Question / Help 2+ Webcams: USB bus bandwidth issues, what's your take?

[LucasG]

So I am doing a bi-weekly electronic music livestream with national DJs and I'm starting to have issues with my webcams and the USB buses being overloaded. I have two Logitech c922x which I have tested on a desktop PC with a pretty good mobo (Z390-A) and apparently the whole mobo has only one USB bus which obviously overloads the bandwidth and the cameras start having issues with showing the feed. I do 720p 30fps and would like to go up to 720p 60fps. I also have a pretty good high end MacBook Pro which also seems to have similar issues. I am debating whether I should spend an upgrade on the desktop PC or the laptop as I also do remote livestreams and the laptop is obviously a winner in portability.

I have researched a little bit and there are some cards you can add to desktop PCs such as this which adds 4 USB buses which can transfer up to 5 GB/s (I'm guessing in addition to the mobo USB bus), it is to be connected on a PCIe-4x lane.

My other though was, is there a way to add USB buses to the MacBook pro through an external device? Meaning I could either use it with the MacBook pro or the Desktop PC depending on the situation.

Any feedback is greatly appreciated.

 

[R1CH]

Add-in PCI-E USB cards, while expensive, completely bypass any motherboard limitations and are explicitly designed for high bandwidth, high power devices as opposed to motherboard ports which are mainly there for basic peripherals.

This card is highly recommended for any serious USB setup:
https://www.amazon.com/Sonnet-Alleg...0-E&qid=1549951351&s=electronics&sr=1-1-fkmr0

or a slightly cheaper version with less power:
https://www.amazon.com/StarTech-USB...=PEXUSB314A2V&qid=1549997020&s=gateway&sr=8-1

For a MacBook, your options are a limited to Thunderbolt peripherals. I'm not familiar enough with Mac to recommend anything, but something like https://arstechnica.com/features/20...ricky-world-of-thunderbolt-3-and-usb-c-docks/ looks like a good place to start.

 

[carlmmii]

Just to chime in for some specific clarification, for the c922, you're talking USB2.0 bandwidth. With a single controller, you're limited to the 480mb/s of the USB2.0 spec (which in real-world applications, is never really achievable). For 2 c922's running at 720p60, it's *theoretically* do-able, but getting it to stay as a reliable feed is a very questionable task. You really need 2 separate USB2.0 host controllers.

Both options R1CH mentioned work for this. The pc way is fairly obvious how this happens. For the MacBook, any thunderbolt peripheral is essentially hooking up a new USB3.1+USB2.0 host controller, which will not cause any bandwidth conflict with any webcams connected to your pre-existing USB controller on the laptop.

 

[LucasG]

In that case, I like the PCI express card idea, but I would like to keep portability and since the MacBook Pro is a 15" high-end (i7, 16 GB fast RAM, etc) would going for something like this do the trick on both computers? https://www.amazon.com/gp/product/B004C3W25M/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1

Or would since the webcams use USB 2.0 bandwidth still have issues with the bus?

 

[R1CH]

That will still be bottlenecked by the single controller on the motherboard, it's more of a port expander.

 

[LucasG]

So basically the issue is that the webcams use USB 2.0 forcefully and they do not know how to avoid going through the same place even though the motherboard is USB 3.0, correct?

From what I understand here, if you provide a good USB hub that can use 3.0/3.1 it should work on the MacBook Pro as it is a Thunderbolt connection (USB3.1+USB2.0) but on the desktop PC it would overload the USB 2.0 controller.