Add ffmpeg example

README.md

@@ -6,7 +6,7 @@ This directory contains different examples of how to use the Workflow DevKit.
 - [Birthday Card Generator](https://github.com/vercel/workflow-examples/tree/main/birthday-card-generator) - Example of how to use the Workflow DevKit to build a birthday card generator.
 - [Custom Adapter](https://github.com/vercel/workflow-examples/tree/main/custom-adapter) - Example of building a custom adapter to run workflows on other frameworks and runtimes, like Bun.
 - [Flight Booking App](https://github.com/vercel/workflow-examples/tree/main/flight-booking-app) - Example of how to use the Workflow DevKit to build a flight booking app.
-
+- [FFmpeg Processing](https://github.com/vercel/workflow-examples/tree/main/ffmpeg-processing) - Express + Workflow DevKit example for building FFmpeg-based media processing workflows.
 - [Kitchen Sink](https://github.com/vercel/workflow-examples/tree/main/kitchen-sink) - Comprehensive reference implementation of all core workflow patterns including steps, control flow, streaming, AI integration, hooks, and batching.
 - [RAG Agent Example](https://github.com/vercel/workflow-examples/tree/main/rag-agent) - Example of how to use the AI SDK with the Workflow DevKit.
 

ffmpeg-processing/.gitignore

@@ -0,0 +1,52 @@
+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.*
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/versions
+
+# testing
+/coverage
+
+# next.js
+/.next/
+/out/
+
+# production
+/build
+
+# misc
+.DS_Store
+*.pem
+
+# debug
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+.pnpm-debug.log*
+
+# local env files
+.env*.local
+.env
+
+# vercel
+.vercel
+
+# typescript
+*.tsbuildinfo
+next-env.d.ts
+
+# workflow
+.well-known
+.swc
+dist
+.workflow-data
+
+# nitro
+.output
+.nitro

ffmpeg-processing/README.md

@@ -0,0 +1,112 @@
+# FFmpeg Processing Example
+
+[![Deploy with Vercel](https://vercel.com/button)](https://vercel.com/new/clone?repository-url=https%3A%2F%2Fgithub.com%2Fvercel%2Fworkflow-examples%2Ftree%2Fmain%2Fffmpeg-processing)
+
+This example demonstrates how to use [Workflow DevKit](https://useworkflow.dev) with Express and Vercel Sandbox to build an **audio compression service**. Audio files are uploaded via multipart/form-data, processed by FFmpeg within a durable workflow running in an isolated sandbox, and streamed directly back in the HTTP response.
+
+## Features
+
+- **Sandbox isolation**: FFmpeg runs in a Vercel Sandbox for secure, isolated processing
+- **Workflow orchestration**: Audio compression is broken into multiple steps (`createSandbox` -> `setupFfmpeg` -> `transcode` -> `streamOutput` -> `stopSandbox`)
+- **Streaming support**: Results are streamed back to the client as they're produced
+- **FFmpeg compression**: Converts audio to AAC codec in M4A container at 128kbps
+
+## Getting Started
+
+### Prerequisites
+
+- **`VERCEL_OIDC_TOKEN`**: The workflow runtime expects the `VERCEL_OIDC_TOKEN` environment variable to be present for `@vercel/sandbox`. When running inside a Vercel Sandbox this is injected automatically; if you run the server outside of Vercel, you must provide a valid OIDC token yourself.
+
+### Local Development
+
+1. Clone this example and install dependencies:
+
+   ```bash
+   git clone https://github.com/vercel/workflow-examples
+   cd workflow-examples/ffmpeg-processing
+   pnpm install
+   ```
+
+2. Link your Vercel project:
+
+   ```bash
+   npx vercel link
+   ```
+3. Fetch the `VERCEL_OIDC_TOKEN`:
+
+   ```bash
+   npx vercel env pull
+   ```
+
+4. Start the development server:
+
+   ```bash
+   pnpm dev
+   ```
+
+5. **Test the audio compression workflow**:
+
+   ```bash
+   # Convert a WAV file to compressed M4A
+   curl -X POST -F "file=@input.wav;type=audio/wav" -H "Expect:" http://localhost:3000/convert --output output.m4a
+   ```
+
+   The endpoint accepts any audio file and returns a compressed M4A file. Be sure to update the audio file extension if not a .wav file.
+
+## API Endpoints
+
+### `POST /convert`
+
+Compresses an uploaded audio file using FFmpeg within a workflow.
+
+**Request:**
+- Content-Type: `multipart/form-data`
+- Field name: `file`
+- Accepted formats: WAV, MP3, OGG, FLAC, AAC, M4A
+
+**Response:**
+- Content-Type: `audio/mp4`
+- Body: Compressed audio file (M4A/AAC at 128kbps)
+
+**Example:**
+```bash
+curl -X POST -F "file=@podcast.wav;type=audio/wav" -H "Expect:" http://localhost:3000/convert --output podcast.m4a
+```
+
+## How It Works
+
+1. **Express route** receives the upload via `multer.memoryStorage()`
+2. **Workflow orchestrates** five steps:
+   - `createSandbox`: Provisions a Vercel Sandbox instance
+   - `setupFfmpeg`: Downloads and installs FFmpeg in the sandbox
+   - `transcode`: Writes input to sandbox, runs FFmpeg to compress audio
+   - `streamOutput`: Streams the compressed file back to the workflow
+   - `stopSandbox`: Cleans up the sandbox instance
+3. **Response** streams the compressed bytes directly to the client
+
+## Project Structure
+
+```
+ffmpeg-processing/
+├── src/
+│   ├── index.ts                          # Express app with /convert route
+│   └── workflows/
+│       └── audio-convert/
+│           ├── index.ts                  # Main workflow orchestration
+│           └── steps/                    # Individual workflow steps
+│               ├── create-sandbox.ts
+│               ├── setup-ffmpeg.ts
+│               ├── transcode.ts
+│               ├── stream-output.ts
+│               └── stop-sandbox.ts
+├── nitro.config.ts                       # Nitro configuration with workflow module
+├── package.json
+├── tsconfig.json
+└── README.md
+```
+
+## Learn More
+
+- [Workflow DevKit Documentation](https://useworkflow.dev)
+- [Express Getting Started Guide](https://useworkflow.dev/docs/getting-started/express)
+- [FFmpeg Documentation](https://ffmpeg.org/documentation.html)

ffmpeg-processing/nitro.config.ts

@@ -0,0 +1,8 @@
+import { defineNitroConfig } from "nitro/config";
+
+export default defineNitroConfig({
+	modules: ["workflow/nitro"],
+	routes: {
+		"/**": { handler: "./src/index.ts", format: "node" },
+	},
+});

ffmpeg-processing/package.json

@@ -0,0 +1,27 @@
+{
+	"name": "ffmpeg-processing",
+	"type": "module",
+	"private": true,
+	"scripts": {
+		"dev": "nitro dev",
+		"build": "nitro build"
+	},
+	"dependencies": {
+		"@vercel/sandbox": "^1.0.4",
+		"cors": "^2.8.5",
+		"express": "^5.2.1",
+		"ms": "^2.1.3",
+		"multer": "^2.0.2",
+		"nitro": "3.0.1-alpha.1",
+		"rollup": "^4.53.3",
+		"workflow": "4.0.1-beta.28"
+	},
+	"devDependencies": {
+		"@types/cors": "^2.8.19",
+		"@types/express": "^5.0.6",
+		"@types/ms": "^2.1.0",
+		"@types/multer": "^2.0.0",
+		"@types/node": "^20.19.25",
+		"typescript": "^5.9.3"
+	}
+}