Video Processing & Analysis

When to use: YouTube video automation, subtitle extraction, transcript analysis, video content indexing, or generating show notes.

Overview

Production-ready tools for video content processing with subtitle extraction, timestamp handling, and AI-powered analysis.

Key Capabilities

✅ YouTube subtitle download (multiple languages)
✅ VTT subtitle parsing with timestamp preservation
✅ Video duration checking
✅ Timestamp validation
✅ Batch screenshot generation
✅ Video metadata extraction

Prerequisites

bash

# Install required tools
npm install -g yt-dlp  # or: pip install yt-dlp

# Install ffmpeg (for video processing)
# macOS
brew install ffmpeg

# Ubuntu/Debian
sudo apt-get install ffmpeg

# Windows
# Download from: https://ffmpeg.org/download.html

Core Operations

1. Download YouTube Subtitles

bash

# Download auto-generated English subtitles
yt-dlp --write-auto-sub --sub-lang en --skip-download \
  --sub-format vtt -o "subtitle.%(ext)s" \
  "https://www.youtube.com/watch?v=VIDEO_ID"

# Download manual subtitles (if available)
yt-dlp --write-sub --sub-lang en --skip-download \
  --sub-format vtt -o "subtitle.%(ext)s" \
  "https://www.youtube.com/watch?v=VIDEO_ID"

# Multiple languages
yt-dlp --write-auto-sub --sub-lang en,zh,ja --skip-download \
  --sub-format vtt -o "subtitle.%(ext)s" \
  "VIDEO_URL"

2. Parse VTT Subtitles with Timestamps

Key Feature: Preserves timing information for quote attribution.

javascript

// VTT Parser (ES5 compatible)
function parseVTT(vttContent) {
  var lines = vttContent.split('\n');
  var segments = [];
  var currentSegment = null;

  for (var i = 0; i < lines.length; i++) {
    var line = lines[i].trim();

    // Timestamp line: 00:01:23.456 --> 00:01:26.789
    if (line.match(/^\d{2}:\d{2}:\d{2}\.\d{3}/)) {
      var timestamps = line.split(' --> ');
      currentSegment = {
        start: timestamps[0],
        end: timestamps[1],
        text: ''
      };
    }
    // Text line
    else if (currentSegment && line.length > 0 && !line.match(/^\d+$/)) {
      currentSegment.text += (currentSegment.text ? ' ' : '') + line;
    }
    // Empty line (segment end)
    else if (currentSegment && line.length === 0) {
      segments.push(currentSegment);
      currentSegment = null;
    }
  }

  return segments;
}

// Convert to timestamped text
function formatWithTimestamps(segments) {
  var result = '';
  for (var i = 0; i < segments.length; i++) {
    var seg = segments[i];
    result += '[' + seg.start.substring(0, 8) + '] ' + seg.text + '\n';
  }
  return result;
}

// Usage
var vttContent = $input.item.binary.data.toString('utf-8');
var segments = parseVTT(vttContent);
var timestampedText = formatWithTimestamps(segments);

return {
  json: {
    transcript: timestampedText,
    segments: segments,
    segmentCount: segments.length
  }
};

3. Video Duration Check

bash

# Get video duration
ffprobe -v error -show_entries format=duration \
  -of default=noprint_wrappers=1:nokey=1 \
  video.mp4

# Get duration in HH:MM:SS format
ffprobe -v error -show_entries format=duration \
  -of default=noprint_wrappers=1:nokey=1 \
  -sexagesimal video.mp4

javascript

// Validate timestamp against video duration
function validateTimestamp(timestamp, videoDuration) {
  // Parse timestamp: 00:01:23 or 01:23
  var parts = timestamp.split(':').map(function(p) {
    return parseInt(p, 10);
  });

  var seconds;
  if (parts.length === 3) {
    seconds = parts[0] * 3600 + parts[1] * 60 + parts[2];
  } else if (parts.length === 2) {
    seconds = parts[0] * 60 + parts[1];
  } else {
    return false;
  }

  return seconds <= videoDuration;
}

4. Batch Screenshot Generation

bash

# Single screenshot at timestamp
ffmpeg -ss 00:01:23 -i video.mp4 -vframes 1 -q:v 2 screenshot.jpg

# Multiple screenshots
# timestamps.txt:
# 00:00:30
# 00:01:45
# 00:03:20

while read timestamp; do
  filename="screenshot_${timestamp//:/}.jpg"
  ffmpeg -ss $timestamp -i video.mp4 -vframes 1 -q:v 2 $filename
done < timestamps.txt

javascript

// Generate screenshot filenames for batch
function generateScreenshotBatch(timestamps, videoFile) {
  var commands = [];

  for (var i = 0; i < timestamps.length; i++) {
    var ts = timestamps[i];
    var filename = 'screenshot_' + ts.replace(/:/g, '') + '.jpg';
    var command = 'ffmpeg -ss ' + ts + ' -i ' + videoFile +
                  ' -vframes 1 -q:v 2 ' + filename;
    commands.push({
      timestamp: ts,
      filename: filename,
      command: command
    });
  }

  return commands;
}

5. Extract Video Metadata

bash

# Get all metadata
ffprobe -v quiet -print_format json -show_format -show_streams video.mp4

# Get specific fields
ffprobe -v error -select_streams v:0 \
  -show_entries stream=width,height,codec_name,bit_rate \
  -of json video.mp4

Complete Workflow: YouTube → Analysis → Notion

[Manual/Webhook Trigger]
    Video URL
    ↓
[Download Subtitle]
    yt-dlp --write-auto-sub
    ↓
[Parse VTT]
    Extract segments with timestamps
    ↓
[AI Analysis]
    Generate summary, quotes, tags
    ↓
[Validate Timestamps]
    Check quotes are within video duration
    ↓
[Download Video]
    (if screenshots needed)
    ↓
[Generate Screenshots]
    For key moments/quotes
    ↓
[Save to Notion]
    Structured data with timestamps

n8n Implementation

Workflow Structure

javascript

// Node 1: Download Subtitle
var execSync = require('child_process').execSync;
var videoUrl = $input.item.json.url;
var outputPath = '/tmp/subtitle.vtt';

var command = 'yt-dlp --write-auto-sub --sub-lang en ' +
              '--skip-download --sub-format vtt ' +
              '-o "' + outputPath + '" "' + videoUrl + '"';

execSync(command);

return {
  json: {
    videoUrl: videoUrl,
    subtitlePath: outputPath
  }
};

javascript

// Node 2: Parse VTT
var fs = require('fs');
var vttContent = fs.readFileSync($input.item.json.subtitlePath, 'utf8');

var segments = parseVTT(vttContent);
var fullTranscript = formatWithTimestamps(segments);

return {
  json: Object.assign({}, $input.item.json, {
    transcript: fullTranscript,
    segments: segments
  })
};

javascript

// Node 3: AI Analysis (use ai-integration skill)
var prompt = 'Analyze this video transcript and extract:\n' +
             '1. Summary (2-3 sentences)\n' +
             '2. Key quotes with their timestamps\n' +
             '3. Main topics/tags\n\n' +
             'Transcript:\n' + $input.item.json.transcript;

// Call AI API...

javascript

// Node 4: Validate Timestamps
var quotes = $input.item.json.aiAnalysis.quotes;
var videoDuration = $input.item.json.duration;

var validQuotes = [];
for (var i = 0; i < quotes.length; i++) {
  var quote = quotes[i];
  if (validateTimestamp(quote.timestamp, videoDuration)) {
    validQuotes.push(quote);
  } else {
    // Adjust or skip invalid timestamps
    console.log('Invalid timestamp: ' + quote.timestamp);
  }
}

return {
  json: Object.assign({}, $input.item.json, {
    validatedQuotes: validQuotes
  })
};

Best Practices

Language Detection: Try auto-generated subtitles first, fall back to manual
Timestamp Format: Always use HH:MM:SS format for consistency
Validation: Check timestamps against video duration before using
Caching: Save downloaded subtitles to avoid re-downloading
Error Handling: Not all videos have subtitles, handle gracefully
File Cleanup: Delete temporary files after processing

Common Patterns

Pattern 1: Video Indexing

YouTube Channel → Get New Videos → Download Subtitles →
Parse & Index → Searchable Database

Pattern 2: Show Notes Generation

Video URL → Subtitles → AI Analysis →
Generate Summary + Timestamps → Export Markdown

Pattern 3: Quote Attribution

Transcript with Timestamps → AI Extract Quotes →
Validate Timestamps → Generate Screenshots →
Create Social Media Posts

Troubleshooting

No subtitles available

javascript

// Try both auto and manual
try {
  execSync('yt-dlp --write-sub ...');  // Manual first
} catch (e) {
  execSync('yt-dlp --write-auto-sub ...');  // Fallback to auto
}

VTT parsing errors

javascript

// Handle malformed VTT
if (!line.match(/^WEBVTT/) && i === 0) {
  throw new Error('Invalid VTT format');
}

Timestamp validation fails

javascript

// Adjust out-of-range timestamps to video end
if (seconds > videoDuration) {
  seconds = videoDuration - 5;  // 5 seconds before end
}

ffmpeg not found

bash

# Check PATH includes ffmpeg
export PATH="/usr/local/bin:/opt/homebrew/bin:$PATH"

Integration with Other Skills

oauth-automation: Authenticate YouTube API
ai-integration: Analyze transcript content
notion-operations: Save structured video data
error-handling: Retry on download failures

Full Code and Documentation

Complete implementations: /mnt/d/work/n8n_agent/n8n-skills/video-processing/

Files:

vtt-subtitle-parser.js - VTT parsing with timestamps
video-duration-checker.js - Duration validation
batch-screenshot.js - Screenshot generation
youtube-downloader.js - Download wrapper
README.md - Complete guide and examples

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video-processing

Install this agent skill to your Project

SKILL.md

Video Processing & Analysis

Overview

Key Capabilities

Prerequisites

Core Operations

1. Download YouTube Subtitles

2. Parse VTT Subtitles with Timestamps

3. Video Duration Check

4. Batch Screenshot Generation

5. Extract Video Metadata

Complete Workflow: YouTube → Analysis → Notion

n8n Implementation

Workflow Structure

Best Practices

Common Patterns

Pattern 1: Video Indexing

Pattern 2: Show Notes Generation

Pattern 3: Quote Attribution

Troubleshooting

No subtitles available

VTT parsing errors

Timestamp validation fails

ffmpeg not found

Integration with Other Skills

Full Code and Documentation