My conference livestreaming setup at GambiConf
Published on September 25, 2022
Table of contents
I volunteered to be the AV team at GambiConf, an in-person conference in Lisbon. Some things didn’t go exactly as planned, so here’s a summary of how things went.
The original plan
We wanted to capture the speaker’s voice, computer screen, and have a camera pointed at the stage. We also wanted to livestream the whole thing. The organizers told me the venue had a large screen, so no need to bring an image projector.
The plan was to use OBS on a dedicated Mini-ITX computer with a bunch of USB-C ports. Then, a Canon camera with “clean HDMI” output would be connected via an HDMI to USB-C capture adapter. We had a wireless microphone whose receiver was connected via 3.5’’ to the camera, so that everything would be synced. Then, the idea was to use an AverMedia LGP 4k to intercept the speaker’s computer connection to the TV and stream it to the OBS machine over USB-C.
Like every plan, it didn’t survive first contact.
OBS machine issues
I purchased most of the pieces recently, but the hard drive was the one from my backup server. This was a mistake. It is slow, causing the full disk encryption unlocking to take around five minutes. If I mistyped the passphrase, I had to wait 5 minutes before being able to try again. I’ve since added an m.2 SSD so I won’t have the same issues again.
Computer screen
I arrived at the venue and hit the first issue almost immediately: the screen had a weird resolution of 1366x768. My fedora powered macbook pro was able to connect to it, but the organizer’s computer (running both MacOS and Windows under Parallels) was having trouble and the AverMedia device also doesn’t support that resolution. I tried to replace the AverMedia with a backup HDMI splitter, but it also didn’t work.
As a last resort, we tried VDO.Ninja, which uses WebRTC to transmit video peer to peer. We connected my laptop to the venue’s screen, loaded VDO.Ninja on both laptops and used the screenshare functionality to cast the speaker’s screen on the venue’s big screen. We had to enable the 1080p option in VDO.Ninja for things to work, otherwise it would default to a low resolution. This worked great, except when one of the speaker was using a VPN, causing some lag between what they had on their computer and what showed up on the big screen.
The VDO.Ninja solution also made it easy to plug the computer screen stream into OBS, as I could just load the same URL as a browser source.
Camera
I had a Canon camera with me with clean HDMI output. I connected it to the OBS machine with a hdmi2usb capture thingie, and it seemed to work… most of the time. If I turned off the camera or temporarily unplugged the cables, OBS would show a blank screen. The camera stream also turned black once after some minutes of operation.
Sometimes, removing and adding the camera source would solve the problem. Sometimes, I’d have to reboot the OBS machine. Instead of relying on this and having to reboot things mid-talk, I switched to a different plan: use a backup smartphone and stream its camera source with VDO.Ninja. Not as fancy as a Canon, but it worked, without any timeouts or disconnections. I forgot to bring a smartphone clamp, but fortunately someone had one of those light ring tripods that we could use.
There were some sound issues: the smartphone was emitting some sort of feedback. I could hear my fingers whenever I touched it, like it was monitoring its own microphone. I couldn’t figure out a way to disable that, so I lowered the volume as far as I could to minimize the issue.
Another advantage of using a smartphone with VDO.Ninja is that we were no longer needed a cable connecting the camera to the OBS machine. This gives us more freedom in placing the camera.
Speaker’s microphone
The plan was to use a Rode Go microphone system, connecting the receiver to the camera. Since we were no longer using the camera, I connected it directy to the mic port on the OBS machine.
At first I was confused because I could hear people talking, but talking directly to the Rode wouldn’t be significantly louder. After a while I figured out that the sound was coming from the smartphone stream instead. After removing that audio source, I still couldn’t hear anything, but eventually found that the receiver had the output pad set to -24dB. After changing this to -9dB, things worked fine.
Conclusions
The first takeaway was that having a backup plan pays off. The AverMedia had the HDMI splitter and VDO.Ninja fallback options. The camera had the smartphone fallback option. I didn’t have a backup plan for the OBS machine and the microphones, but those were the pieces less likely to fail.
Another takeaway was that being a single-person AV team isn’t really feasible. I had to recruit someone to monitor the livestream, someone to help me debug the audio problems, and the organizer set up the OBS layout himself.
The whole thing was very tiring, but rewarding. My day started at 5AM and ended at 2AM because I had to travel from Porto to Lisbon and back, I spent most of the morning on my knees messing with cables, and I was monitoring everything during the afternoon. Nevertheless, it was a fun experience, I met some interesting folks, and now I know what works and what needs improving.
You can check the final result on GambiConf’s youtube channel. I really enjoyed the talks that I managed to watch, so I recommend checking them out. Here’s a picture of final setup:
