youtube-transcript

# YouTube Transcript Downloader

This skill helps download transcripts (subtitles/captions) from YouTube videos using yt-dlp.

## When to Use This Skill

Activate this skill when the user:
- Provides a YouTube URL and wants the transcript
- Asks to "download transcript from YouTube"
- Wants to "get captions" or "get subtitles" from a video
- Asks to "transcribe a YouTube video"
- Needs text content from a YouTube video

## How It Works

### Priority Order:
1. **Check if yt-dlp is installed** - install if needed
2. **List available subtitles** - see what's actually available
3. **Try manual subtitles first** (`--write-sub`) - highest quality
4. **Fallback to auto-generated** (`--write-auto-sub`) - usually available
5. **Last resort: Whisper transcription** - if no subtitles exist (requires user confirmation)
6. **Confirm the download** and show the user where the file is saved
7. **Optionally clean up** the VTT format if the user wants plain text

## Installation Check

**IMPORTANT**: Always check if yt-dlp is installed first:

```bash
which yt-dlp || command -v yt-dlp
```

### If Not Installed

Attempt automatic installation based on the system:

**macOS (Homebrew)**:
```bash
brew install yt-dlp
```

**Linux (apt/Debian/Ubuntu)**:
```bash
sudo apt update && sudo apt install -y yt-dlp
```

**Alternative (pip - works on all systems)**:
```bash
pip3 install yt-dlp
# or
python3 -m pip install yt-dlp
```

**If installation fails**: Inform the user they need to install yt-dlp manually and provide them with installation instructions from https://github.com/yt-dlp/yt-dlp#installation

## Check Available Subtitles

**ALWAYS do this first** before attempting to download:

```bash
yt-dlp --list-subs "YOUTUBE_URL"
```

This shows what subtitle types are available without downloading anything. Look for:
- Manual subtitles (better quality)
- Auto-generated subtitles (usually available)
- Available languages

## Download Strategy

### Option 1: Manual Subtitles (Preferred)

Try this first - highest quality, human-created:

```bash
yt-dlp --write-sub --skip-download --output "OUTPUT_NAME" "YOUTUBE_URL"
```

### Option 2: Auto-Generated Subtitles (Fallback)

If manual subtitles aren't available:

```bash
yt-dlp --write-auto-sub --skip-download --output "OUTPUT_NAME" "YOUTUBE_URL"
```

Both commands create a `.vtt` file (WebVTT subtitle format).

## Option 3: Whisper Transcription (Last Resort)

**ONLY use this if both manual and auto-generated subtitles are unavailable.**

### Step 1: Show File Size and Ask for Confirmation

```bash
# Get audio file size estimate
yt-dlp --print "%(filesize,filesize_approx)s" -f "bestaudio" "YOUTUBE_URL"

# Or get duration to estimate
yt-dlp --print "%(duration)s %(title)s" "YOUTUBE_URL"
```

**IMPORTANT**: Display the file size to the user and ask: "No subtitles are available. I can download the audio (approximately X MB) and transcribe it using Whisper. Would you like to proceed?"

**Wait for user confirmation before continuing.**

### Step 2: Check for Whisper Installation

```bash
command -v whisper
```

If not installed, ask user: "Whisper is not installed. Install it with `pip install openai-whisper` (requires ~1-3GB for models)? This is a one-time installation."

**Wait for user confirmation before installing.**

Install if approved:
```bash
pip3 install openai-whisper
```

### Step 3: Download Audio Only

```bash
yt-dlp -x --audio-format mp3 --output "audio_%(id)s.%(ext)s" "YOUTUBE_URL"
```

### Step 4: Transcribe with Whisper

```bash
# Auto-detect language (recommended)
whisper audio_VIDEO_ID.mp3 --model base --output_format vtt

# Or specify language if known
whisper audio_VIDEO_ID.mp3 --model base --language en --output_format vtt
```

**Model Options** (stick to `base` for now):
- `tiny` - fastest, least accurate (~1GB)
- `base` - good balance (~1GB) ← **USE THIS**
- `small` - better accuracy (~2GB)
- `medium` - very good (~5GB)
- `large` - best accuracy (~10GB)

### Step 5: Cleanup

After transcription completes, ask user: "Transcription complete! Would you like me to delete the audio file to save space?"

If yes:
```bash
rm audio_VIDEO_ID.mp3
```

## Getting Video Information

### Extract Video Title (for filename)

```bash
yt-dlp --print "%(title)s" "YOUTUBE_URL"
```

Use this to create meaningful filenames based on the video title. Clean the title for filesystem compatibility:
- Replace `/` with `-`
- Replace special characters that might cause issues
- Consider using sanitized version: `$(yt-dlp --print "%(title)s" "URL" | tr '/' '-' | tr ':' '-')`

## Post-Processing

### Convert to Plain Text (Recommended)

YouTube's auto-generated VTT files contain **duplicate lines** because captions are shown progressively with overlapping timestamps. Always deduplicate when converting to plain text while preserving the original speaking order.

```bash
python3 -c "
import sys, re
seen = set()
with open('transcript.en.vtt', 'r') as f:
    for line in f:
        line = line.strip()
        if line and not line.startswith('WEBVTT') and not line.startswith('Kind:') and not line.startswith('Language:') and '-->' not in line:
            clean = re.sub('<[^>]*>', '', line)
            clean = clean.replace('&amp;', '&').replace('&gt;', '>').replace('&lt;', '<')
            if clean and clean not in seen:
                print(clean)
                seen.add(clean)
" > transcript.txt
```

### Complete Post-Processing with Video Title

```bash
# Get video title
VIDEO_TITLE=$(yt-dlp --print "%(title)s" "YOUTUBE_URL" | tr '/' '_' | tr ':' '-' | tr '?' '' | tr '"' '')

# Find the VTT file
VTT_FILE=$(ls *.vtt | head -n 1)

# Convert with deduplication
python3 -c "
import sys, re
seen = set()
with open('$VTT_FILE', 'r') as f:
    for line in f:
        line = line.strip()
        if line and not line.startswith('WEBVTT') and not line.startswith('Kind:') and not line.startswith('Language:') and '-->' not in line:
            clean = re.sub('<[^>]*>', '', line)
            clean = clean.replace('&amp;', '&').replace('&gt;', '>').replace('&lt;', '<')
            if clean and clean not in seen:
                print(clean)
                seen.add(clean)
" > "${VIDEO_TITLE}.txt"

echo "✓ Saved to: ${VIDEO_TITLE}.txt"

# Clean up VTT file
rm "$VTT_FILE"
echo "✓ Cleaned up temporary VTT file"
```

## Output Formats

- **VTT format** (`.vtt`): Includes timestamps and formatting, good for video players
- **Plain text** (`.txt`): Just the text content, good for reading or analysis

## Tips

- The filename will be `{output_name}.{language_code}.vtt` (e.g., `transcript.en.vtt`)
- Most YouTube videos have auto-generated English subtitles
- Some videos may have multiple language options
- If auto-subtitles aren't available, try `--write-sub` instead for manual subtitles

## Complete Workflow Example

```bash
VIDEO_URL="https://www.youtube.com/watch?v=dQw4w9WgXcQ"

# Get video title for filename
VIDEO_TITLE=$(yt-dlp --print "%(title)s" "$VIDEO_URL" | tr '/' '_' | tr ':' '-' | tr '?' '' | tr '"' '')
OUTPUT_NAME="transcript_temp"

# ============================================
# STEP 1: Check if yt-dlp is installed
# ============================================
if ! command -v yt-dlp &> /dev/null; then
    echo "yt-dlp not found, attempting to install..."
    if command -v brew &> /dev/null; then
        brew install yt-dlp
    elif command -v apt &> /dev/null; then
        sudo apt update && sudo apt install -y yt-dlp
    else
        pip3 install yt-dlp
    fi
fi

# ============================================
# STEP 2: List available subtitles
# ============================================
echo "Checking available subtitles..."
yt-dlp --list-subs "$VIDEO_URL"

# ============================================
# STEP 3: Try manual subtitles first
# ============================================
echo "Attempting to download manual subtitles..."
if yt-dlp --write-sub --skip-download --output "$OUTPUT_NAME" "$VIDEO_URL" 2>/dev/null; then
    echo "✓ Manual subtitles downloaded successfully!"
    ls -lh ${OUTPUT_NAME}.*
else
    # ============================================
    # STEP 4: Fallback to auto-generated
    # ============================================
    echo "Manual subtitles not available. Trying auto-generated..."
    if yt-dlp --write-auto-sub --skip-download --output "$OUTPUT_NAME" "$VIDEO_URL" 2>/dev/null; then
        echo "✓ Auto-generated subtitles downloaded successfully!"
        ls -lh ${OUTPUT_NAME}.*
    else
        # ============================================
        # STEP 5: Last resort - Whisper transcription
        # ============================================
        echo "⚠ No subtitles available for this video."

        # Get file size
        FILE_SIZE=$(yt-dlp --print "%(filesize_approx)s" -f "bestaudio" "$VIDEO_URL")
        DURATION=$(yt-dlp --print "%(duration)s" "$VIDEO_URL")
        TITLE=$(yt-dlp --print "%(title)s" "$VIDEO_URL")

        echo "Video: $TITLE"
        echo "Duration: $((DURATION / 60)) minutes"
        echo "Audio size: ~$((FILE_SIZE / 1024 / 1024)) MB"
        echo ""
        echo "Would you like to download and transcribe with Whisper? (y/n)"
        read -r RESPONSE

        if [[ "$RESPONSE" =~ ^[Yy]$ ]]; then
            # Check for Whisper
            if ! command -v whisper &> /dev/null; then
                echo "Whisper not installed. Install now? (requires ~1-3GB) (y/n)"
                read -r INSTALL_RESPONSE
                if [[ "$INSTALL_RESPONSE" =~ ^[Yy]$ ]]; then
                    pip3 install openai-whisper
                else
                    echo "Cannot proceed without Whisper. Exiting."
                    exit 1
                fi
            fi

            # Download audio
            echo "Downloading audio..."
            yt-dlp -x --audio-format mp3 --output "audio_%(id)s.%(ext)s" "$VIDEO_URL"

            # Get the actual audio filename
            AUDIO_FILE=$(ls audio_*.mp3 | head -n 1)

            # Transcribe
            echo "Transcribing with Whisper (this may take a few minutes)..."
            whisper "$AUDIO_FILE" --model base --output_format vtt

            # Cleanup
            echo "Transcription complete! Delete audio file? (y/n)"
            read -r CLEANUP_RESPONSE
            if [[ "$CLEANUP_RESPONSE" =~ ^[Yy]$ ]]; then
                rm "$AUDIO_FILE"
                echo "Audio file deleted."
            fi

            ls -lh *.vtt
        else
            echo "Transcription cancelled."
            exit 0
        fi
    fi
fi

# ============================================
# STEP 6: Convert to readable plain text with deduplication
# ============================================
VTT_FILE=$(ls ${OUTPUT_NAME}*.vtt 2>/dev/null || ls *.vtt | head -n 1)
if [ -f "$VTT_FILE" ]; then
    echo "Converting to readable format and removing duplicates..."
    python3 -c "
import sys, re
seen = set()
with open('$VTT_FILE', 'r') as f:
    for line in f:
        line = line.strip()
        if line and not line.startswith('WEBVTT') and not line.startswith('Kind:') and not line.startswith('Language:') and '-->' not in line:
            clean = re.sub('<[^>]*>', '', line)
            clean = clean.replace('&amp;', '&').replace('&gt;', '>').replace('&lt;', '<')
            if clean and clean not in seen:
                print(clean)
                seen.add(clean)
" > "${VIDEO_TITLE}.txt"
    echo "✓ Saved to: ${VIDEO_TITLE}.txt"

    # Clean up temporary VTT file
    rm "$VTT_FILE"
    echo "✓ Cleaned up temporary VTT file"
else
    echo "⚠ No VTT file found to convert"
fi

echo "✓ Complete!"
```

**Note**: This complete workflow handles all scenarios with proper error checking and user prompts at each decision point.

## Error Handling

### Common Issues and Solutions:

**1. yt-dlp not installed**
- Attempt automatic installation based on system (Homebrew/apt/pip)
- If installation fails, provide manual installation link
- Verify installation before proceeding

**2. No subtitles available**
- List available subtitles first to confirm
- Try both `--write-sub` and `--write-auto-sub`
- If both fail, offer Whisper transcription option
- Show file size and ask for user confirmation before downloading audio

**3. Invalid or private video**
- Check if URL is correct format: `https://www.youtube.com/watch?v=VIDEO_ID`
- Some videos may be private, age-restricted, or geo-blocked
- Inform user of the specific error from yt-dlp

**4. Whisper installation fails**
- May require system dependencies (ffmpeg, rust)
- Provide fallback: "Install manually with: `pip3 install openai-whisper`"
- Check available disk space (models require 1-10GB depending on size)

**5. Download interrupted or failed**
- Check internet connection
- Verify sufficient disk space
- Try again with `--no-check-certificate` if SSL issues occur

**6. Multiple subtitle languages**
- By default, yt-dlp downloads all available languages
- Can specify with `--sub-langs en` for English only
- List available with `--list-subs` first

### Best Practices:

- ✅ Always check what's available before attempting download (`--list-subs`)
- ✅ Verify success at each step before proceeding to next
- ✅ Ask user before large downloads (audio files, Whisper models)
- ✅ Clean up temporary files after processing
- ✅ Provide clear feedback about what's happening at each stage
- ✅ Handle errors gracefully with helpful messages