Summarize YouTube videos

This tutorial demonstrates how to build a conversational application that allows users to summarize YouTube videos and chat about their contents using natural language.

1. Set up your project
2. Import the required dependencies
3. Configure Genkit and the default model
4. Get the video URL from the command line
5. Set up the prompt
6. Generate the response
7. Run the app

Prerequisites

Before starting work, you should have these prerequisites set up:

• Node.js v20+
• npm

Implementation Steps

After setting up your dependencies, you can build the project.

1. Set up your project

1. Create a directory structure and a file to hold your source code.

   $ mkdir -p summarize-a-video/src && \
   cd summarize-a-video && \
   touch src/index.ts
   

2. Initialize a new TypeScript project.

   $ npm init -y
   

3. Install the following Genkit dependencies to use Genkit in your project:

   $ npm i genkit @genkit-ai/googleai
   

   • genkit provides Genkit core capabilities.
   • @genkit-ai/googleai provides access to the Google AI Gemini models.

4. Get and configure your model API key

   To use the Gemini API, which this tutorial uses, you must first configure an API key. If you don't already have one, create a key in Google AI Studio.

   The Gemini API provides a generous free-of-charge tier and does not require a credit card to get started.

   After creating your API key, set the GEMINI_API_KEY environment variable to your key with the following command:

   $ export GEMINI_API_KEY=<your API key>
   

2. Import the required dependencies

In the index.ts file that you created, add the following lines to import the dependencies required for this project:

import { gemini, googleAI } from '@genkit-ai/googleai';
import { genkit } from 'genkit';

• The first line imports the googleAI plugin and the gemini model loader function from the @genkit-ai/googleai package, enabling access to Google's Gemini models.

3. Configure Genkit and the default model

Add the following lines to configure Genkit and set Gemini 2.0 Flash as the default model.

const ai = genkit({
  plugins: [googleAI()],
  model: gemini('gemini-2.0-flash'),
});

You can then add a skeleton for the code and error-handling.

(async () => {
  try {
    // Step 1: get command line arguments

    // Step 2: construct prompt

    // Step 3: process video

  } catch (error) {
    console.error("Error processing video:", error);
  }
})(); // <-- don't forget the trailing parentheses to call the function!

4. Parse the command line and get the video URL

Add code to read the URL of the video that was passed in from the command line.

  // Step 1: get command line arguments
  const videoURL = process.argv[2];
  if (!videoURL) {
    console.error("Please provide a video URL as a command line argument.");
    process.exit(1);
  }

5. Set up the prompt

Add code to set up the prompt:

  // Step 2: construct prompt
  const prompt = process.argv[3] || "Please summarize the following video:";

• This const declaration defines a default prompt if the user doesn't pass in one of their own from the command line.

6. Generate the response

Add the following code to pass a multimodal prompt to the model:

  // Step 3: process video
  const { text } = await ai.generate({
    prompt: [
      { text: prompt },
      { media: { url: videoURL, contentType: "video/mp4" } }
    ],
  });
  console.log(text);

This code snippet calls the ai.generate method to send a multimodal prompt to the model. The prompt consists of two parts:

• { text: prompt }: This is the text prompt that you defined earlier.
• { media: { url: videoURL, contentType: "video/mp4" } }: This is the URL of the video that you provided as a command-line argument. The contentType is set to video/mp4 to indicate that the URL points to an MP4 video file.

The ai.generate method returns an object containing the generated text, which is then logged to the console.

7. Run the app

To run the app, open the terminal in the root folder of your project, then run the following command:

npx tsx src/index.ts https://www.youtube.com/watch\?v\=YUgXJkNqH9Q

After a moment, a summary of the video you provided appears.

You can pass in other prompts as well. For example:

npx tsx src/index.ts https://www.youtube.com/watch\?v\=YUgXJkNqH9Q "Transcribe this video"