What the platform does that your laptop can't
It turns one stream into thousands. Your encoder, whether that is OBS on a laptop or a box on the camera, can only send one copy, and that copy has to fit in the venue's upload. Everything after that is the platform's job: take the stream in somewhere close to the venue, carry it to the channel, and hand it to each viewer from a city near them, so a crowd in Europe is not pulling video across the Atlantic.
That split is also why the same setup works for a graduation of 300 or a concert of 30,000. The venue side does not change; only the delivery side grows.
How much bandwidth will your audience need?
Multiply the bitrate you send by the number of people watching at the same moment. A two-hour church service with 2,000 people tuned in at its busiest point, streamed at 6 Mbps, needs 12 Gbps going out for as long as they stay. These are our own sums, rounded:
| Watching at once | 2 Mbps stream | 6 Mbps stream | Data per hour at 6 Mbps |
|---|---|---|---|
| 500 | 1 Gbps | 3 Gbps | 1.35 TB |
| 2,000 | 4 Gbps | 12 Gbps | 5.4 TB |
| 10,000 | 20 Gbps | 60 Gbps | 27 TB |
| 50,000 | 100 Gbps | 300 Gbps | 135 TB |
Each viewer at 6 Mbps uses about 2.7 GB an hour, and at 2 Mbps about 0.9 GB. Guess the peak honestly: people who registered are not people watching at the same second, but a keynote or a kick-off can bring most of them in at once.
Why one big server stops being enough
Because its network port fills up long before its processor does. Our dedicated streaming servers page puts a 1 Gbps port at about 133 viewers of 1080p video at 6 Mbps, keeping a fifth of the port spare. Faster ports raise that, but the machine still sits in a single city, so everyone far away waits on a long route.
Own a server when your audience is steady and modest, or when you want to run your own streaming software. For one night when the crowd is many times its usual size, a CDN is the tool: the load is split between cities, and every city pulls each piece of video from your channel just once.
Choosing a picture everyone can play
Pick the quality your viewers' connections can keep up with, not the best your camera can make. Apple's HLS authoring spec gives one possible set of H.264 rungs; here are some of them:
| Picture | Average kbit/s | Frame rate |
|---|---|---|
| 640 x 360 | 365 | up to 30 fps |
| 768 x 432 | 730 or 1,100 | up to 30 fps |
| 960 x 540 | 2,000 | same as source |
| 1920 x 1080 | 6,000 or 7,800 | same as source |
Apple's own defaults point the same way: iOS viewers on Wi-Fi should start on the 2,000 kbit/s rung, and those on a phone network on the 730 one. On our CDN an event carries the one quality you pick when you book it, set to match what your encoder sends, and each viewer receives exactly that. So a sharper picture also makes every viewer heavier, which the table above turns into capacity. Our player goes up to 1080p, so there is no point sending more.
Setting up the encoder, step by step
- Choose the encoder. Software like OBS, vMix or Wirecast on a laptop, or a hardware unit; our hardware encoders page covers Teradek, Cerevo LiveShell and Epiphan Pearl units for video.
- Plug it in. OBS's own advice is to stream over a cable. Keep the encoder off the guest Wi-Fi.
- Test the upload and set the bitrate. OBS suggests beginning at three quarters of the upload you measured, then lowering it if frames drop.
- Set keyframes to every 2 seconds. That is what Apple's HLS spec recommends for IDR frames, and each video segment has to begin with one.
- Paste the server details. Your dashboard prints them ready to paste: for RTMP the server is
rtmp://ingest.video.primcast.com/followed by your channel's name, with your stream name and login. In OBS they go under Settings, Stream, with the service set to Custom. - Watch the warnings. If OBS says encoding is overloaded, its performance guide suggests a lower output resolution, or 30 fps instead of 60.
The ingest name points you at whichever of our cities is closest, so the long and unpredictable stretch of the journey happens on our links, not on your upload.
When the venue's internet is shaky: SRT
Use SRT. It sends over UDP and quietly re-sends packets the line loses, as long as they arrive within a buffer called latency; the SRT library's default is 120 ms, and both ends settle on the larger value either of them asks for. A shared stadium uplink or a hotspot abroad is exactly where it pays off. You will find an SRT port and a passphrase, unique to the channel, in your dashboard. In OBS the full address goes in the Server box, the stream key is left blank, and settings are added on the end:
srt://HOST:PORT?passphrase=YOUR_PASSPHRASE&latency=2000000OBS reads the latency in microseconds, so 2000000 is two seconds; its guide asks for no less than two and a half round trips between your encoder and the ingest. The passphrase sits inside the server address you saved in OBS, so anyone with that laptop has it; treat the laptop as a key. More on the protocol in our SRT streaming guide.
How far behind the room will viewers be?
Usually a quarter of a minute or more, and that is normal. HLS sends video in segments: Apple recommends 6-second segments and wants at least six in the playlist of a live stream, and the HLS standard, RFC 8216, says a player should not start less than three target durations before the playlist's end. With 6-second segments that is about 18 seconds behind the room before anything else adds delay (our arithmetic). For a concert or a sermon nobody notices. It matters if you want the online audience to vote or ask questions in the moment, so collect them through chat with someone reading them out.
Your event on Primcast, from booking to wrap
- Book: in the event streaming builder, choose the days, hours, peak audience (six sizes, from 100 people up to 50,000) and picture quality. You see the total before checkout.
- Get the channel: it is created on the CDN by itself once payment clears; the encoder settings land in your dashboard and your welcome email. Book a few days early.
- Rehearse: the channel works straight away, so the dress rehearsal runs on exactly what your audience will see.
- Go live: connect over RTMP, SRT or WHIP at the nearest city, and switch on up to 5 restreams to YouTube, Facebook or Twitch without a second encoder. Doing that from your own upload instead is covered in our multistreaming guide.
- On air and after: the Live tab shows each viewer's country and player as they join; download the list for sponsors when you wrap.
Each viewer plays from whichever of our five cities is closest: Bucharest, Amsterdam, New York, Miami or San Francisco. If one city stops answering it leaves the rotation within 60-120 seconds and its viewers move to the next nearest. The video CDN page shows who is served from where.
The audience you book is enforced on the channel, so book for the peak. The builder goes up to 50,000 at once; for more, talk to us in the chat. If big nights come most months, Platinum includes event mode and carries 25,000 viewers per channel.
Questions people ask
- Do I need a fast internet line at the venue?
- Only fast enough for one stream, since the platform makes the copies. OBS suggests keeping the bitrate around three quarters of the upload you measured, so a 6 Mbps picture wants roughly 8 Mbps of steady upload. Test it on the day and at the hour you will go live.
- Will my event reach viewers abroad?
- Yes. Each viewer is sent to the closest of our 5 cities in North America and Europe, and Asia-Pacific viewers start from San Francisco. Your encoder also connects to the city nearest the venue.
- Can I put the stream on our website and on YouTube?
- Yes. Embed our player on your site, then set up restream targets (YouTube, Facebook and Twitch, or a custom RTMP destination), five at most, all fed by one encoder.
- What if the encoder drops mid-event?
- Reconnect the encoder, and if it hangs, the Live tab lets you disconnect it or restart the channel yourself, at any hour. Use SRT on an unreliable line, and in OBS consider the beta dynamic-bitrate setting, which gives up some picture quality to avoid dropped frames when the line is congested.
- How soon can the channel be ready?
- It is created automatically once your payment clears. We still suggest booking a few days early, because the rehearsal is what catches the problems.