How to add a watermark or logo to an Ant Media Server live stream

· 04 Aug 2026

A watermark is a simple way to identify the owner or source of a live video. It can keep a brand visible when a stream is embedded elsewhere, provide attribution when clips are shared, and discourage basic forms of unauthorized reuse.

In this post we’ll walk through the options for watermarking live video with Ant Media Server, and then go hands-on with the Stamp plugin to burn a logo directly into a live broadcast using nothing more than a REST API call.

Server and client side watermarks

Before reaching for a plugin, it’s worth understanding the two fundamentally different ways a watermark can end up on a viewer’s screen.

A player-side watermark is drawn in the browser or app on top of the video element, after the stream has already left the server. It costs nothing in server processing, and you can even show a different overlay per viewer. The catch is that it’s cosmetic: anyone with access to the underlying stream URL can play it in a different player and the watermark simply won’t be there.

A server-side watermark, by contrast, is composited into the video frames themselves before they’re re-encoded. Once it’s baked in, it shows up in every compatible player and in any redistributed copy of the stream, which is exactly what you want for branding or anti-piracy purposes. The trade-off is that the server now has to decode, modify, and re-encode every frame, which adds processing overhead. For larger deployments — multiple concurrent streams or several renditions per stream — Ant Media Server recommends running on GPU-enabled hardware to absorb that extra cost.

Stamp capabilities

Stamp for Ant Media Server implements the server-side approach. It’s a commercial plugin that lets you decorate a live stream with image, text, ticker, clock, and even full HTML overlays, all driven through a REST API. Because control happens over HTTP, you can add or remove overlays with curl, a Postman collection, or straight from your own application — nothing about it is tied to a specific broadcast tool. Version 2.0.0 and later also support rendering complete web pages as overlays, which opens the door to using cloud overlay providers such as Singular.live or Overlays.uno directly on top of an Ant Media Server stream.

Requirements

Before installing Stamp, make sure you have the following in place:

A working Ant Media Server installation
The Stamp plugin JAR and a valid license — without a license the plugin still runs, just in a time-limited trial mode
An application configured on the server, such as the default LiveApp
Adaptive Streaming enabled with at least one rendition
A live source: OBS, vMix, FFmpeg, or anything else that can push RTMP/SRT/WebRTC into Ant Media Server
The watermark asset itself, as a PNG, JPEG, or animated GIF

If your logo needs to sit cleanly over the video with a transparent background, a transparent PNG is the format to reach for — it avoids the white or black box you’d get from a JPEG.

Installation

The full installation procedure is documented on the Stamp installation page, but the short version looks like this:

Download ams-stamp-x.y.z.jar and place it in the Ant Media Server plugins directory:

cd /usr/local/antmedia/plugins
sudo wget https://streamtoolbox.com/download/ams-stamp-2.3.0.jar

If you have a license file, copy it into Ant Media Server’s conf directory. Without one, Stamp logs a message on startup and runs in time-limited trial mode instead of refusing to start.
Restart the service so the plugin is picked up:
```
sudo systemctl restart antmedia.service
```
Check the Ant Media Server log for a Stamp startup entry for your application to confirm the plugin loaded correctly.

By default, Stamp starts with a calibration grid overlaid on every stream. It’s genuinely useful the first time around: the grid confirms that frames are actually being processed by the plugin, and the coordinate labels make it easy to work out where to place your first overlay.

Once you’ve got your bearings, turn the grid off by adding the following line to /usr/local/antmedia/conf/stamp.conf:

stamp.calibrate.grid=false

Any change to stamp.conf requires another restart of Ant Media Server to take effect.

Stream preparation

With the plugin installed, switch over to the Ant Media Server management panel to prepare the application that will receive your stream. Open the application’s settings, enable Adaptive Streaming, and configure at least one rendition — Stamp needs a transcoded rendition to draw on, and adaptive streaming is what makes that available. Pick a resolution and bitrate that match your source and your audience, and keep an eye on system load and any frame-processing warnings in the log, especially if you’re running several streams through the same server. For heavier workloads, Ant Media Server’s GPU guidance is worth following so the transcoding and overlay work don’t become a bottleneck.

Stream publication

Next, point your encoder - OBS, vMix, FFmpeg, or whatever you’re already using - at the application you just configured:

Server: rtmp://your-server.example:1935/LiveApp
Stream key: myStream

Before moving on to watermarking, confirm you can actually play back the transcoded stream.

Watermark instruction

With a live, transcoded stream running, adding a watermark is a single POST request to Stamp’s instructions endpoint:

curl --request POST \
  'http://localhost:5080/LiveApp/rest/stamp/instructions' \
  --header 'Content-Type: application/json' \
  --data-raw '
{
  "id": "watermark-1",
  "start": "now",
  "end": "2100.01.01 00:00:00.000",
  "image": "/tmp/live-logo.png",
  "position": {
    "x": 10,
    "y": 10,
    "anchor": "top-left"
  }
}'

Replace localhost with your Ant Media Server’s hostname when calling this from outside the server itself. A few fields are worth calling out:

id — a unique identifier you choose, used later to update or delete this instruction
start — when the overlay becomes active; now activates it immediately
end — when the overlay expires
image — the image source (more on the supported formats below)
position — placement coordinates and anchor point

In this example, /tmp/live-logo.png needs to exist on the Ant Media Server host itself and be readable by the process running the server. The position block places it 10 pixels in from the top-left corner. The result is a logo composited directly into the video frames:

Supported image sources

Stamp doesn’t require the image to already live on the server — the image field accepts three different kinds of sources, and which one you pick depends mostly on where your logo is coming from.

Server file

The simplest option: point image at a path that’s readable by the Ant Media Server process, for example /tmp/live-logo.png. This is the approach used above.

Base64 data URL

If the caller doesn’t have access to the server’s filesystem and the image is small, you can embed it directly in the request as a base64 data URL. Generate the unwrapped base64 payload with:

base64 -w 0 live-logo.png

and pass it as the image value:

"image": "data:image/png;base64,PASTE_BASE64_DATA_HERE"

This is convenient for automation that has no server access at all, but it does inflate the size of every request. For anything beyond a small icon, prefer a server file or an external URL instead.

External URL

You can also point image straight at a direct, unauthenticated HTTP or HTTPS URL:

"image": "https://example.com/assets/live-logo.png"

Stamp downloads and caches the image server-side, so the directory it writes to — /var/tmp by default — needs to be writable by the Ant Media Server process. That location can be changed with the stamp.image.cache setting if /var/tmp isn’t suitable in your environment. For production use, favor a stable URL for the asset; if the underlying image changes frequently, either version the URL or update the instruction with a fresh one rather than relying on cache invalidation.

Animated GIF

All three source types — local path, data URL, or external URL — also work with animated GIFs. Combined with the duration field, this is a handy way to run a time-boxed animated bumper:

{
  "id": "animated-watermark",
  "start": "now",
  "duration": 30,
  "image": "https://example.com/assets/animated-logo.gif",
  "position": {
    "x": 10,
    "y": 10,
    "anchor": "top-left"
  }
}

Watermark removal and replacement

An active or scheduled instruction can be removed at any time by its ID:

curl --request DELETE \
  'http://localhost:5080/LiveApp/rest/stamp/instructions/watermark-1'

To replace a watermark, either delete the old instruction and submit a new one, or update the existing instruction directly through the Stamp API. Either way, giving your instructions stable, descriptive IDs up front pays off later — it makes automating watermark changes much simpler than having to look up generated IDs first.

Postman operation

If you’d rather not hand-craft curl commands, Stamp ships a Postman collection with ready-made requests for adding and removing watermarks. Import it, fill in your environment-specific values — server address, application name, stream name, and the asset path or URL — and you have a repeatable way to test overlay changes without writing any code.

API security

Because the Stamp API can modify a live output in real time, it’s worth treating it with the same care as any other administrative endpoint on your server. Restrict access using Ant Media Server’s REST API IP filter or JWT authentication, serve the API over HTTPS rather than plain HTTP, and keep any administrative token out of client-side or end-user-facing scripts.