DeepSRT - SRT Provider

A Cloudflare Worker template that allows you to deploy your own DeepSRT Provider on Cloudflare. This provider serves as a static file server for SRT files stored in Cloudflare R2 storage.

Overview

This worker provides direct URL mapping to R2 bucket objects, specifically designed to serve subtitle files (.srt) from a Cloudflare R2 bucket. This implementation follows the DeepSRT Provider RFC which defines the standard interface for DeepSRT Providers.

This project is designed to be ready to use out-of-the-box, allowing you to build and deploy a fully functional DeepSRT provider on Cloudflare with minimal configuration. Simply set up your R2 bucket, deploy the worker, and you'll have a production-ready subtitle provider service.

URL Mapping

The worker maps URLs directly to R2 bucket paths:

• https://worker_name.sub_domain.workers.dev/srt/ → s3://{bucket_name}/srt/
• https://worker_name.sub_domain.workers.dev/srt/Ty3wqBxb0UE/default/Ty3wqBxb0UE.srt → s3://{bucket_name}/srt/Ty3wqBxb0UE/default/Ty3wqBxb0UE.srt

URL Format Structure

The URL format follows this structure:

• {worker_domain}/srt/{video_id}/{language}/{video_id}.srt

Where:

• {worker_domain} is your Cloudflare Worker domain
• {video_id} is the YouTube video ID
• {language} is the language code (e.g., 'en', 'zh-TW')

Cache Strategy

The worker implements a cache strategy to improve performance:

• Cache hits are served directly from Cloudflare's edge cache
• Cache misses are fetched from R2 and then cached
• Cache-Control headers are set to optimize caching behavior
• Etag headers are used for validation

Error Handling

The worker provides appropriate error responses:

• 404 Not Found for missing files
• 500 Internal Server Error for R2 access issues

Architecture

flowchart LR
    A[Client] -->|Request| B[Cloudflare Worker]
    B -->|Fetch| C[R2 Bucket]
    C -->|Response| B
    B -->|Response| A

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Quick Start

You can quickly bootstrap a new DeepSRT Provider project using the following command:

npm create cloudflare@latest <YOUR_PROJECT_NAME> -- --template=DeepSRT/deepsrt-provider

This will create a new project based on this template with all the necessary files and configurations.

Setup

1. Install dependencies:

   npm install

2. Configure your R2 bucket in wrangler.jsonc:

   {
     "r2_buckets": [
       {
         "binding": "DEEPSRT_BUCKET",
         "bucket_name": "${your_bucket_name}"
       }
     ]
   }

Development

# Start local development server
npm run dev

# Deploy to Cloudflare Workers
npm run deploy

DeepSRT Ecosystem

The following diagram illustrates how the DeepSRT Provider fits into the broader DeepSRT ecosystem:

flowchart TB
    %% User flow
    Browser[Browser] --> Extension[DeepSRT Extension]
    Extension --> YouTube[YouTube]
    YouTube -->|No subtitles available| ProviderSystem[SRT Provider System]
    ProviderSystem --> CustomProvider[Custom SRT Provider]
    CustomProvider --> CloudflareWorker[This Cloudflare Worker]
    CloudflareWorker --> R2Storage[Cloudflare R2 Storage]
    
    %% Whisper flow
    WhisperService[Whisper Service] -->| Download video| YouTube
    WhisperService -->|Transcribe to SRT| SRT[SRT File]
    SRT -->|Upload SRT| R2Storage
    
    %% Styling
    classDef browser fill:#F8F8F8,stroke:#999,stroke-width:1px,color:#333
    classDef extension fill:#4285F4,stroke:#2A56C6,stroke-width:1px,color:white
    classDef youtube fill:#FF0000,stroke:#CC0000,stroke-width:1px,color:white
    classDef provider fill:#34A853,stroke:#268039,stroke-width:1px,color:white
    classDef worker fill:#F4B400,stroke:#F09800,stroke-width:1px,color:white
    classDef storage fill:#7B68EE,stroke:#5D4AB7,stroke-width:1px,color:white
    classDef whisper fill:#16A085,stroke:#0E6655,stroke-width:1px,color:white
    
    class Browser browser
    class Extension extension
    class YouTube youtube
    class ProviderSystem,CustomProvider provider
    class CloudflareWorker worker
    class R2Storage storage
    class WhisperService,SRT whisper

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User Flow

When a user watches a YouTube video:

1. The DeepSRT browser extension first tries to load subtitles from YouTube's native API
2. If no subtitles are available, the extension falls back to configured SRT providers
3. Your custom DeepSRT Provider (this Cloudflare Worker) serves SRT files from your R2 storage
4. The extension displays the subtitles to the user in the browser

Whisper Transcription Flow

To populate your R2 storage with SRT files:

1. The Whisper service downloads videos from YouTube
2. Whisper transcribes the audio into SRT format
3. The generated SRT files are uploaded to your R2 storage
4. These SRT files are now available to be served by your DeepSRT Provider

This template allows you to quickly deploy your own DeepSRT Provider that can be configured in the extension, enabling subtitle support for videos that don't have official captions.

Features

• Direct path mapping from URLs to R2 objects
• Proper content type headers for SRT files
• Error handling for missing files
• Simple and efficient request processing

Requirements

• Cloudflare Workers account
• Cloudflare R2 bucket configured
• Node.js and npm installed locally

Configure AWS CLI for R2

In ~/.aws/config

[profile cloudflare]
region = auto
endpoint_url = https://<your-cloudflare-account-id>.r2.cloudflarestorage.com

To find your Cloudflare account ID:

1. Go to https://dash.cloudflare.com
2. Check the URL in the browser, it should look like:

https://dash.cloudflare.com/<your-cloudflare-account-id>/home/domains

Configure credentials for AWS CLI:

$ aws --profile cloudflare configure

Go to CloudFlare dashboard -> R2 -> Manage API tokens to generate a credentials.

In your shell, createn an alias like this

alias r2='aws --profile cloudflare s3'

Now you can use the r2 alias to manage your R2 bucket. e.g.

# list buckets
$ r2 ls
# create a bucket
$ r2 mb s3://<your-bucket-name>
# sync files
$ r2 sync <local-directory> s3://<your-bucket-name>

To sync local SRT files to R2 bucket, run:

$ r2 sync <local-directory>/srt/ s3://<your-bucket-name>/srt/

To cp a single .srt file to remote

$ r2 cp video_id.srt  s3://<your-bucket-name>/srt/video_id/default/video_id.srt