Building a Powerful FFmpeg CLI Tool: A Bash Script Deep Dive

The Problem

Working with video and audio files often requires multiple FFmpeg commands, each with different flags and parameters. Typing these commands repeatedly is tedious, error-prone, and breaks workflow. I needed a single, interactive tool that could handle common media operations with a clean interface.

The Solution

I built a bash script that combines FFmpeg's power with fzf (fuzzy finder) for an intuitive, menu-driven experience. Here's what it does and how it works.

Concepts Used

Before diving into the code, let's break down the key concepts this script demonstrates:

1. Shell Scripting Fundamentals

Variable declarations and color codes
Conditional statements (if, case)
Input/output redirection (>&2)
Command substitution

2. fzf (Fuzzy Finder)

Interactive menu selection
Custom prompts and headers
Reverse layout for better UX
Integration with shell pipelines

3. File Operations

find command with file type filtering
Pattern matching with -iname flags
Directory depth limiting (-maxdepth)
String manipulation with sed

4. FFmpeg Operations

Format conversion
Video filters (-vf)
Codec selection (-c:v, -c:a)
Time-based clipping (-ss, -to)
Frame extraction

5. User Interaction

Interactive prompts with read
Error handling and validation
Color-coded output for feedback
Directory creation for outputs

6. ANSI Color Codes

Terminal text coloring
Status indicators (green=success, red=error, yellow=warning)
Reset codes for proper formatting

The Script Breakdown

#!/bin/bash
 
# Color definitions for terminal output
GREEN="\033[0;32m"
RED="\033[0;31m"
YELLOW="\033[1;33m"
RESET="\033[0m"
PURPLE="\e[35m"

Why colors? Visual feedback makes the tool more user-friendly. Green for success, red for errors, yellow for warnings.

echo -e "${GREEN}Welcome to FFMPEG CLI Tool.${RESET}" >&2
echo "" >&2

>&2: Redirects output to stderr. This ensures messages appear even when output is piped.

operation=$(printf "1. Format Conversion\n2. Convert to BNW\n3. Extract Audio\n4. Clip Media\n5. Extract frames" | fzf --prompt="Choose the operation to peform" --layout=reverse --header="Choose what you want to do:")

fzf Integration:

printf creates a menu list
Piped to fzf for interactive selection
--layout=reverse puts the prompt at the top
--header adds a title
Result stored in $operation variable

if [[ -n "$operation" ]]; then
  echo -e "${GREEN}Select a media file from the current directory:${RESET}"
  media_file=$(find . -maxdepth 1 -type f \( -iname "*.mp4" -o -iname "*.mkv" -o -iname "*.avi" -o -iname "*.webm" \) | sed 's|^\./||' | fzf --prompt="File: " --header="Pick a video file to process:")
else
  echo -e "${RED}No option selected. Aborting...!${RESET}"
fi

File Selection:

find . -maxdepth 1: Search only current directory
-type f: Files only (not directories)
$ -iname "*.mp4" -o ... $: Multiple file extensions (case-insensitive)
sed 's|^\./||': Remove ./ prefix for cleaner display
Piped to fzf for interactive file selection

case "$operation" in
"1. Convert to BNW")
  ffmpeg -i $media_file -vf format=gray -c:v libx264 -preset ultrafast -crf 28 -c:a copy bnw_$media_file.mp4
  ;;

Case Statement: Handles different operations. This one converts to black & white:

-vf format=gray: Video filter for grayscale
-c:v libx264: H.264 video codec
-preset ultrafast: Encoding speed (faster = larger file)
-crf 28: Quality setting (higher = lower quality, smaller file)
-c:a copy: Copy audio without re-encoding

"3. Extract Audio")
  ffmpeg -i "$media_file" -q:a 0 -map a "${media_file%.*}.mp3"
  ;;

Audio Extraction:

-q:a 0: Highest audio quality
-map a: Map only audio stream
"${media_file%.*}": Remove file extension, add .mp3

"5. Extract Frames")
  mkdir -p frames
  ffmpeg -i "$media_file" -vf "fps=1" frames/frame_%04d.png
  echo -e "${GREEN}Frames extracted to ./frames directory${RESET}"
  ;;

Frame Extraction:

mkdir -p frames: Create directory (won't error if exists)
-vf "fps=1": Extract 1 frame per second
frame_%04d.png: Sequential naming (frame_0001.png, frame_0002.png, etc.)

"4. Clip Media")
  read -p "Start time (e.g., 00:00:15): " start
  read -p "Duration (e.g., 00:00:17): " end
  read -p "Enter name of output file: " output
  ffmpeg -hide_banner -loglevel error -y -ss "$start" -to "$end" -i "$media_file" -c:v libx264 -c:a aac "${output}.mp4"
  echo -e "${GREEN}Clipped video saved as $output${RESET}"
  ;;

Video Clipping:

read -p: Interactive prompt for user input
-hide_banner -loglevel error: Suppress FFmpeg output (only errors)
-y: Overwrite output file without asking
-ss "$start": Start time
-to "$end": End time
-c:a aac: AAC audio codec

Key Features

1. Interactive Menus

No need to remember command syntax. Just select from a menu.

2. Fuzzy File Finding

Type part of a filename to quickly find it. No need to type full paths.

3. Error Prevention

Validates operation selection
Checks file existence (implicitly via find)
Provides clear error messages

4. Flexible Input

Works with multiple video formats
Handles spaces in filenames (quotes)
Supports relative paths

5. User Feedback

Color-coded messages
Clear success/error indicators
Progress information

Usage Example

$ ./ffmpeg-tool.sh
Welcome to FFMPEG CLI Tool.
 
# fzf menu appears
Choose what you want to do:
> 4. Clip Media
  3. Extract Audio
  5. Extract Frames
  ...
 
# After selection, file picker appears
Pick a video file to process:
> video.mp4
  another-video.mkv
  ...
 
# For clipping, prompts appear
Start time (e.g., 00:00:15): 00:01:30
Duration (e.g., 00:00:17): 00:00:30
Enter name of output file: my-clip
 
# Success message
Clipped video saved as my-clip

Improvements You Could Make

Add More Operations: Resize, rotate, add watermarks
Batch Processing: Process multiple files at once
Progress Bars: Show encoding progress
Presets: Save common settings as presets
Configuration File: Store default settings
Error Handling: Better validation and error recovery
Preview: Show video preview before processing

The Complete Script

Here's the full script for reference:

#!/bin/bash
 
GREEN="\033[0;32m"
RED="\033[0;31m"
YELLOW="\033[1;33m"
RESET="\033[0m"
PURPLE="\e[35m"
 
echo -e "${GREEN}Welcome to FFMPEG CLI Tool.${RESET}" >&2
echo "" >&2
 
operation=$(printf "1. Format Conversion\n2. Convert to BNW\n3. Extract Audio\n4. Clip Media\n5. Extract frames" | fzf --prompt="Choose the operation to peform" --layout=reverse --header="Choose what you want to do:")
 
if [[ -n "$operation" ]]; then
  echo -e "${GREEN}Select a media file from the current directory:${RESET}"
  media_file=$(find . -maxdepth 1 -type f \( -iname "*.mp4" -o -iname "*.mkv" -o -iname "*.avi" -o -iname "*.webm" \) | sed 's|^\./||' |
    fzf --prompt="File: " --header="Pick a video file to process:")
 
else
  echo -e "${RED}No option selected. Aborting...!${RESET}"
fi
 
case "$operation" in
"1. Convert to BNW")
  ffmpeg -i $media_file -vf format=gray -c:v libx264 -preset ultrafast -crf 28 -c:a copy bnw_$media_file.mp4
  ;;
"3. Extract Audio")
  ffmpeg -i "$media_file" -q:a 0 -map a "${media_file%.*}.mp3"
  ;;
"5. Extract Frames")
  mkdir -p frames
  ffmpeg -i "$media_file" -vf "fps=1" frames/frame_%04d.png
  echo -e "${GREEN}Frames extracted to ./frames directory${RESET}"
  ;;
"4. Clip Media")
  read -p "Start time (e.g., 00:00:15): " start
  read -p "Duration (e.g., 00:00:17): " end
  read -p "Enter name of output file: " output
  ffmpeg -hide_banner -loglevel error -y -ss "$start" -to "$end" -i "$media_file" -c:v libx264 -c:a aac "${output}.mp4"
  echo -e "${GREEN}Clipped video saved as $output${RESET}"
  ;;
esac

Takeaways

This script demonstrates how simple tools can create powerful workflows:

fzf makes CLI tools user-friendly
Bash scripting automates repetitive tasks
FFmpeg handles complex media operations
Color coding improves user experience

By combining these concepts, we've created a tool that's both powerful and accessible—proving that you don't need a GUI to have a great user experience.

Want to extend this script or have questions? Check out the FFmpeg documentation and fzf GitHub repo for more ideas!