Sometimes, I need to post longer videos on social media that are limited to a few minutes in duration. Manually splitting a longer video into segments is for amateurs.

The script below takes two command-line arguments: -f [/file_path/file_name.mp4] and -d [maximum_segment_duration_minutes]

The script will add small labels in the top left-hand corner of each resulting video segment indicating the segment’s number in the sequence. Comments in the script explain how to disable this feature if you don’t need it.

The trick to having this script work is having a version of ffmpeg that supports libharfbuzz and a few other features. You can read more about compiling ffmpeg from source here.

The script is below, and you can also download it from my GitHub repo.

The script


if [ ! -f "${font}" ]; then
    echo "Font file not found. Please update the font path in the script." >&2
    exit 1

# Function to convert seconds to HH:MM:SS format
convert_to_hms() {
    local total_seconds=$1
    printf "%02d:%02d:%02d" $(("${total_seconds}"/3600)) $(("${total_seconds}"%3600/60)) $(("${total_seconds}"%60))

# Parse command line arguments
while getopts f:d: flag
  case "${flag}" in
      f) video_path=${OPTARG};;
      d) segment_length_minutes=${OPTARG};;
      *) echo "Invalid flag: ${flag}" >&2
         exit 1;;

if [[ -z "${video_path}" || -z "${segment_length_minutes}" ]]; then
    echo "Usage: $0 -f [input video file path] -d [max duration of each segment in minutes]"
    exit 1

if [[ "$segment_length_minutes" =~ ^[0-9]+$ ]] ; then
   echo "Error: Video duration must be a positive integer."
   exit 1

if [ ! -f "${video_path}" ]; then
    echo "Input video file not found." >&2
    exit 1

# Convert segment length from minutes to seconds 
segment_length=$(("${segment_length_minutes}" * 60))

# Get the duration of the video in seconds
duration=$(ffprobe -i "${video_path}" -show_entries format=duration -v quiet -of csv="p=0")

# Calculate the number of segments needed
num_segments=$(echo "($duration / $segment_length) + 1" | bc)

# Use ffmpeg to split the video and add text
for ((i=0; i<num_segments; i++)); do
    start_time=$(echo "$i * ${segment_length}" | bc)
    start_time_hms=$(convert_to_hms "${start_time}")
    output_file=$(printf "segment_${random}_%03d.mp4" $i)
    part_number=$(printf "Part %d" $((i+1)))

    # The following command will also attach the "Part X" text to the video. If you don't want that, 
    # you can remove the `-vf` option and that entire line from the command below.
    ffmpeg -ss "${start_time_hms}" -i "${video_path}" \
    -vf "drawtext=fontfile=${font}:text='${part_number}':x=10:y=10:fontsize=24:fontcolor=white:box=1:boxcolor=black@0.5:boxborderw=5" \
    -t "${segment_length}" -c:a copy -y "${output_file}"