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What is exactly the reason Oculus Link requires at least USB 3.0?

KarstenS80
Adventurer
As the following measurement of Advanced USB Port Monitor shows, Oculus Link is using a maximum bandwidth of 110 - 120 MBits/s from the PC to the Oculus Quest and around 8.5 MBit/s from the Quest to the PC.

5438qre7vqux.jpg

USB 2.0 is supporting a bandwidth of upto 480 MBit/s. So thats more than enough, even for keeping the latency low.

Advantages would be:
  • less trouble with connection issues
  • possible longer cables
  • possible thinner cables
So why do we need an USB 3.0 connection?
17 REPLIES 17

Anonymous
Not applicable
Hey there,
I don't own a Quest, but I don't need it to be sure that your figures are wrong. We're talking about a 75 Hz FHD 3D video stream. And it's not "Youtube FHD" (which is compressed as f*ck, to the point that 1080p is actually closer to real 720p), it's real FHD. It's not 120Mb/sec only. It's much higher.

Bandwidth is the sole reason people choose a higher USB standard.

Anonymous
Not applicable
lol well if true - then you have some problems... The now-aging USB 2.0 standard can theoretically transfer data at a very high 480 megabits per second (mbps), or 60 megabytes per second (MBps). You are saying it takes between 110 and 130 MBps - thus that's almost twice the size xD

USB 3.0 (also known as SuperSpeed USB) has a maximum bandwidth rate of 5 gbps (gigabits per second). That translates to 640 MBps (megabytes per second)—ten times faster than USB 2.0 (aka Hi-Speed USB

Also, keep in mind power usage and other factors such as the fact USB3.0 does allow channeling of the data.

Granted, there is another issue such as the controller/SOC does have a limit in its trans-coder that has another issue limiting it from using full bandwidth of the USB3.0 spec - but that would be consider a different issue all together.

KarstenS80
Adventurer

 but I don't need it to be sure that your figures are wrong. We're talking about a 75 Hz FHD 3D video stream. And it's not "Youtube FHD" (which is compressed as f*ck, to the point that 1080p is actually closer to real 720p), it's real FHD.


Compressed into a H264 stream by the hardware encoder of the GPU. You can see the usage of the encoder, when you look at the right place in the Windows Task manager.

And its not 2 times FHD. At the maximum configuration in the Oculus Debug tool its a 2912x16xx side by side image.

Even in Virtual Deskop with its 35 MBit/s at max and compressed to HEVC (h264 is another story at this bitrate) the onliest difference I can see is 4:2:0 of VD vs. 4:4:4 of OL.

Youtube compresses FHD somwhere beolow 5 MBit/s. That are worlds in difference. So your comparision is just ... trash.

It's not 120Mb/sec only.


First: I wrote MBits/s, not Mb/s. If you don't even know this difference, I wonder how you start a discussion.


 Second: This value is very plausible, as I don't expect the H264 encoder in the GPU and/or the H264 decoder in the Quest can handle much higher bitrates.

nalex66
MVP
MVP
The reason for USB3 is full duplex communication (both directions at the same time). Tracking data and controller inputs need to travel to the PC while video feed is streaming to the headset. USB2 would queue the signals to transmit one way at a time, and add to latency. 

DK2, CV1, Go, Quest, Quest 2, Quest 3.


Try my game: Cyclops Island Demo

Anonymous
Not applicable

nalex66 said:

The reason for USB3 is full duplex communication (both directions at the same time). Tracking data and controller inputs need to travel to the PC while video feed is streaming to the headset. USB2 would queue the signals to transmit one way at a time, and add to latency. 



Nice. A simple explanation without charts and numbers. Just in time to stop the name calling.



First: I wrote MBits/s, not Mb/s. If you don't even know this difference, I wonder how you start a discussion.




He didn't start one, you did.
Before you posted, did you consider that smarter people than us work for Ocubook? If USB 2 was okay, they would have used it.

TomCgcmfc
MVP
MVP
Honestly, there are soooo many people who want everything to run on their potato PC's with win7, XP, and usb 2.0, maybe even 1.0, lol!
i9 13900K water cooled, RTX4090, Z790 MB w/wifi6e, 32Gb 6400 ram, 2x2TB SSD, 1000W PSU, Win 11, QPro, Q3, w/Link and Air Link, Vive Pro1 with 2x2.0 base stations, Etsy lens mod and Index Controllers

U_n_i_v_e_r_s_a_l
Adventurer
Usb 2.0 is more prone to errors. You're telling me you've never received 'usb device has malfunctioned' windows 10 notification?

Anonymous
Not applicable
@KarstenS80
I know the difference, but you clearly don't, buddy. Mb means Megabits. MB means Megabytes. Your data show Megabits/sec, which is the same as Mb/sec. USB 2 has a 480 Mb/sec, which is 60MB/secs, which is not enough for a VR feed.

I don't see why you're offended, I just said your data was wrong and explained why USB 2.0 was not enough. There are other ways to relieve stress than insulting someone you don't know, especially when it's someone answering your question.

Also, what nalex said.

Digikid1
Consultant


First: I wrote MBits/s, not Mb/s. If you don't even know this difference, I wonder how you start a discussion.

It appears that YOU don't know the difference.

Capital B NO MATTER HOW YOU PUT IT means BYTES
Little b means BITS

Bits are SMALLER than BYTES

Once you learn how to tell the difference you will be better off.

It's like when people say they have 50 Megabyte Internet when they don't.  They have 50 Megabit.