save_transcript_js

Capture Zoom Meeting Transcripts with RTMS

This sample receives live Zoom meeting transcripts through RTMS and persists each stream as WebVTT, SubRip, plain text, and a canonical JSON Lines event log. It supports concurrent meetings, duplicate-event suppression, restart recovery, and configurable retention.

Prerequisites

• Node.js 22 or newer
• A Zoom app with RTMS enabled
• Event subscriptions for meeting.rtms_started and meeting.rtms_stopped
• A public HTTPS webhook endpoint during local development

See Zoom App Setup and the RTMSManager documentation for the shared Marketplace and RTMS configuration.

Import manifest.json to create the user-managed Zoom General App. Replace the development and production domain placeholders first. The manifest requests only meeting:read:meeting_transcript and subscribes to the RTMS started and stopped events.

Setup

npm install
cp .env.example .env
node index.js

Configure the Marketplace webhook endpoint as your public base URL plus WEBHOOK_PATH, for example https://example.ngrok.app/webhook.

Configuration

Variable	Default	Purpose
ZOOM_SECRET_TOKEN	required	Validates webhook challenges and signed deliveries
ZOOM_CLIENT_ID	required	Zoom app client ID used by RTMS
ZOOM_CLIENT_SECRET	required	Zoom app client secret used by RTMS
PORT	3000	HTTP server port
WEBHOOK_PATH	/webhook	Zoom webhook route
WEBHOOK_TIMESTAMP_TOLERANCE_SECONDS	300	Maximum age of a signed webhook
MEDIA_SOCKET_CONNECTION_MODE	split	RTMS media socket mode
TRANSCRIPT_OUTPUT_DIR	recordings	Output directory, resolved from this sample folder
TRANSCRIPT_RETENTION_DAYS	30	Delete inactive stream folders older than this; 0 disables deletion
TRANSCRIPT_CLEANUP_INTERVAL_HOURS	6	Cleanup frequency; 0 disables scheduled cleanup
TRANSCRIPT_DEDUP_WINDOW_EVENTS	10000	Recent event fingerprints retained per active or recovered stream

Transcript files can contain meeting content and participant names. Set retention according to your privacy and compliance requirements and restrict access to TRANSCRIPT_OUTPUT_DIR.

Storage Layout

Each rtms_stream_id has independent timing, counters, writes, and deduplication state:

recordings/
  <meeting-id-and-hash>/
    <stream-id-and-hash>/
      events.jsonl
      metadata.json
      transcript.vtt
      transcript.srt
      transcript.txt

The hashes prevent different IDs that sanitize to the same filesystem name from colliding. Participant names and transcript text are normalized and escaped before they are placed in VTT or SRT cues.

events.jsonl is the canonical append-only record. On first use after a process restart, the sample reads this log, removes an incomplete trailing record if necessary, restores the SRT counter and timing origin, restores the configured deduplication window, and rebuilds VTT/SRT/TXT. This also repairs projections left partially written by a crash.

All filesystem work uses asynchronous APIs. Events for one stream are serialized to preserve order, while separate streams can write concurrently. Duplicate fingerprints are ignored before another subtitle cue is appended.

Webhook Security

Normal webhook deliveries are verified against the exact raw request body using x-zm-signature, x-zm-request-timestamp, and ZOOM_SECRET_TOKEN. Missing, invalid, or stale signatures are rejected. Verified normal deliveries receive HTTP 200 before RTMS processing begins. URL-validation challenges are signed with the same secret token.

Testing

npm test

The tests cover concurrent stream isolation, VTT/SRT escaping, replay deduplication, restart recovery, and retention cleanup.

Docker

Build from the repository root because the multi-stage Dockerfile copies the shared JavaScript library:

docker build -f transcript/save_transcript_js/Dockerfile -t rtms-save-transcript .
docker run --rm \
  --env-file transcript/save_transcript_js/.env \
  -p 3000:3000 \
  -v rtms-transcripts:/app/recordings \
  rtms-save-transcript

The volume is required if transcript files must survive container replacement. Runtime secrets are supplied through --env-file and are not copied into the image.

Key Files

• index.js: HTTP server, signed webhook handling, and RTMS event wiring
• writeTranscriptToVtt.js: isolated asynchronous transcript storage and recovery
• writeTranscriptToVtt.test.js: persistence and safety tests
• .env.example: complete configuration template