StreamLive ProStream with SRT from OBS, vMix or a hardware encoder
Stream to StreamLive Pro with SRT from OBS, vMix or a hardware encoder: the SRT address, passphrase, stream ID and latency, field by field, and when SRT helps.
SRT is the protocol to choose when the line between you and us is the weak point: a mobile connection at an outdoor event, a venue's shared Wi-Fi, a long international path. StreamLive Pro gives every broadcast an SRT address on the Encoder card. You send SRT to us; we send the broadcast on to each network in the protocol that network takes. This page shows where each part of the SRT address goes in OBS, vMix and hardware encoders. What SRT is, and how it compares with RTMP and RTMPS, is in RTMP vs RTMPS vs SRT: which one to use and when.
Before you start
- A paid plan. Encoder ingest, SRT included, is on the paid plans. In the 7-day trial the Encoder card shows "On paid plans".
- An encoder that can send SRT in Caller mode. StreamLive Pro receives encoder streams through Cloudflare Stream, which supports SRT Caller mode only (Cloudflare Stream: Start a live stream, checked 5 November 2026). Caller means your encoder dials out to our address. Listener or Rendezvous will not connect.
- H.264 video and AAC audio. The same page lists these as the only accepted codecs, for SRT as for RTMP.
What the Encoder card gives you
Open the SRT tab on the card. You see:
- SRT URL, starting with srt://. It holds the host name and the port, and it may also hold a streamid= part that identifies your broadcast. There is no separate key field on this tab.
- Passphrase, a separate masked row with its own copy button, when the broadcast has one. The passphrase encrypts the connection, and a push without it is refused.
Steps
- Open the encoder panel. Click New stream at the top of the dashboard, choose Stream from software like OBS (RTMP / SRT), and open the SRT tab on the Encoder card.
- Copy the SRT URL and the passphrase. Use the copy buttons. Paste them into a text editor for a moment so you can see the parts.
- Build the address for OBS. In OBS, Settings, Stream: Service Custom, the SRT address in Server, and Stream Key left empty (OBS's SRT guide says the key is not used). If the card showed a Passphrase, add it to the end of the address: &passphrase= followed by the value, or ?passphrase= if the address has no question mark yet (OBS: SRT streaming guide).
- Or fill the vMix fields. In vMix, Settings, Outputs, click the cog next to an output and tick Enable SRT. Type: Caller. Hostname: the part between srt:// and the colon. Port: the number after the colon. Stream ID: the value after streamid=, if the address has one. Passphrase: the value from the card (vMix: SRT).
- Or fill a hardware encoder. Most SRT encoders ask for the same parts: mode Caller, host, port, stream ID and passphrase. Some take the whole srt:// address in one field. Check your encoder's manual for which one it wants.
- Set latency. See the next section. If unsure, start with the encoder's default and raise it if the picture breaks up.
- Tick channels and start. Switch on your destinations in the Channels list, keep the page open, then start the encoder. StreamLive Pro shows that the stream was detected and sends it to the ticked channels.
Latency: the one SRT setting to understand
SRT resends lost packets within a time window you set, called latency. A larger window survives a worse line, at the cost of extra delay before the picture reaches us.
| Encoder | Unit | Published guidance |
|---|---|---|
| OBS | microseconds, in the address as latency= | At least 2.5 times the round-trip time to the server. Default 120 ms; latency=1000000 is one second (OBS SRT guide) |
| vMix | milliseconds, in the Latency field | At least 4 times the ping to the destination, for example 80 for a 20 ms ping (vMix: SRT) |
When SRT helps, and when it does not
- Helps: packet loss on mobile, Wi-Fi or long routes. RTMP runs over TCP and stalls while it resends; SRT recovers inside its window.
- Does not help: an upload that is simply too small for the bitrate. SRT cannot send more than the line carries. Lower the bitrate instead (Upload speed and bitrate for multistreaming).
- On a good wired line, RTMPS is simpler and works as well. Use the setup in Connect OBS to StreamLive Pro and multistream.
What can go wrong
| Symptom | Likely cause | Fix |
|---|---|---|
| OBS fails to connect over SRT | Passphrase missing or mistyped in the address | Copy it again and add it as passphrase= at the end of the address |
| vMix fails to connect | Type is Listener or Rendezvous | Set Type to Caller |
| Connects, no picture | HEVC chosen in the encoder | Choose H264 |
| Picture breaks up every few seconds | Latency too low for the line | Raise latency, for example to one second |
| Works on RTMP, not on SRT | The network blocks outgoing UDP | Use the RTMPS tab, which runs on port 443 |
If none of these fit, see My encoder says it is streaming, but there is no picture.
Frequently asked questions
Does StreamLive Pro accept SRT?
Yes, on the paid plans. Every broadcast has an SRT address on the Encoder card, plus a passphrase when the broadcast has one. Your encoder must use Caller mode.
Where do the passphrase and stream ID go in OBS?
Both go into the address in the Server field, as passphrase= and streamid= parameters. The Stream Key field stays empty for SRT.
What latency should I set for SRT?
OBS's guide says at least 2.5 times the round-trip time to the server; vMix's says at least 4 times the ping. Start there and raise it if the picture breaks up.
Do YouTube and Facebook receive SRT?
They receive the broadcast from our servers in the protocol each one accepts. SRT is only the leg from your encoder to StreamLive Pro.
Is SRT better than RTMP?
Only on a lossy line. On a stable wired connection RTMPS is simpler and works as well.
Keep reading
A printable live stream checklist: test broadcasts, stream keys, sound check, backup internet, what to do if the stream drops, and the work after it ends.
Upload speed and bitrate for multistreamingYouTube's bitrate table for 720p to 4K, the upload you need to multistream from OBS vs a relay, CBR and 2-second keyframes, and how to test your connection.
RTMP vs RTMPS vs SRT: which one to use and whenRTMP vs RTMPS vs SRT compared: transport, ports, encryption, how each handles a bad line, which networks accept which, and how to choose for your encoder.
OBS vs Streamlabs vs vMix: which desktop software (2026)OBS Studio, Streamlabs Desktop and vMix compared on systems, price model, multistreaming and who each fits, from their own pages, checked 5 November 2026.
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