Late reply, but I've been doing live streaming out of our car for a long time with mixed success.
I chased the idea of just sending a signal from car to pits. I think it's possible over radio channels, My dad's co-worker is a massive radio nerd (I mean that positively) and claimed he could get it working, but we never circled back to it, I'll have to poke him again once COVID is less of a thing. Before I met him I was down rabbit holes trying to figure out how much power I could throw through 2.4gHz wifi signals trying to create a car-to-pits link. But I think I would have wound up chatting with the FCC if I kept after that, mostly because I'm sure I would have done it wrong a few times trying to figure it out.
The easiest method for most teams is to just throw it to the internet through a phone or hot spot. Your limiting factor here is cell bandwidth, a booster can't really get you around that. Some tracks just have crap service, and when you put several hundred people in the area all on phones, you are limited on what you can punch through. Here on the east coast I know streaming works amazing at NH, because they're setup to handle NASCAR crowds. PittRace is so-so, there is a signal dropout area from turns 5-8. NJ is ok, and CT is ok.
The best success I ever had was sticking a phone in the car and just using the ustream app. Worked flawlessly everywhere I tried it. Then they nerfed the platform and I had to start over.
I know people who are having success with Yi cameras connected to a phone/hotspot. You can chase that route, it's cheapish and works.
My setup uses some more expensive equipment, but it has advantages. My hardware list is as follows:
1. GoPro (doesn't matter what one, just needs HDMI out)
2. Cervo Live Shell 2
3. Prepaid hotspot
The liveshell is a middle man of sorts who's job is to take a raw video stream and compress it to meet the available bandwidth. This functionality seems to be baked into the newer Yi cameras and probably the latest gopros too, but the difference is that the live shell can be accessed remotely allowing you to make changes to the stream from the pits.
From my garage I can tweak bandwidth settings, add text overlays to say who's driving, stop and restart the stream, stop it from streaming to youtube and move it to another video service if I really wanted to. It's really handy. And because it is handling all the live stream stuff, the gopro can just sit there and record and not care what else is happening. That way after the race we have full res video on the camera, we don't lose recording if the live stream drops out.
These days the only reason we'll loose a live stream is if one device looses power. I have dedicated 5V power sources for each device in the car, and I use hotmelt glue to secure the USB connectors into each device so they can't shake loose, but sometimes things still go wrong and something turns off halfway through the day. Not a ton you can do to combat that. If we can keep all the devices on and powered the stream works well however.
If you want an idea of what ours looks like at a track with good signal, this was NH last year https://youtu.be/KZZ3UUizx9w?t=2991
This was NJ 2018 where the service is worse and forces more compression to stream. https://youtu.be/k15_NMp3kkA?t=2597
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