Convenient ffmpeg shell functions

.bashrc

#######################################
# Displays a yes/no prompt to continue that repeats until input matches.
# Arguments:
#   $1 - (optional) a string representing the yes/no question to ask
#   $2 - (optional) a string representing the prompt style.
# Returns:
#   0 to proceed further (indicates "yes"), 1 to stop (indicates "no").
#######################################
continue_prompt() {
    local prompt default reply

    if [ "${2:-}" = "Y" ]; then
        prompt="Y/n"
        default=Y
    elif [ "${2:-}" = "N" ]; then
        prompt="y/N"
        default=N
    else
        prompt="y/n"
        default=
    fi

    while true; do

        # Display the prompt.
        echo -n "$1 [$prompt] "

        # Read the answer from tty (avoids stdin issues).
        read reply </dev/tty

        # Default case for empty user reply.
        if [ -z "$reply" ]; then
            reply=$default
        fi

        # Check if the reply is valid.
        case "$reply" in
            Y*|y*) return 0 ;;
            N*|n*) return 1 ;;
        esac

    done
}

#######################################
# Create a center crop MP4 of a video with the specified width using ffmpeg.
# Note: assumes a three character file extension and maintains input height.
# Globals:
#   ffmpeg available on the path.
# Arguments:
#   $1 - (required) path to a video file from which to create a cropped video.
#   $2 - (required) integer value in pixels for the width of the cropped video.
# Outputs:
#   Writes new video to the same directory as the input file.
#######################################
ff_center_crop() {
    outputname="${1%????} (Center Crop).mp4"
    echo "Input file: ${1}"
    echo "Output file: ${outputname}"
    echo "Crop width (pixels): ${2}"
    if continue_prompt "Do you want to proceed?"; then
        echo "Running..."
        ffmpeg -i "$1" -filter:v "crop=$2:in_h" -c:a copy "$outputname"
    else
        echo "Exiting..."
    fi 
}

#######################################
# Create a CounterClockwise 90degree rotated MP4 of a video using ffmpeg.
# Note: assumes a three character file extension.
# Globals:
#   ffmpeg available on the path.
# Arguments:
#   $1 - (required) path to a video file from which to create a rotated video.
# Outputs:
#   Writes new video to the same directory as the input file.
#######################################
ff_rotate_video_cc90() {
    outputname="${1%????} (Rotated).mp4"
    echo "Input file: ${1}"
    echo "Output file: ${outputname}"
    if continue_prompt "Do you want to proceed?"; then
        echo "Running..."
        ffmpeg -i "$1" -vf "transpose=2" -vcodec libx264 -crf 22 -pix_fmt yuv420p "$outputname"
    else
        echo "Exiting..."
    fi 
    
}

#######################################
# Create a 10fps GIF from a video using ffmpeg.
# Note: assumes a three character file extension.
# Globals:
#   ffmpeg available on the path.
# Arguments:
#   $1 - (required) path to a video file from which to create a GIF.
#   $2 - (required) integer value in pixels for the width of the output GIF.
# Outputs:
#   Writes a GIF to the same directory as the input file.
#######################################
ff_gif() {
    outputname="${1%????}_${2}.gif"
    echo "Input file: ${1}"
    echo "Output file: ${outputname}"
    echo "Output width (pixels): ${2}"
    if continue_prompt "Do you want to proceed?"; then
        echo "Running..."
        ffmpeg -i "$1" -vf "fps=10,scale=$2:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" -loop 0 $outputname
    else
        echo "Exiting..."
    fi 
}

#######################################
# Create a 15fps animated WebP from a video using ffmpeg.
# Note: assumes a three character file extension.
# Globals:
#   ffmpeg available on the path.
# Arguments:
#   $1 - (required) path to a video file from which to create a GIF.
#   $2 - (required) integer value in pixels for the width of the output GIF.
# Outputs:
#   Writes a GIF to the same directory as the input file.
#######################################
ff_webp() {
    outputname="${1%????}_${2}.webp"
    echo "Input file: ${1}"
    echo "Output file: ${outputname}"
    echo "Output width (pixels): ${2}"
    if continue_prompt "Do you want to proceed?"; then
        echo "Running..."
        ffmpeg -i "$1" -vf "fps=15,scale=$2:-1:flags=lanczos" -vcodec libwebp -lossless 0 -compression_level 6 -q:v 50 -loop 0 -preset picture -an -vsync 0 $outputname
    else
        echo "Exiting..."
    fi 
}