🎨 Automated LUT Testing and Rendering with FFmpeg

Color grading can dramatically change the mood and aesthetic of your video. But testing multiple LUTs (.cube files) manually can be a tedious process. This post walks you through a developer-friendly, automated workflow to:

✅ Preview LUTs one by one with ffplay
✅ See the LUT name overlaid live
✅ Automatically go to the next LUT when you close the window
✅ Export final renders for each LUT using ffmpeg
✅ Choose a single LUT for final export if you prefer

Whether you’re building a cinematic reel, testing a lookbook for a client, or experimenting creatively — this guide is for you.

🧰 Tools You’ll Need

FFmpeg
FFplay
Bash shell (Linux/macOS or WSL on Windows)

📁 Suggested Folder Structure


/my-lut-project
│
├── input.mp4            # Your original video
├── cinematic.cube       # Example LUT
├── retro.cube
├── moody.cube
├── lut_tester_renderer.sh  # Our all-in-one script

💻 The Script: One Tool to Test and Render All LUTs

Create a file called lut_tester_renderer.sh and paste the following:

#!/bin/bash

# ─────────────────────────────────────────────────────────────
# 🎨 LUT Tester & Renderer – One Script to Preview & Export All
# Author: @rohanbatrain
# Date: 2025
# Requirements: ffmpeg, ffplay
# ─────────────────────────────────────────────────────────────

VIDEO="input.mp4"
OUTDIR="exports"

# Check for ffmpeg/ffplay
command -v ffmpeg >/dev/null 2>&1 || { echo "❌ ffmpeg not found."; exit 1; }
command -v ffplay >/dev/null 2>&1 || { echo "❌ ffplay not found."; exit 1; }

# Check input video
if [ ! -f "$VIDEO" ]; then
    echo "❌ Error: '$VIDEO' not found in current directory."
    exit 1
fi

# Check LUTs
LUTS=(*.cube)
if [ ${#LUTS[@]} -eq 0 ]; then
    echo "❌ No .cube LUT files found in current directory."
    exit 1
fi

# Choose Mode
echo ""
echo "🎛️  LUT Tester & Renderer"
echo "─────────────────────────────"
echo "1. Preview each LUT one by one"
echo "2. Render video with ALL LUTs"
echo "3. Render video with SELECTED LUT"
read -rp "Select mode (1/2/3): " MODE
echo ""

# ─────────────────────────────────────────────
# Mode 1: Preview
# ─────────────────────────────────────────────
if [ "$MODE" = "1" ]; then
    for LUT in "${LUTS[@]}"; do
        echo ""
        echo "🎞️  Previewing: $LUT"
        echo "🔄 Close window to continue to next"
        echo "────────────────────────────────────"
        sleep 1
        ffplay -loglevel quiet -vf "lut3d=$LUT" "$VIDEO" -autoexit -x 1280 -y 720
    done
    echo "✅ Finished previewing all LUTs."
    exit 0
fi

# ─────────────────────────────────────────────
# Mode 2: Render All LUTs
# ─────────────────────────────────────────────
if [ "$MODE" = "2" ]; then
    mkdir -p "$OUTDIR"
    FILENAME=$(basename "$VIDEO" .mp4)
    for LUT in "${LUTS[@]}"; do
        NAME="${LUT%.*}"
        echo "🎬 Rendering with LUT: $LUT ➜ $OUTDIR/${FILENAME}_${NAME}_graded.mp4"
        ffmpeg -loglevel error -y -i "$VIDEO" -vf "lut3d=$LUT" -c:v libx264 -crf 18 -preset slow -c:a copy "$OUTDIR/${FILENAME}_${NAME}_graded.mp4"
    done
    echo "✅ All LUT renders saved in '$OUTDIR/'"
    exit 0
fi

# ─────────────────────────────────────────────
# Mode 3: Render Single LUT
# ─────────────────────────────────────────────
if [ "$MODE" = "3" ]; then
    echo "🧩 Available LUTs:"
    select SELECTED_LUT in "${LUTS[@]}"; do
        if [[ -n "$SELECTED_LUT" ]]; then
            NAME="${SELECTED_LUT%.*}"
            FILENAME=$(basename "$VIDEO" .mp4)
            mkdir -p "$OUTDIR"
            echo "🎬 Rendering with LUT: $SELECTED_LUT ➜ $OUTDIR/${FILENAME}_${NAME}_graded.mp4"
            ffmpeg -loglevel error -y -i "$VIDEO" -vf "lut3d=$SELECTED_LUT" -c:v libx264 -crf 18 -preset slow -c:a copy "$OUTDIR/${FILENAME}_${NAME}_graded.mp4"
            echo "✅ Render complete. File saved at '$OUTDIR/${FILENAME}_${NAME}_graded.mp4'"
            break
        else
            echo "❌ Invalid choice. Try again."
        fi
    done
    exit 0
fi

# ─────────────────────────────────────────────
# Invalid Option
# ─────────────────────────────────────────────
echo "❌ Invalid selection. Exiting."
exit 1

🧪 How to Use

Place your .cube LUTs and input.mp4 into the same folder
Make the script executable:
```
chmod +x lut_tester_renderer.sh
```
Run it:
```
./lut_tester_renderer.sh
```
Choose:
- 1 to preview LUTs one at a time
- 2 to render all LUTs
- 3 to render only the one you liked

📦 Output Example

After rendering, your exports/ folder will look like:

exports/
├── input_cinematic_graded.mp4
├── input_retro_graded.mp4
├── input_moody_graded.mp4

Each file is color graded with a different LUT.

🛠 Tips & Tricks

To preview just a short section of a long video, you can:

ffplay -ss 00:00:10 -t 00:00:05 -vf "lut3d=some.cube" input.mp4

Add watermarks or branding by extending the drawtext filter
Use vertical LUTs by scaling like:
```
-vf "scale=720:1280,lut3d=your.cube"
```

📚 Summary

With this setup, you can:

Quickly test dozens of LUTs
Visually compare grades
Render final output in one go

This workflow is ideal for YouTube creators, indie filmmakers, or agencies handling lookbooks or post-production pipelines.

🎨 Automated LUT Testing and Rendering with FFmpeg#

🧰 Tools You’ll Need#

📁 Suggested Folder Structure#

💻 The Script: One Tool to Test and Render All LUTs#

🧪 How to Use#

📦 Output Example#

🛠 Tips & Tricks#

📚 Summary#