4 '
	codec_formatted='ProRes-4444-23.976'
	pixel_format=' -pix_fmt yuv422p10le '
	;;
	"7")
	codec=' -vcodec prores_ks -profile:v 5 '
	codec_formatted='ProRes-4444HQ-23.976'
	pixel_format=' -pix_fmt yuv422p10le '
	;;
	"8")
	codec=' -vcodec h264 '
	codec_formatted='H.264-23.976'
	;;
	"9")
	codec=' -vcodec libx265 '
	codec_formatted='H.265-HEVC-(libx)-23.976'
	;;
	*)
	echo -e "\nPlease choose 1-9."
	echo
	prompt_for_codec # Poor man's while loop.
	;;
	esac
	}

	# Prompt user for source directory only if 'transcode all' was used.
	#
	prompt_for_source_directory()
	{
	if [[ ${task} == "transcode_all" ]]
	then
	echo -e "\n${LIGHTYELLOW}Source directory for video files:${RESET}"
	read -e -i ${DEFAULT_TRANSCODE_DIRECTORY} source_directory
	fi
	}

	# Transcode all video files in a supplied directory. Identifies files that match the
	# types stored in FILE_TYPES.
	#
	# I'm just going to say it: I couldn't figure out how to get a directory listing
	# directly into an array. My workaround is to put the directory listing into a temp file
	# file first, and then move it from the temp file into an array. I'm not proud.
	#
	transcode_all()
	{
	tmp_video_list=$( mktemp ) \|\| exit 1 # Temporary file to store identified video files.
	# If mktemp fails for any reason, exit with an error.
	local -a video_files # Array to store identified video files.

	# For loop identifies all the files in the source directory that match FILE_TYPES
	# and stores them in tmp_video_list.
	for i in ${FILE_TYPES}
	do
	ls 2> /dev/null 1>> "${tmp_video_list}" "${source_directory}"${i}
	done

	# While loop reads tmp_video_list and adds each line to array variable video_files[].
	while IFS= read -r line
	do
	video_files+=("${line}")
	done < "${tmp_video_list}"

	rm ${tmp_video_list} # Remove the temp file.

	# Display the list of files to be transcoded for the user.
	echo -e "\n${LIGHTYELLOW}Found ${#video_files[@]} files:${RESET}"
	for ((i = 0; i < ${#video_files[@]}; i++))
	do
	echo -e ${LIGHTYELLOW}$((i+1)).${RESET}$( basename "${video_files[$i]}" )
	done
	echo

	# Display a final confirmation of the target directory.
	echo -e "${LIGHTYELLOW}Transcoding to:${RESET}"
	echo -e "${target_dir}\n"

	# Transcode each file contained in array variable video_files[].
	if ask "${LIGHTYELLOW}Proceed?${RESET}" Y
	then
	echo
	for ((i = 0; i < ${#video_files[@]}; i++))
	do
	# Assign input_file-name for code readability.
	input_file_name=$( basename "${video_files[$i]}" )

	# Display the current file for the user.
	echo -e "${LIGHTYELLOW}Transcoding ${RESET}${input_file_name}..."

	# Transcode the current file.
	ffmpeg -i "${video_files[$i]}" ${codec} ${OPTIONS} ${padding_option} \
	"${target_dir}${prefix}-${input_file_name%.*}-${codec_formatted}-PCM16b48k.mov"
	done
	else echo -e "Exiting.\n"
	fi
	}

	# Transcode a single file provided as an argument to the script.
	# Prompt for optional filename prefix, start time and duration to encode.
	#
	transcode_one()
	{
	echo -e "\n${LIGHTYELLOW}Transcoding${RESET}"
	echo -e "${LIGHTRED}${input_file_name}${RESET}"
	echo -e "${LIGHTYELLOW}to${RESET}"
	echo -e "${input_path_name}"

	# Prompt user for encoding start time.
	echo -e -n "\n${LIGHTYELLOW}Enter start time in the format HH:MM:SS "
	echo -e "(leave empty for beginning):${RESET}"
	read start

	# Check if start value is empty. If not, set the start option.
	if [[ ! -z ${start} ]]
	then
	start=" -ss ${start} "
	fi

	# Prompt user for encoding length.
	echo -e -n "${LIGHTYELLOW}Enter encode length in the format HH:MM:SS "
	echo -e "(leave empty for entire video):${RESET}"
	read length

	# Check if length value is empty. If not, set the length option.
	if [[ ! -z ${length} ]]
	then
	length=" -t ${length} "
	fi

	# Display a message for the user and transcode the file.
	echo -e "${LIGHTYELLOW}Transcoding${RESET} ${LIGHTRED}${input_file_name}${LIGHTYELLOW}...${RESET}"
	ffmpeg ${start} ${length} -i "${file_name}" \
	${codec} ${OPTIONS} ${pixel_format} ${padding_option} \
	"${target_dir}/${prefix}-${input_file_name%.*}-${codec_formatted}-PCM16b48k.mov"
	echo -e -n "\n${target_dir}/${LIGHTRED}${prefix}${input_file_name%.*}-${codec_formatted}-"
	echo -e "PCM16b48k.mov${LIGHTYELLOW} done.${RESET}"
	}

	############## MAIN ROUTINE ###############

	# Configure some options.
	#
	determine_task # Use command line argument to determine which task to execute.
	prompt_for_codec # Prompt user for codec.
	prompt_for_prefix # Prompt user for prefix for transcoded files.
	prompt_for_padding # Ask user if padding is desired.
	prompt_for_source_directory # Prompt user for source directory if transcode all is used.
	prompt_for_target_dir # Prompt user for destination directory.
	create_target_dir # Confirm destination directory exists, create if necessary.

	# Execute transcoding job.
	#
	${task} # Executes either transcode_one() or transcode_all().
	exit 0 # Exit successfully.

	#
	# Written by jmatthewturner
	# https://github.com/jmatthewturner
	# https://www.youtube.com/jmatthewturner/
	#
	# https://gist.github.com/jmatthewturner/6b7034d13f4027f73c7982ecadf006ec
	#