How does OBS live streaming work with web overlay?

[learnOBS]

Hi I am new to obs, and wondering technically how does OBS work?
I know there is no server, everything is done on the computer runs OBS.
So if I am live streaming videos to youtube, how does that work if I have web overlay?

If there is no overlay, OBS get the data from the webcamera and mic, and encode it (mp4?) and send the data to youtube?
If there is overlay, I guess before the mp4 is sent to youtube, it also needs to add the weboverlay on top of the data then send to youtube?
then, does OBS uses its own code to add the overlay or use ffmpeg or other lib to do the job? If the content is 1080p, does it require a high end computer to do the overlay stuff? If streaming at 30fps, so the overlay must be done in less than 33ms per frame, so a fast machine is required?

I am looking for a solution on mobile phone, there is no OBS for mobile. Thus I am wondering if the above can be done on mobile phone. I am worried about the processing power of the mobile, may not be able to encode a frame (with overlay) in less than 33ms.

Any inputs?

Thanks!

 

[AaronD]

What's a web overlay? Is it different from simply having one source on top of another like PowerPoint objects? 'Cause OBS does that natively. The resulting grid of pixels, with one single color per pixel, is then sent to the encoder, and the resulting bitstream goes to a streaming server and/or a file.

Encoding takes a LOT of work, and is required for either streaming or recording. Compared to that, compositing (putting one thing on top of another and determining the final grid of single colors) hardly takes anything, even though it's completely uncompressed at that point.

A couple years ago, I tried OBS on a Raspberry Pi 4. It would capture and display 1920x1080p30 just fine, but it fell apart as soon as I tried to record it. So the Pi 4 can composite, but not encode. There are reports of the Pi 5 encoding successfully, but I haven't tried it myself.

I am looking for a solution on mobile phone, there is no OBS for mobile. Thus I am wondering if the above can be done on mobile phone. I am worried about the processing power of the mobile, may not be able to encode a frame (with overlay) in less than 33ms.

The reason that OBS doesn't exist for mobile, is performance. Mobile systems are (still) not all that powerful. They have tricks to give a job more time and/or resources than we realize, like sending raw or cheaply compressed data to the cloud and getting the answer back, or distracting the user while a single-shot job continues in the background. Live media can't do that.

If the job itself were possible on a mobile device, then I would expect OBS to follow soon. But so far, it's not, by a pretty big margin.

If you have to produce something in the boonies, see if you can get a Mobile Workstation laptop, or a desktop tower, to that location. Run OBS on that, and use the phone as a camera and/or a mobile hotspot. Nothing more.