EchoWizard Backend 🧙‍♂️

The backend service for EchoWizard, an AI-powered tool that transcribes and comprehends audio files (including YouTube videos), then generates intelligent summaries and answers questions with precise timestamps.

🔧 Tech Stack

Node.js + Express – RESTful API server
Google Gemini GenAI – Audio comprehension (summaries and question answering)
AssemblyAI – Transcription and timestamp extraction
yt-dlp – YouTube audio extraction
Multer – File upload handling

✨ Features

Upload audio files or provide a YouTube video URL
Transcribe audio with sentence-level timestamps
Generate detailed summaries with cited timestamps
Ask follow-up questions and receive timestamped answers
Automatically deletes temporary files after processing

🔌 API Endpoints

`POST /summarize-upload`

Description: Upload an audio file or provide a YouTube URL to receive a timestamped transcript and structured summary.

Request (multipart/form-data):

audio – (optional) an audio file to upload
youtubeUrl – (optional) YouTube video URL to process

Response:

{
  "summary": "Structured summary with timestamps",
  "fileUri": "Google Gemini uploaded file URI",
  "mimeType": "audio/mpeg",
  "transcript": "Formatted transcript with timestamps"
}

`POST /answer`

Description: Ask a question about an already-processed audio file.

Request (multipart/form-data):

fileUri – The URI returned from /summarize-upload
mimeType – audio/mpeg
transcript - Timestamped transcript from /summarize-upload
question - Your question

Response:

"A helpful answer based on the transcript and audio, with timestamps included where relevant."

🧪 Running Locally

1. Clone and install

git clone https://github.com/your-username/echowizard-backend.git
cd echowizard-backend
npm install

2. Add your .env

Create a .env file in the root:

ASSEMBLYAI_API_KEY=your_assemblyai_key
GEMINI_API_KEY=your_google_genai_api_key
PROJECT_ID=your_google_project_id

3. Start the server

npm start

Server will run at http://localhost:3000

📁 Project Structure

.
├── index.js                 # Main Express app
├── helpers/
│   ├── assembly.js          # Transcription logic
│   └── downloadYoutube.js   # YouTube MP3 downloader
├── uploads/                 # Temp audio files
├── .env                     # API keys (not committed)
└── README.md