How to Send and Receive SRT Streams in vMix
This tutorial shows one practical workflow: send an SRT stream from vMix to Callaba, then receive the same SRT feed back in vMix to confirm that the stream is arriving correctly. It is useful when you want a low-latency contribution path and you also need a clean way to validate or monitor the feed.
You will set up the outgoing SRT stream first, then use the Receiver URL from Callaba to bring the stream back into vMix. By the end, you will have one reliable path for publishing and another for checking that the live signal is really there.
What you need before you start
- An active Callaba environment where you can create an SRT server.
- vMix installed on the machine that will send and receive the stream.
- A video source ready in vMix, such as a camera, file, playlist, or another live input.
- Enough control over the network path to allow the required SRT port and traffic.
If you are new to the platform, start with How to launch Callaba Cloud Live Streaming. If you want to compare transport choices first, see SRT vs RTMP.
Before you open the vMix SRT settings, use the live widget as a quick operational reference. It keeps attention on the two signals that usually explain SRT behavior first in production: incoming bitrate and network RTT. If RTT drifts upward while the stream is still pushing the same bitrate, the path may be losing enough timing headroom to make your current SRT settings less forgiving.
Send an SRT stream from vMix to Callaba
1. Add the video source in vMix
Start vMix and click Add Input. Add the source you want to broadcast. In this example it is a music video, but the same flow works with cameras, playlists, NDI, RTMP, or other supported inputs.
The left vMix window is the preview and the right window is the live output. After adding your source, send it to output with Cut or Fade.
2. Open the SRT output settings in vMix
Open Settings in the upper-right corner, then go to Outputs / NDI / SRT. This is where you choose which output you want to send and how vMix should package it.
Click the gear icon next to the output you want to use for SRT.
3. Keep the vMix SRT settings window open
In the SRT settings window, choose the audio bus and resolution you want to use. You do not need to finish this step yet. Keep the window open because you will return to it after creating the SRT server in Callaba.
4. Create the SRT server in Callaba
Open Callaba, go to SRT servers, and click Add New. Give the server a clear name, then set the two ports:
- Port: the publisher port used by vMix to send the stream
- Receiver port: the port used later when you want to receive the stream back
Save the server when the values are ready.
5. Open the connection details
Click Info on the SRT server. This screen shows the exact parameters you need for sending and receiving.
6. Copy the send-side values into vMix
For the outgoing stream, copy the values from the publish side into vMix:
- SRT Hostname: the server IP or hostname without
srt:// - Port: the publisher port
- Stream ID (optional): the value shown in the Connection via Stream ID tab
Paste these values into the vMix SRT settings window you kept open earlier.
7. Start sending the SRT stream
Once the host, port, and optional Stream ID are correct, enable the SRT output in vMix. The stream now starts going to the Callaba server. You can monitor or restart it later from the gear icon next to External at the bottom of the vMix interface.
Receive the same SRT stream back in vMix
This step is useful when you want to confirm that the signal is really reaching the server, or when you need a local monitoring copy of the same contribution feed.
8. Add a new SRT input in vMix
In vMix, click Add Input, open Stream / SRT, and set Stream Type to SRT (Caller).
Now use the values from the Receiver URL in Callaba. A typical Receiver URL looks like this:
srt://12.34.56.78:1935?streamid=output/mynewsrt/srt-stream-01
vMix needs these values extracted from that URL:
- Hostname: the server IP or hostname
- Port: the receiver port
- Stream ID: the value from the query string, for example
output/mynewsrt/srt-stream-01
9. Prevent an audio or video loop
If you are sending and receiving the same stream on the same machine, make sure the incoming SRT input does not go back to the same master/output path. Otherwise you can create an echo loop in audio or a recursive video loop.
10. Confirm that the feed is live
If everything is correct, the incoming SRT feed appears in vMix and you will see the active audio indicator for that input.
11. Reset the input if the signal stalls
If the signal stops, latency grows unexpectedly, or the stream appears to freeze, reset the incoming SRT input in vMix. You can also reset the outgoing SRT output from the External controls.
What to check if the stream does not appear
- Make sure the hostname, port, and Stream ID are copied exactly as shown in Callaba.
- Verify that you are using the correct side of the setup: publish values for sending, receiver values for receiving.
- Confirm that the chosen SRT port is reachable and not blocked by firewall or network policy.
- Check that the outgoing vMix output is actually enabled before troubleshooting the receive side.
- If you run sender and receiver on the same machine, double-check audio routing to avoid loops that make the result look broken.
Common problems and fixes
No video appears in the receiving input
Most often this means the receive-side hostname, port, or Stream ID does not exactly match the Receiver URL in Callaba. Re-copy the values and try again.
The stream was live, then stalled or accumulated delay
Reset the receiving input first. If the problem persists, reset the outgoing SRT output and check the network path. If the route is unstable, review your SRT latency strategy with this SRT latency guide.
The audio repeats with an echo effect
This usually means the received SRT signal is being mixed back into the same master path as the original output. Remove it from the return path and test again.
You need broader compatibility than SRT gives you
If the receiving destination or workflow does not support SRT cleanly, compare it with RTMP vs SRT and decide whether RTMP is the better publishing path for that stage.
When this workflow is useful
This pattern is especially useful when vMix is your live production tool but you want Callaba to act as the stable SRT boundary. It gives you one managed place to receive the contribution feed, inspect it, and then hand it off to other workflows or monitoring tasks without rebuilding the stream path every time.