Encoder Settings for vMix

Before you start

In Recast for Business, open Stream Inputs and choose + Stream Input. Pick RTMP or SRT — the choice is fixed once the input is created.

Recast then shows the values your encoder needs. Copy them from there rather than retyping them:

• RTMP STREAM URL — SRT STREAM URL
• STREAM KEY — STREAM ID
• SRT input shows: PASSPHRASE

Note that an SRT input labels its credential STREAM ID, not Stream Key. It is the same value, under the name SRT uses for it.

Then confirm all three of these, or your stream will be refused:

1. The stream input exists and you have its credentials
2. The stream input is attached to a video
3. That video is not a draft

A new stream input is switched off. Recast switches it on only when it is attached to a live, non-draft video.

Settings for Recast

• Great — Resolution: 1080p · FPS: 30 · Video bitrate: 5000 kbps
• Good — Resolution: 720p · FPS: 30 · Video bitrate: 3500 kbps
• Works — Resolution: 480p · FPS: 30 · Video bitrate: 1000 kbps

• Video codec — H.264
• Profile — Main
• Rate control — CBR
• Keyframe interval — 2 seconds
• Audio codec — AAC
• Audio bitrate — 128 kbps
• Audio sample rate — 48 kHz
• Audio channels — Stereo

Use no more than 50% of your measured upload bandwidth.

Where these go in vMix

Streaming quality is set in Settings → Outputs / NDI → Streaming, then the cog beside your destination, under Quality.

Choose a preset that matches your tier, then check the custom settings behind it. vMix presets do not always use a 2-second keyframe interval, so set it explicitly:

• Video Bitrate — From the table above
• Profile — Main
• Keyframes / GOP — 2 seconds, or 60 frames at 30 fps
• Rate Control — CBR
• Audio Bitrate — 128
• Audio Sample Rate — 48000

RTMP setup

Which URL? Recast displays rtmp://global-live.mux.com:5222/app as your RTMP STREAM URL, and that works. This guide uses rtmps:// on port 443 instead: it is the same Mux ingest wrapped in TLS, so your stream key is not sent in clear text, and port 443 passes through restrictive venue networks that block port 5222. Use whichever your encoder supports.

This is the recommended path for vMix.

1. Open Settings and go to the Outputs / NDI tab.
2. Beside Streaming, click the cog icon.
3. Pick an unused destination slot (vMix supports several at once).
4. Set Destination to Custom RTMP Server.
5. Fill in:
   • URL — rtmps://global-live.mux.com:443/app
   • Stream Name or Key — Your Recast Stream Key

1. Leave username and password blank.
2. Click OK, then Start beside Streaming on the main interface.

European users can use rtmps://eu-west.live.mux.com/app instead. If your vMix version will not accept an rtmps:// URL, use rtmp://global-live.mux.com:5222/app.

SRT setup

vMix uses separate fields rather than a single connection URL.

1. Open Settings → Outputs / NDI.
2. Beside the output channel you want to send, click the cog icon.
3. Set the output type to SRT.
4. Fill in:
   • Type — Caller
   • Hostname — global-live.mux.com
   • Port — 6001
   • Stream ID — Your Recast STREAM ID
   • Passphrase — Your Recast PASSPHRASE
   • Latency — 500
   • Key Length — set this to 16. vMix expresses key length as a number you multiply by 8 to get bits, so 16 is AES-128, which is what Recast requires. The default of 32 is 256-bit and will be refused at the handshake.

1. Click OK and start the output.

Note that Type must be Caller. Mux listens for incoming connections; vMix places the call.

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Confirm you're live

1. Press Start beside Streaming. The button turns red and the main interface shows a streaming indicator.
2. Hover the streaming indicator to see the current bitrate and dropped-frame count. You want a steady bitrate near your configured value and no climbing drop count.
3. Open the video in Recast. Allow 20 to 30 seconds — standard latency means that delay is expected.

Known quirks

vMix can stream to several destinations at once. Useful, but each one consumes upload bandwidth and CPU. If you are also sending to a social platform, your 50% headroom rule applies to the total, not to the Recast stream alone.

Presets override your keyframe interval. Changing the quality preset can silently reset the GOP length. Set the keyframe interval last, and re-check it after any preset change.

Hardware encoding. vMix can use NVIDIA NVENC where available, which frees considerable CPU on a busy production. Confirm the profile is still Main and the keyframe interval is still 2 seconds after switching — hardware encoder defaults differ.

Do not chase low latency. Recast streams run at standard latency (20–30 seconds) by design. Shortening the keyframe interval will not change what viewers see and will make the stream more fragile.

One protocol per stream input. A Recast stream input is created as either RTMP or SRT and cannot be switched afterwards.

Troubleshooting

vMix says it is streaming, but Recast shows nothing

Check the stream input is attached to a video and that the video is not a draft. vMix will show a healthy stream while Recast rejects it.

Then wait a full 30 seconds before concluding anything.

Streaming fails to start

1. Stream input not attached to a live, non-draft video
2. Wrong stream key — copy and paste it again
3. Trailing whitespace in the key
4. Protocol mismatch — an SRT Recast input will not accept RTMP
5. rtmps:// unsupported by your vMix version — try rtmp:// on port 5222
6. For SRT: encryption key length — see the unverified note above

Stream drops repeatedly

Usually bandwidth, especially if vMix is sending to more than one destination. Disable the other destinations and see whether Recast stabilises.

Then: use a cable rather than wifi, and check that recording to disk is not saturating the same drive vMix is streaming from.

You have 30 minutes to reconnect before Recast treats the stream as ended.

Viewers see stuttering

Check the dropped-frame count on the streaming indicator. If it is climbing, reduce the bitrate or drop a tier.

If it is not, look at vMix's Performance meters. A render load near 100% means the production itself is the bottleneck — reduce the number of active inputs, or lower the vMix master resolution.

Audio missing or out of sync

Confirm the stream audio is AAC at 48 kHz stereo in the streaming quality settings. 44.1 kHz is a common default and produces silence rather than an error.

For drift, check that your audio source and video source are not on separate clocks. vMix offers a per-input audio delay under the input's settings if you need to correct a fixed offset.

Getting help

Include your vMix version and edition, the protocol, the bitrate and resolution, your measured upload speed, and how many destinations you are streaming to simultaneously.

More detail: Recast live ingest reference

Sources

• vMix: SRT — Secure Reliable Transport
• Mux: Configuring your broadcast software for RTMP streams
• Mux: Use SRT to live stream

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